9.3Photosynthesis
光合作用英文版 Photosynthesis
Steps of Photosynthesis
• Light hits reaction centers of chlorophyll, found in chloroplasts
• Chlorophyll vibrates and causes water to break apart.
• Oxygen is released into air • Hydrogen remains in chloroplast
(ATP and NADPH drive the reduction
of CO2 to C6H12O6.)
Light Independent Reactions aka Calvin Cycle
CO2 is added to the 5-C sugar RuBP by the enzyme rubisco.
THE BASICS OF PHOTOSYNTHESIS
• Almost all plants are photosynthetic autotrophs, as are some bacteria and protists
– Autotrophs generate their own organic matter through photosynthesis
• Chloroplasts absorb light energy and convert it to chemical energy
Light
Reflected light
Absorbed light
Transmitted light
Chloroplast
AN OVERVIEW OF PHOTOSYNTHESIS
– Sunlight energy is transformed to energy stored in the form of chemical bonds
植物的光合作用Photosynthesis
第三章植物的光合作用Photosynthesis in Plant一、名词解释：1.光合作用（photosynthesis） 2 .光合膜（photosynthetic membrane）3.量子效率(quantum efficiency) 4.荧光现象与磷光现象（Fluorecence and phosphorecence）5.反应中心色素reaction centre pigment 6.聚光色素light-harvesting pigment或antenna pigment（天线色素) 7 Primary reaction 原初反应8.光合反应中心(Photochemical reaction centre) 9.红降(red drop) 10.爱默生效应（Emerson effect）11.光系统（photosystem）12.光合链（photosynthetic reaction）13.PQ循环（PQ cycle） 14.光合磷酸化photosynthetic phosphorylation or photophosphorylation 15. 希尔反应16. 磷酸运转器17.同化能力（assimilatory power）18.碳同化CO2 assimilation in photosynthesis 19.卡尔文循环（C3途径，还原戊糖途径）C3 photosynthetic pathway (Calvin cycle, RPPP) 20.C4途径C4 photosynthetic pathway 21.景天科酸代谢Crassulacean acid metabolism (CAM) pathway22.光呼吸（photorespiration） 23.光补偿点light compensation point(LCP) 24. light saturation point(LSP) 25.光合作用的光抑制Photoinhibition 26.二氧化碳补偿点CO2 compensation point27.二氧化碳饱和点CO2saturation point28.光合“午休现象”(midday depression of photosynthesis) 29.光能利用率Efficiency for solar energy utilization30.光合速率(photosynthetic rate)31.净光合速率(net photosynthetic rate，Pn)二、写出下列符号的中文名称PQ PC Fd NADP +RuBP PGAGAP DHAP FBP F6P G6P Ru5P PEPCAM TP HP OAA CF 1 - CF 0 PS ⅠPS ⅡBSC Mal FNR Rubico三、填空题1. 光合作用是一种氧化还原反应，在反应中被还原，被氧化。
Lesson-2-Photosynthesis 生物专业英语
Photosynthesis
Contents
• Warming–up • Words and phrases • Text Analysis • Simple exercise • Further references
Warming–up
人类对光合作用的科学研究至少已经进 行了300多年，最近100年来与光合作用有关 的研究已经获得了6次诺贝尔奖。时至今日， 仍有许多问题需要探索。
环式光合磷酸化：
从PSⅠ产生的电子，经过Fd和细胞色素b6/f
等后，引起了ATP的形成，降低能位，又经PC
回到原来的起点P700，形成tophosphorylation
n. 非环形光合磷酸化[作用]
Noncyclic photophosphorylation is coupled to noncyclic electron flow, the electrons being used to reduce NADP+ as well as to make ATP.
叶绿体中叶绿素的分布
5. Chloroplast [ 'klɔ(:)rəplɑ:st ]
n.叶绿体
A plastid in which photosynthesis is carried out. Chloroplasts occur in all photosynthetic organisms except photosynthetic bacteria and blue-green algae.
叶绿体的形态与分布
叶绿体的结构
1 双层膜：内膜为选择 性屏障。
2 基质：CO2同化；淀 粉形成
3 基粒：由类囊体垛叠 而成的绿色颗粒。
Photosynthesis
The Calvin cycle
• 3 molecules of CO2 are ‘fixed’ into glyceraldehyde 3phosphate (G3P) • Phases: 1- Carbon fixation~ each CO2 is attached to RuBP (rubisco enzyme) 2- Reduction~ electrons from NADPH reduces to G3P; ATP used up 3- Regeneration~ G3P rearranged to RuBP; ATP used; cycle continues
Calvin Cycle, net synthesis
• For each G3P (and for 3 CO2)……. Consumption of 9 ATP’s & 6 NADPH (light reactions regenerate these molecules) • G3P can then be used by the plant to make glucose and other organic compounds
Photosynthesis: an overview
• Redox process • H2O is split, e(along w/ H+) are transferred to CO2, reducing it to sugar • 2 major steps: • light reactions (“photo”) √ NADP+ (electron acceptor) to NADPH •√Photophosphorylation •ADP ---> ATP Calvin cycle (“synthesis”) √ Carbon fixation:carbon into organics
Photosynthesis
第二步，称暗反应，二氧化碳被还原成碳水化合物， 这步反应依赖电子载体NADPH以及第一步反应产生 的ATP。
Lesson two
Lesson two
Both sets of reactions take place in chloroplasts. Most of the enzymes and pigments for the lightdependent reactions are embedded in the thylakoid membrane of chloroplasts. The dark reactions take place in the stroma.
Lesson two
Lesson two
所有的光合作用生物含有不同等级的叶绿素和一 个或多个类胡萝卜素（光合作用的辅助色素）。 称作天线复合体的色素分子群存在于类囊体中。
Lesson two
Lesson two
Light striking any one of the pigment molecules is funneled to a special chlorophyll a molecule, termed a reaction-center chlorophyll, which directly participates in photosynthesis.).
Lesson two
Lesson two
During the light-dependent reactions of photosynthesis, as the absorbing molecule returns to the ground state, the "excess" excitation energy is transmitted to other molecules and stored as chemical energy.
生物专业英语 Photosynthesis
Photosynthesis
Photosynthesis
• It is a process used by plants and other organisms to convert light energy into chemical energy；
但是细胞呼吸作用是高度放能，释放能量的过程，而光合 作用需要能量, 并且是高度吸能的过程。
Cellular respiration
2019/6/3
9
Introduction
Photosynthesis occurs only in the chlorophyll-containing cells of green plants, algae, and certain protists and bacteria.
光合作用只发生在含有叶绿素的绿色植物细胞、藻类、某 些原生生物和细菌之中。
From the point of view of chemistry and energetics, it is the opposite of cellular respiration.
从化学和能量学角度来看，它是细胞呼吸作用的逆反应。
Whereas cellular respiration is highly exergonic and releases energy, photosynthesis requires energy and is highly endergonic.
Jan van Helmont (mid-17th century)
Discovery— 1771 Important year
• The air that had been "injured" by the candle and the mouse could be restored by a plant.
第3章光合作用-PPT资料106页
photo system II （PSII）：颗粒较大，主要 分布在类囊体的垛叠区。可被DCMU抑制。
2. 类囊体膜上的4个蛋白复合体
光系统II(PSII)复合物
组成：
PSII反应中心蛋白：D1D2
LHCII 放氧复合体（OEC）
作用： 水的光解放氧，提供电子
其中： 中心色素分子：P680 原初电子受体：Pheo 原初电子供体：Z(Tyr) 十几种多肽及QA，QB等传递体
放氧本质：氧化还原反应
Hill反应—离体叶绿体，加入电子受体(如Fe3+)，在
COOCH3 +(CH3COO)2Cu→
COOC20H39
C32H30ON4Cu
COOCH3 + 2CH3COOH
COOC20H39
铜代叶绿素，兰绿色
d) 叶绿素不溶于水，但溶于乙醇、乙醚、丙酮等有机溶 剂，chla呈兰绿色，chlb呈黄绿色。
2)类胡萝卜素：
a)组成： 胡萝卜素：C40H56，叶黄素：C40H56O2，后者是前 者衍生的二元醇。
2）温度：温度影响酶活性。最适30℃，最低2~4℃，最高40℃。 3）矿质元素：
N、Mg (chl的组成成分)； Fe、Cu、Zn (chl合成的活化剂)； Mn 维持类囊体结构 因缺乏矿质元素而影响chl合成，导致缺绿症chlorosis
4）水：缺水影响chl，加速分解
§3 Process of photosynthesis--
Chapter 3 Photosynthesis
§1 光合作用及其重要性
小学六年级英语作文命题多维细目表
小学六年级英语作文命题多维细目表全文共3篇示例，供读者参考篇1Title: Multiple Dimensions of English Essay Topics for Sixth GradeIntroduction:In sixth grade, students are expected to further develop their English language skills and improve their writing abilities. To help them achieve this, it is important to provide them with diverse and engaging essay topics that cover a wide range of subjects and themes. This multi-dimensional approach will not only enhance their language proficiency but also stimulate their creativity and critical thinking abilities.Topic 1: Personal NarrativeDescribe a memorable experience from your childhood and how it has impacted your life.- Include details such as the time, place, people involved, and your emotions.- Reflect on the lessons learned from this experience and how it has shaped your personality.Topic 2: Argumentative EssayShould students be allowed to use cellphones in school? Provide reasons for your opinion.- Discuss the advantages and disadvantages of using cellphones in the classroom.- Consider the impact of cellphone use on student behavior, academic performance, and social interactions.Topic 3: Descriptive EssayWrite a detailed description of your favorite place in nature and what makes it special to you.- Use sensory details to paint a vivid picture of the natural setting.- Explain why this place is important to you and how it makes you feel.Topic 4: Persuasive EssayWhy is it important to protect the environment? Convince your readers to take action to preserve the Earth.- Present evidence of environmental degradation and its consequences.- Propose solutions and encourage others to adopteco-friendly practices.Topic 5: Expository EssayExplain the process of photosynthesis and its significance in the environment.- Define photosynthesis and how plants produce oxygen and food.- Explore the role of sunlight, water, and carbon dioxide in the photosynthetic process.Conclusion:By providing students with a variety of English essay topics, we can encourage them to explore different writing styles, express their thoughts and opinions, and develop essential communication skills. Through engaging with multi-dimensional themes, students can enhance their language proficiency and critical thinking abilities, preparing them for future academic and personal success.篇2Title: Multi-dimensional Detailed Outline for Sixth Grade English CompositionIntroduction:As sixth graders, our English compositions are becoming more complex and require a deeper level of understanding and organization. To help you better structure your writing, here is a multi-dimensional detailed outline that can guide you through the process of crafting a well-structured and cohesive composition.Outline:I. Introduction- Hook- Thesis statementII. Body paragraphsA. Topic sentenceB. Supporting details1. Explanation2. Examples3. QuotesC. Transition sentenceIII. Conclusion- Restate thesis- Summary of main points- Call to action or food for thoughtIV. RevisionA. Check for grammar and spelling errorsB. Ensure coherence and cohesionC. Use transition words and phrasesD. Seek feedback from peers or teachersV. Final draftA. Proper formattingB. Neat handwriting or formattingC. Double-check for mistakesConclusion:By following this multi-dimensional detailed outline, you can improve the structure and organization of your Englishcompositions. Remember to take your time, plan ahead, and revise your work before submitting the final draft. Good luck with your writing!篇3Grades 6 English Composition Multi-Dimensional Detailed Contents Table1. Introduction1.1 Purpose of the composition1.2 Structure and organization1.3 Language usage and grammar2. Narrative Writing2.1 Personal Narrative2.1.1 Describe a memorable experience2.1.2 Reflect on a lesson learned2.2 Fictional Narrative2.2.1 Create characters and develop a plot2.2.2 Use dialogue effectively3. Descriptive Writing3.1 Describing a Person3.1.1 Physical appearance and personality traits3.1.2 Actions and behaviors3.2 Describing a Place3.2.1 Physical characteristics and setting3.2.2 Sensory details and emotions evoked4. Expository Writing4.1 Informative Essay4.1.1 Research and present information on a topic4.1.2 Organize ideas logically and cohesively4.2 Persuasive Essay4.2.1 Present arguments and support with evidence4.2.2 Address counterarguments and develop a strong conclusion5. Argumentative Writing5.1 Defend a Position5.1.1 Identify a controversial issue5.1.2 Formulate arguments and counterarguments5.2 Debate5.2.1 Research both sides of an argument5.2.2 Engage in a structured debate with peers6. Poetry6.1 Haiku6.1.1 Follow the 5-7-5 syllable pattern6.1.2 Capture a moment or feeling in nature6.2 Free Verse6.2.1 Experiment with form and structure6.2.2 Use vivid imagery and figurative language7. Editing and Revision7.1 Peer Editing7.1.1 Provide constructive feedback to peers7.1.2 Revise own work based on feedback received7.2 Grammar and Mechanics7.2.1 Correct spelling and punctuation errors7.2.2 Use appropriate verb tense and sentence structure8. Presentation and Delivery8.1 Public Speaking8.1.1 Prepare and deliver a speech on a topic of interest8.1.2 Engage the audience through voice and gestures8.2 Visual Aids8.2.1 Create and use visual aids to enhance presentations8.2.2 Incorporate multimedia elements effectively9. Conclusion9.1 Summarize key skills and concepts learned9.2 Reflect on growth and improvement in writing abilities9.3 Share future goals and aspirations in English compositionThis detailed contents table provides a comprehensive overview of the various aspects of English composition that will be covered in the sixth-grade curriculum. Students will have the opportunity to explore different types of writing, develop their skills in editing and revision, and enhance their abilities in presentation and delivery. By engaging with thesemulti-dimensional tasks, students will not only improve their writing proficiency but also cultivate a lifelong appreciation for the power of language and communication.。
compare练习题
一、词汇比较1. 选择正确的同义词或反义词：1.1. (a) abundant (b) abundant (c) abundant1.2. (a) delighted (b) delighted (c) delighted1.3. (a) delicate (b) delicate (c) delicate2. 选择正确的拼写：2.2. (a) enormous (b) enormous (c) enormous2.3. (a) independent (b) independent (c) independent二、语法比较1. 选择正确的时态：3.1. (a) I am walking (b) I walked (c) I will walk3.2. (a) She has eaten (b) She eat (c) She will eat3.3. (a) They are reading (b) They read (c) Theywill read2. 选择正确的语态：3.4. (a) The book was written him (b) The book writes him (c) The book is written him3.5. (a) The cake was eaten us (b) The cake eats us (c) The cake is eaten us3.6. (a) The letter was sent from her (b) The letter sends from her (c) The letter is sent from her三、句子结构比较1. 选择正确的句子结构：4.1. (a) She doesn't like coffee. (b) She likes not coffee. (c) She likes coffee not.4.2. (a) He was given a book her. (b) He gives a book her. (c) He is given a book her.4.3. (a) They will go to the park if it rains. (b) They go to the park if it rains. (c) They will go to the park if it rains.2. 选择正确的连接词：4.4. (a) Although he is tired, he continues working.(b) Because he is tired, he continues working. (c) If he is tired, he continues working.4.5. (a) She is not only a good student but also a talented singer. (b) She is not only a good student and a talented singer. (c) She is not only a good student or a talented singer.4.6. (a) I prefer tea to coffee. (b) I prefer tea than coffee. (c) I prefer tea from coffee.四、阅读理解比较1. 根据文章内容选择正确的答案：5.1. What is the main idea of the article?(a) The importance of exercise.(b) The benefits of healthy eating.(c) The effects of stress on the body.5.2. Why does the author mention the experiment?(a) To show the effects of exercise on the brain.(b) To discuss the importance of sleep.(c) To explain the benefits of meditation.5.3. What is the author's opinion on the topic?(a) Exercise is not necessary for good health.(b) Sleep is more important than exercise.(c) Both exercise and sleep are essential for health.2. 根据文章内容判断正误：5.4. The article states that exercise can improve memory.(a) True(b) False5.5. The author suggests that meditation can reduce stress.(a) True(b) False5.6. The article concludes that sleep is the most important factor for overall health.(a) True(b) False五、写作比较6.1. Describe a place you visited recently.6.2. Write about a person who has influenced you.6.3. Explain why you think technology is importantin today's world.6.4. The impact of social media on society6.5. The benefits of learning a second language6.6. The importance of environmental conservation六、文化知识比较1. 选择正确的文化习俗：7.1. In Japan, it is polite to (a) remove shoesbefore entering a home (b) wear shoes inside a home (c) eat with chopsticks7.3. In India, it is customary to (a) greet with a handshake (b) use the right hand for eating (c) remove shoes before entering a temple2. 选择正确的文化传统：7.4. Diwali is a festival celebrated in (a) China (b) India (c) Japan7.5. The Christmas tree is a tradition from (a)Italy (b) Germany (c) Mexico七、数学比较1. 选择正确的计算结果：8.1. 7 + 5 × 3 = (a) 22 (b) 18 (c) 248.2. 12 ÷ 4 + 6 = (a) 9 (b) 12 (c) 158.3. 8 2 × 2 = (a) 4 (b) 6 (c) 82. 选择正确的几何图形：8.4. A shape with four equal sides and angles is a(a) rectangle (b) square (c) triangle8.5. A shape with three sides and three angles is a(a) circle (b) pentagon (c) triangle8.6. A shape with two parallel sides is a (a) trapezoid (b) rectangle (c) circle八、科学知识比较1. 选择正确的科学事实：9.1. The smallest unit of matter is a (a) atom (b) molecule (c) cell9.2. The process of photosynthesis occurs in the (a) leaves (b) roots (c) flowers9.3. The force that pulls objects towards the center of the Earth is called (a) gravity (b) magnetism (c) friction2. 选择正确的科学原理：9.4. The law of conservation of energy states that(a) energy can be created or destroyed (b) energy cannot be created or destroyed (c) energy is always in motion9.5. The theory of evolution natural selection was proposed (a) Isaac Newton (b) Charles Darwin (c) Albert Einstein9.6. The speed of light in a vacuum is approximately(a) 1,000 km/s (b) 300,000 km/s (c) 1,000,000 km/s九、历史知识比较10.1. The Great Wall of China was built during the(a) Roman Empire (b) Han Dynasty (c) Ottoman Empire10.2. The Magna Carta was signed in the year (a) 1215 (b) 1066 (c) 148510.3. The French Revolution began in the year (a) 1789 (b) 1799 (c) 18042. 选择正确的历史人物：10.4. The first woman to fly solo across theAtlantic Ocean was (a) Amelia Earhart (b) Bessie Coleman (c) Harriet Quim10.5. The father of modern medicine is considered to be (a) Hippocrates (b) Galen (c) Paracelsus10.6. The person who discovered the Americas is widely believed to be (a) Christopher Columbus (b) Vasco da Gama (c) Ferdinand Magellan十、地理知识比较1. 选择正确的地理位置：11.1. The Amazon River is located in (a) North America (b) South America (c) Europe11.2. The Great Barrier Reef is off the coast of (a) Australia (b) Japan (c) Brazil11.3. The Sahara Desert is in (a) North Africa (b) South Africa (c) Central Africa11.4. The highest mountain peak in the world is (a) Mount Everest (b) Mount Kilimanjaro (c) Mount Fuji11.5. The Nile River is the longest river in (a) Asia(b) Africa (c) Europe11.6. The Amazon Rainforest is located in (a) Central America (b) South America (c) North America十二、语言运用比较1. 选择正确的语法结构：12.1. "She is ________ to speak three languages." (a) able (b) capable (c) skilled12.2. "The book ________ on the table is mine." (a) lies (b) lays (c) lays12.3. "I ________ to the store, but I changed my mind." (a) was going (b) went (c) am going2. 选择正确的动词形式：12.4. "If I ________ you, I would ________." (a) were; go (b) am; go (c) was; went12.5. "She ________ her homework last night." (a)did (b) does (c) is doing12.6. "They ________ in the garden when it startedto rain." (a) were playing (b) played (c) have played 十三、逻辑推理比较1. 根据逻辑关系选择正确的选项：13.1. If A is true, then B must be (a) false (b)true (c) unknown13.2. If A is false, then B must be (a) false (b)true (c) unknown13.3. If A and B are both true, then C must be (a) true (b) false (c) unknown2. 解决逻辑谜题：13.4. Three friends went to a movie. One bought a ticket for $10, the second bought a ticket for $7, and thethird bought a ticket for $5. The total cost was $22. How much did each person pay?13.5. There are five boxes, each containing adifferent color ball. The balls are red, blue, green, yellow, and black. You know that the red ball is not in the first box, the blue ball is not in the second box, the green ball is not in the third box, the yellow ball is not in the fourth box, and the black ball is not in the fifth box. Which boxcontains the black ball?13.6. A man has three keys, one of which opens a box containing a valuable ring. The keys are labeled A, B, and C. The keys are placed in a row on a table. The following statements are true:A is to the left of B.C is not to the right of B.The key that opens the box is not labeled A.Which key opens the box?十四、生活常识比较1. 选择正确的健康建议：14.2. Regular exercise is important for (a)improving sleep quality (b) reducing stress levels (c) both a and b14.3. A balanced diet includes (a) fruits and vegetables (b) whole grains (c) all of the above2. 选择正确的日常习惯：14.4. It is best to brush your teeth (a) after breakfast (b) before bedtime (c) both a and b14.5. To avoid a cold, it is important to (a) wash your hands regularly (b) get enough sleep (c) both a and b14.6. When cooking, it is safe to consume (a) raw eggs (b) wellcooked meat (c) both a and b十五、社会问题比较1. 选择正确的社会问题解决方案：15.1. To reduce traffic congestion, cities should (a) build more roads (b) implement public transportation (c) botha and b15.2. To improve education, schools should (a) increase funding (b) provide more resources (c) both a and b2. 选择正确的15.4. Which of the following is a key factor in promoting economic growth?(a) Lower taxes (b) Increased government spending (c) Both a and b(a) Raise the minimum wage (b) Implement progressive taxation (c) Both a and b十六、艺术与文学比较1. 选择正确的艺术作品描述：16.1. "The Starry Night" is a painting (a) Leonardo da Vinci (b) Vincent van Gogh (c) Pablo Picasso16.2. The play "Hamlet" was written (a) William Shakespeare (b) George Bernard Shaw (c) Arthur Miller16.3. The novel "1984" is a dystopian work (a) J.K. Rowling (b) George Orwell (c) Aldous Huxley2. 选择正确的文学作品分析：16.4. The character Sherlock Holmes is known for his(a) detective skills (b) love of the outdoors (c) mathematical prowess16.5. The poem "Do not go gentle into that good night" is a work (a) Robert Frost (b) Dylan Thomas (c) Langston Hughes16.6. The novel "Pride and Prejudice" is a classic example of (a) science fiction (b) romance (c) historical fiction十七、经济知识比较1. 选择正确的经济术语：17.1. The term "inflation" refers to (a) theincrease in the value of money (b) the decrease in the valueof money (c) the increase in the price of goods and services17.2. "GDP" stands for (a) Gross Domestic Product (b) Gross Domestic Profit (c) Gross Domestic People17.3. "Monetarism" is an economic theory that emphasizes the importance of (a) government spending (b) monetary policy (c) fiscal policy2. 选择正确的经济活动：17.6. A "budget deficit" occurs when (a) government spending exceeds revenue (b) government revenue exceeds spending (c) both a and b十八、科技发展比较1. 选择正确的科技发明：18.1. The World Wide Web was created (a) Tim BernersLee (b) Steve Jobs (c) Bill Gates18.3. The iPhone was introduced (a) Microsoft (b) Apple (c) Google2. 选择正确的科技趋势：18.4. Artificial intelligence is being used to (a) improve healthcare (b) automate manufacturing (c) both a andb18.5. The Internet of Things (IoT) is expected to (a) increase energy consumption (b) improve efficiency (c) both a and b答案一、词汇比较1. 1.1. (b) abundant1.2. (a) delighted1.3. (c) delicate2.2. (b) enormous2.3. (c) independent二、语法比较1. 3.1. (c) I will walk3.2. (a) She has eaten3.3. (a) They are reading2. 3.4. (c) The letter is written him3.5. (c) The cake is eaten us3.6. (c) The letter is sent from her三、句子结构比较1. 4.1. (a) She doesn't like coffee.4.2. (c) The cake was eaten us.4.3. (a) They will go to the park if it rains.2. 4.4. (a) Although he is tired, he continues working.4.5. (a) She is not only a good student but also a talented singer.4.6. (a) I prefer tea to coffee.四、阅读理解比较1. 5.1. (b) The benefits of healthy eating.5.2. (a) To show the effects of exercise on the brain.5.3. (c) Both exercise and sleep are essential for health.2. 5.4. (a) True5.5. (a) True5.6. (b) False五、写作比较1. 6.1. (略)6.2. (略)6.3. (略)2. 6.4. (略)6.5. (略)6.6. (略)六、文化知识比较1. 7.1. (a) remove shoes before entering a home7.2. (b) have a threecourse meal7.3. (b) use the right hand for eating2. 7.4. (b) India7.5. (b) Germany7.6. (a) Egypt七、数学比较1. 8.1. (c) 248.2. (a) 98.3. (a) 42. 8.4. (b) square8.5. (c) triangle8.6. (a) trapezoid八、科学知识比较1. 9.1. (a) atom9.2. (a) leaves9.3. (a) gravity2. 9.4. (b) energy cannot be created or destroyed 9.5. (b) Charles Darwin9.6. (b) 300,000 km/s九、历史知识比较1. 10.1. (b) Han Dynasty10.2. (a) 121510.3. (a) 17892. 10.4. (a) Amelia Earhart10.5. (a) Hippocrates10.6. (a) Christopher Columbus十、地理知识比较1. 11.1. (b) South America11.2. (a) Australia11.3. (a) North Africa2. 11.4. (a) Mount Everest 11.5. (b) Africa11.6. (b) South America 十一、语言运用比较1. 12.1. (b) capable12.2. (a) lies12.3. (a) was going2. 12.4. (a) were going; go 12.5. (a) did12.6. (a) were playing 十二、逻辑推理比较1. 13.1. (b) true13.2. (a) false13.3. (a) true2. 13.4. (略)13.5. (略)13.6. (略)十三、生活常识比较1. 14.1. (c) water14.2. (c)。
光合作用 图文并茂 PHOTOSYNTHESIS(1)
EACH ELECTRONIC ENERGY LEVEL HAS
VIBRATIONAL AND ROTATIONAL SUB-STATES
POSSIBLE FATES OF EXCITED ELECTRON
INTERNAL CONVERSION (A FAST PROCESS)
“LIGHT-HARVESTING COMPLEXES (LHCs)
LIGHT ENERGY IS PASSED BY EXCITON TRANSFER TO THE REACTION CENTER
THESE HAVE SLIGHTLY LOWER EXCITATION ENERGIES >90% EFFICIENCY OF THE TRANSFER PROCESS!
CHLOROPLASTS
STRUCTURE IS VERY SIMILAR TO MITOCHONDRIA
PROBABLY EVOLVED FROM A CYANOBAN-PHOTOSYNTHETIC EUKARYOTE (SYMBIOSIS)
CO2 + H2O (CH2O) + O2
CO2 IS REDUCED H2O IS OXIDIZED
THERE ARE TWO PHASES IN PHOTOSYNTHESIS
THE “LIGHT REACTION”
H2O IS SPLIT
2 H2O O2 + 4 [H]
“ANTENNA” CHLOROPHYLLS
THERE ARE ~ 300 CHLOROPHYLL MOLECULES PER REACTION CENTER THE FUNCTION OF MOST CHLOROPHYLLS IS TO GATHER LIGHT ACT LIKE ANTENNAS
PhotosynthesisandRespiration
Experiment31CBiology with Handhelds31C - 1Photosynthesis and RespirationPlants make sugar, storing the energy of the sun into chemical energy, by the process ofphotosynthesis. When they require energy, they can tap the stored energy in sugar by a process called cellular respiration.The process of photosynthesis involves the use of light energy to convert carbon dioxide and water into sugar, oxygen, and other organic compounds. This process is often summarized by the following reaction:6 H 2O + 6 CO 2 + light energy → C 6H 12O 6 + 6 O 2Cellular respiration refers to the process of converting the chemical energy of organic molecules into a form immediately usable by organisms. Glucose may be oxidized completely if sufficient oxygen is available by the following equation:C 6H 12O 6 + 6 O 2 → 6 H 2O + 6 CO 2 + energyAll organisms, including plants and animals, oxidize glucose for energy. Often, this energy is used to convert ADP and phosphate into ATP.OBJECTIVESIn this experiment, you will• Use an O 2 Gas Sensor to measure the amount of oxygen gas consumed or produced by aplant during respiration and photosynthesis.• Use a CO 2 Gas Sensor to measure the amount of carbon dioxide consumed or produced by a plant during respiration and photosynthesis.•Determine the rate of respiration and photosynthesis of a plant.Figure 1Experiment 31C31C - 2Biology with HandheldsMATERIALSLabPro interface 250 mL respiration chamber Palm handheld plant leavesData Pro program 500 mL tissue culture flask Vernier O 2 Gas Sensor lampVernier CO 2 Gas Sensor aluminum foil CO 2–O 2 TeeforcepsPROCEDURE1.Plug the O 2 Gas Sensor into Channel 1 of the LabPro interface. Plug the CO 2 Gas Sensor into Channel 2 of the LabPro interface. Connect the handheld to the LabPro using the interface cable. Firmly press in the cable ends.2.Press the power button on the handheld to turn it on. To start Data Pro, tap the Data Pro iconon the Applications screen. Choose New from the Data Pro menu or tapto reset the program.3.Set up the handheld and interface for an O 2 Gas Sensor and CO 2 Gas Sensor.a. If the handheld displays O2 GAS (ppt) in CH 1 and CO2 GAS(ppt) in CH 2 proceed directly to Step 4. If it does not, continue with this step to set up your sensor manually.b. On the Main screen, tap .c.Tap to select Channel 1.d. Press the Scroll buttons on the handheld to scroll through the list of sensors.e. Choose OXYGEN GAS(ppt) from the list of sensors.f. Tap to select Channel 2.g. Press the Scroll buttons on the handheld to scroll through the list of sensors.h. Choose CO2 GAS(ppt) from the sensor menu.i. Tap to return to the Main screen.4.Obtain several leaves from the resource table and blot them dry, if damp, between two pieces of paper towel.5.Place the leaves into the respiration chamber, using forceps if necessary. Wrap the respiration chamber in aluminum foil so that no light reaches the leaves.6.Insert the CO 2–O 2 Tee into the neck of the respiration chamber. Place the O 2 Gas Sensor into the CO 2–O 2 Tee as shown in Figure 1. Insert the sensor snugly into the Tee. The O 2 Gas Sensor should remain vertical throughout the experiment. Place the CO 2 Gas Sensor into the Tee directly across from the respiration chamber as shown in Figure 1. Gently twist the stopper on the shaft of the CO 2 Gas Sensor into the chamber opening. Do not twist the shaft of the CO 2 Gas Sensor or you may damage it.7.Wait ten minutes, then tapto begin data collection.8.When data collection has finished, remove the aluminum foil from around the respirationchamber.Photosynthesis and RespirationBiology with Handhelds31C - 39.Fill the tissue culture flask with water and place it between the lamp and the respirationchamber. The flask will act as a heat shield to protect the plant leaves.10.Turn the lamp on. Place the lamp as close to the leaves as reasonable. Do not let the lamptouch the tissue culture flask.11.Tap on the y-axis of the displayed graph and choose CH1: O2 GAS(ppt). A graph of oxygengas vs. time. Sketch a copy of your graph in the Graph section below.Tap on the y-axis of the displayed graph and choose CH2: CO2 GAS(ppt). A graph of carbon dioxide gas vs. time. Sketch a copy of your graph in the Graph section below.12.Perform a linear regression to calculate the rate of respiration/photosynthesis.a.Tap, then tap .b. Note that CH2: CO2 GAS(ppm) is the Data to Fit. The linear regression statistics displayed will be for the CO 2 Gas Sensor.c. Choose Linear as the Fit Equation.d. From the Fit Equation menu, choose Linear. The linear-regression statistics for these two data columns are displayed for the equation in the formy = ax + b e. Enter the value of the slope, a , as the rate of respiration/photosynthesis for the CO 2 Gas Sensor in Table 1.13.Calculate the rate of respiration/photosynthesis for the O 2 Gas Sensor.a. At the top of the screen, tap CH2: CO2 GAS(ppt) and choose CH1: O2 GAS(ppt) as the Data to Fit.b. The linear-regression statistics for these two data columns are displayed for the equation in the formy = ax + b c. Enter the value of the slope, a , as the rate of respiration/photosynthesis for the O 2 Gas Sensor in Table 1.d.Tap to view the fitted curve with your data.e. Tap once again to return to the Graph screen.14.Repeat Steps 8 – 13 to collect data with the plant exposed to light.15.Remove the plant leaves from the respiration chamber, using forceps if necessary. Clean and dry the respiration chamber.Experiment 31C31C - 4Biology with HandheldsDATATable 1LeavesO 2 rate ofproduction/consumption(ppt/s)CO2 rate ofproduction/consumption(ppt/s)In the dark In the lightGRAPHSDarknessO 2 Gas vs . Time CO 2 Gas vs . TimeLightO 2 Gas vs . Time CO 2 Gas vs . TimeQUESTIONS1.Were either of the rate values for CO 2 a positive number? If so, what is the biological significance of this?2.Were either of the rate values for O 2 a negative number? If so, what is the biological significance of this?3.Do you have evidence that cellular respiration occurred in leaves? Explain.Photosynthesis and RespirationBiology with Handhelds31C - 54.Do you have evidence that photosynthesis occurred in leaves? Explain.5.List five factors that might influence the rate of oxygen production or consumption in leaves.Explain how you think each will affect the rate?EXTENSIONS1.Design and perform an experiment to test one of the factors that might influence the rate of oxygen production or consumption in Question 5.pare the rates of photosynthesis and respiration among various types of plants.ExperimentTEACHER INFORMATION31CBiology with Calculators31C - 1 TPhotosynthesis and Respiration1.Spinach leaves purchased from a grocery store work very well and are readily available any time of the year. For best results, keep the leaves cool until they are to be used. Just before use, expose the leaves to bright light for 5 minutes.2. A fluorescent ring lamp works very well since it bathes the plant in light from all sides and it gives off very little heat. When using a ring lamp as shown below, it is not necessary to use aheat shield.3.If tissue culture flasks are not available, a beaker or flask of water will also work. The tissue culture flask is very thin, however, and will allow leaves to receive much more light from the same lamp.4.To extend the life of the O 2 Gas Sensor, always store the sensor upright in the box in which it was shipped.5.The waiting time before taking data may need to be adjusted depending on the rate ofdiffusion of the oxygen gas and the carbon dioxide gas. Monitor the gas concentrations and start collecting data when the levels of gas begin to move in the correct direction.6.The stopper included with the CO 2 Gas Sensor is slit to allow easy application and removal from the probe. When students are placing the probe in the CO 2–O 2 Tee, they should gently twist the stopper into the adapter opening. Warn the students not to twist the probe shaft or they may damage the sensing unit.7.To conserve battery power, we suggest that AC Adapters be used to power the interfaces rather than batteries when working with the CO2 Gas Sensor. An AC Adapter is shipped with each LabPro interface at the time of purchase. If you are using the CBL 2, you can purchase a Vernier AC Adapter for $10 (order code–IPS).Experiment 31C31C - 2 TBiology with CalculatorsSAMPLE RESULTSTable 1LeavesO2 rate ofproduction/consumption(ppt/s)CO 2 rate ofproduction/consumption(ppt/s)In the dark xxxx xxxx In the lightxxxxxxxxGRAPHSDarknessO 2 Gas vs . TimeCO 2 Gas vs . TimeLightO 2 Gas vs . Time CO 2 Gas vs . TimeANSWERS TO QUESTIONSAnswers have been removed from the online versions of Vernier curriculum material in order to prevent inappropriate student use.Graphs and data tables have also been obscured. Full answers and sample data are available in the print versions of these labs.。
Photosynthesis
10PhotosynthesisConcept Outline10.1What is photosynthesis?The Chloroplast as a Photosynthetic Machine.Thehighly organized system of membranes in chloroplasts isessential to the functioning of photosynthesis.10.2Learning about photosynthesis: An experimentaljourney.The Role of Soil and Water.The added mass of agrowing plant comes mostly from photosynthesis. In plants, water supplies the electrons used to reduce carbon dioxide.Discovery of the Light-Independent Reactions.Photosynthesis is a two-stage process. Only the first stagedirectly requires light.The Role of Light.The oxygen released during greenplant photosynthesis comes from water, and carbon atomsfrom carbon dioxide are incorporated into organic molecules.The Role of Reducing Power.Electrons released fromthe splitting of water reduce NADP+; ATP and NADPHare then used to reduce CO2and form simple sugars. 10.3Pigments capture energy from sunlight.The Biophysics of Light.The energy in sunlight occursin “packets” called photons, which are absorbed by pigments.Chlorophylls and Carotenoids.Photosyntheticpigments absorb light and harvest its energy.Organizing Pigments into Photosystems.Aphotosystem uses light energy to eject an energized electron.How Photosystems Convert Light to Chemical Energy.Some bacteria rely on a single photosystem to produceATP. Plants use two photosystems in series to generateenough energy to reduce NADP+and generate ATP.How the Two Photosystems of Plants Work Together.Photosystems II and I drive the synthesis of the ATP andNADPH needed to form organic molecules.10.4Cells use the energy and reducing power capturedby the light reactions to make organic molecules.The Calvin Cycle.ATP and NADPH are used to buildorganic molecules, a process reversed in mitochondria.Reactions of the Calvin Cycle.Ribulose bisphosphatebinds CO2in the process of carbon fixation.Photorespiration.The enzyme that catalyzes carbonfixation also affects CO2release.L ife on earth would be impossible without photosyn-thesis. Every oxygen atom in the air we breathe was once part of a water molecule, liberated by photosynthesis. The energy released by the burning of coal, firewood, gasoline, and natural gas, and by our bodies’ burning of all the food we eat—all, directly or indirectly, has been cap-tured from sunlight by photosynthesis. It is vitally impor-tant that we understand photosynthesis. Research may en-able us to improve crop yields and land use, important goals in an increasingly crowded world. In the previous chapter we described how cells extract chemical energy from food molecules and use that energy to power their activities. In this chapter, we will examine photosynthesis, the process by which organisms capture energy from sun-light and use it to build food molecules rich in chemicalenergy (figure 10.1).FIGURE 10.1Capturing energy.These sunflower plants, growing vigorously in the August sun, are capturing light energy for conversion into chemical energy through photosynthesis.18310.1What is photosynthesis?Stoma Bundle sheathChloroplastsInnermembraneGranumFIGURE 10.2Journey into a leaf.A plant leaf possesses a thick layer of cells (the mesophyll) rich in chloroplasts. The flattened thylakoids in the chloroplast are stacked into columns called grana (singular, granum). The light reactions take place on the thylakoid184Part III Energeticssis takes place in three stages: (1) capturing energy from sunlight; (2) using the energy to make ATP and reducing power in the form of a compound called NADPH; and (3)using the ATP and NADPH to power the synthesis of organic molecules from CO2in the air (carbon fixation).The first two stages take place in the presence of light and are commonly called the light reactions.The third stage, the formation of organic molecules from atmos-pheric CO2, is called the Calvin cycle.As long as ATP and NADPH are available, the Calvin cycle may occur in the absence of light.The following simple equation summarizes the overall process of photosynthesis:6 CO2+ 12 H2O + light —→C6H12O6+ 6 H2O + 6 O2 carbon water glucose water oxygen dioxideInside the ChloroplastThe internal membranes of chloroplasts are organized into sacs called thylakoids,and often numerous thylakoids are stacked on one another in columns called grana.The thy-lakoid membranes house the photosynthetic pigments for capturing light energy and the machinery to make ATP. Surrounding the thylakoid membrane system is a semiliq-uid substance called stroma.The stroma houses the en-zymes needed to assemble carbon molecules. In the mem-branes of thylakoids, photosynthetic pigments are clustered together to form a photosystem.Each pigment molecule within the photosystem is capa-ble of capturing photons,which are packets of energy. A lat-tice of proteins holds the pigments in close contact with one another. When light of a proper wavelength strikes a pigment molecule in the photosystem, the resulting excita-tion passes from one chlorophyll molecule to another. The excited electron is not transferred physically—it is the en-ergy that passes from one molecule to another. A crude analogy to this form of energy transfer is the initial “break”in a game of pool. If the cue ball squarely hits the point of the triangular array of 15 pool balls, the two balls at the far corners of the triangle fly off, but none of the central balls move. The energy passes through the central balls to the most distant ones.Eventually the energy arrives at a key chlorophyll mole-cule that is touching a membrane-bound protein. The en-ergy is transferred as an excited electron to that protein, which passes it on to a series of other membrane proteins that put the energy to work making ATP and NADPH and building organic molecules. The photosystem thus acts as a large antenna, gathering the light harvested by many indi-vidual pigment molecules.The reactions of photosynthesis take place withinthylakoid membranes within chloroplasts in leaf cells.Chapter 10Photosynthesis185 SunlightLight reactionsH2OPhotosystemThylakoidFIGURE 10.2 (continued)membrane and generate the ATP and NADPH that fuel the Calvin cycle. The fluid interior matrix of a chloroplast, the stroma, contains the enzymes that carry out the Calvin cycle.The Role of Soil and WaterThe story of how we learned about photosynthesis is one of the most interesting in science and serves as a good intro-duction to this complex process. The story starts over 300 years ago, with a simple but carefully designed experiment by a Belgian doctor, Jan Baptista van Helmont (1577–1644). From the time of the Greeks, plants were thought to obtain their food from the soil, literally sucking it up with their roots; van Helmont thought of a simple way to test the idea. He planted a small willow tree in a pot of soil after weighing the tree and the soil. The tree grew in the pot for several years, during which time van Helmont added only water. At the end of five years, the tree was much larger: its weight had increased by 74.4 kilograms. However, all of this added mass could not have come from the soil,because the soil in the pot weighed only 57 grams less than it had five years earlier! With this experiment, van Helmont demonstrated that the substance of the plant was not produced only from the soil. He incorrectly concluded that mainly the water he had been adding accounted for the plant’s increased mass.A hundred years passed before the story became clearer. The key clue was provided by the English scientist Joseph Priestly, in his pioneering studies of the properties of air. On the 17th of August, 1771, Priestly “accidentally hit upon a method of restoring air that had been injured by the burning of candles.” He “put a [living] sprig of mint into air in which a wax candle had burnt out and found that, on the 27th of the same month, another candle could be burned in this same air.” Somehow, the vegetation seemed to have restored the air! Priestly found that while a mouse could not breathe candle-exhausted air, air “restored” by vegetation was not “at all inconvenient to a mouse.” The key clue was that living vegetation adds something to the air.How does vegetation “restore” air? Twenty-five years later, Dutch physician Jan Ingenhousz solved the puzzle. Working over several years, Ingenhousz reproduced and significantly extended Priestly’s results, demonstrating that air was restored only in the presence of sunlight, and only by a plant’s green leaves, not by its roots. He proposed that the green parts of the plant carry out a process (which we now call photosynthesis) that uses sunlight to split carbon dioxide (CO2) into carbon and oxygen. He suggested that the oxygen was released as O2gas into the air, while the carbon atom combined with water to form carbohydrates. His proposal was a good guess, even though the later step was subsequently modified. Chemists later found that the proportions of carbon, oxygen, and hydrogen atoms in car-bohydrates are indeed about one atom of carbon per mole-cule of water (as the term carbohydrate indicates). A Swiss botanist found in 1804 that water was a necessary reactant. By the end of that century the overall reaction for photo-synthesis could be written as:CO2+ H2O + light energy —→(CH2O) + O2 It turns out, however, that there’s more to it than that. When researchers began to examine the process in more detail in the last century, the role of light proved to be un-expectedly complex.Van Helmont showed that soil did not add mass to agrowing plant. Priestly and Ingenhousz and others then worked out the basic chemical reaction. Discovery of the Light-Independent ReactionsIngenhousz’s early equation for photosynthesis includes one factor we have not discussed: light energy. What role does light play in photosynthesis? At the beginning of the previous century, the English plant physiologist F. F. Blackman began to address the question of the role of light in photosynthesis. In 1905, he came to the startling conclu-sion that photosynthesis is in fact a two-stage process, only one of which uses light directly.Blackman measured the effects of different light inten-sities, CO2concentrations, and temperatures on photo-synthesis. As long as light intensity was relatively low, he found photosynthesis could be accelerated by increasing the amount of light, but not by increasing the tempera-ture or CO2concentration (figure 10.3). At high light in-tensities, however, an increase in temperature or CO2 concentration greatly accelerated photosynthesis. Black-man concluded that photosynthesis consists of an initial set of what he called “light” reactions, that are largely in-dependent of temperature, and a second set of “dark” re-actions, that seemed to be independent of light but lim-ited by CO2. Do not be confused by Blackman’s labels—the so-called “dark” reactions occur in the light (in fact, they require the products of the light reactions); their name simply indicates that light is not directly in-volved in those reactions.Blackman found that increased temperature increases the rate of the dark carbon-reducing reactions, but only up to about 35°C. Higher temperatures caused the rate to fall off rapidly. Because 35°C is the temperature at which many plant enzymes begin to be denatured (the hydrogen bonds that hold an enzyme in its particular catalytic shape begin to be disrupted), Blackman concluded that enzymes must carry out the dark reactions.Blackman showed that capturing photosynthetic energy requires sunlight, while building organic moleculesdoes not.186Part III Energetics10.2Learning about photosynthesis: An experimental journey.The Role of LightThe role of light in the so-called light and dark reactions was worked out in the 1930s by C. B. van Niel, then a graduate student at Stanford University studying photosynthesis in bacteria. One of the types of bacteria he was studying, the purple sulfur bacteria, does not release oxygen during photosynthesis; instead, they convert hydrogen sulfide (H2S) into globules of pure elemental sulfur that accumulate inside themselves. The process that van Niel observed wasCO2+ 2 H2S + light energy →(CH2O) + H2O + 2 S The striking parallel between this equation and Ingenhousz’s equation led van Niel to propose that the generalized process of photosynthesis is in factCO2+ 2 H2A + light energy →(CH2O) + H2O + 2 A In this equation, the substance H2A serves as an electron donor. In photosynthesis performed by green plants, H2A is water, while among purple sulfur bacteria, H2A is hydrogen sulfide. The product, A, comes from the splitting of H2A. Therefore, the O2produced during green plant photosyn-thesis results from splitting water, not car-bon dioxide.When isotopes came into common use in biology in the early 1950s, it became possible to test van Niel’s revolu-tionary proposal. Investigators examined photosynthesis in green plants supplied with 18O water; they found that the 18O label ended up in oxygen gas rather than in carbohy-drate, just as van Niel had predicted:CO2+ 2 H218O + light energy —→(CH2O) + H2O + 18O2In algae and green plants, the carbohydrate typically pro-duced by photosynthesis is the sugar glucose, which has six carbons. The complete balanced equation for photosynthe-sis in these organisms thus becomes6 CO2+ 12 H2O + light energy —→C6H12O6+ 6 O2+ 6 H2O.We now know that the first stage of photosynthesis, the light reactions, uses the energy of light to reduce NADP (an electron carrier molecule) to NADPH and to manufac-ture ATP. The NADPH and ATP from the first stage of photosynthesis are then used in the second stage, the Calvin cycle, to reduce the carbon in carbon dioxide and form a simple sugar whose carbon skeleton can be used to synthesize other organic molecules.Van Niel discovered that photosynthesis splits watermolecules, incorporating the carbon atoms of carbondioxide gas and the hydrogen atoms of water intoorganic molecules and leaving oxygen gas. The Role of Reducing PowerIn his pioneering work on the light reactions, van Niel had further proposed that the reducing power (H+) generated by the splitting of water was used to convert CO2into organic matter in a process he called carbon fixation. Was he right?In the 1950s Robin Hill demonstrated that van Niel was indeed right, and that light energy could be used to generate reducing power. Chloroplasts isolated from leaf cells were able to reduce a dye and release oxygen in response to light. Later experiments showed that the electrons released from water were transferred to NADP+. Arnon and coworkers showed that illuminated chloroplasts deprived of CO2accu-mulate ATP. If CO2is then introduced, neither ATP nor NADPH accumulate, and the CO2is assimilated into organic molecules. These experiments are important for three rea-sons. First, they firmly demonstrate that photosynthesis oc-curs only within chloroplasts. Second, they show that the light-dependent reactions use light energy to reduce NADP+ and to manufacture ATP. Thirdly, they confirm that the ATP and NADPH from this early stage of photosynthesis are then used in the later light-independent reactions to reduce carbon dioxide, forming simple sugars.Hill showed that plants can use light energy to generate reducing power. The incorporation of carbon dioxideinto organic molecules in the light-independentreactions is called carbon fixation.Chapter 10Photosynthesis187 sFIGURE 10.3Discovery of the dark reactions. (a) Blackman measured photosynthesis rates under differing light intensities, CO2concentrations, and temperatures. (b) As this graph shows, light is the limiting factor at low light intensities, while temperature and CO2 concentration are the limiting factors at higher light intensities.The Biophysics of LightWhere is the energy in light? What is there in sunlight that a plant can use toreduce carbon dioxide? This is themystery of photosynthesis, the one fac-tor fundamentally different fromprocesses such as respiration. To an-swer these questions, we will need toconsider the physical nature of light it-self. James Clerk Maxwell had theo-rized that light was an electromagnetic wave—that is, that light movedthrough the air as oscillating electric and magnetic fields. Proof of this camein a curious experiment carried out in alaboratory in Germany in 1887. A young physicist, Heinrich Hertz, was attempting to verify a highly mathe-matical theory that predicted the exis-tence of electromagnetic waves. To see whether such waves existed, Hertz de-signed a clever experiment. On oneside of a room he constructed a powerful spark generatorthat consisted of two large, shiny metal spheres standingnear each other on tall, slender rods. When a very high sta-tic electrical charge was built up on one sphere, sparkswould jump across to the other sphere.After constructing this device, Hertz set out to investigate whether the sparking would create invisible electromagneticwaves, so-called radio waves, as predicted by the mathemati-cal theory. On the other side of the room, he placed theworld’s first radio receiver, a thin metal hoop on an insulat-ing stand. There was a small gap at the bottom of the hoop,so that the hoop did not quite form a complete circle. WhenHertz turned on the spark generator across the room, he sawtiny sparks passing across the gap in the hoop! This was thefirst demonstration of radio waves. But Hertz noted anothercurious phenomenon. When UV light was shining acrossthe gap on the hoop, the sparks were produced more readily.This unexpected facilitation, called the photoelectric effect,puzzled investigators for many years.The photoelectric effect was finally explained using aconcept proposed by Max Planck in 1901. Planck devel-oped an equation that predicted the blackbody radiationcurve based upon the assumption that light and other formsof radiation behaved as units of energy called photons. In1905 Albert Einstein explained the photoelectric effect uti-lizing the photon concept. Ultraviolet light has photons ofsufficient energy that when they fell on the loop, electronswere ejected from the metal surface. The photons hadtransferred their energy to the electrons, literally blastingthem from the ends of the hoop and thus facilitating the passage of the electric spark induced by the radio waves.Visible wavelengths of light were unable to remove the electrons because their photons did not have enough en-ergy to free the electrons from the metal surface at the ends of the hoop.The Energy in PhotonsPhotons do not all possess the same amount of energy (fig-ure 10.4). Instead, the energy content of a photon is in-versely proportional to the wavelength of the light: short-wavelength light contains photons of higher energy than long-wavelength light. X rays, which contain a great deal of energy, have very short wavelengths—much shorter than visi-ble light, making them ideal for high-resolution microscopes.Hertz had noted that the strength of the photoelectric effect depends on the wavelength of light; short wave-lengths are much more effective than long ones in produc-ing the photoelectric effect. Einstein’s theory of the photo-electric effect provides an explanation: sunlight contains photons of many different energy levels, only some of which our eyes perceive as visible light. The highest energy photons, at the short-wavelength end of the electromag-netic spectrum (see figure 10.4), are gamma rays, with wavelengths of less than 1 nanometer; the lowest energy photons, with wavelengths of up to thousands of meters,are radio waves. Within the visible portion of the spectrum,violet light has the shortest wavelength and the most ener-getic photons, and red light has the longest wavelength and the least energetic photons.188Part IIIEnergetics10.3Pigments capture energy from sunlight.FIGURE 10.4The electromagnetic spectrum.Light is a form of electromagnetic energy convenientlythought of as a wave. The shorter the wavelength of light, the greater its energy. Visible light represents only a small part of the electromagnetic spectrum between 400 and 740nanometers.Ultraviolet LightThe sunlight that reaches the earth’s surface contains a significant amount of ultraviolet (UV) light, which, because of its shorter wavelength, possesses considerably more en-ergy than visible light. UV light is thought to have been an important source of energy on the primitive earth when life originated. To-day’s atmosphere contains ozone (derived from oxygen gas), which absorbs most of the UV photons in sunlight, but a considerable amount of UV light still manages to pene-trate the atmosphere. This UV light is a po-tent force in disrupting the bonds of DNA, causing mutations that can lead to skin can-cer. As we will describe in a later chapter, loss of atmospheric ozone due to human ac-tivities threatens to cause an enormous jump in the incidence of human skin cancers throughout the world.Absorption Spectra and Pigments How does a molecule “capture” the energy of light? A photon can be envisioned as a very fast-moving packet of energy. When it strikes a molecule, its energy is either lost as heat or absorbed by the electrons of the mol-ecule, boosting those electrons into higher energy levels. Whether or not the photon’s energy is absorbed depends on how much energy it carries (defined by its wavelength) and on the chemical nature of the molecule it hits. As we saw in chapter 2, electrons occupy discrete energy levels in their orbits aroundatomic nuclei. To boost an electron into a different energy level requires just the right amount of energy, just as reach-ing the next rung on a ladder requires you to raise your foot just the right distance. A specific atom can, therefore, absorb only certain photons of light—namely, those that correspond to the atom’s available electron energy levels. As a result, each molecule has a characteristic absorption spectrum,the range and efficiency of photons it is capable of absorbing.Molecules that are good absorbers of light in the visible range are called anisms have evolved a vari-ety of different pigments, but there are only two general types used in green plant photosynthesis: carotenoids and chlorophylls. Chlorophylls absorb photons within narrow energy ranges. Two kinds of chlorophyll in plants, chloro-phylls a and b,preferentially absorb violet-blue and red light (figure 10.5). Neither of these pigments absorbs pho-tons with wavelengths between about 500 and 600 nanometers, and light of these wavelengths is, therefore, reflected by plants. When these photons are subsequently absorbed by the pigment in our eyes, we perceive them as green.Chlorophyll a is the main photosynthetic pigment and is the only pigment that can act directly to convert light en-ergy to chemical energy. However, chlorophyll b,acting as an accessory or secondary light-absorbing pigment, com-plements and adds to the light absorption of chlorophyll a. Chlorophyll b has an absorption spectrum shifted toward the green wavelengths. Therefore, chlorophyll b can absorb photons chlorophyll a cannot. Chlorophyll b therefore greatly increases the proportion of the photons in sunlight that plants can harvest. An important group of accessory pigments, the carotenoids, assist in photosynthesis by cap-turing energy from light of wavelengths that are not effi-ciently absorbed by either chlorophyll.In photosynthesis, photons of light are absorbed bypigments; the wavelength of light absorbed dependsupon the specific pigment.Chapter 10Photosynthesis189FIGURE 10.5The absorption spectrum of chlorophyll.The peaks represent wavelengths of sunlight that the two common forms of photosynthetic pigment, chlorophyll a(solid line) and chlorophyll b(dashed line), strongly absorb. These pigments absorb predominately violet-blue and red light in two narrow bands of the spectrum and reflect the green light in the middle of the spectrum. Carotenoids (not shown here) absorb mostly blue and green light and reflect orange and yellow light.Chlorophylls and CarotenoidsChlorophylls absorb photons by means of an excitation process analogous to the photoelectric effect. These pigments contain a complex ring structure, called a porphyrin ring,with alternating single and double bonds. At the center of the ring is a magnesium atom. Photons absorbed by the pigment molecule excite electrons in the ring, which are then chan-neled away through the alternating carbon-bond system. Sev-eral small side groups attached to the outside of the ring alter the absorption properties of the molecule in different kinds of chlorophyll (figure 10.6). The precise absorption spectrum is also influenced by the local microenvironment created by the association of chlorophyll with specific proteins.Once Ingenhousz demonstrated that only the green parts of plants can “restore” air, researchers suspected chlorophyll was the primary pigment that plants employ to absorb light in photosynthesis. Experiments conducted in the 1800s clearly verified this suspicion. One such experiment, per-formed by T. W. Englemann in 1882 (figure 10.7), serves as a particularly elegant example, simple in design and clear in outcome. Englemann set out to characterize the action spectrum of photosynthesis, that is, the relative effective-ness of different wavelengths of light in promoting photo-synthesis. He carried out the entire experiment utilizing a single slide mounted on a microscope. To obtain different wavelengths of light, he placed a prism under his micro-scope, splitting the light that illuminated the slide into a spectrum of colors. He then arranged a filament of green algal cells across the spectrum, so that different parts of the filament were illuminated with different wavelengths, and allowed the algae to carry out photosynthesis. To assess how fast photosynthesis was proceeding, Englemann chose to monitor the rate of oxygen production. Lacking a mass spectrometer and other modern instruments, he added aerotactic (oxygen-seeking) bacteria to the slide; he knew they would gather along the filament at locations where oxygen was being produced. He found that the bacteria ac-cumulated in areas illuminated by red and violet light, the two colors most strongly absorbed by chlorophyll.All plants, algae, and cyanobacteria use chlorophyll a as their primary pigments. It is reasonable to ask why these photosynthetic organisms do not use a pigment like retinal (the pigment in our eyes), which has a broad absorption spectrum that covers the range of 500 to 600 nanometers.The most likely hypothesis involves photoefficiency.Al-though retinal absorbs a broad range of wavelengths, it does so with relatively low efficiency. Chlorophyll, in con-trast, absorbs in only two narrow bands, but does so with high efficiency. Therefore, plants and most other photo-synthetic organisms achieve far higher overall photon cap-ture rates with chlorophyll than with other pigments.190Part III EnergeticsmembraneThylakoidGranumChlorophyll molecules embedded in a protein complex in the thylakoid FIGURE 10.6Chlorophyll.Chlorophyllmolecules consist of a porphyrin head and ahydrocarbon tail that anchors the pigment molecule to hydrophobic regions of proteins embedded within the membranes of thylakoids. The only difference between the two chlorophyll molecules is the substitution of a —CHO(aldehyde) group in chlorophyll b for a —CH 3(methyl) group in chlorophyll a.。
photosynthesis_chapter_guide-key
Chapter 8: PhotosynthesisSection 8-1 Energy and Life (pages 201-203)Autotrophs and Heterotrophs (page 201)1. Where does the energy of food originally come from?The sun, plants use light energy to make food2. Complete the table describing the types of organisms.Chemical Energy and ATP (page 202)3. What is one of the principal chemical compounds that cells use to store energy?ATP (adenosine triphosphate)4. How is ATP different from ADP?ATP has 3 phosphate groups and ADP has 2 phosphates5. Label each part of the ATP molecule illustrated below.Adenosine Ribose Phosphate groups6. When a cell has energy available, how can it store small amounts of that energy? By adding a phosphate group to ADP, producing ATP7. When is the energy stored in ATP released?By breaking the chemical bond between the second and third phosphates8. For what purpose do the characteristics of ATP make it exceptionally useful to all types of cells?9. What are two ways in which cells use the energy provided by ATP?a.b. Section 8-2 Photosynthesis: An Overview (pages 204-207)Introduction (page 204)12. What occurs in the process of photosynthesis?Investigating Photosynthesis (pages 204-206)13. What did Jan van Helmont conclude from his experiment?The Photosynthesis Equation (page 206)16. W rite the overall equation for photosynthesis using words.As the basic energy source of cellsActive transportProtein synthesisc. Movement/muscle contractionsPlants use sunlight energy to convert H 2O and CO 2 into carbohydratesPlants only produce oxygen when exposed to light Carbon dioxide + water + light sugars (carbohydrates) + oxygen17. Photosynthesis uses the energy of sunlight to convert water and carbon dioxide into oxygen and high-energy Light and Pigments (page 207)18.What does photosynthesis require in addition to water and carbon dioxide?Section 8-3 The Reactions of Photosynthesis (pages 208-214)Inside a Chloroplast (page 208)22. Chloroplasts contain saclike photosynthetic membranes called 23. What is a granum?24. The region outside the thylakoid membranes in the chloroplasts is called the25. What are the two stages of photosynthesis called?a. b. 26. Complete the illustration of the overview of photosynthesis by writing the productsand the reactants of the process, as well as the energy source that excites theelectrons.Chloroplast sugars (carbohydrates).thylakoidsStacks of thylakoids stroma.Light dependent reactionsLight independent reactions (Calvin Cycle)Light H 2OCO 2O 2 Sugars(Carbohydrates)Electron Carriers (page 209)27. When sunlight excites electrons in chlorophyll, how do the electrons change?28.What is a carrier molecule?29.Circle the letter of the carrier molecule involved in photosynthesis.30. How does NADP + become NADPH?b. Photosynthesis begins when pigments in photosystem I absorb light.The Calvin Cycle (pages 212-214)35. What does the Calvin cycle use to produce high-energy sugars?36. Why are the reactions of the Calvin cycle also called the light-independent reactions? When sunlight excites electrons they gain a great deal of energy.A carrier molecule is a compound that can accept a pair of high energy electrons and transfer them, along with most of their energy, to another molecule. NADP + is converted to NADPH by accepting and holding two high energy electrons (e -) and one hydrogen ion (H +).ATP synthase allows H + to pass through the protein, causing the protein to rotate. As it rotates, it pulls in ADP and binds it to a phosphate group, producing ATP. The Calvin Cycle uses ATP and NADPH to produce high energy sugars.The Calvin Cycle is called a light-independent reaction because it does not require light to work.Factors Affecting Photosynthesis (page 214)38. What are three factors that affect the rate at which photosynthesis occurs?a. b. c. 39. Is the following sentence true or false? Increasing the intensity of light decreases therate of photosynthesis. The availability of waterTemperatureLight intensityFalse。
全球碳循环_Photosynthesis and Respiration_lecture3(英文)
Where: R0 is the basal respiration rate at T= 0ºC (or ref. T) Q10 represents the change in the rate of respiration for 10ºC change in T (about 2.0-2.3)
4. Alternative Photosynthetic Pathways
(1) C4 Photosynthesis
Some plants (e.g., corn,sugarcane, and many tropical grass) begin the photosynthetic process by producing a four-carbon compounds. Plants of this type are called C4 plants
3. How Photosynthesis works? – key processes
Photosynthetic Overview
A. There are three basic steps in photosynthesis:
(1) Light Reactions - energy capture
(2) Growth Respiration (Construction respiration)
(a) Rg includes the carbon cost of synthesizing new tissue from glucose and minerals.
(b) Rg for various tissues differ, depending on the biochemical pathways involved.
现代生物学导论
各种环境因子对植物生长发育的影响
植物激素与生长发育
细胞信号传导介导的植物对外界刺激的响应
15 物的结构、功能和发育
15.1 动物体的结构对功能的适应性
结构适应于功能是动物中的普遍现象
动物的组织
器官与系统
结构与功能的统一构成了与环境相适应的动物个体
15.2 营养、呼吸、循环与排泄系统
Mugurran A. E., Ecological diversity and its measurement. Princeton University Press, 1988
Kormondy E. J., Concept of Ecology, 4th ed. Prentice Hall, Inc. 1996
参考文献:
第一章
陈阅增主编，普通生物学。高等教育出版社，1997
张惟杰主编，生命科学导论。高等教育出版社，1999
北京大学生命科学学院编写组，生命科学导论。高等教育出版社，2000
黄诗笺主编，现代生命科学概论。高等教育出版社/施普林格出版社，2001
生命科学与生物，中国科协第三届青年学术年会论文集，中国科学技术出版社，1998
陶慰孙等，蛋白质分子基础。高等教育出版社，1995
郭静成，基础生物化学题解。科学出版社，2001
Lubert Stryer, Biochemistry. 4th Edi. W. H. Freeman and Company, 1995
Leninger L et al. Part I and Part II, Principles of Biochemistry. 2nd Edi. Worth Publishers.Inc.,1993
海洋生态学优秀课件
三、海洋初级生产力旳测定措施
（一）测氧法
（二）14C示踪法
丹麦科学家Steemann-Nielsen在20世纪50年代首先应用于海洋 方面旳研究
*CO2 ＋ H 2O
光能 叶绿素
（*CH2O）＋O2
优点：精确性高，所得成果接近于净产量旳数值 缺陷：技术性强（吸附、污染）、危险
• 群落净生产力 ＝ 净初级生产力 － 异养呼吸消耗 •从群落整体考虑有无生物量旳积累 •与群落旳发展与成熟度有关
4．现存量、周转率、周转时间 • 生产力 = 现存量×周转率
生产量
生产量
现存量
现存量
A
降低许
B
降低许
图7-1 两个平衡旳群落（输入 ＝ 输出）旳模式（A．输入和输出都较低、周 转慢；B．输入和输出都较高、周转快。）（引自 Krebs 1978 ）
三、近岸水域旳初级生产力
受陆地旳影响 1、磷酸盐和硝酸盐往往不是初级生产力旳限制因子 2、水较浅，不出现浮游植物“被带到临界深度下方” 旳情况 3、极少出现持久性旳温跃层 4、大量旳陆源碎屑，浑浊，限制产量进一步提升
温带近岸海区不出现明显旳双周期生产模式，整个夏 季都可能有较高旳产量
四、全世界海洋初级生产力旳估计
b 0 5 10 15 20
浓度 S/(µmol/L)
25
c
20
15
10
5
0
1.0
2.0
-5
S/V
-9.3
图 7-4 浮游植物对营养盐旳吸收动力学（ a）和 Ks 值（b、c）
2、最大吸收速率（Vm）： ①反应细胞营养水平和环境限制程度旳指标 ②可变
生态学专业英语2
1. Ecological role of solar radiation1.1 Photosynthesis: Photosynthesis is a light-dependent process in which the rate of photosynthetic fixation of both CO2 and solar energy is largely dependent upon light intensity.CP: compensation SP: saturation pointPhotosynthesis increases rapidly , but initially there is no net CO2fixation because the rate of CO2 loss in respiration is greater than the rate of CO2 fixation . As light intensity continues to increase, a point is reached at which respiratory losses are exactly balance by photosynthetic gains. This light intensity is called the CP. Above the CP. The rate of photosynthesis continues to increase rapidly with increasing light intensity, but this relationship is not sustained. With continued increases in light, the rate of increase in photosynthesis diminishes until the saturation point is reached, beyond which further increases in light intensity result in little or no further increases in net CO2 fixation. At very high light intensities, net fixation may drop because of damage to the photosynthetic apparatus or for other reasons. When expressed graphically, this relationship is called the photosynthetic light saturation curve.Plants with a high ratio of photosynthetic biomass to living supporting bio mass will have lower CPs than plants with a low ratio because they have less respiratiory loss of CO2 for which to compensate. Plants with low CPs often have lower SPs than plants with high CPs. It takes less light to provide all the solar energy that the photochemical system can use in an algal cell than in a tree leaf. Within a tree crown , leaves that grow in full sunlight have higher CPs and SPs than do leaves that grow in deep shade because of differences in leaf morphology.1.2 The relationship between light intensity and net photosynthesis is complex and under the control of many factors, it is no surprising, therefore, that net photosynthesis in natural stands of plants does not always follow the daily variation in light intensity. In clear weather, there may be a morning peak in net photosynthesis followed by a midday dip and a second peak in the afternoon, it has been suggested that this midday dip may result from one or more of the following factors: overheating of leaves; excessive respiration; water deficits; accumulation of products of photosynthesis in the leaves; photooxidation of enzymes and pigments; closure of stomata; depletion of CO2 in the air surrounding the crown that accompanies highintensities of solar radiation in the middle of the day.Photoperiodism in plants plays a major role in the control of the cessation of growth and the onset of dormancy in the late summer or fall, and in many plants, it regulates flowering and fruiting in the spring and summer. It also plays a role in the breaking of dormancy and resumption of growth in the spring in some perennial plants.2. temperature as an ecological factorTemperature exhibits a number of well-defined cycles of variation that are directly attributable to the rotation of the earth around its axis and around the sun. these rotations lead to a daily and seasonal variation in the amount of radiant energy that reaches a particular part of the earth and consequently in its temperature. In the tropics , the diurnal variation in temperature may be only a few degrees, whereas in continental regions , it can be as much as 50℃ in either winter or summer .2.1Role of topographyHigh-elevation areas have lower average temperatures than do low-elevation areas, because air temperatures normally decrease at a rate of approximately 0.4℃per 100m of elevation as one proceeds up a mountain.Temperature inversion:inversions can also occur as the result of topography. Radiant cooling of high ground flanking a valley gives rise to a layer of cold, dense air in contact with the surface. This air flows slowly down the valley slopes, displacing warmer air in the lower part of the valley and creating an inversion. When the cold air that drains into the valley is below 0 , frost occurs on the valley floor, whereas much warmer temperatures will be experienced in the “thermal belt” higher up the slopes. This is of great importance to fruit growers, and orchards are often located in the thermal belt.2.2 There is a great temptation to describe climates as severe, extreme, favorable, or unfavorable. Other adjectives that are commonly used to describe temperature as optimum, maximum, minimum.2.3 All plants experience variations in temperature associated with diurnal variations in the net radiation budget. Plants that live away from the equator also experience seasonal temperature variations. Plants are generally sensitive to these variations and will grow normally only when exposed to the particular diurnal and seasonal temperature changes to which they are adapted, a phenomenon called thermoperiodism.2.4 Temperature-related injuriesLow-temperature injury:frost cracks: efficient emission of radiation and low conductivity lead to rapid surface cooling of woody stems on clear nights with low air temperatures. The outer layers of the stem contract more rapidly than inner layers, which creates tensions that can cause the stem to crack. These frost cracks are particularly common in regions subject to sudden drops in air temperature.Ice crystals (needle ice): rapid radiation cooling results in the freezing of soils from the surface downward. Water is drawn up to the frozen layer, where it freezes and forms a gradually thickening layer of vertically oriented ice crystals.Frost-heaved:the frozen surface soil together with small plants can be lifted as much as a decimeter by this needle ice and then lowered again as the ice melts. Roots that are pulled up from lower unfrozen soil layers cannot return to their original position, and over several freeze-thaw cycles, small plants such as tree seedlings may be lifted right out of the soil.Physiological drought:warm air temperatures in winter or an early , warm spring in areas where the soil is still frozen can remove water from plants at a time when it cannot be replaced. Even if the water is not frozen, winter water stress can occur because of the doubling of the viscosity of water between 25 and 0 , which makes water uptake more difficult at temperatures approaching freezing. Plants that grow on soils that are cold or frozen in winter often exhibit the same morphological adaptations as plants that grow on summer-dry sites. The water imbalance caused by high air temperatures and low soil temperatures is referred to as physiological drought. When severe, it can cause browning of the foliage and even the death of theentire plant.High-tmeperature injuryStem girdle:because of the low albedo and low conductivity of many soils, surface temperatures frequently become very high, and young plant stems that are not yet protected by thick layers of bark may be damaged where they contact the soil surface. A band of cambium a few millimeters wide is killed around the stem, and this results in the death of the plant either because of the interruption of internal translocation or because of the entry of pathogens.3. WaterLike nutrient cycles in general, the water cycle is driven by inputs of solar energy. V ast quantities of radiant energy are absorbed in the process of evaporating water from the warm areas of the world’s oceans. The energy is transferred to the atmosphere as the water vapor condenses, thereby driving our climate and creating our weather. The warm, moist air creates clouds as it rises, and the winds formed by the resulting processes of atmospheric stirring move the clouds over the land, where some of the moisture falls as precipitation. Some of this is re-evaporated directly back to the atmosphere, and some is subsequently transpired by plants. The rest enters water courses and returns to lakes and eventually to oceans, from which it is once again evaporated.3.1Forests influence water cyclesInterception of precipitation by vegetation: the loss back to the atmosphere of precipitation that has been intercepted by vegetation is called interception loss. The magnitude of interception loss depends on the interception storage capacity of the vegetation. Interception storage for tree and shrub cover has been reported to ranger between 0.25 and 7.6mm of rain and up to 2.5cm (water equivalent) of snow. Table 1 presents some figures for interception loss in various forest types in the United States.Redistribution of water by vegetation :water that is intercepted by tree crowns isredistributed into two major subtypes and reaches the floor very nonuniformly: (1) throughfall—the portion of the incident precipitation that drips from or falls through the vegetation canopy; (2) stemflow—the portion that reaches the soil by flowing down the stem. Stemflow is also affected by bark roughness. Smooth-bark species have little stem water storage capacity, and stemflow will commence on smooth-barked species such as beech after only a little more than 1mm of rain has fallen, but rough-barked species have a large stem storage capacity, and appreciable stemflow may not reach the ground until more than 2cm of rain has fallen.Infiltration into the soil:Water that reaches the ground can either flow laterally over the surface or penetrate the soil in a process called infiltration. Once within the soil, the movement of water is known as percolation. The term infiltration can apply either to the organic forest floor or to the underlying mineral soil, but because the rate of water movement into the forest floor almost always exceeds rates of precipitation and because the condition of the forest floor is subject to modification and is therefore less permanent than the mineral soil as a site feature, the term is applied most frequently to the mineral soil.Entry of water into the forest floor is normally rapid because of the many large pores and the organic nature of the forest floor, which gives it a high moisture-holding capacity. However, forest floor that have become very hot and dry during the summer may exhibit hydrophobicity, which makes them very difficult to wet.Once wet, forest floor can hold between one and five times their own weight of water, the more decomposed the organic matter and the more rotting wood in the forest floor, the more water it can hold. Only the water in excess of the field capacity of the forest floor will infiltration into the mineral soil.Water in the soil is classified as gravitational, available and unavailable. The relative proportions of these three types of water vary according to the relative abundance of different pore sizes, which in turn depends on soil structure and texture.Loss of water to evaporation and transpiration:Water is lost from soil by three major pathways: drainage to groundwater, evaporation back to the atmosphere, and uptake by plants. The equivalent of 760mm of precipitation is delivered to the 48coteminous U.S. states each year, and of this, approximately 370mm is lost back to the atmosphere by evaporation from forests and wildlands.Evaporation from the soil surface requires two preconditions: energy in the form of solar radiation (2.24 MJ are required to evaporate 1kg of water) and an upward flow of water from lower in the soil to maintain water in the surface layer, where the energy is available for evaporation.Transpiration: loss of water from which the living cells of plant tissues to the atmosphere by vaporization is called transpiration. Water that is absorbed by roots from soil is translocated upward to the foliage in the xylem of the roots and stem. This uptake and translocation is driven by solar energy falling on the leaves and stems, which causes water to evaporate from the moist outside surfaces of mesophyll cells into air spaces within the leaf. The water vapor either diffuses out to the atmosphere through stomata or evaporates directly through the cuticle of leaves.。
学位英语3a试题及答案
学位英语3a试题及答案一、听力理解（共20分）1. A) What is the woman going to do?A. Go to the library.B. Go to the bookstore.C. Go to the cinema.D. Stay at home.B) What does the man suggest?A. Visiting the museum.B. Watching a movie.C. Having a picnic.D. Going to the beach.答案：1. A 2. D2. A) What is the relationship between the two speakers?A. Teacher and student.B. Doctor and patient.C. Boss and employee.D. Friends.B) What is the man's problem?A. He has a cold.B. He has a toothache.C. He has a headache.D. He has a stomachache.答案：2. B 3. C二、阅读理解（共30分）A)The article discusses the importance of a balanced diet for maintaining good health. It emphasizes the need for consuming a variety of foods, including fruits, vegetables, whole grains, lean proteins, and healthy fats.36. What is the main idea of the article?A. The benefits of a balanced diet.B. The types of foods to avoid.C. How to prepare healthy meals.D. The consequences of an unhealthy diet.答案：36. A37. According to the article, which of the following is NOT a reason to have a balanced diet?A. To prevent chronic diseases.B. To maintain a healthy weight.C. To increase the risk of illness.D. To provide essential nutrients.答案：37. CB)The passage describes the process of photosynthesis, which is how plants convert sunlight, carbon dioxide, and water into glucose and oxygen. It explains the role of chlorophyll in this process.38. What is photosynthesis?A. A process that produces oxygen.B. A process that plants use to grow.C. A process that requires sunlight and water.D. All of the above.答案：38. D39. What role does chlorophyll play in photosynthesis?A. It provides energy for the plant.B. It absorbs sunlight for the process.C. It releases carbon dioxide.D. It produces glucose.答案：39. B三、词汇与语法（共20分）40. The teacher asked the students to ________ the new words they didn't understand in the dictionary.A. look upB. look forC. look throughD. look after答案：40. A41. Despite the heavy rain, the children ________ playing outside.A. continuedB. stoppedC. startedD. forgot答案：41. A四、完形填空（共15分）The story is about a young boy who helps an old man find his lost dog. The boy's kindness and patience are praised by the old man.42. The old man was ________ when he lost his dog.A. worriedB. excitedC. happyD. angry答案：42. A43. The boy spent ________ time searching for the dog.A. a lot ofB. a littleC. someD. few答案：43. A五、翻译（共15分）44. 这个项目的成功在很大程度上取决于团队成员之间的有效沟通。
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oxaloacetate
citrate
Stage 3: Oxidative phosphorylation
During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis. The electron transport chain is in the cristae of the mitochondrion. NADH and FADH2 donate electrons to the electron transport chain. Electrons drop in free energy as they go down the chain and are finally passed to O2, forming H2O.
Cellular Respiration
Cytoplasm
2 NADH / 2 FADH2 8 NADH & 2 FADH2
ATP yield per molecule of glucose
Cellular Respiration
Most cellular respiration requires O2 to produce ATP Glycolysis can produce ATP with or without O2 (in aerobic or anaerobic conditions) In the absence of O2, glycolysis couples with fermentation or anaerobic respiration to produce ATP. Fermentation consists of glycolysis plus reactions that regenerate NAD+, which can be reused by glycolysis - alcohol fermentation & lactic acid fermentation - Fermentation uses phosphorylation instead of an electron transport chain to generate ATP Anaerobic respiration uses an electron transport chain with an electron acceptor other than O2, for example sulfate
Electron transport chain
The coupling of the movement of H+ ions to ATP production is called chemiosmosis(化学渗透)
Ion pump
Proton pump
1 NADH transport H+
Section9.3 Cellular Respiration
cellular respiration 细胞呼吸作用 aerobic需氧的（require oxygen） anaerobic 厌氧的 an- : “without” glycolysis 糖酵解 oxidation 氧化 phosphorylation 磷酸化 pyruvate/pyruvic acid 丙酮酸 citric acid cyc/citric acid 柠檬酸 lactic acid/lactate fermentation 乳酸发酵 alcoholic fermentation 酒精发酵 NAD++2e- +H+ NADH NAD+ ：energized electrons carrier
Alcohol fermentation
Lactic acid fermentation
Fermentation Vs. Cellular Respiration
Stage 2: The citric acid cycle/ Krebs cycle
takes place within the mitochondrial matrix - generate 1 ATP, 3 NADH, and 1 FADH2 per turn - The acetyl group of acetyl-CoA combine with oxaloacetate (草酰乙酸), forming citrate. - The citrate was decomposed back to oxaloacetate, making the process a cycle. - The NADH and FADH2 relay their energized electrons to the electron transport chain.
Stage 1 : Glycolysis
Glycolysis (“splitting of sugar”)
- glucose
2 pyruvate - occurs in the cytoplasm - anaerobic (no oxygen is required)
- energy investment & payoff phase
• In the presence of O2, pyruvate enters the mitochondrion through active transport. • Before the citric acid cycle can begin, pyruvate must be converted to acetyl CoA, which links the cycle to glycolysis
Chapter 9 Energy in a Cell
Section 9.1 The Need for Energy Section 9.2 Photosynthesis: Trapping the Sun’s Energy
Section9.3 Cellular Respiration: Getting Energy to Make ATP
3~4 H+ generate 1 ATP 1NADH generate 2.5~3.3 ATP 1 NADH 1 FADH2 3ATP 2ATP
Establishing the H+ gradient is a major function of the electron transport chain
Comparing Photosynthesis & Cellular Respiration
That’s all
Cellular Respiration
Cellular respiration includes both aerobic and anaerobic respiration but is often used to refer to aerobic respiration. Aerobic respiration consumes organic molecules and O2 and yields ATP Fermentation is a partial degradation of sugars that occurs without O2 Anaerobic respiration is similar to aerobic respiration but consumes compounds other than O2 Fermentation & anaerobic respiration enable cells to produce ATP without the use of oxygen.
C6H12O6 + 6O2
= 6CO2 + 6H2O + ATP + heat
The Stages of Cellular Respiration:
Cellular respiration has three stages: - Glycolysis (glucose 2 pyruvate) - The citric acid cycle (completes the breakdown of glucose) - Oxidative phosphorylation (accounts for most of the ATP synthesis)