中国农大考博试题

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中国农业大学生物化学试题(博士)

中国农业大学生物化学试题(博士)中国农业科学院和中国农业大学2021年动物遗传育种与繁殖专业的博士入学试题（回忆版），上半部分是动物分子生物学，下半部分是家畜遗传育种。

中国农业大学生物学院的一些专业也参加了动物分子生物学的学习。

一、条款：rq―pcr微卫星dnasnpsars转换同源重组可变剪切基因簇端粒酶无义突变2。

简短回答1.真核生物rna聚合酶启动子的特点2.转座子的作用机理及遗传效应3.核糖核酸中戊糖2’―oh的作用4.z―dna的结构和生物学作用5.终止子和终止密码的区别6.说明免疫球蛋白基因重排的过程。

《动物遗传学》一、名词：育种目标REML连锁不平衡，小效应多基因和主效应基因的家族选择÷II。

简要回答：1.mas的原理、方法及应用？2.哈代-温伯格原理的基本内容3.什么是个体育种值？blup相对于常规选择的优点？4.近交增量为0.05，计算15代的近交系数5.杂交繁育体系的结构及其应用6.生产性能测定的几种方法及应用7.后代测定将延长世代间隔，但为什么它仍用于奶牛育种？8.（不记得了）三、计算（记不起没有原始数据）1.关于遗传进展和辅助选择的计算2.通过母系回归和半同胞相关估计遗传力。

四、问答1.家畜遗传多样性保护的意义，存在的问题及对策2.阐述了分子数量遗传学的主要研究内容、方法、进展和观点。

（以上信息仅基于记忆。

如有任何差异，请原谅我）中国农大2021分子遗传学博士研究生入学考试试题一、请说出10位对分子遗传学发展做出贡献的诺贝尔奖得主。

他们的重要成就是什么？30 '2. 什么是RNA编辑？它是如何编辑的？15'三、举出2-3种基因组测序或功能基因组研究的策略，并加以说明。

20'四、发起人的作用是什么？原核启动子的结构特征是什么？10 '5. 在大肠杆菌和真核生物中启动蛋白质合成有什么区别？10'六.真核转录因子的三个DNA结构域的简要描述10'96年饲料学1.猪和反刍动物在消化和代谢方面CHO的异同2 EFA的定义和营养功能3 EAA有什么4.反刍动物如何利用npn5.ndf、adf表示什么意义6.bv7.饲料中的抗营养素8 hi9.尼克酸营养功能10.cu的功能11.胰液所含e有那些12.理想蛋白97饲料学1.尝试描述单胃动物和反刍动物之间碳水化合物代谢的差异2.如何评估单胃动物饲料3 ndf、adf的净能量值4.说明其营养功能：zn\\cu\\mn\\se\\co5.维生素的功能：核黄素、烟酸、泛酸、叶酸和维生素K北师大98术语解释（2/22）1构象2肽平面3半保留拷贝4核酸杂交5转肽6米氏常数7过渡态8.空体积9.共价修饰调节10.盐析作用11.转录增强子二.填空(1/25)1.蛋白质元素的组成以____的平均含量为特征，数量为_%2。

(完整word)中国农业大学土壤学考博真题答案要点

一、名词解释1. aerosolic dust(烟尘）：是燃煤和工业生产过程中排放出来的固体颗粒物.它的主要成份是二氧化硅﹑氧化铝﹑氧化铁﹑氧化钙和未经燃烧的炭微粒等.(04)2. base saturation percentage（盐基饱和度）：土壤吸附的交换性盐基离子占交换性阳离子总量的百分数。

3。

hydraulic conductivity（导水率):单位时间通过单位面积的水量。

（04）4. desalization（去盐化）：土壤中可溶性盐通过降水、灌溉洗盐、开沟排水，降低地下水位等措施,迁移到下层或排出土体的过程，称为脱盐作用（去盐化）。

5。

hysteresis（滞后作用）：土壤吸湿（水）过程中，水吸力随含水量增加而降低的速度较快。

土壤脱湿（水）过程中，水吸力随含水量减少而增大的速度较慢.同一土壤的两种水分特征曲线不重合。

砂质土的滞后现象比粘质土更明显.6. solum（风化层）:地壳表层的岩石经风化作用，形成的疏松的堆积物。

7。

soil productivity(土地生产力）：土壤肥力因素的各种性质，土壤的自然认为条件构成了土壤生产力。

(04)8. precision agriculture(精准农业）：是利用全球定位系统（GPS）、地理信息系统(GIS）、连续数据采集传感器（CDS）、遥感（RS）、变率处理设备(VRT）和决策支持系统(DSS）等现代高新技术，获取农田小区作物产量和影响作物生长的环境因素(如土壤结构、地形、植物营养、含水量、病虫草害等）实际存在的空间及时间差异性信息,分析影响小区产量差异的原因，并采取技术上可行、经济上有效的调控措施,区域对待，按需实施定位调控的“处方农业"。

即利用卫星、遥感、计算机和自动控制等高新技术于农业生产，以提高产量，降低能耗.（02、04、07）9. pedology（发生土壤学):19世纪末，俄罗斯学者道库恰耶夫提出。

认为土壤是地壳表层岩石、矿物的风化产物，在气候、生物、地形、时间等因素的作用下形成的特殊的自然体。

中国农大食品学院专业考博试题

2004年中国农大食品学院考博专业课的考题：1、什么是食品科学。

它的主要内容是什么？2、食品中的主要营养成分有哪些？它们的主要作用各是什么？3、食品科学在我国小康社会建设中的主要作用。

4、对我国食品安全现状的评价及建议。

5、食品加工过程中存在的安全性问题。

6、叙述果蔬制品加工工艺流程。

7、食品添加剂种类、作用。

现代食品加工技术。

2002年生物化学（食品学院西区）一．名次解释（2分/个）1．中心法则2．半保留复制3．β－氧化4．三羧酸循环5．酶活性中心6．糖异生＃乙酰辅酶A经一系列氧化、脱羧，最终生成CO2和H2O并产生能量的过程称三羧酸循环。

二．填空（共48分）1．真核生物的mRNA的前体称为hnRNA，mRNA 3‘端有_______结构。

2．酮体包括______,_________,__________3．饥饿时主要供能物质是________,糖异生主要原料丙酮酸。

4．遗传密码由5‘向3‘方向阅读，tRNA的反密码与mRNA的碱基互补，核糖体由__________和蛋白质。

5．氨基酸脱氨后生成_______, ________, _________, ________, _____________, _______, __________，主要脱氨方式是__________。

6．AMP和GMP是由IMP合成的。

7．DNA的变性温度用Tm表示，范围是__________。

8．主要的生物氧化链是NADH和________。

9．蛋白质二级结构是________, _________, __________和________。

10．Km值表示____________________________________。

11．甘油先转化成________________进入糖代谢途径，彻底氧化产生______ATP。

12．原核生物中的起始信号是___________，该信号中前段碱基与核糖体中16s rRNA碱基互补，该信号在肽链中代表的氨基酸是______________________。

中国农业大学博士入学考试动物生物化学试题

2007年一．名词解释（15×2’）：核小体α-螺旋chargraff’s规则顺反子糖酵解二．问答题（70’）一共10道题，分值不同1．蛋白质的结构层次分为那些？他们间的关系是什么？2．DNA双螺旋结构的结构特征。

3．说明16C脂肪酸完全氧化的全过程，及能量的耗费和释放。

4．比较体内DNA复制与体外PCR间的异同点。

5．试述你对RNAi的认识。

6．试述谷氨酸在氨基酸的代谢中的作用。

7．叙述甘油经过异生生成糖的过程。

8．机体饥饿状态下体内营养物质代谢的变化。

2003年一、名词解释（12分共6个每题2分）β-氧化氧化磷酸化鸟氨酸循环糖有氧氧化半保留复制核糖体二、填空（共32分1空1分）三、问答题（共56分7道题每题8分）1．苯丙氨酸的代谢途径。

2．三大营养物质的相互转化。

3．机体清除强酸的途径。

4．写出糖代谢为脂肪合成提供的所有原料。

5．试述tRNA的结构特点及其在蛋白质合成中的作用。

6．DNA聚合酶和RNA聚合酶的相同点和不同点。

2002年a)名词解释1．半抗原2．中心法则3．抗原决定族4．脂肪酸氧化b)填空1．氨基酸脱氨产物——、——、——、——、——2．抗体的种类——及进化序列——3．葡萄糖代谢的关键物质——、——、——4．密码子序列从——到——、启始密码子——其代表——5．mRNA前体——6．酮体在——生成，在——利用c)简答题1．在饥饿状态下三大营养物质代谢2．单克隆抗体和多克隆抗的区别多抗和单抗特性比较：1.均一性。

一种单抗中，每个抗体的化学结构和氨基酸顺序都相同，只有一种Ig亚类。

即单抗是一种纯度很高的均一抗体。

而从不同动物，不同时期所得到的多抗，各有不同的化学组成。

多抗是多种种类和亚类Ig的混合物。

2.稳定性。

单抗的稳定较差，对PH变化敏感，对热不稳定，提纯过程中易变性，而多抗的稳定性则较好。

3.特异性。

单抗是单一地针对抗原的某一决定簇，所以用它进行血清学反应时，特异性强，敏感性高，一般不发生交叉反应。

中国农业大学考博生化试题

2002年一、名词解释：（20分）1.同源蛋白质(homologous protein)2. 构型(configuration)3.构象(conformation)4. 钙调蛋白(calmodulin, CAM or CaM)5.逆转座子(retrotransposon)二、以动物细胞或植物细胞为例说明细胞中的膜结构及其功能。

（12分）三、在研究位置基因的功能时往往采用推定的该基因所编码的氨基酸序列与已知功能的蛋白质的氨基酸序列比较来推断，你认为这种比较应采用什么原则？为什么？（12分）四、真核基因在原核细胞中表达的蛋白质常常失去生物活性，为什么？举例说明。

五、简述信号肽的结构特点、功能和从蛋白质产物中切除的机理。

（12分）六、分子筛、离子交换和亲和层析是三种分离、醇化蛋白质的方法，你如何根据所要分离、纯化的蛋白质的性质选择使用。

（12分）七、酶联免疫吸附实验（ELISA）的基本原理是什么？如何用此方法检测样品中的抗原和抗体？（12分）八、某一个蛋白，SDS凝胶电泳表明其分子量位于16900于37100标准带之间，当用巯基乙醇和碘乙酸处理该蛋白后经SDS凝胶电泳分析仍得到一条带，但分子量接近标准带13370处，请推断此蛋白质的结构？为什么第二次用前要加碘乙酸？2003年一、简要解释下列名词（每词5分，共30分）1、寡糖与多糖2、端粒酶3、酮体4、生糖氨基酸与生酮氨基酸5、终止子和终止因子6、分子伴侣（molecular chaperone）二、以下问答题任选7题回答（每题10分，共70分）：1、简述关于生物膜运输的分子机制的几种主要假设以及他们间的相互关系。

2、蛋白质磷酸化和去磷酸化的生物学意义是什么？3、请解释酶促反应的前馈和反馈（feedforward 和feedback）及其意义。

4、什么机制保证了DNA复制的准确性？5、神经和肌肉等细胞活动的直接供能者是ATP。

然而，ATP在细胞中含量很低，在哺乳动物肌肉中仅3 - 8mmol / kg。

中国农大考博试题

中国农大考博试题分子生物学试题 961 什么是原癌基因？（4）它们怎样被反转录病毒激活？（16分）2 什么是tumor supperssor gene？（4分）举例说明它的调控功能。

（16分）3 细胞染色体的异常如何导致癌基因的激活？（20分）4 解释以下名词：(1) gene knock-out (5分)(2) molecular hybridization (5分)(3) restriction fragment length polymorphism (5分)(4) human genome project (5分)5 G蛋白的结构特点信其功能（20分）6 apoptosis的特征与其生理及病理意义（10分）已知它的调控基因有哪些？（10分）以上6题任选5题回答。

一. 名词解释(2/40)1. 间体2. 血影3. 脂质体4. 巴氏小体5. 成熟促进因子(MPF)6. Hela细胞株7. IL-28. 周期蛋白9. 等位排斥 10. G0期细胞 11. 转基因动物12. 同源异形染色体 13. 联会复合体 14. G蛋白 15. 胞质板 16. 信号转换17. 核骨架 18. 多线染色体 19. 染色体组 20. 原癌基因二. 问答题(10/60)1. 简述细胞膜的结构和功能2. 什么是核基质?其结构和功能如何?3. 简述蛋白质月末的信号假说.4. 什么是染色体的袢环模型?5. 什么是单克隆抗体技术?有何应用价值?6. 简述肌醇酯信号通路.2000：1．如何发现或寻找新基因？2．什么是蛋白质组（蛋白质组学）？与基因组差别？主要内容及策略？3． DNA结合蛋白的几种结构花式？modif（画简图）4．真核基因在原核表达的难点及对策？5．基因knock out与knock in：6．差异显示：7．酵母双杂交：8．基因芯片：中国农大2003分子遗传学博士研究生入学考试试题一、请举出对分子遗传学发展做出贡献的诺贝尔奖获得者10名，其重要成就如何？ 30'二、何谓RNA编辑，是如何进行编辑的？15'三、举出2-3种基因组测序或功能基因组研究的策略，并加以说明。

中国农业大学博士入学考试英语试题

Part I Listening Comprehension (30 questions, 20 points)Section A (20 questions, 10 points)Directions: In this part, you will hear short conversations between two people. After each conversation, you will hear a question about the conversation. The conversation and questions will not be repeated. After you hear a question, read the four possible answers in your testbook and choose the best answer. Then, on your answer sheet, find the number of the question and draw a line crossing the letter that corresponds to the letter of the answer you have chosen.Example: You will hear:You will read: A) 2 hoursB) 3 hoursC) 4 hoursD) 5 hours1.A) He will be in the line for a long time.B) He has had experience coming to a line and waiting for a long time.C) He will not line up and wait.D) He doesn’t mind getting up early because lines don’t bother him.2.A) She isn’t knowledgeable about where things are on campus.B) The people outside are very good to ask.C) The man should not ask the registration office.D) The registration is outside of the building.3.A) Do a better job of guessing what she is expecting.B) Go talk to the professor and find out what her expectations are.C) Keep trying to work harder.D) Complain to the dean about professor Merrington’s str ict marking.4.A) He didn’t pay for it as expected.B) He bought a Horizon.C) He paid a lot for it.D) He didn’t pay that much although you might think he had..5.A) Come to the cafeteria early to get a place.B) Start cooking instead of eating out.C) Move out of the campus housing.D) Stop complaining.6.A) She is a great outdoor type.B) It is unusual for her to go mountain climbing.C) Shania prefers mountain climbing.D) Shania doesn’t really like the outdoor.7.A) Go in a couple of weeks later.B) Come as soon as he finished his case.C) Not go and work on his assignment.D) Come as soon as he is not so far behind.8.A) Who is begging the professor for money.B) What is bothering the professor.C) Why the professor is so upset.D) Who is giving the professor trouble.9.A) She doesn’t want to play here.B) He should decide where to play.C) He should call someone else.D) She would have to be there to decide.10.A) She is late for something.B) She was bored.C) She thinks they shouldn’t wa it.D) She thinks more should be achieved.11.A) He is too busy to go.B) He is late for her assignment.C) He would like to go but is afraid she cannot play well.D) He will go as soon as the assignment is finished.12.A) She thinks there is no chance of it happening.B) She thinks it’s quite possible under the circumstancesC) She is ambivalent.D) She would rather just help nurses.13.A) The man’s hand will get cold.B) The man needs to wear gloves.C) The man should hold the skis himself.D) The man should wear thinner gloves.14.A) Marge’s proofreading costs a lot.B) It will take one day for Marge to get back.C) Marge could do it but it will mean more delay.D) Marge may or may not do it.15.A) He thinks the woman should practice more.B) He think s she hasn’t practiced enough.C) He thinks the woman is now perfect at the new program.D) He thinks she practiced a lot so it’s now paying off.16.A) Look after if she is paid.B) Call Maggie to look after the dog.C) Not look after the dog.D) Look after the dog.17.A) The location of the computer.B) The new schedule.C) How to find a new home.D) The address of the website.18.A) She can go any day, but Friday is the best time.B) She can’t go any day.C) She can only go on Friday.D) She can go any day except Friday.19.A) Go to the Reeds Hotel pool.B) Arrange for a party at Reeds Hotel.C) Remind her to get things ready quickly.D) Confirm bookings at Reeds Hotel.20.A) Bill’s email is on the internet.B) Bill’s number is listed on the internet.C) Bill’s number might be on the listing on the internet.D) Bill may have moved.Section B (10 questions, 10 points)Directions: In this section, you will hear 3 short passages. At the end of each passage, you will hear some questions. Both the passage and the question will be spoken only once. After you hear a question, you must choose the best answer from the four choices marked A, B, C, and D, and decide which is the best answer. Then mark the corresponding letter on the Answer Sheet with a single line through the center.Passage 1Questions 21 to 23 are based on the passage you’ve just heard.21. A) In ancient China.B) In ancient Egypt.C) In ancient Greece.D) In ancient Rome.22. A) In ancient Egypt only members of the royal family were allowed to useumbrellas.B) By the late 16th century the English people began to use umbrellas.C) The umbrella changed much in style in the 18th century.D) The umbrella was initially used as a sunshade.23. A) When and how the umbrella was invented.B) The making of the umbrella.C) The history of the use of the umbrella.D) The different uses of the umbrella.Passage 2Questions 24 to 27 are based on the passage you’ve just heard.24. A) Both the players and the spectators are protected.B) The players have to catch beetles in their cars.C) The ball is extremely big.D) The players have to catch the ball while driving.25. A) Dangerous.B) Exciting but dangerous.C) Protective.D) Popular.26. A) He thinks the game will be as popular as football.B) He thinks the game will be more popular than football.C) He doesn’t think the game will be more popular than football.D) He doesn’t think the game will be popular at all.27. A) Americans are only interested in new things.B) The game is popular both in America and Europe.C) Football is no longer very popular in America.D) The game can be dangerous for both the players and the spectators.Passage 3Questions 28 to 30 are based on t he passage you’ve just heard.28. A) Scientists and comets.B) The origin of comets.C) Place of comets in the solar system.D) Man’s study of comets.29. A) In 1760 B.C.B) In 1770 B.C.C) In 1780B.C.D) In 1750 B.C.30. A) The wor d ‘comet’ comes form Greek.B) People used to think that comets brought bad news as well as good news.C) Edward Halley died in 1758.D) Halley’s Comet will reappear in 2062.Part II. Vocabulary (25 questions, 25 points)Section ADirections: There 15 incomplete sentences in this section. For each sentence there are four choices marked A, B,C and D. Choose the one that best completes the sentence. Then mark the corresponding letter in theAnswer Sheet with a single line through the center.31. The first thing to do in seeking a position is to determine exactly what you want to do, not ______ a vagueobjective but with a definite goal.A) in any term B) in terms of C) in high terms D) in set terms32. Energy shortage, soaring inflation, rampant unemployment and threat of war have made adults Americansnervous, and that sense of pervasive worry has been ______ the nations’ youth.A)went on to D) keep up with C) passed on to D) hold on to33. The idea of trying to cheat the income tax authorities ______ his principles, he had a strong sense of civicresponsibility.A)went against B) fought against C) leaned against D) over against34. If anyone can think of a better course of action, I ______ suggestions.A) would like to B) am delighted to C) am in open D) am open to35. With technological developments, some labor-intensive industries have ______ high-tech industries.A) given up B) stepped aside C) stood along D) yielded to36. You are looking bit ______ this morning; you must have had too much alcohol last night.A)blank B) fragile C) blue D) dizzy37. As she is ______ to eggs, she cannot eat one without breaking into a rash.A) partial B) accustomed C) allergic D) relevant38. She still looks weak though her fever ______ after she took some medicine.A) educed B) caught C) got off D) came down39. Relations between the two countries began to ______ in 1965.A) deteriorate B) cease C) accelerate D) stimulate40. Economic activity has been organized on the ______ of cheap and abundant oil from the beginning of the 20thcentury until early the 21st century.A)gist B) notion C) rationale D) premise41. Owing to a/an ______ lack of lower-income housing, the municipal government is embarrassed by theimpressing housing issue.A)acute B) stressful C) demanding D) urgent42. The idea that machines could be made to fly seemed ______ two hundred years ago.A) original B) eccentric C) terrific D) splendid43. The policy ______ it necessary for the town’s safety to arrest mo st speeders.A) narrated B) elaborated C) deemed D) commended44. If you do something on _____, you do it because you suddenly want to, although you haven’t planned to.A)impulse B) pulse C) impromptu D) imminence45. If ______ numbers provide any pro of, America’s universities and colleges are the envy of the world, for theUnited States’ 3,500 institutions were flooded with 407,530 students from 193 different countries last year.A)definite B) strong C) fundamental D) sheerSection BDirections: Choose the one word or phrase that best keeps the meaning of the sentence if it is substituted for the underlined word or phrase.46. Shortage of land and funding are blamed for the city’s inadequate green space.A) complained about B) are liable for C) accused of D) are damned as47. The hostess didn’t know what to do, as she hadn’t got enough food to go round so many people.A)give service to B) cater for C) be enough for D) sate oneself with48. The government stressed that high production rate should not be achieved at the expense of work quality.A)at any expense B) at the cost of C) at any cost D) to the extension of49. The idea that we cannot leave everything to free market forces seems to gain groundA)be acknowledged B) be accepted C) stand still D) get the ground of50. It is reported that the country’s national debt amounts in aggregate to four thousand million dollars.A)as a whole B) on the whole C) total to D) sum up51. At its last meeting, the Council endorsed changes intended to modernize the building.A)modified B) approved C) signed D) donated52. The United States committed a breach of international practice.A) violation B) concession C) offence D) compromise53. From the start, the plan was doomed to failure, so all his effort was in vain.A) expected B) supposed C) condemned D) promised54. In feudal society where there existed a rigid hierarchy of power, the poor had no chance of advancementexcept that they could pass many different levels of examinations.A) criteria B) layer C) degree D) rank55. You shouldn’t have criticized her so harshly. You have hurt her ego.A) self esteem B) self image C) image D) esteem.Part III. Reading Comprehension (20 questions, 40 points)Directions: Read the following passages and answer the multiple-choice questions after each passage.Passage 1Too Many Science Ph. D.’s?Something is wrong when a lot of young scientists, after achieving Ph.D.'s. are feeling like losers.Its a given that the job market for science positions in academe is bleak. A doctorate is supposed to be a ticket to a dream job, but many Ph.D.'s aren't even landing their third or fourth choices.But with reliable statistics hard to come by, the scientific community is at odds over whether it is producing too many Ph.D.'s. Some scientists believe that doctoral programs should be practicing "birth control," cutting back the number of graduate students they admit. Most., however, say the answer lies in changing doctoral education which they say has been too focused on producing university scientists."It's really destructive to the profession to have the sense that Ph.D.'s aren't valued," says Ronald Breslow, a chemist at Columbia University and president of the American Chemical Society.Young scientists in the post-Cold War era are facing two major difficulties: many have had to work in postdoctoral or temporary research positions for four years orlonger, because they can't find jobs. Others, like Kathryn S. Jones, have found jobs but can't find financing for their research. Ms. Jones, a retrovirologist, got a non-tenure-track position as a research assistant professor at the University of Maryland at Baltimore, but is about to lose the job because she hasn't landed a major grant."I have a Ph.D.," says Ms. Jones, who earned it at the Albert Einstein College of'' Medicine, "I've given my data at international meetings. But because of the small percentage of success in this field, I walk around feeling like a failure."By the end of this month, the start-up money that Ms. Jones received three years ago, when she was hired by the university and the Veterans Administration medical Center on the campus, will be gone. She can keep her laboratory and her titles for up to a year, and could be back in business if she g ets a grant. But she’s not hopeful. In fact, she’s thinking about getting certified to teach high-school biology. “I have to wonder if I want to be the last rat leaving a sinking ship,” she says.A report published last spring, called “Reshaping the Graduate Education of Scientists and Engineers,” has sparked a national debate about doctoral education. Written by scholars and policy makers, it was sponsored by the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine.According to the report, the proportion of science and engineering Ph.D.'s employed by academe fell to 43 per cent in 1991. the most recent year for which statistics were available, from 5 I per cent in 1977. The 1993 unemployment rate was only 2 per cent for recent Ph.D. recipients and 1.6 per cent for all scientists and engineers, it said. Those figures seem low, but they include Ph.D.'s in temporary or post-doctoral positions."There is an oversupply of recent graduates for research positions in academic laboratories and federal and industrial labs," says Phillip A. Griffiths, director of the Institute for Advanced Study in Princeton, N.J., and chairman of the panel that wrote the report. "Beyond that, it becomes quite a bit more murky. There certainly is an oversupply of unmet expectations."Since the job market varies by field, the report said it would be unwise to set across-the-board limits on graduate enrollment. Instead, it suggested broadening Ph.D. programs for students who aren't planning standard academic careers.Scientific societies provide a more up-to-date picture of the job-market, and it is grim. In December, the Joint Policy Board for Mathematics announced an unemployment rate of 14.7 per cent for the 1,226 Ph.D.'s awarded in the field in 1994——1995——the highest rate ever reported. An additional 4.2 percent of the Ph.D.'s were in part-time jobs, and of those employed in academe, 61 per cent were not in positions eligible for tenure.Anne C. Petersen, deputy director of the National Science Foundation, acknowledges that the N.S.F. was late in recognizing the job-market woes. “The anxiety some young people have is really obvious,” she says.Foundation officials are uncertain what exactly is happening, she says, because of gaps in the data collected on Ph.D's. But the N.S.F. is committed to improving its data collection, so that better information on where Ph.D.send up is available. In the next few years, she says, the foundation will also direct money to new models of doctoral education, other than the standard one presuming that a Ph.D. will become a professor."The Ph.D. should be construed in our society more like the law degree," she says. "A lot of people go to law school with no plans to practice law."But Mark S Wrighton, president of Washington University in St. Louis and a noted chemist, believes that the Ph.D. experience should continue to be "research-intensive." He says more federal money should be put directly into the hands of graduate students, allowing them to work on their own research ideas ——and to make themselves more remarkable —and less given to the research projects of professors who hire graduate students as research assistants.56. After achieving Ph.D's, a lot of young scientists are feeling like losers, because _______.A) they have no faith in the academeB) they can only choose from three or four positionsC) it is very difficult for them to find a desirable jobD) it is impossible for them to carry out scientific work57. As we all know, the job market for science position in academe is _______.A) tight B) challenging C) small D) exclusive58. Which of the following is true according to the article?A)A) Some scientists believe that there are too many doctoral programs.B)B) Reliable statistics suggest that there are not enough Ph.D's for science positions.C)C) Most scientists argue that doctoral education should produce more competent Ph.D's.D)D) Scholars hope that the job market will be open to more Ph.D's.59. What can we learn from the experience of Ms. Jones?A)The start-up money can last three years.B)Every Ph.D has financial problems.C)Postdoctoral position is a good choice.D)Grant, jobs, and title are interrelated.60. In order to reshape the Graduate Education of Scientists and Engineers, which of thefollowing suggestions is mentioned?A)To set limits on graduate enrollment in all fields.B)To direct money to new models of doctoral education.C)To broaden Ph. D programs for students who are to be professors.D)To hire graduate students as research assistants.Passage TwoOur Love-Hate Affair with TechnologyThe entertainment we enjoy is a measure of who we are. Two recent movies ——last summers Star Wars and November's Close Encounters of the Third Kind—suggest that Americans are both fascinated with and horrified by the technological world we have shaped.Neither movie pretends to great seriousness. Star Wars is a light confection about another galaxy and era and a young man named Luke Skywalker who, thanks to an improbable series of coincidences, is drawn into a death battle against the galaxy's wicked emperor. En route to victory, he encounters a fair princess and wins her heart, if not her hand. (This is the age of liberation.)Close Encounters of the Third Kind concerns Roy Neary, an ordinary American who has an encounter with a UFO and becomes obsessed with his search for an explanation. His mission is impeded by those who do not believe in the existence of UFOs; by those who would prefer to wish the perplexing UFOs out of existence; and by those in power who, to prevent panic, deny the existence of UFOs. Luke Skywalker and every adventurer-hero since Odysseus, Neary finds an available pretty girl to accompany him on his lonely mission. In the last frame, though, he achieves a goal more lofty than marriage ——he strides into a UFO and, the ultimate American pioneer, flies away with the strange Visitors to destinations unknown.From the popularity of Star Wars, the likely success of Close Encounters, and the increasing respectability ofthe whole genre of science fiction, it is clear that our age, more than its predecessors, needs whatever consolation or reassurance science fiction affords. If all art is to some extent escapist, one might ask what it is that we are escaping from.An answer, I think, is hidden in the films' imagery. In StarWars, Luke Skywalker ekes out a living as a "moisture farmer" (whatever that may be) in a bleak desert on the remote planet of Tatooine. Apparently, the reason he lives in such an unfruitful place rather than in galactic Palm Springs is that there is no galactic Palm Springs: Evil technology has reduced the universe to wind and sand. If the technocrats (技术专家治国论者) were not so vicious and self-serving, the land would be more fruitful. Luke's mission is to replace the Bad technocrats with the Good, which he does. In a closing ceremony disturbingly reminiscent of Nuremberg Nazi rallies, Luke is rewarded with a medal (and a wink) by the princess, who represents the new, benevolent ruling class.Similarly, in Close Encounters, the world in which Roy Neary lives is corrupted by bad technology. Director Stephen Spielberg focuses his camera critically on all the mechanical paraphernalia (器材) ——toy trains, hair dryers, TV's ——with which we surround ourselves. The way the Visitors from the other planet make their presence known is by wreaking havoc on technology; turning on toys, stereos. TVs, in the dead of night; turning off the telephones and the electricity; and bewildering the air traffic scanners. The vision that obsesses Roy Neary, though, is not one of a Thoreauvian cabin in the woods, where evil technology may never trespass, but rather one of a technologically perfect world, where all the circuits enhance man's happiness.Like Neary and Skywalke, Americans are perplexed by the failure of technology to supply us with a meaningful life or a decent environment to live in. For every wonderful achievement, technology seems to deal us an equivalent kick in the shins. Travel has become more efficient and less civilized. Television has helped to raise a generation of unprecedentedly educated six-year-olds and increasingly illiterate high school seniors. We can enjoy completely enclosed and comfortable environments hundreds of feet above the sidewalk until, as witness the NewYork City blackout last summer, someone pulls the plug and the environments become inaccessible and uninhabitable. Only the most naive believe we can escape our increasingly technological environment. Recognizing that the technologizing trend is irreversible, we fantasize, with Skywalker and Neary, about a world where all the machines work with us, rather than against us, where the computer does not obstinately mis-bill, and where jets disgorge (卸下) our luggage intact at correct destinations.Regrettably, as both these films imply, the "perfect" technocracy is one over which ordinary mortals can exercise no influence. The enormity and complexity of the system preclude nonexpert involvement. Our only options in such a world would be to replace the bad technocrats, as Skywalker does, evade them, as Neary does, or trust that in their loving-kindness they will make the machines produce what we desire. Our democratic methods of trying to control our exploding technology may be less than "perfect," but they do leave man some room in which to manage his destiny.61. What is Roy Neary's mission?A) To find a pretty girl.B) To look for an explanation about UFOs.C) To fly away to destinations unknown.D) To be a member of the world of UFOs.62. What can we learn from the increasing popularity of the whole genre of science fiction according to theauthor?A) Bad technology has caused serious problems.B) Science fiction is an art of escapism.C) We need more reassurance than our ancestors.D) Science fiction offers us more entertainment than any other art63. We can infer from the passage that the author thinks that __________.A) humans are more vicious and self-serving than any other creatureB) there does not exist a Palm Springs in the universeC) farmers can only eke out a livingD) our world has been seriously damaged by evil technology64. According to the author; every technological achievementA)has changed our living styleB)has made the environment more inhabitableC)has brought us more harm than benefitD)has enhanced people’s happiness65. What is the attitude of the author toward technology?A) Supportive.B) Negative.C) Tolerant.E)Cautious.Passage ThreeComputers BugYear 2,000 Bug Unstoppable for Some ComputersWith 500 days left until the year 2,000, experts said last week, that it may already be too late for many companies to defuse the millennium computer time bomb.According to the Gartner Group, a US high-technology consultant agency, nearly a quarter of all worldwide companies have not yet started work on plans to solve the year 2,000 problems.This means most of these organizations will effectively be unable to fix their system in time.The Gartner group, which said last year that the millennium bomb rehabilitation would cost between US$300 billion and US$ 600 billion worldwide, also said in the repot published this month that only 50 percent of companies that had projects to eliminate the bug planned to test their corrected systems.Dangerous PolicyExperts said this was a dangerous policy, because correcting computer programmes often introduced new flaws. Testing was essential.The millennium computer bomb is a legacy from shortcuts by software writers, who in the name of economy expressed years with just the final two digits rather than four.When clocks tick past midnight on December 31, 1999, many unrectified computers and chips will interpret the double zero as 1900.This will turn many computer programmes to mush. Unchecked, many public utilities, assembly lines, bank teller machines, traffic lights and lifts may shut down.Some experts say the problem has been grossly exaggerated by software companies seeking to scare customers into buying the latest, bug-free products.But Graham Titterington, consultant at London consultancy Ovum, does not share this optimistic view.“The situation is pretty critical. Most companies are doing something, but are they doing enough?” he said in an interview.Titterington also said that for the vast majority of business there was no extemal check on the effectiveness of their remedial work.Running out of TimeMitul Mehta, senior European research manager at Frost & Sullivan in London, said time was running out for many companies.Companies now could only pinpoint vital computer systems for fixing. Less crucial systems would just have to run the risk of crashing and be fixed later, Mehta said.“Some crucial areas apart from computers are not getting enough attention. I don’t think networking companies have their act together – meaning manufacturers of routers, switches and network equipment like Bay (network company) and Cisco (Systems company), these kinds of companies,” Mehta said.He sa id: “ Anybody looking at their system now is probably too late anyway.”Critical SituationIn his report, Gartner Group millennium research director, Lou Marcoccio, said that of the 15,000 companies and government agencies surveyed, 23 percent had not started millennium bomb projects. Of these, 86 percent were small companies which would not have a chance to correct their systems unless they began immediately. The Gartmer report said most Western European companies and the United States had made good progress. Germany was a notable laggard.“:Eastern Europe, Russia, India, pakistan, Southeast Asia, Japan, most of South America, most of middle east and Central Africa all lag the United States by more than 21 months.“Most of Western Europe is six mo nths behind the United States, except for Germany which is 21 months behind, and France, which is eight to 10 months behind.“The US government had the lead on all other national governments by an even wider margin than the companies in those countries. Most government agencies are significantly behind the United States.” The report。

中国农业大学考博英语阅读理解真题解析

中国农业大学考博英语阅读理解真题解析Directions：You are going to read a list of headings and a text about whatparents are supposed to do to guide their children into adulthood.Choose a heading from the list A——G that best fits the meaning ofeach numbered part of the text(41——45)。

The first and lastparagraphs of the text are not numbered.There are two extra headingsthat you do not need to use.Mark your answers on ANSWER SHEET1.(10points)A.Set a Good Example for Your KidsB.Build Your Kid's Work SkillsC.Place Time Limits on Leisure ActivitiesD.Talk about the Future on a Regular BasisE.Help Kids Develop Coping StrategiesF.Help Your Kids Figure Out Who They AreG.Build Your Kids Sense of ResponsibilityHow Can a Parent Help?（PS:The way to contact yumingkaobo TEL:si ling ling-liu liu ba-liu jiu qi ba QQ:772678537) Mothers and fathers can do a lot to ensure a safe landing in earlyadulthood for their kids.Even if a job's starting salary seems toosmall to satisfy an emerging adult's need for rapid content，thetransition from school to work can be less of a setback if the start-upadult is ready for the move.Here are a few measures，drawn from mybook Ready or Not，Here Life Comes，that parents can take to preventwhat I call“work-life unread ness”。

中国农业大学生物化学考博

1、下列三种符号各代表那种氨基酸：Leu、Ile、Val，阐明其代谢特点。

2、肝脏在动物代谢中的作用。

3、乙酰辅酶A的代谢途径。

4、举例说明核酸和蛋白质的相互作用。

5、蛋白质的二级结构。

6、 DNA的半保留复制如何用试验证明。

7、密码子和反密码子的区别。

8、复制叉的结构。

中国农业大学1996年博士研究生入学考试试题（生物化学）1、 DNA双螺旋结构中除Waston-Crick提出的外，还有哪些，说明其结构。

2、蛋白质的右手螺旋结构。

3、 DNA的超螺旋结构？哪些DNA结构易形成超螺旋结构。

4、用蛋白质结构特点说明抗原、抗体结合的机理。

5、反刍动物利用纤维素的代谢过程。

6、真核生物mRNA结构特点。

7、蛋白质中Lys的测定方法。

8、肽、肽键、肽链、蛋白质的概念9、计算等电点。

10、体液PH调控机制。

11、复制、转录何以保证其忠实性。

中国农业大学1997年博士研究生入学考试试题（生物化学）1、反刍动物的蛋白质代谢。

2、蛋白质的一级结构及其在结构层次中的作用。

3、酮体的生成？它与糖代谢的关系。

4、羊毛衫热水洗涤后容易皱缩，而蚕丝蛋白则没有这种现象，为什么？5、真核生物与原核生物DNA复制的不同之处？DNA复制具备什么条件？6、当溶液的PH为丙氨酸等电点时，它以什么形式存在？7、操纵子与操纵基因的概念？它们在基因表达中的作用？8、核糖体的功能？真核与原核生物核糖体的不同？9、氨基酸层析的分离依据于氨基酸的那些特性？离子交换层析中选择洗脱液应该那些因素？中国农业大学1998年博士研究生入学考试试题（生物化学）1、蛋白质二级结构定义并举例说明。

2、 AA滴定曲线的定义与含义。

3、 Km值计算方法。

4、反刍动物能量来源。

5、原核、真核生物基因表达区别。

6、 tRNA反密码定义；Wobble Hyothesis内容。

7、概念：肽键、多肽、操纵子、DNA半保留复制、核小体、过瘤胃蛋白。

1、 1、反刍动物蛋白质代谢特点。

中国农业大学植物营养学历年考博真题

中国农业大学植物营养学历年考博真题1992年中国农业大学植物营养学考博真题1、名词解释自由空间：由细胞间隙、细胞壁微孔和细胞壁与原生质膜之间的空隙组成，它允许外部溶液通过扩散可自由进入。

（92、93、94）短距离运输：根外介质中的养分从根表皮细胞进入根内经皮层组织到达中柱的迁移过程叫养分的横向运输。

由于其迁移距离短，又称为短距离运输。

（92、94、96、02、不清）矿质营养临界期：植物生长发育的某一时期，对某种养分要求的绝对数量不多但很迫切，并且当养分供应不足或元素间数量不平衡时将对植物生长发育造成难以弥补的损失，这个时期就叫做植物营养的临界期。

（92）有益矿质元素：除了必需营养元素外，还有一些营养元素，对植物生长发育具有良好的刺激作用，或为某些植物种类所必需，但不是所有植物种类所必需，称为有益元素。

（92、94、95、96、不清）根际效应：根际环境对微生物的影响一般称为根际效应。

这种效应首先是通过营养选择与富集作用，使在根际发育的微生物种类、数量以及优势生理类群不同于根际外，同时它在很大程度上是微生物活性对最终决定作物产量与品质的一种反映。

（92、93、94）肥料交互作用效应：两种具有促进作用的肥料同时供应时，作用效果大于单独作用效果的现象。

随机：（92、93、94）土壤养分的空间有效性：（92、94）肥料的迭加利用率：在一次施肥之后，连续种植各季作物总吸肥料量占施肥料量的百分率。

最小养分律：作物产量受土壤中相对含量最少的养分所控制，作物产量的高低则随最小养分补充量的多少而变化。

（92、99、不清）2、当代植物营养科学有哪些研究方向？并简述其内涵和进展。

（92、94、95、96、97、98、00、不清）答：研究方向：根际研究，土壤养分生物有效性的概念；植物营养性状的遗传学研究；植物营养与微生物；植物营养与分子生物学；植物营养与生态学进展：十多年来，我国的植物营养学研究一直瞄准国际前沿，并与信息技术、生物技术、环境科学和生态学等学科交叉融合，不但扩展了研究领域，也促进了本学科的迅速发展，而且形成了许多新的生长点和突破口，在国际上逐渐形成了自己的特色。

近3年来中国农大考博免疫试题

近3年考题如下：微生物与免疫:一名词解释（3分X10个）抗原漂移持续性感染慢病毒感染流氏细胞术亚病毒朊病毒缺陷性干扰颗粒（注考题均为英文给出，先翻译后解释）二简答：1。

负链RNA病毒复制过程（5分）2。

内源性抗原和外源性抗原递呈过程（5分）3。

沙门氏菌的鉴定流程（10分）三问答1。

有些疾病一定要用基因工程疫苗来预防，试举2到3例并解释原因。

2。

PRRSV 能引起免疫抑制，试设计试验证明之。

2001年兽医传染病（20分X5个）1．针对疯牛病我国应采取的国策2。

以新城疫和喘气病为例介绍对这两类疾病的不同对策。

3.我国兽医防疫水平不高，表现在哪些方面4.从兽医防疫角度，谈谈引种应注意的几个问题。

5。

谈谈规模化养殖场免疫程序的制定及其评价标准。

2000年兽医传染病（未注明的全为简答）免疫失败的原因。

病毒分类的依据。

请设计一种基因工程疫苗的设计思路。

（20分）什么叫自然疫源性疾病，试举几种。

朊病毒产生的疾病有哪几种？常用的几种分子生物学试验技术，说明其原理。

（20分）我国扑灭的传染病有哪些。

我国动物防疫法从哪一天开始实施。

2003年博士生入学考试微生物与免疫：一名词解释（20分，每题2分）1．回复突变2．Prion 3．Infectious nucleio acid 4．MAC 5．Cytokine 6．重构型抗体7．CTL 8．溶原化9．内源性抗原10．合胞体二、简述题（30分）1.缺损病毒有哪些形式？有何生物学意文？（4分）2．微RNA病毒科有几个属，各写出一种兽医上重要的动物病毒。

（3分）3．病毒的持续性感染有哪些类型？各有何特点？（4分）4．动脉炎病毒科的成员有哪些？举例说明其结构蛋白的组成（6分）5．简述参与抗胞内菌感染的特异性细胞免疫的因素及其功能。

（6分）6．抗体产生的初次应答和再次应答各有何特点？在免疫防制工作中有何实际指导意义？（7分）三、问答题（50分）1．简述各种分子生物学诊断技术的原理并举例说明在动物病毒病诊断中的应用（15分）2．设计检测猪繁殖与呼吸综合征病毒抗体的阻断ELISA（Blocking ELISA）方法。

中国农业科学院和农大动物营养博士考题

中国农业科学院和农大动物营养博士考题2021年中国农科院动物营养博士考题真题名词解释pendfconjugatedlinoleicacid猜谜任选四举例说明氨基酸消化率的测定方法？奶牛低乳汁综合症的原因及研究进展？以畜禽为例说明热境应激对其的影响叶酸的生物学功能、缺乏症，叶酸与vb12的关系英国、美国、中国的能量体系有什么不同？能量体系之间的换算公式论述任选二以畜禽为基准表明幼年动物的生长对成年的影响分子生物学技术在动物营养中的营养及研究进展营养平衡对动物来说具有重要意义，以单胃或反刍动物为例说明纤维素与对它营养素吸收的影响及平衡对动物健康的意义2021中国农科院动物营养博士考题真题简答题1.反刍动物限制性氨基酸的研究方法？对照动物产品和食糜氨基酸组成的差异展开排序，例如单个氨基酸的消化道灌入，乳腺氨基酸的稀释，所需aa的消化道灌入、aa吸收率的方法测评aa的限制性顺序r2752.必需脂肪酸？猪的脂肪消化，吸收，代谢？3.家禽碘的营养？r3194.犊牛消化生理特点？r377,r131,r401论述题1.瘤胃微生物的研究进展？2.共轭亚油酸对猪生长性能的促进作用机制？p141农科院畜牧所<>博士研究生入学考试试题2021年1、如何评价锰的生物利用效率，影响其利用效率的因素有哪些？2、什么是蛋白质周转及其影响因素3、营养素对猪免疫系统功能拉艾的促进作用以及寡糖如何充分发挥功能性促进作用4、反刍动物与单胃动物脂肪代谢的区别，共轭亚油酸的生物合成途径以及如何通过营养手段展开调控5、综合分析基因、环境和营养对畜禽肉品品质的影响农科院畜牧所<>博士研究生入学考试试题2021年1、阴阳离子均衡在家禽上的促进作用、应用领域（20分后）2、断奶仔猪的营养生理特点？怎样做好仔猪的饲料添加剂？（20分）3、提高奶牛小肠aa消化率的方法措施（20分）4、酶制剂的最新研究。

你的观点与看法。

（20分）5、现在我国畜牧业所遭遇的问题存有哪些？你做为一名农业科学研究者的观点。

中国农业大学植物营养学考博真题答案要点

一、名词解释1. 质外体运输：养分通过细胞间隙、细胞壁到达内皮层凯氏带处，进行跨膜运输进入共质体，进入中柱的过程。

（95、不清）2. 奢侈吸收：介质中的养分浓度影响根系的吸收。

当介质中养分浓度过高时，根系细胞对养分的吸收选择性降低，被动进入细胞或通过质外体途径进入植物输导组织，造成植物体内养分浓度过高，但尚未达到毒害作用的现象。

（93、95）3. 交互作用：即正连应效应。

两种具有促进作用的矿质元素同时供应时，作用效果大于单独作用效果的现象。

（92、95、01）4. 有益元素(Beneficial element)：除了必需营养元素外，还有一些营养元素，对植物生长发育具有良好的刺激作用，或为某些植物种类所必需，但不是所有植物种类所必需，称为有益元素。

（92、94、95、96、不清）5. 根际：指受植物根系活动影响，在物理、化学、生物学性质上不同于土体的那部分微域土区。

根际的范围很小，一般在离根轴表面数毫米之内。

（94、95、不清）6. 根际效应：根际环境对微生物的影响一般称为根际效应。

（92、93、94）7. 质外体：由细胞壁、细胞间隙、木质部空腔所组成的连续体。

（97、99、00、01、02、不清）8. 共质体：由细胞的原生质（不包括液泡）组成，穿过细胞壁的胞间连丝把细胞与细胞连成一个整体，这些相互联系起来的原生质整体成为共质体。

（02）9. 以磷增氮：指通过对豆科作物，特别是豆科绿肥施用磷肥，促进作物根瘤的形成和根瘤菌固定空气中的氮素，以增加作物氮素营养和土壤含氮量。

（96、99、00）10. 根分泌物：指植物生长过程中，根向生长基质释放的有机物质的总称。

一般占C同化量的5~25%。

包括渗出物、分泌物、黏胶质、分解物与脱落物。

（99、不清）11. 专一性根分泌物：特定的植物受某一养分胁迫专一性诱导，在体内合成，并通过主动分泌进入根际的代谢产物。

2023年中国农科院历年考博试题汇总

中国农科院历年考博基因工程概论试题2023年中国农科院博士入学基因工程概论试题一、简答题1、聚丙烯酰胺、琼脂糖在dna电泳中的区别是什么？2、举出动物转基因的两种方法，并说明其原理。

3、双脱氧法测序的原理。

4、以拟南芥或玉米为例，说明转座子标签法进行基因转移的原理。

5、southern印迹的原理及应用。

三、试论述植物基因工程研究进展以及在农业生产上的意义。

2023年中国农科院博士入学基因工程概论试题一、名词解释1、限制性内切酶2、同裂酶3、核酶4、2μ环5、hat选择6、ti质粒7、t-dna8、同功trna9、反义trna 10、有义链11、α互补12、基因文库13、cdna 14、染色体步查二．简答题01、举两种植物基因转移的方法?简述其原理。

2、southern印迹的基本原理，这种方法有何应用。

3、噬菌体与cos作载体有何区别？4、aflp的原理及其应用5、普通pcr与rapd有何区别，何谓普通pcr？6、何谓双元载体，简述其组装过程及其作用机理？三、判断题1、无论用哪种转化方法均可用pbr322作载体2、进入细菌的外来dna之所以被降解，是由于细菌只修饰自身dna，不修饰外来dna3、只有粘粒端才可以被连接起来4、用自身作引物合成的cdna链，往往cdna并不完整1998年中国农科院博士入学基因工程概论试题一、什么是基因工程，基因工程在农业生产上有何意义？二、简答：1、聚丙烯酰胺凝胶电泳和琼脂糖凝胶电泳应用有何特点？2、举两种植物基因转移的方法?简述其原理。

3、双脱氧法测序的原理4、转座子标签法克隆植物基因的原理5、southern印迹的基本原理，这种方法有何应用？6、在dna复制过程中会形成一种复制体（replisome）的结构，它是由哪几部分组成的？7、sanger测序法的基本原理是什么？1999年中国农科院博士入学基因工程概论试题一．名词解释：1．cdna 2 ti质粒3. 2u环4. hat选择5 a互补6 yac 7 转导8 基因文库9 限制性内切酶10 染色体步查二．问答题：1 举例说明两种植物转基因的方法。

中国农业大学博士入学考试动物生物化学试题

中国农业大学博士入学考试动物生物化学试题中国农业大学1995年博士研究生入学考试试题,生物化学, 1、下列三种符号各代表那种氨基酸:Leu、Ile、Val，阐明其代谢特点。

Leu是亮氨酸、Ile是异亮氨酸、Val是缬氨酸。

是支链氨基酸，为必需氨基酸。

这三种氨基酸分解代谢的开始阶段基本相同，即首先经转氛基作用，生成各自相应的α-酮酸，其后分别进行代谢，经过若干步骤，缬氨酸分解产生琥珀酸单酰辅酶A;亮氮酸产生乙酰辅酶A及乙酰乙酰辅酶A;异亮氨酸产生乙酰辅酶A及琥珀酸单酰辅酶A。

所以，这三种氨基酸分别是生糖氨基酸、生酮氨基酸及生糖兼生酮氨基酸。

支链氨基酸的分解代谢主要在骨骼肌中进行。

2、肝脏在动物代谢中的作用。

?肝在糖代谢中的作用:肝的糖代谢不仅为自身的生理活动提供能量，还为其他器官的能量需要提供葡萄糖。

?带葡萄糖激酶和丙酮酸激酶活性较高，是糖酵解的主要区域;I带磷酸烯醇式丙酮酸激酶、果糖1,6-二磷酸酶和葡萄糖-6-磷酸酶的活性较高，是糖异生的主要区域。

肝通过糖原的合成与分解、糖的异生作用来维持血糖浓度的稳定，保障全身各组织，尤其是大脑和红细胞的能量供应。

在饱食时，除少量葡萄糖氧化分解外，大多数被合成为糖原贮存起来。

空腹时，糖原分解释放出葡萄糖进入血液，供中枢神经系统和红细胞等利用。

饥饿状态下，糖异生作用加强，这是肝供应血糖的主要途径。

?肝在脂类代谢中的作用:?肝在脂类的消化、吸收、合成、分解与运输过程中均具有重要作用。

肝可利用胆固醇转化为胆汁酸，然后分泌进入肠道而促进脂肪。

?内质网中的酯化作用和线粒体内的氧化作用。

肝合成甘油三酯、磷脂和胆固醇，并以VLDL的形式分泌入血，供其他组织器官摄取与利用。

在肝中线粒体、脂酸主要进行β-氧化产生的乙酰CoA而合成酮体，然后进入血液中供其他组织利用。

?肝在蛋白质代谢中的作用:?除γ-球蛋白外，几乎所有的血浆蛋白质由肝合成，如清(白)蛋白、凝血酶原、纤维蛋白原以及多种载脂蛋白和血浆部分球蛋白。