Biology Notes Lesssons 1-2

Why is photosynthesis important?
• Photosynthesis is vital for all aerobic life (有氧 生活) on Earth. • In addition to maintaining normal levels of oxygen in the atmosphere 气氛 , photosynthesis is the source of energy for nearly all life on earth
The Cytoskeleton 细胞骨架
• is a cellular "scaffolding" or "skeleton" contained within a cell's cytoplasm and is made out of protein. • The cytoskeleton is present in all cells • It has structures such as flagella, cilia and lamellipodia and plays important roles in both intracellular transport胞内运输(the movement of vesicles and organelles, for example) and cellular division.
Intermediate filaments 中间丝
• Like actin filaments, they function in the maintenance of cell-shape by bearing tension (microtubules, by contrast, resist compression). It may be useful to think of micro- and intermediate filaments as cables, and of microtubules as cellular support beam
Steps of Photosynthesis
Light energy/reactions and Photosynthetic cells
• In the light reactions, one molecule (分子) of the pigment chlorophyll absorbs one photon (光子) and loses one electron. • Not all wavelengths 波长 of light can support photosynthesis. • For example, in green plants, the action spectrum行动谱 resembles the absorption spectrum (吸收光谱) for chlorophylls 叶绿素 and carotenoids (类胡萝卜素) with peaks for violet-blue and red light.
• This process occurs in plants and some algae 藻类 • Plants need only light energy, CO2, and H2O to make sugar. • The process of photosynthesis takes place in the chloroplasts 叶绿体 specifically using chlorophyll (叶 绿素) , the green pigment (颜料) involved in photosynthesis.
Cellular Movements
• is concerned with all types of movement at the cellular level. • One type: • Chemotaxis 趋化 is the phenomenon whereby somatic cells体细胞, bacteria菌, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment
Organelles 细胞器
• specialized subunit(s) within a cell that has a specific function, and is usually separately enclosed within its own lipid bilayer脂质双分 子层 • most cell biologists细胞生物学家consider the term organelle to be synonymous with "cell compartment", other cell biologists choose to limit the term organelle to include only those that are DNA-containing
Polysome
Exocytosis
Plastids
Flagellum
Cilia
Phagocytosis
Photosynthesis 光合作用
• is the process of converting light energy to chemical energy and storing it in the bonds of sugar.
Microtubules 微管
• Microtubules are hollow cylinders, most commonly comprising 13 protofilaments which, in turn, are polymers聚合物 of alpha and beta tubulin微管蛋白. • They have a very dynamic behaviour, and are commonly organized by the centrosome.
External cell movement
• Cellular movement is accomplished by cilia and flagella. • Cilia are hair-like structures that can beat in synchrony causing the movement of unicellular paramecium. • Cilia are also found in specialize linings in eukaryotes. For example, cilia sweep fluids past stationary cells in the lining of trachea and tubes of female oviduct. • Flagella are whip-like appendages that undulate to move cells. They are longer than cilia, but have similar internal structures made of microtubules
Nucleus 核
• is a membrane-enclosed organelle found in eukaryotic cells. • It contains most of the cell's genetic material, along with a large variety of proteins, such as histones 组蛋白, to form chromosomes 染色 体 • The main structures making up the nucleus are the nuclear envelope 核膜, a double membrane that encloses the entire organelle
• Therefore, there would only be two broad classes of organelles (i.e. those that contain their own DNA, and have originated from endosymbiotic bacteria): • mitochondria (in almost all eukaryotes) • Plastids质 (e.g. in plants, algae, and some protists).
Microfilaments 微丝 (actin filaments)
• These are the thinnest filaments of the cytoskeleton. • They are composed of linear polymers of actin 肌动蛋白subunits, and generate force by elongation at one end of the filament coupled with shrinkage at the other, causing net movement of the intervening strand
What Are the Steps of Photosynthesis?
• Photosynthesis consists of both light-dependent reactions 光反应 and light-independent reactions. • In plants, the so-called "light" reactions occur within the chloroplast thylakoids 叶绿体类囊体 , where chlorophyll pigments 颜料 reside. • When light energy reaches the pigment molecules, it energizes the electrons 电子 within them, • these electrons are moved to an electron transport chain in the thylakoid membrane
Bio-English Class Notes
Weeks 2-4
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Cytoplasm 细胞质
• The cytoplasm is the gel-like substance that holds all the cell's internal sub-structures (called organelles), except for the nucleus • It is within the cytoplasm that most cellular activities occur, such as many metabolic pathways代谢途径 including glycolysis糖酵解, and processes such as cell division • Within cytoplasmic fluid are nutrients营养素 , ions离子, and soluble proteins可溶性蛋白
• Every step in the electron transport chain 电 子传递链 then brings each electron to a lower energy state and harnesses its energy by producing ATP and NADPH. • Meanwhile, each chlorophyll molecule replaces its lost electron with an electron from water; this process essentially splits water molecules to produce oxygen