第五章 代謝之基本法則 前言
Forms of energy: 能量的定義 : Capacity to do work 動能 (Kinetic energy) 位能 (Potential energy) 熱能 (Heat) 化學能 (Chemical energy)
What Can Cells Do with Energy? Energy inputs become coupled to energy-requiring processes Cells use energy for: Chemical work Mechanical work Electrochemical work
熱力學第一定律: 多少能量可以利用 The total amount of energy in the universe remains constant 2. Energy can undergo conversions from one form to another, but it cannot be created or destroyed 熱力學第二定律: 能量單向流動 1. The sun is life’s primary energy source 2. Producers trap energy from the sun and convert it into chemical bond energy 3.All organisms use the energy stored in the bonds of organic compounds to do work
Entropy Measure of degree of disorder in a system The world of life can resist the flow toward maximum entropy only because it is resupplied with energy from the sun
Energy Changes & Cellular Work Energy changes in cells tend to run spontaneously in the direction that results in a decrease in usable energy
Endergonic Reactions Exergonic Reactions
ATP—細胞能量的流通 Cells “earn” ATP in exergonic reactions Cells “spend” ATP in endergonic reactions
脢的結構與功能 脢的四個特徵: 脢只是使反應加速而已 脢可以重複使用 脢催化正反方向的反應 脢有基質特異性
脢與基質的交互作用 鎖與鑰匙模式(Key and lock model) 誘導與適合模式 (Induced-fit model)
影響脢活動的因子 脢與環境的關係 回饋反應
Cell Membranes Show Selective Permeability O2, CO2, and other small nonpolar molecules;and H2O C6H12O6, and other large, polar (water-soluble) molecules; ions such as H+, Na+, CI-, Ca++; plus H2O hydrogen-bonded to them X
濃度梯度的利用與對抗 擴散 (Diffusion) 被動運輸 (Passive transport) 主動運輸 (Active transport)
擴散 (Diffusion)
Concentration gradient facilitated diffusion low lipid bilayer Concentration gradient P energy input high DIFFUSION ACROSS LIPID BILAYER PASSIVE TRANSPORT facilitated diffusion ACTIVE TRANSPORT Lipid-soluble molecules and water molecules diffuse across Water-soluble molecules and ions diffuse through interior of transport proteins. No energy boost required. Specific solutes pumped across, through transport proteins against gradient; requires energy boost Fig. 5.25a, p. 91
被動運輸 (Passive transport)
主動運輸 (Active transport)
透過膜的水分子移動方式 滲透作用 (Osmosis) 張力的影響 (Tonicity) 液壓的影響 (Osmotic pressure)
滲透作用 (Osmosis)
張力的影響 (Tonicity)
液壓的影響 (Osmotic pressure)
原生質萎縮 (Plasmolysis)
Bulk Transport 胞泌作用(Exocytosis) 內吞作用 (Endocytosis) 胞飲作用 (Phagocytosis)