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Human Physiology: The Mechanism of Body Function - part 2

Chất xúc tác làm tăng tốc độ của một phản ứng bằng cách hạ thấp năng lượng kích hoạt. VI. Các đặc tính của các phản ứng hồi phục và không thể đảo ngược được liệt kê trong Bảng 4-3. VII. Hướng net, trong đó tiền thu được phản ứng có thể được thay đổi, theo pháp luật tác dụng khối lượng, bằng cách tăng hoặc giảm nồng độ của chất phản ứng hoặc sản phẩm. | Vander et al. Human Physiology The Mechanism of Body Function Eighth Edition 4. Protein Activity and Cellular Metabolism The McGraw-Hill Companies 2001 I. Basic Cell Functions Protein Activity and Cellular Metabolism CHAPTER FOUR 69 FIGURE 4-17 Flow of chemical energy from fuel molecules to ATP and heat and from ATP to energy-requiring cell functions. Ễnĩ SECTION B SUMMARY In adults the rates at which organic molecules are continuously synthesized anabolism and broken down catabolism are approximately equal. Chemical Reactions I. The difference in the energy content of reactants and products is the amount of energy measured in calories that is released or added during a reaction. II. The energy released during a chemical reaction either is released as heat or is transferred to other molecules. III. The four factors that can alter the rate of a chemical reaction are listed in Table 4-2. IV. The activation energy required to initiate the breaking of chemical bonds in a reaction is usually acquired through collisions with other molecules. V. Catalysts increase the rate of a reaction by lowering the activation energy. VI. The characteristics of reversible and irreversible reactions are listed in Table 4-3. VII. The net direction in which a reaction proceeds can be altered according to the law of mass action by increases or decreases in the concentrations of reactants or products. Enzymes I. Nearly all chemical reactions in the body are catalyzed by enzymes the characteristics of which are summarized in Table 4-4. II. Some enzymes require small concentrations of cofactors for activity. a. The binding of trace metal cofactors maintains the conformation of the enzyme s binding site so that it is able to bind substrate. b. Coenzymes derived from vitamins transfer small groups of atoms from one substrate to another. The coenzyme is regenerated in the course of these reactions and can be used over and over again. Regulation of Enzyme-Mediated Reactions The rates of .