Shier, Butler, and Lewis: Hole’s Human Anatomy and Physiology, 10th ed.
Chapter 4: Cellular Metabolism
Chapter 4: Cellular Metabolism
I. Metabolic Processes
1. Metabolism is the sum total of chemical reactions within cells. 2. In metabolic reactions, the product of one reaction serves as starting materials for another metabolic reaction. 3. This chapter explores how metabolic pathways supply a cell with energy and how other biochemical processes enable a cell to produce proteins. 4. Two types of metabolic reactions and pathways are anabolism and catabolism. 5. In anabolism, larger molecules are constructed from smaller ones. 6. In catabolism, larger molecules are broken down into smaller ones. 7. Anabolism requires energy.
8. Catabolism releases energy.
1. Anabolism provides all the substances required for cellular growth and repair. 2. Dehydration synthesis joins many simple sugar molecules to from larger molecules of glycogen. 3. When monosaccharides are joined, they form glycogen and a hydroxyl group from one monosaccharide and a hydrogen atom from another monosaccharide are removed. 4. The H and OH react to produce water.
5. Glycerol and fatty acid molecules join by dehydration synthesis to form fat molecules. 6. The result is three water molecules and one fat molecule. 7. Dehydration synthesis also builds proteins by joining amino acids. 8. The type of bond that holds amino acids together is a peptide bond. 9. A polypeptide is a chain of amino acids.
1. Catabolism is a group of physiological processes that break down larger molecules into smaller ones. 2. An example of catabolism is hydrolysis, which can decompose carbohydrates, lipids, and proteins. 3. In hydrolysis, a water molecule is split.
4. The hydrolysis of a disaccharide results in two monosaccharides. 5. When the bond between simple sugars break, water supplies a hydrogen atom to one sugar molecule and a hydroxyl group to the other. 6. Hydrolysis is the reverse of dehydration synthesis.
7. Hydrolysis breaks down carbohydrates into monosaccharides. 8. Hydrolysis breaks down fats into glycerol and fatty acids. 9. Hydrolysis breaks down proteins into amino acids.
10. Hydrolysis breaks down nucleic acids into nucleotides.
II. Control of Metabolic Reactions
A. Enzyme Action
1. Metabolic reactions require energy before they proceed.
2. Heat energy increases the rate at which molecules move and the frequency of molecular collisions. 3. The collisions of particles increase the likelihood of interactions among the electrons of the molecules that can form new chemical bonds. 4. Enzymes are usually globular proteins that promote specific chemical reactions within cells by lowering the activation energy required to start these chemical reactions. 5. Enzymes are needed in very small quantities because as they work, they are not consumed and can function repeatedly. 6. Enzyme specificity is the tendency of an enzyme to act only a particular substrate. 7. A substrate is a substance on which an enzymes acts.
8. The substrate of catalase is hydrogen peroxide.
9. The ability of an enzyme to identify a substrate depends on the shape of its active site. 10. Active sites are regions of enzymes that bind specifically to substrates. 11. The interaction of the enzyme-substrate complex causes chemical bonds to be strained in a substrate in a way that makes a chemical reaction more likely to occur. 12. The speed of enzyme-catalyzed reactions depends on the number of enzymes and substrate molecules. 13. Metabolic pathways are sequences of enzyme-controlled reactions. 14. Enzyme names are often derived from the names of their substrates with the suffix –ase added.
B. Cofactors and Coenzymes
1. A cofactor helps an active site obtain its appropriate shape of helps bind the enzyme to its substrate. 2. Examples of cofactors include...
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