Chapter 5: Microbial Metabolism
Below you will find answers to the "Review" study questions found at the end of this chapter in Microbiology: An Introduction, 7th edition.
  1. Metabolism is the sum of all chemical reactions that occur within a living organism.
  2. Catabolic reactions break down organic compounds and release energy, while anabolic reactions use the products of catabolism and energy to build cell material.
  3. When the enzyme and substrate combine, the substrate molecule will be transformed.
  4. When the competitive inhibitor binds to the enzyme, the enzyme will not be able to bind with the substrate.
  5. When the noncompetitive inhibitor binds to the enzyme, the active site of the enzyme will be changed so the enzyme cannot bind with the substrate.
  6. The noncompetitive inhibitor.
  7. (a) is the Calvin-Benson cycle, (b) is glycolysis, and (c) is the Krebs cycle.
  8. Glycerol is catabolized by pathway (b) as dihydroxyacetone phosphate. Fatty acids by pathway (c) as acetyl groups.
  9. In pathway (c) at -ketoglutaric acid.
  10. Glyceraldehyde-3-phosphate from the Calvin-Benson cycle enters glycolysis. Pyruvic acid from glycolysis is decarboxylated to produce acetyl for the Krebs cycle.
  11. In (a), between glucose and glyceraldehyde-3-phosphate.
  12. The conversion of pyruvic acid to acetyl, isocitric acid to -ketoglutaric acid, and -ketoglutaric acid to succinyl~CoA.
  13. By pathway (c) as acetyl groups.
Uses / Produces
Calvin-Benson cycle / 6 NADPH
Glycolysis / 2 NADH
Pyruvic acid------>acetyl / 1 NADH
Isocitric acid------> -ketoglutaric acid / 1 NADH
-ketoglutaric acid------>Succinyl~CoA / 1 NADH
Succinic acid------>Fumaric acid / 1 FADH2
Malic acid------>Oxaloacetic acid / 1 NADH
  1. Dihydroxyacetone phosphate; acetyl; oxaloacetic acid; -ketoglutaric acid.
  2. The optimum temperature for an enzyme is one that favors movement of molecules so the enzyme can "find" its substrate. Lower temperatures will decrease the rate of collisions and the rate of reactions. Increased temperatures will denature the enzyme.
  3. Ethyl alcohol, lactic acid, butyl alcohol, acetone, and glycerol are some of the possible products. Refer to Table 5.4 and Figure 5.18b.
Organism / Carbon Source / Energy Source
Photoautotroph / CO2 / Light
Photoheterotroph / Organic molecules / Light
Chemoautotroph / CO2 / Inorganic molecules
Chemoheterotroph / Organic molecules / Organic molecules
ATP generated by / Reaction
Photophosphorylation / An electron, liberated from chlorophyll by light, is passed down an electron transport chain.
Oxidative phosphorylation / Cytochrome c passes two electrons to cytochrome a.
Substrate-level phosphorylation /
  1. Oxidation-reduction: A coupled reaction in which one substance is oxidized and one is reduced.
  2. The final electron acceptor in aerobic respiration is molecular oxygen; in anaerobic respiration, it is another inorganic molecule.
  3. In cyclic photophosphorylation, electrons are returned to chlorophyll. In noncyclic photophosphorylation, chlorophyll receives electrons from hydrogen atoms.
  4. The pentose phosphate pathway produces pentoses for the synthesis of nucleic acids, precursors for the synthesis of glucose by photosynthesizing organisms, precursors in the synthesis of certain amino acids, and NADPH.
  5. Oxidation
  6. Reactions requiring ATP are coupled with reactions that produce ATP.

  7. The reaction rate will increase until the enzymes are saturated.

Below you will find answers to the "Multiple-Choice" study questions found at the end of this chapter in Microbiology: An Introduction, 7th edition.
  1. a
  2. d
  3. b
  4. c
  5. c
  6. b
  7. b
  8. a
  9. c
  10. b
Note: The answers to the Critical Thinking and Clinical Applications questions are available to instructors only, and are found in the Instructor's Manual.