BIOD 171 Microbiology Module 2 – Latest Updated 2025–2026 | Microbial
Metabolism, Enzymes & Energy | Solved Questions + Rationales
1. Which answer best identifies or explains the sum of all chemical reactions occurring in a cell?
A. metabolism
B. taxonomy
C. osmosis
D. sporulation only
Answer: A. metabolism
Rationale: Metabolism includes both energy-releasing catabolic reactions and energy-requiring anabolic
reactions.
2. Which answer best identifies or explains reactions that break complex molecules into simpler
molecules and often release energy?
A. anabolic reactions
B. polymerization only
C. catabolic reactions
D. isotonic reactions
Answer: C. catabolic reactions
Rationale: Catabolism breaks down molecules and commonly releases usable energy.
3. Which answer best identifies or explains reactions that build complex molecules from simpler
precursors?
A. lysis reactions
B. anabolic reactions
C. fermentation only
D. catabolic reactions
Answer: B. anabolic reactions
Rationale: Anabolism requires energy to synthesize cellular structures and macromolecules.
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,4. Which answer best identifies or explains the activation energy of a chemical reaction?
A. the amount of enzyme consumed
B. the energy barrier that must be overcome for the reaction to proceed
C. the total ATP produced
D. the pH optimum only
Answer: B. the energy barrier that must be overcome for the reaction to proceed
Rationale: Activation energy is the minimum energy needed to reach the transition state.
5. Which answer best identifies or explains the principal effect of an enzyme on a reaction?
A. lowering activation energy without being consumed
B. raising activation energy
C. serving as the reaction product
D. changing the final equilibrium constant
Answer: A. lowering activation energy without being consumed
Rationale: Enzymes accelerate reactions by lowering activation energy and are regenerated after
catalysis.
6. Which answer best identifies or explains the region of an enzyme where the substrate binds?
A. the active site
B. the nucleoid
C. the capsule
D. the ribosomal P site only
Answer: A. the active site
Rationale: The active site has chemical and structural features that recognize and bind the substrate.
7. Which answer best identifies or explains a competitive inhibitor?
A. a molecule that binds only DNA
B. a molecule that permanently increases substrate concentration
C. a molecule that competes with substrate for the enzyme active site
D. an ATP molecule used as a product
Answer: C. a molecule that competes with substrate for the enzyme active site
Rationale: Competitive inhibitors reduce substrate binding by occupying the active site.
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, 8. Which answer best identifies or explains a cofactor?
A. an enzyme product
B. a nonprotein helper required by some enzymes
C. a membrane lipid
D. a bacterial chromosome
Answer: B. a nonprotein helper required by some enzymes
Rationale: Many enzymes require metal ions or organic coenzymes to function properly.
9. Which answer best identifies or explains oxidation?
A. gain of protons only
B. loss of electrons
C. gain of electrons
D. production of peptidoglycan
Answer: B. loss of electrons
Rationale: Oxidation is loss of electrons; reduction is gain of electrons.
10. Which answer best identifies or explains reduction?
A. loss of electrons
B. loss of all protons
C. gain of electrons
D. breakdown of ATP only
Answer: C. gain of electrons
Rationale: Reduction means gaining electrons in a redox reaction.
11. Which answer best identifies or explains the role of NAD+ in metabolism?
A. forming bacterial flagella
B. serving as a cell-wall polymer
C. acting as a ribosome
D. acting as an electron carrier that can be reduced to NADH
Answer: D. acting as an electron carrier that can be reduced to NADH
Rationale: NAD+ accepts electrons and hydrogen during catabolic reactions and carries reducing power
as NADH.
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Metabolism, Enzymes & Energy | Solved Questions + Rationales
1. Which answer best identifies or explains the sum of all chemical reactions occurring in a cell?
A. metabolism
B. taxonomy
C. osmosis
D. sporulation only
Answer: A. metabolism
Rationale: Metabolism includes both energy-releasing catabolic reactions and energy-requiring anabolic
reactions.
2. Which answer best identifies or explains reactions that break complex molecules into simpler
molecules and often release energy?
A. anabolic reactions
B. polymerization only
C. catabolic reactions
D. isotonic reactions
Answer: C. catabolic reactions
Rationale: Catabolism breaks down molecules and commonly releases usable energy.
3. Which answer best identifies or explains reactions that build complex molecules from simpler
precursors?
A. lysis reactions
B. anabolic reactions
C. fermentation only
D. catabolic reactions
Answer: B. anabolic reactions
Rationale: Anabolism requires energy to synthesize cellular structures and macromolecules.
Page 1
,4. Which answer best identifies or explains the activation energy of a chemical reaction?
A. the amount of enzyme consumed
B. the energy barrier that must be overcome for the reaction to proceed
C. the total ATP produced
D. the pH optimum only
Answer: B. the energy barrier that must be overcome for the reaction to proceed
Rationale: Activation energy is the minimum energy needed to reach the transition state.
5. Which answer best identifies or explains the principal effect of an enzyme on a reaction?
A. lowering activation energy without being consumed
B. raising activation energy
C. serving as the reaction product
D. changing the final equilibrium constant
Answer: A. lowering activation energy without being consumed
Rationale: Enzymes accelerate reactions by lowering activation energy and are regenerated after
catalysis.
6. Which answer best identifies or explains the region of an enzyme where the substrate binds?
A. the active site
B. the nucleoid
C. the capsule
D. the ribosomal P site only
Answer: A. the active site
Rationale: The active site has chemical and structural features that recognize and bind the substrate.
7. Which answer best identifies or explains a competitive inhibitor?
A. a molecule that binds only DNA
B. a molecule that permanently increases substrate concentration
C. a molecule that competes with substrate for the enzyme active site
D. an ATP molecule used as a product
Answer: C. a molecule that competes with substrate for the enzyme active site
Rationale: Competitive inhibitors reduce substrate binding by occupying the active site.
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, 8. Which answer best identifies or explains a cofactor?
A. an enzyme product
B. a nonprotein helper required by some enzymes
C. a membrane lipid
D. a bacterial chromosome
Answer: B. a nonprotein helper required by some enzymes
Rationale: Many enzymes require metal ions or organic coenzymes to function properly.
9. Which answer best identifies or explains oxidation?
A. gain of protons only
B. loss of electrons
C. gain of electrons
D. production of peptidoglycan
Answer: B. loss of electrons
Rationale: Oxidation is loss of electrons; reduction is gain of electrons.
10. Which answer best identifies or explains reduction?
A. loss of electrons
B. loss of all protons
C. gain of electrons
D. breakdown of ATP only
Answer: C. gain of electrons
Rationale: Reduction means gaining electrons in a redox reaction.
11. Which answer best identifies or explains the role of NAD+ in metabolism?
A. forming bacterial flagella
B. serving as a cell-wall polymer
C. acting as a ribosome
D. acting as an electron carrier that can be reduced to NADH
Answer: D. acting as an electron carrier that can be reduced to NADH
Rationale: NAD+ accepts electrons and hydrogen during catabolic reactions and carries reducing power
as NADH.
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