Question 1

Which of the following best describes an amphibolic pathway, and which metabolic cycle is a classic example of this type of pathway?

Accepted Answer

A pathway that participates in both the breakdown and biosynthesis of molecules; the Krebs cycle is an example.

Question 2

During glycolysis, what is the net gain of ATP and NADH molecules per molecule of glucose, and by which mechanism is ATP generated?

Accepted Answer

2 ATP and 2 NADH by substrate-level phosphorylation

Question 3

Which of the following statements about enzyme action is CORRECT?

Accepted Answer

Enzymes lower the activation energy but do not change the overall free energy ($$\Delta G) of $$the reaction.

Question 4

A patient is given a sulfa drug to treat a bacterial infection. This drug acts as a competitive inhibitor. Which of the following best explains how the drug works?

Accepted Answer

It competes with the natural substrate (PABA) for the enzyme's active site, blocking folate synthesis.

Question 5

Which of the following correctly matches the oxidized and reduced forms of the electron carrier NAD?

Accepted Answer

NAD$$^+ is $$the oxidized form; NADH is the reduced form.

Question 6

Which of the following best explains why fermentation is necessary for some cells under anaerobic conditions?

Accepted Answer

Fermentation regenerates NAD$$^+$$, allowing glycolysis to continue in the absence of an electron transport chain.

Question 7

Which of the following is the correct sequence of events in aerobic cellular respiration, starting with glucose?

Accepted Answer

Glycolysis → intermediate step → Krebs cycle → electron transport chain

Question 8

In the electron transport chain (ETC) of aerobic respiration, what is the final electron acceptor, and what is the main consequence of electron flow through the ETC?

Accepted Answer

O$$_2$$; formation of a proton gradient across the membrane

Question 9

Which of the following best describes chemiosmosis in the context of cellular respiration?

Accepted Answer

The movement of H$$^+$$ ions down their electrochemical gradient through ATP synthase, generating ATP

Question 10

A bacterial cell is growing in an environment lacking oxygen but containing nitrate (NO$$_3^-). $$Which metabolic process is the cell most likely using, and what is the role of nitrate?

Accepted Answer

Anaerobic respiration; nitrate acts as the terminal electron acceptor in the ETC.

Question 11

Which of the following statements about substrate-level phosphorylation and oxidative phosphorylation is TRUE?

Accepted Answer

Substrate-level phosphorylation involves direct transfer of a phosphate to ADP by an enzyme, while oxidative phosphorylation uses ATP synthase and a proton gradient.

Question 12

Which of the following would most likely result from a mutation that causes an enzyme to lose its ability to bind its cofactor?

Accepted Answer

The enzyme would become an apoenzyme and lose its catalytic activity.

Question 13

Which of the following best explains why excessive heat can permanently damage an enzyme, while cooling only slows its activity?

Accepted Answer

Excessive heat denatures the enzyme's structure, while cooling reduces molecular motion without altering structure.

Question 14

Which vitamin-derived coenzyme is correctly matched with its associated electron carrier?

Accepted Answer

Vitamin B$$_2 ($$riboflavin) with FAD/FMN

Question 15

Which of the following is a key reason why fermentation yields much less ATP per glucose than aerobic respiration?

Accepted Answer

Fermentation does not use an electron transport chain or oxidative phosphorylation.

Question 16

A scientist adds more substrate to a reaction catalyzed by an enzyme that is already saturated. What will happen to the reaction rate?

Accepted Answer

The reaction rate will remain constant because all enzyme active sites are occupied.

Question 17

Which of the following best describes the role of kinases and phosphatases in enzyme regulation?

Accepted Answer

Kinases add phosphate groups; phosphatases remove them.

Question 18

Which of the following is a product of homolactic fermentation, and what is the net ATP yield per glucose?

Accepted Answer

Lactate; 2 ATP

Question 19

Which of the following best describes the fate of NADH and FADH$$_2$$ produced during the Krebs cycle?

Accepted Answer

They deliver electrons to the electron transport chain, contributing to the proton gradient.

Question 20

Which of the following is TRUE regarding the location of metabolic pathways in prokaryotes versus eukaryotes?

Accepted Answer

In eukaryotes, glycolysis occurs in the cytosol, and the Krebs cycle occurs in the mitochondrial matrix.

Microbial Metabolism: Study Guide and Key Concepts

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