Q: During anaerobic conditions in human muscle cells, which process allows glycolysis to continue?

Pyruvate is converted to lactate, regenerating $$\text{NAD}^+.$$

Question 1

Which of the following best explains why glucose does not spontaneously combust in cells, even though the reaction is thermodynamically favorable?

Accepted Answer

The activation energy barrier prevents the reaction from occurring spontaneously.

Question 2

Which statement about enzymes is TRUE?

Accepted Answer

Enzymes lower the activation energy ($$E_a) $$required for a reaction.

Question 3

A scientist is studying an enzyme-catalyzed reaction. She increases the substrate concentration but observes that the reaction rate plateaus. Which explanation best fits this observation?

Accepted Answer

The enzyme has become saturated; all active sites are occupied.

Question 4

Which of the following best describes the role of NADH in cellular respiration?

Accepted Answer

NADH donates electrons to the electron transport chain, leading to ATP production.

Question 5

During anaerobic conditions in human muscle cells, which process allows glycolysis to continue?

Accepted Answer

Pyruvate is converted to lactate, regenerating $$	ext{NAD}^+.$$

Question 6

Which of the following is NOT a mechanism by which enzymes speed up chemical reactions?

Accepted Answer

Enzymes increase the temperature of the reaction environment.

Question 7

A patient has a genetic mutation that prevents the production of coenzyme A (CoA). Which step of cellular respiration would be directly affected?

Accepted Answer

Pyruvate oxidation (the 'Link Reaction')

Question 8

Which of the following statements about glycolysis is CORRECT?

Accepted Answer

Glycolysis produces a net gain of 2 ATP per glucose molecule.

Question 9

In the electron transport chain, what is the final electron acceptor?

Accepted Answer

Oxygen ($$	ext{O}_2)$$

Question 10

Which of the following best explains why NADH produced during glycolysis yields less ATP than NADH produced during the Krebs cycle?

Accepted Answer

Glycolysis NADH enters the electron transport chain less efficiently, resulting in less proton pumping.

Question 11

Which process is responsible for the majority of ATP production in aerobic cellular respiration?

Accepted Answer

Oxidative phosphorylation via the electron transport chain

Question 12

A competitive inhibitor affects enzyme activity by:

Accepted Answer

Binding to the active site and preventing substrate binding.

Question 13

Which of the following is an example of substrate-level phosphorylation?

Accepted Answer

ATP production during glycolysis.

Question 14

If a cell is deprived of oxygen, which of the following will occur?

Accepted Answer

The electron transport chain will stop, and only glycolysis will produce ATP.

Question 15

Which of the following is TRUE regarding the citric acid cycle (Krebs cycle)?

Accepted Answer

It fully oxidizes acetyl-CoA to $$	ext{CO}_2.$$

Question 16

Which factor does NOT directly affect enzyme activity?

Accepted Answer

Glucose concentration in the blood

Question 17

Which of the following is a correct sequence for the flow of energy in aerobic cellular respiration?

Accepted Answer

Glucose $$\rightarrow$$ Pyruvate $$\rightarrow$$ Acetyl-CoA $$\rightarrow$$ Krebs Cycle $$\rightarrow$$ ETC $$\rightarrow$$ ATP

Question 18

Which of the following statements about fermentation is CORRECT?

Accepted Answer

Fermentation regenerates $$	ext{NAD}^+$$, allowing glycolysis to continue.

Question 19

A yeast cell is placed in an anaerobic environment. Which products will be formed from glucose metabolism?

Accepted Answer

Ethanol and $$	ext{CO}_2$$

Question 20

Which of the following best describes the induced-fit model of enzyme action?

Accepted Answer

The enzyme changes shape upon substrate binding to better accommodate the substrate.

Enzymes and Chemotrophic Energy Metabolism: Activation Energy, Catalysis, and Cellular Respiration(week 6)

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