Question 1

Which metabolic pathway is bypassed in cells that utilize the glyoxylate cycle, and what is the main consequence for ATP production per molecule of glucose?

Accepted Answer

Part of the TCA cycle is bypassed, resulting in fewer ATP produced per molecule of glucose.

Question 2

Fluoroacetate poisoning is lethal because it disrupts central carbon metabolism. Which enzyme does fluoroacetate competitively inhibit, and what is the result?

Accepted Answer

It inhibits aconitase, blocking the TCA cycle and ATP synthesis.

Question 3

Arsenate can replace phosphate in biochemical reactions. What is the effect of arsenate substitution in glycolysis, specifically at the step involving 1,3-bisphosphoglycerate?

Accepted Answer

It results in no net ATP production during glycolysis.

Question 4

A 2010 Science article claimed a bacterium could use arsenate instead of phosphate for growth. What was the outcome of this claim?

Accepted Answer

It was refuted by later studies and ranked as a major scientific failure.

Question 5

If arsenate only interfered with glycolysis, would arsenic poisoning have a bigger, smaller, or equal impact on a cell that performs aerobic cellular respiration compared to a cell that performs fermentation?

Accepted Answer

Smaller impact on aerobic respiration because most ATP comes from the TCA cycle and oxidative phosphorylation.

Question 6

Cyanide is a potent toxin because it blocks complex IV of the electron transport chain. What is the immediate effect on cellular metabolism?

Accepted Answer

NADH accumulates in the mitochondrial matrix as electron flow stops.

Question 7

Oligomycin is an antibiotic that blocks ATP synthase. What happens to the concentration of protons ($$H^+) in $$the mitochondrial intermembrane space after oligomycin exposure?

Accepted Answer

Proton concentration increases because protons cannot flow through ATP synthase.

Question 8

FCCP is an ionophore that facilitates proton transport across the mitochondrial membrane. What is the effect of FCCP on ATP synthesis?

Accepted Answer

ATP synthesis decreases because the proton gradient is dissipated.

Question 9

Which toxin would cause the concentration of NAD$$^+ in $$the mitochondrial matrix to decrease, and why?

Accepted Answer

Cyanide, because it blocks complex IV, preventing NADH oxidation.

Question 10

A cell exposed to fluoroacetate will form fluorocitrate. What is the consequence for the TCA cycle and ATP production?

Accepted Answer

The TCA cycle is blocked at aconitase, reducing ATP production.

Question 11

If a cell with the glyoxylate bypass is exposed to a toxin that blocks the conversion of isocitrate to α-ketoglutarate, how does this affect ATP yield per glucose?

Accepted Answer

ATP yield decreases because fewer NADH and FADH$$_2$$ are produced.

Question 12

Which of the following best explains why arsenate poisoning results in no net ATP production during glycolysis?

Accepted Answer

Arsenate replaces phosphate in the formation of 1,3-bisphosphoglycerate, bypassing substrate-level phosphorylation.

Question 13

Which toxin would cause the concentration of ATP in the mitochondrial matrix to decrease, but the proton gradient to remain high?

Accepted Answer

Oligomycin

Question 14

If arsenate only interfered with the TCA cycle, would arsenic poisoning have a bigger, smaller, or equal impact on a cell that performs aerobic cellular respiration compared to a cell that performs fermentation?

Accepted Answer

Bigger impact on aerobic respiration because the TCA cycle is essential for ATP production.

Question 15

Which of the following equations correctly represents the net ATP yield from aerobic respiration of one molecule of glucose in a typical eukaryotic cell?

Accepted Answer

$$C_6H_{12}O_6$ + 6O_2 \rightarrow 6CO_2 + 6H_2O + 36\ ATP$$

Question 16

Which toxin would cause the concentration of protons ($$H^+) in $$the mitochondrial intermembrane space to decrease, and why?

Accepted Answer

FCCP, because it allows protons to flow freely across the membrane, dissipating the gradient.

Question 17

Which of the following statements about the electron transport chain is correct?

Accepted Answer

Complex IV is blocked by cyanide, preventing oxygen from acting as the final electron acceptor.

Question 18

A cell exposed to FCCP will experience which of the following changes in mitochondrial metabolism?

Accepted Answer

Decreased ATP synthesis due to loss of proton gradient.

Cellular Respiration and Metabolic Poisons: Mechanisms and Effects

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