Q: What are the net products of the link reaction per glucose molecule?

$$2 \times$$ acetyl-CoA, $$2 \times$$ NADH, $$2 \times$$ $$CO_2$$

Q: Which of the following is a correct summary equation for the Krebs cycle per two acetyl-CoA molecules?

$$2 \text{ Acetyl-CoA} + 6 \text{ NAD}^+ + 2 \text{ FAD} + 2 \text{ ADP} \rightarrow 4 \text{ CO}_2 + 6 \text{ NADH} + 2 \text{ FADH}_2 + 2 \text{ ATP}$$

Question 1

Which of the following best describes the main purpose of pyruvate oxidation (the link reaction) in cellular respiration?

Accepted Answer

To convert pyruvate into a form that can enter the Krebs cycle by producing acetyl-CoA

Question 2

During the link reaction, which molecule acts as the carrier for the acetyl group into the Krebs cycle?

Accepted Answer

Coenzyme A (CoA)

Question 3

Which enzyme complex is responsible for catalyzing the three steps of pyruvate oxidation?

Accepted Answer

Pyruvate dehydrogenase complex

Question 4

What are the net products of the link reaction per glucose molecule?

Accepted Answer

$$2 	imes$$ acetyl-CoA, $$2 	imes$$ NADH, $$2 	imes$$ $$CO_2$$

Question 5

Which of the following steps in the Krebs cycle directly produces ATP (or GTP) by substrate-level phosphorylation?

Accepted Answer

Conversion of succinyl-CoA to succinate

Question 6

In the Krebs cycle, which molecule is regenerated at the end of each cycle, allowing the cycle to continue?

Accepted Answer

Oxaloacetate

Question 7

Which of the following correctly matches the step with its associated electron carrier product in the Krebs cycle?

Accepted Answer

Oxidation of isocitrate to alpha-ketoglutarate produces NADH

Question 8

If a cell is unable to regenerate NAD+ during the Krebs cycle, which of the following would most likely occur?

Accepted Answer

The cycle would stop at steps requiring NAD+ as an electron acceptor

Question 9

Which of the following is a correct summary equation for the Krebs cycle per two acetyl-CoA molecules?

Accepted Answer

$$2 	ext{ Acetyl-CoA} + 6 	ext{ NAD}^+ + 2 	ext{ FAD} + 2 	ext{ ADP} ightarrow 4 	ext{ CO}_2 + 6 	ext{ NADH} + 2 	ext{ FADH}_2 + 2 	ext{ ATP}$$

Question 10

A mutation in the gene encoding isocitrate dehydrogenase would most directly affect which step of the Krebs cycle?

Accepted Answer

Oxidation of isocitrate to alpha-ketoglutarate

Question 11

Which of the following best explains why the Krebs cycle is considered a 'closed loop'?

Accepted Answer

The final product, oxaloacetate, is used to initiate the next cycle

Question 12

In prokaryotes, where does the Krebs cycle occur?

Accepted Answer

Cytoplasm

Question 13

Which of the following is a direct result of the oxidation of alpha-ketoglutarate in the Krebs cycle?

Accepted Answer

Formation of succinyl-CoA and release of $$CO_2$$

Question 14

A patient has a deficiency in Coenzyme A. Which process would be most directly impaired?

Accepted Answer

Formation of acetyl-CoA from pyruvate

Question 15

Which of the following steps in cellular respiration produces the greatest number of reduced electron carriers (NADH and $$FADH_2) $$per glucose molecule?

Accepted Answer

Krebs cycle

Question 16

If a toxin inhibits the enzyme succinate dehydrogenase, which product would decrease in the cell?

Accepted Answer

$$FADH_2$$

Question 17

Which of the following best describes the fate of the carbon atoms from glucose after completion of the Krebs cycle?

Accepted Answer

They are released as $$CO_2$$

Question 18

A researcher adds a labeled oxygen isotope ($$^{18}O) to a $$cell culture. In which molecule would you expect to find the labeled oxygen after the Krebs cycle is complete?

Accepted Answer

$$CO_2$$

Question 19

Which of the following is a correct sequence of events during the link reaction?

Accepted Answer

Removal of carboxyl group as $$CO_2$$, oxidation of two-carbon molecule, attachment to CoA

Pyruvate Oxidation and the Krebs Cycle: Cellular Respiration Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards