Q: Which of the following is the correct balanced equation for the products of the Krebs cycle per two acetyl groups?

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

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

Question 2

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

Accepted Answer

Coenzyme A (CoA)

Question 3

Which of the following is a net product of the link reaction per glucose molecule?

Accepted Answer

2 Acetyl-CoA

Question 4

What is the correct sequence of events during the link reaction?

Accepted Answer

Carboxyl group removal, oxidation, CoA binding

Question 5

Which enzyme complex is responsible for catalyzing the link reaction?

Accepted Answer

Pyruvate dehydrogenase complex

Question 6

In the Krebs cycle, what is the fate of the two carbons from acetyl-CoA?

Accepted Answer

They are released as CO2

Question 7

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

Accepted Answer

Conversion of succinyl-CoA to succinate

Question 8

How many NADH molecules are produced from one turn of the Krebs cycle?

Accepted Answer

3

Question 9

Which molecule is regenerated at the end of the Krebs cycle, allowing the cycle to continue?

Accepted Answer

Oxaloacetate

Question 10

If a cell is deprived of NAD+, which step in the Krebs cycle would be directly affected first?

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

Its final product, oxaloacetate, is used to start the next cycle

Question 12

In prokaryotes, where does the Krebs cycle occur?

Accepted Answer

Cytoplasm

Question 13

Which of the following is the correct balanced equation for the products of the Krebs cycle per two acetyl groups?

Accepted Answer

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

Question 14

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 15

Which molecule is reduced during the oxidation of succinate to fumarate in the Krebs cycle?

Accepted Answer

FAD

Question 16

If a cell is unable to regenerate oxaloacetate, what would be the immediate consequence for the Krebs cycle?

Accepted Answer

The cycle would stop because acetyl-CoA could not enter

Question 17

Which of the following best describes the role of NADH and FADH2 produced in the Krebs cycle?

Accepted Answer

They donate electrons to the electron transport chain for oxidative phosphorylation

Question 18

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

Accepted Answer

Conversion of pyruvate to acetyl-CoA

Question 19

Which of the following steps in cellular respiration is responsible for the majority of CO2 production in aerobic organisms?

Accepted Answer

Krebs cycle and link reaction

Question 20

If a toxin inhibits the enzyme that catalyzes the conversion of alpha-ketoglutarate to succinyl-CoA, which of the following would most likely accumulate?

Accepted Answer

Alpha-ketoglutarate

Pyruvate Oxidation and the Krebs Cycle: Cellular Respiration Pathways

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