Question 1

During intense exercise, muscle cells switch from aerobic to anaerobic metabolism. What is the primary reason for the conversion of pyruvate to lactate under these conditions?

Accepted Answer

To regenerate NAD+ so glycolysis can continue producing ATP

Question 2

Which enzyme catalyzes the conversion of pyruvate to lactate in human muscle cells during anaerobic conditions?

Accepted Answer

Lactate dehydrogenase

Question 3

What is the chemical equation for the conversion of pyruvate to lactate in anaerobic glycolysis?

Accepted Answer

$$\mathrm{Pyruvate} + \mathrm{NADH} + \mathrm{H}^+ \rightarrow \mathrm{Lactate} + \mathrm{NAD}^+$$

Question 4

Why is lactate accumulation in muscles considered disruptive during prolonged anaerobic activity?

Accepted Answer

It leads to a decrease in muscle pH, causing fatigue

Question 5

After intense exercise, how is lactate typically processed in the body when oxygen becomes available again?

Accepted Answer

It is converted back to pyruvate and used in aerobic metabolism

Question 6

Which of the following best describes the role of NAD+ in glycolysis?

Accepted Answer

NAD+ accepts electrons during glycolysis, allowing ATP production to continue

Question 7

In yeast cells, what is the end product of anaerobic metabolism of pyruvate?

Accepted Answer

Ethanol

Question 8

Which of the following statements about ATP production in anaerobic glycolysis is correct?

Accepted Answer

Anaerobic glycolysis produces less ATP per glucose than aerobic metabolism

Question 9

A patient with a genetic deficiency in lactate dehydrogenase would most likely experience which of the following during intense exercise?

Accepted Answer

Impaired regeneration of NAD+, leading to early muscle fatigue

Question 10

Which of the following best explains why oxygen is required for efficient ATP production in muscle cells?

Accepted Answer

Oxygen acts as the final electron acceptor in the electron transport chain, allowing oxidative phosphorylation to produce large amounts of ATP

Question 11

Which of the following is the correct sequence of energy systems used during exercise, from shortest to longest duration?

Accepted Answer

Stored ATP → Stored Glycogen → Aerobic metabolism

Question 12

Which chemical structure represents lactate?

Accepted Answer

$$\mathrm{CH}_3\mathrm{CH}(OH)\mathrm{COO}^-$$

Question 13

Which of the following is a direct consequence of insufficient oxygen supply to muscle mitochondria during exercise?

Accepted Answer

Increased conversion of pyruvate to lactate

Question 14

If a muscle cell cannot regenerate NAD+ during anaerobic exercise, what will happen to glycolysis?

Accepted Answer

Glycolysis will slow down or stop

Question 15

Which of the following best describes the fate of pyruvate in human cells under aerobic conditions?

Accepted Answer

It enters the mitochondria and is converted to acetyl-CoA for the Krebs cycle

Question 16

A sprinter uses stored ATP for the first few seconds of a race. Which equation best represents the breakdown of ATP to release energy?

Accepted Answer

$$\mathrm{ATP} ightarrow \mathrm{ADP} + \mathrm{P}_i + 	ext{energy}$$

Question 17

Which of the following is a real-world consequence of impaired lactate clearance after exercise?

Accepted Answer

Prolonged muscle soreness and delayed recovery

Question 18

Which process resumes in muscle cells when oxygen levels return after anaerobic exercise?

Accepted Answer

Oxidative phosphorylation

Question 19

Which of the following is NOT a function of lactate production in muscle cells?

Accepted Answer

Increasing the efficiency of aerobic metabolism

Question 20

During a marathon, which energy system predominates after the first few minutes of running?

Accepted Answer

Aerobic metabolism of carbohydrates and fats

Cellular Energy Systems: Glycolysis, Fermentation, and ATP Production

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