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 lowers the pH, leading to muscle fatigue and discomfort

Question 5

After exercise, when oxygen levels return to normal, what happens to the accumulated lactate in muscle cells?

Accepted Answer

It is converted back to pyruvate and used in oxidative phosphorylation

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 glucose?

Accepted Answer

Ethanol

Question 8

Which of the following statements about stored ATP in muscle cells is correct?

Accepted Answer

Stored ATP provides energy for only a few seconds of intense activity

Question 9

A patient is experiencing muscle fatigue during a sprint. Which energy system is primarily responsible for ATP production at this stage?

Accepted Answer

Anaerobic glycolysis of glycogen

Question 10

Which of the following is a multi-step process that integrates glycolysis and oxidative phosphorylation in muscle cells during moderate exercise?

Accepted Answer

Glucose is converted to pyruvate via glycolysis, then pyruvate enters the mitochondria for oxidative phosphorylation

Question 11

Which of the following equations correctly represents the net ATP yield from anaerobic glycolysis of one glucose molecule?

Accepted Answer

$$\mathrm{Glucose} \rightarrow 2 \mathrm{Lactate} + 2 \mathrm{ATP}$$

Question 12

During recovery after intense exercise, which process helps restore muscle pH and energy balance?

Accepted Answer

Conversion of lactate to pyruvate followed by oxidative phosphorylation

Question 13

Which of the following best explains why oxygen is required for oxidative phosphorylation?

Accepted Answer

Oxygen acts as the final electron acceptor in the electron transport chain

Question 14

A sprinter uses stored glycogen for energy during a race. Which pathway is primarily responsible for converting glycogen to ATP under anaerobic conditions?

Accepted Answer

Glycogenolysis followed by glycolysis and conversion of pyruvate to lactate

Question 15

Which of the following is a consequence of insufficient NAD+ availability during glycolysis?

Accepted Answer

Glycolysis slows down or stops, reducing ATP production

Question 16

Which of the following best describes the time course of energy system activation during exercise?

Accepted Answer

Stored ATP is used first, followed by glycolysis, then oxidative phosphorylation

Question 17

Which of the following is a real-world application of understanding anaerobic metabolism in clinical settings?

Accepted Answer

Managing lactic acidosis in patients with impaired oxygen delivery

Anaerobic Metabolism and Energy Systems in Human Physiology

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