Anaerobic Respiration

Question 1

During a 40‑second intense rope‑skipping session, Sam feels a sharp burning in his calves right after he stops. Which of the following best explains why the buildup of lactic acid makes his muscles hurt and become fatigued?

Accepted Answer

The accumulated lactic acid lowers the pH inside muscle cells, interfering with the proteins that cause contraction, so the muscles become stiff and painful.

Answer

Lactic acid is a poisonous waste that kills muscle cells, causing immediate pain and fatigue.

Answer

Producing lactic acid releases extra energy that the muscles cannot use quickly enough, creating a painful backup.

Answer

The lactic acid uses up the remaining oxygen in the blood, leaving no oxygen for the muscles, so they stop working.

Question 2

After a 30‑second all‑out sprint, Maya stops running. Her breathing stays elevated for several minutes, and the burning feeling in her legs disappears after about 4 minutes. Which statement best describes what is happening inside her muscles during this recovery period?

Accepted Answer

The extra oxygen taken in is used to convert the accumulated lactic acid back into pyruvate, which is then fully broken down in the mitochondria to produce ATP and to replenish the muscle’s ATP and phosphocreatine stores.

Answer

The muscles continue to produce lactic acid anaerobically even after stopping, and the higher breathing rate supplies oxygen to keep this process going.

Answer

The body repays the oxygen debt by increasing the rate of glycolysis, which generates more ATP without needing oxygen, and the extra oxygen is used only to warm the blood.

Answer

The elevated breathing simply removes the excess carbon dioxide produced during the sprint, and the lactic acid disappears because it evaporates through the skin.

Question 3

When Maya’s leg muscles run out of oxygen during a 30‑second sprint, the cells switch to anaerobic respiration. Which word equation correctly shows the overall reaction that occurs in her muscles?

Accepted Answer

Glucose → Lactic acid + 2 ATP

Answer

Glucose + O₂ → Carbon dioxide + Water + Energy

Answer

Glucose → Ethanol + CO₂ + Energy

Answer

Glucose + O₂ → Lactic acid + CO₂ + H₂O

Try three questions

During a 40‑second intense rope‑skipping session, Sam feels a sharp burning in his calves right after he stops. Which of the following best explains why the buildup of lactic acid makes his muscles hurt and become fatigued?

After a 30‑second all‑out sprint, Maya stops running. Her breathing stays elevated for several minutes, and the burning feeling in her legs disappears after about 4 minutes. Which statement best describes what is happening inside her muscles during this recovery period?

When Maya’s leg muscles run out of oxygen during a 30‑second sprint, the cells switch to anaerobic respiration. Which word equation correctly shows the overall reaction that occurs in her muscles?

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