MCAT Biology Question 100: Answer and Explanation

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Question: 100

10. Which of the following is involved in the body's primary blood-buffering mechanism?

  • A. Fluid intake
  • B. Absorption of nutrients in the gastrointestinal system
  • C. Carbon dioxide produced from metabolism
  • D. Hormones released by the kidney

Correct Answer: C

Explanation:

Carbon dioxide is a byproduct of metabolism in cells that later combines with water to form bicarbonate in a reaction catalyzed by carbonic anhydrase. This system is blood plasma's most important buffer system. Food and fluid absorption are not significant sources of buffering, eliminating choices (A) and (B). While the kidney can be involved in acid–base balance, it is through its filtration, secretion, and reabsorption mechanisms, not hormones, eliminating choice (D).

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