MCAT Biology Question 133: Answer and Explanation

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Question: 133

13. Which of the following biomolecules does NOT drain to the liver before arriving at the right side of the heart?

  • A. Cholecalciferol (Vitamin D)
  • B. Threonine (an amino acid)
  • C. Fructose (a monosaccharide)
  • D. Pantothenic acid (vitamin B5)

Correct Answer: A

Explanation:

While the capillaries from the intestine come together to form the portal vein, which drains to the liver, the lacteals come together to form the thoracic duct, which drains directly into the left subclavian vein. Therefore, fat-soluble compounds do not pass through the liver before reaching the right heart. Only choice (A), vitamin D, is fat-soluble.

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