MCAT Biochemistry Question 35: Answer and Explanation
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Question: 35
5. Hormones are found in the body in very low concentrations, but tend to have a strong effect. What type of receptor are hormones most likely to act on?
I. Ligand-gated ion channels
II. Enzyme-linked receptors
III. G protein-coupled receptors
- A. I only
- B. III only
- C. II and III only
- D. I, II, and III
Correct Answer: C
Explanation:
For a ligand present in low quantities to have a strong action, we expect it to initiate a second messenger cascade system. Second messenger systems amplify signals because enzymes can catalyze a reaction more than once while they are active, and often activate other enzymes. Both enzyme-linked receptors and G protein-coupled receptors use second messenger systems, while ion channels do not.