MCAT Biology Question 71: Answer and Explanation
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Question: 71
11. A scientist discovers a new hormone that is relatively large in size and triggers the conversion of ATP to cAMP. Which of the following best describes the type of hormone that was discovered?
- A. Amino acid-derivative hormone
- B. Peptide hormone
- C. Steroid hormone
- D. Tropic hormone
Correct Answer: B
Explanation:
The question stem indicates that the newly discovered hormone functions as a first messenger, stimulating the conversion of ATP to cAMP; cAMP functions as a second messenger, triggering a signaling cascade in the cell. Hormones that act via secondary messengers and are relatively large in size (short peptides or complex polypeptides) are peptide hormones. This hormone could be a tropic hormone, but it is also entirely possible for it to be a direct hormone; thus, choice (D) can be eliminated.