MCAT Biology Question 36: Answer and Explanation
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Question: 36
6. A cell releases a substance that diffuses through the environment, resulting in differentiation of a nearby cell. This is an example of what type of cell–cell communication?
- A. Autocrine
- B. Juxtacrine
- C. Paracrine
- D. Endocrine
Correct Answer: C
Explanation:
The question stem states that a cell releases a substance that diffuses through the environment and causes differentiation of a nearby cell. Because the cell is acting on another nearby cell, and the molecule spreads by diffusion, this is an example of paracrine signaling. Autocrine signaling, choice (A), occurs when a molecule secreted by a cell results in an effect on the same cell. Juxtacrine signaling, choice (B), occurs between adjacent cells, but the signal does not spread by diffusion. In endocrine signaling, choice (D), a molecule is secreted that travels via the bloodstream to a distant target. Choice (C) is therefore the correct answer.