A student observed a boundary in both plant and animal cells that controls entry and exit of substances. Which of the following structures is likely being observed?
- A. Mitochondria
- B. Golgi apparatus
- C. Plasma membrane
- D. Cell wall
Explanation
The plasma membrane is present in every cell and is partially permeable, so it decides what enters and leaves, which is exactly the function described. The cell wall is the trap: it is a boundary too, but it occurs only in plants and is fully permeable, so it controls nothing. The words both plant and animal are what rule it out.
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