Suppose that scientists developed a protocell with a membrane that allowed all molecules to cross in or out of it.Would this membrane serve the function of a cell membrane?
A) Yes, because it would allow all molecules to cross either way.
B) Yes, because it would maintain an internal environment in the protocell similar to the external environment.
C) Yes, because it would form a complete sphere.
D) No, because it would not maintain an internal environment in the protocell that was different from the external environment.
E) No, because a cell's membrane is able to keep all molecules from moving across its border.

Question

Quizplus · Accepted Answer

The cell membrane serves the function of maintaining an internal environment in the cell that is different from the external environment. If a protocell membrane allowed all molecules to cross in or out, it would not be able to maintain a distinct internal environment and would not serve the function of a cell membrane. Therefore, option D is correct. Options A, B, and C are incorrect because allowing all molecules to cross would not necessarily make the protocell membrane function like a cell membrane. Option E is incorrect because a cell's membrane does not keep all molecules from moving across its border - it selectively allows certain molecules to cross while blocking others.

Suppose That Scientists Developed a Protocell with a Membrane That