Question

question: 4
which statement best describes the plasma membrane of a living plant cell?
the plasma membrane of a plant cell is
a. designed to allow for the free flow of all protein substances to move into and out of the cell.

b. composed of two layers of proteins and carbohydrates only.

c. composed of two layers of proteins with floating molecules of lipids only.

d. designed to allow certain substances to enter and certain substances to exit the cell.

Explanation:

• Option A: The plasma membrane is selectively permeable, not allowing all protein substances to freely flow in and out. So A is incorrect.
• Option B: The plasma membrane is composed of a phospholipid bilayer (two layers of phospholipids) with proteins and some carbohydrates, not just proteins and carbohydrates. So B is incorrect.
• Option C: The plasma membrane has a phospholipid bilayer (not two layers of proteins) with proteins and lipids (and some carbohydrates), so C is incorrect.
• Option D: The plasma membrane is selectively permeable, meaning it allows certain substances to enter and certain substances to exit the cell, which is the correct description.

Answer:

D. designed to allow certain substances to enter and certain substances to exit the cell.