AP BIOLOGY

Detailed explanation-1: -The plasma membrane, or the cell membrane, provides protection for a cell. It also provides a fixed environment inside the cell, and that membrane has several different functions. One is to transport nutrients into the cell and also to transport toxic substances out of the cell.

Detailed explanation-2: -Specialized proteins in the cell membrane regulate the concentration of specific molecules inside the cell. Membrane transport proteins are specific and selective for the molecules they move, and they often use energy to catalyze passage.

Detailed explanation-3: -The cell membrane, therefore, has two functions: first, to be a barrier keeping the constituents of the cell in and unwanted substances out and, second, to be a gate allowing transport into the cell of essential nutrients and movement from the cell of waste products.