Biology

The correct answer is: A.They selectively allow things into and out of the cell.

Proteins embedded in the cell membrane have several key functions, but one of their most important roles is selective transport. These membrane proteins regulate the movement of substances (such as ions, nutrients, and waste products) into and out of the cell. There are two main types of proteins involved in transport:

1.Channel proteins: Form pores in the membrane, allowing specific molecules or ions to pass through by diffusion.

2.Carrier proteins: Bind to specific substances and undergo conformational chan...