Answer : The correct answer is -
1.They help control what enters and leaves the cell.
Some molecules can not cross the lipid bilayer membrane (cell membrane) of cells (such as large polar molecules and hydrophilic molecules).
There are special carbohydrate and protein that are embedded in the membrane and act like Transmembrane channels or transporters, which assist in the trasport of such molecules (like amino acids and proteins) on both sides across the cell.
Thus, option 1) is the right answer.
