What is the primary (main) function of lipid molecules in the plasma membrane? - To provide an energy source for most cell activities.

- To provide a substance for enzyme activity in the cell.

- To provide a place to collect and store waste products within the cell.

-To provide a barrier to the movement of substances in and out of the cell.

to provide a barrier to the movement of substances in and out of the cell

Explanation:

Lipid molecules in the plasma membrane form a lipid bilayer which creates a semi-permeable barrier between the inside and the outside of the cell. Water and small molecules can cross the membrane. Other large molecules like ions cannot.

Hope that helps.

littering streams           is the answer