EVERYDAY SCIENCE

Detailed explanation-1: -The cell membrane, also called the plasma membrane, is found in all cells and separates the interior of the cell from the outside environment. The cell membrane consists of a lipid bilayer that is semipermeable. The cell membrane regulates the transport of materials entering and exiting the cell.

Detailed explanation-2: -The membrane is selectively permeable because substances do not cross it indiscriminately. Some molecules, such as hydrocarbons and oxygen can cross the membrane. Many large molecules (such as glucose and other sugars) cannot. Water can pass through between the lipids. Ions such as H+ or Na+ cannot.

Detailed explanation-3: -Most biological molecules are unable to diffuse through the phospholipid bilayer, so the plasma membrane forms a barrier that blocks the free exchange of molecules between the cytoplasm and the external environment of the cell.

Detailed explanation-4: -The plasma membrane is selectively permeable; it regulates what passes from one side to the other. A selectively permeable membrane will allow water to flow freely while limiting the passage of molecules, especially large molecules or those with a charge.