Concept:Every living cell is covered by a thin, elastic, transparent, semi-permeable and regenerative membrane called cell membrane also called plasma membrane or plasmalemma.The cell membrane separates the internal environment of the cell from the external environment.This membrane helps in regulating the entrance and exit of molecules into and out of the cell.Explanation:It is made up of cellulose. (incorrect)Cell membrane is made up of a phospholipid bilayer. Phospholipids are lipids that contain a phosphate group.There is one hydrophilic head and two hydrophobic tails on the phospholipids. Proteins are embedded in the lipid bilayers.It is a permeable structure for all substances. (incorrect)A permeable membrane allows all substances to pass freely through it. The plasma membrane, on the other hand, is composed of lipids arranged in a bilayer that allows only hydrophobic substances to pass through it and is selectively permeable in nature.It is flexible and enables the cell to engulf many materials. (correct)The plasma membrane is made up of organic molecules known as lipids and proteins that are flexible.The flexibility of the cell membrane also allows the cell to take in food and other materials from its surroundings.It does not allow diffusion of gases like oxygen and carbon dioxide. (incorrect)Only the smallest molecules, such as water, carbon dioxide, and oxygen, can pass freely through cell membranes.