Describe the biological need for cells to be surrounded by a membrane that is selectively permeable for different materials

Every cell is surrounded by a cell membrane which is semi-permeable in nature. The need for cells to be surrounded by a semi-permeable membrane is to control the passage of material coming in and going out of the cell.

This membrane helps the cell to maintain a homeostatic condition inside the cell by allowing selective molecules to cross across the cell. The homeostatic condition is necessary for the proper functioning of the cell and cell survival.

Cell membrane is made up of lipid bilayer which contains membrane proteins embedded into it. Some proteins are freely movable in the cell membranes due to the fluid nature of the membrane.

These proteins are necessary for selective transport of substances across the membrane. These are also called transporter proteins.

an active site is a region that is present on an enzyme where the reactants or the substrate molecules we can say bind and experience a chemical reaction. the substrate is basically a reactant whose concentration is changing and that is converting into a product after binding at the active site of an enzyme

answer: c.

explanation: