Which part of the cell membrane prevents the cell from dissolving in water

Fatty acids

Explanation:

The cell membrane is made up of phospholipids( contains glycerol, two fatty acids and a phosphate group) which are arranged in parallel sheets forming two hemi leaflets with their polar head groups facing the aqueous intracellular and extracellular solutions and their non-polar fatty acid chains interacting laterally within the hydrophobic core of the membrane.

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