Q. What are the respective functions of phospholipids, carbohydrates and proteins of the cell membrane?

Membrane phospholipids have a structural function they form the bilipid membrane that constitutes the cell membrane itself.

Membrane proteins have numerous specialized functions. Some of them are channels for substances to pass through the membrane, others are signalers and receptors of information, others are enzymes, others are cell identifiers (cellular labels) and there are still those that play a part in the adhesion complexes between cells or between the internal surface of the membrane and the cytosketeleton.

Membrane carbohydrates, associated to lipids or to proteins, are found in the outer surface of the cell membrane and they have in general labeling functions for recognition of the cell by other substances and cells for instance, they differentiate red blood cells in relation to the ABO blood group system immune modulation functions, pathogen sensitization functions, etc