Answer: Proteins.
Explanation:
Proteins are organic molecules made of amino acids which are arranged in a linear chain and joined together through a peptide bond.
Membrane proteins are classified depending on their location:
- Integral membrane proteins are part of a cell membrane and can either penetrate the membrane or associate with one side of a membrane.
- Peripheral membrane proteins are transiently associated with the cell membrane.
They perform many important functions:
- Membrane receptor proteins: relay signals between the internal and external environments.
- Transport proteins: move molecules and ions across the membrane.
- Membrane enzymes: transform a molecule into another form
- Cell adhesion molecules: allow cells to identify each other.
