H1 Biology and H2 Biology
What is the role of Proteins in Cell Membranes?
Notes from the video ‘H2 Biology Tuition | H1 Biology Tuition | Role of Protein in Cell Membrane’:
In this Biology tutorial, we would learn what are the roles of proteins in cell membranes.
Proteins facilitate the transport of molecules across the membrane.
For example, proteins allow facilitated diffusion of polar, charged molecules or ions across the membrane via transmembrane channels or carrier proteins,
Proteins assist in the active transport of polar/charged molecules or ions across the membrane via protein pumps, against the concentration gradient, with the expenditure of ATP.
Proteins may act as enzymes that catalyze chemical reactions.
Enzymes have a specific active site which is complementary in conformation and charge to the substrate.
Effective collisions between enzyme and substrate form a temporary enzyme-substrate complex.
Enzyme-substrate complexes are held together by weak interactions such as hydrogen bonds, ionic bonds, and hydrophobic interactions.
Enzyme lowers the activation energy by:
- Aligning substrates next to each other in the active site to increase the chances of the reaction occurring.
- Causing strains on the bonds in the substrate to be broken as they bind to the active site.
- Orientating the substrates such that their bonds are exposed to chemical attack
- Providing a favorable microenvironment
- Participating directly in catalysis with R groups of amino acid residues in acid-‐base catalysis.
This increases the proportion of substrate molecules with energy greater than the activation energy which allows the reaction to proceed faster than an uncatalyzed reaction.
Proteins may also act as a receptor protein which a specific ligand can bind.
This forms the ligand-receptor complex and initiates an intracellular signaling cascade for signal transduction.