Question

Give specific functions of membrane proteins: Transport, Enzymatic activity, Signal transduction, cell-cell transduction, intercellular joining, attachment to the cytoskeleton and extracellular matrix (ECM)

Answer 1

Specific functions of membrane proteins:

Transport: Membrane proteins are involved in the movement of ions, smaller molecules, sugars across the lipid bilayer. They are integral proteins and span the entire region of the membrane and facilitate transport of molecules through active transport or by facilitated diffusion.

Enzymatic activity: Membrane proteins act as enzymes by catalysing chemical reactions. Exampes include oxidoreductase, hydrolases which are involved in the conversion of substrates to products.

Signal transduction: Membrane proteins when activated by G proteins relay signals; binds to chemical messengers which sends a message into the cell causing chemical reaction.

Cell-cell transduction: Membrane proteins functioning as intracellular signalling proteins pass the signal to the organelles of the cell. This is facilitated by binding of signal molecule to the receptor rotein thus activating signalling cascade.

Intercellular joining: Transmembrane proteins of opposite cells attach in a tight zipper like fashion; no leakage is found. Cytoplasmic plaques of two cells bind with the aid of intermediate filaments of keratin known as desmosomes also mediates intercellular joining.

Attachment to the cytoskeleton and extracellular matrix: Membrane proteins attach to the cytoskeleton to maintain cell shape and stabilise other proteins. Integrins are proteins that attach to both cytoskeleton and to the extracellular matrix. The fibres of proteins together with carbohydrates fills spaces between cells ans supports cells in a tissue.