Question

Explain how structural properties of proteins acting at the cell membrane enable their function. Provide examples from at least two proteins, and use diagrams and chemical structures to illustrate your answer wherever possible.

Answer 1

Selectivity of plasma membrane depends on the lipid bilayer and proteins present in it.

1.The peripheral proteins exist on the surface of bilayer. They are attached by ionic and polar bonds to polar head of lipids forming (microdomains)called lipid rafts.These are areas on membrane having predominently glycospingolipids and cholestrol. These lipid rafts are implicated in endocytosis,G protein signaling and binding of viral pathogens.

2.The integral membrane proteins are deeply embeded in the bilayer, some of these are called transmembrane proteins. These can serve as Receptors, Tissue specific antigens, Ion channels, Membrane based enzymes etc.

The functions of proteins are maintained because of their ability to recognize and interact with variety of molecules.The 3D structural confirmation promised and maintains the functional characteristics. The 3D structure in turn sepeda on the primer structure. So, Any Difference in primery structure May Produce a protein which can not serve Its function.

Exampls to be considered are Enzymes, Transport protes and structural proteins.

Enzymes have perticular configurations which can recognize substrate (lock key hypothesis).The substrate are brought in close proximity for reaction to proceed.

Transport protein are present on membrane responsible for uniport,symport ,antiport,facilitated diffusion,aquaporins etc

Struktural proteins like collagcollagen is utmost importance. Tripleks helical structure is responsible for Its tensile strength. Difference in arrangements of collagen fibrills in tissues give diff stres. Heat denatured collagen is cacalled gelatin.

Difference structure of protein 1ry, 2ry, tertiary and quaternary. On heating higher structures coverted into lower ones and lose Its functions.