Question

What is a lipid raft? What evidence supports this theory? What evidence was found that somewhat challenges the existence of lipid rafts? How might the cytoskeleton influence raft behavior?

Answer 1

ANS:Lipid rafts are the subdomains of plama membrane that usually contains higher concentration of cholestrol ,glycosphingolipids and proteins.

Evidence that supports this theory

• Techniques such as high-resolution and time-lapse in situ atomic force microscopy are usedd in order to prove the evidence of the theory.
• Most of the rafts are basically of the size 100-300 nm,and possess irregular shape.
• Cholestrol leads to formation and stability of the protein domains.
• BAND III is one of the important protein of lipid raft in the inner leaflet of erythrocyte membranes,hence indicating that the lipid rafts are the functional domain of plasma membrane.

Evidence that challenges the existence of lipid raft theory

• Singer and Nicolson model postulated a uniform lipid bilayer irregularly studded with protein molecules.
• membranes were not regular and the lipids existed in a disorderly manner.
• The single -molecule method usually defines the force that drives the formation and dynamics of membrane domains.This theory has been outlined by the concept of proteomics and lipidomics.

Influence of cytoskeleton on lipid raft behaviour

• The interaction of MLR and cytoskeletal components lead to MLR assembly that eventually results in the cytoskeletal dynamics that further lead to the movement of lipid raft membrane domain.
• MLR assembly on the other hand depend upon the actin and cholestrol in order to adhere to the cell membrane and it regulates lateral diffusion of membrane proteins and lipids.