Question

Discuss the general structure and function of lipid rafts

Compare the 3 types of membrane proteins in terms of their affinity for the hydrophobic interior of the membrane and the functions they typically have in cells. Think about how some of these functions are dependent on the presence of other types of membrane proteins (e.g. given that some peripheral membrane proteins anchor integral membrane proteins, how would removing peripheral proteins affect the mobility of integral membrane proteins?)

Discuss the meaning of membrane asymmetry

Explain why integral membrane proteins are considered amphipathic.

Answer 1

Lipid rafts are the microdomains of the cell membrane which are higly rich in cholestrol ans sphingolipids. They are characterized by the presence of GPI-anchor proteins (Glycosyl-phosphatidyl-inositol) and also those proteins which are involved in signalling transduction pathways. Lipid rafts ranges from 5-30 nm in size and have the clusters of sphingolipids, strultural proteins and cholestrol that akes it more tightly packed than the surrounding phospholipid bilayer. Lipid rafts make distinct microdomains which have a tendency to diffuse freely across the membrane. They are resistant to solubilizing effect by most detergents. They are said to be dynamic in nature, being capable of assembling and dis-assembling rapidly.

Functions:

1. Lipid rafts helps in collection of proteins required for the signal transmission.

2. They could act as signal tranmitting molecules or thy may decrease the signal transmission process by nhibiting the signals potentially.

3. Caveolin type lipid rafts are involved in cholestrol transportation and endocytosis.