Question

Membrane bilayers are of vital importance and are highly diverse. 

a. Describe two general functions of biological membranes. 

b. Give three examples of how biological membranes differ in composition. 

Answer 1

a. The general functions of the biological membranes are:

1. They function in maintaining a homeostatic environment inside the cell compared to the outside and keeps all the enzymes or proteins within their respective organelles and also maintains pH of different organelles such as the lysosomes have an acidic pH.

2. They function in the signal transduction pathways. The receptors are present on the membrane which bind to the ligand on the extracellular face and transmit the signals by cleaving or activating the proteins attached to the cytoplasmic face of the cell. For example GPCR is activated by a ligand by binding to the exoplasmic face and the proteins such as adenylyl cylase which are the cytoplasmic face proteins are activated by the G sub unit protein.

b. Three examples of how biological membranes differ in composition:

1. The membrane of the cell has more unsaturated lipids and cholesterol when the temperature of the surroundings rises as a result the membrane becomes more fluidic.

2. When the temperature drops or decreases, the saturated lipid content increases and the membrane becomes less fluidic.

3. The membrane contains integral protein, surface proteins and different kinds of proteins to facilitate signalling events in the cell.

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