Question

1. Explain the principle of differential centrifugation and its applications. What is the difference between differential centrifugation and rate-zonal centrifugation?

2. When we quote centrifugation conditions in a protocol, what information do we need to provide? Why is it better to quote relative centrifugal force rather than speed (revolutions per minute) when writing a centrifugation protocol?

3. The two eukaryotic ribosomal subunits are referred to as the 40S and the 60S ribosomal subunits. Yet the intact ribosome is referred to as the 80S ribosome. Explain why this is so and explain what the “S” means.

Answer 1

1 Ans: Differential centrifugation is used to separate particles purely based on size and density. The denser particles demonstrate a higher sedimentation rate and thus, settle fast in pellets while less dense particles have a low sedimentation rate and remain in the supernatant following centrifugation.

Applications of differential centrifugation-

1. Separation of organelle and sub-cellular particles

2. For purification of nanoparticles

3. To analyze cell-membrane components

Difference between differential centrifugation and Rate-zonal centrifugation-

Differential centrifugation separates particles based on density and size while rate-zonal centrifugation separates particles based only on size (they don't differ in density)