Question

In cell fractionation, the various fractions obtained during differential centrifugation are_________.
A. Plastidial, mitochondrial and microsomal.
B. Nuclear, mitochondrial and microsomal.
C. Nuclear, plastidial and cytosol.
D. Plastidial, microsomal and cytosol.

Answer 1

Cellular fractionation is defined as a process used to prevent the components of cells along with retaining their individual function and nature. In other words, it is the splitting of cells in order to expose its organelles for future study or various other purposes. It involves a series of steps.

Complete answer:
Now, let’s have a look at the process.
- This method was originally used for the location of different biochemical processes occurring in our bodies.
- It involves three basic steps-

A. Extraction- The cell organelles and biochemical molecules are extracted in such conditions (isotonic sucrose) so as to maintain the biochemical nature. This is called a cell-free system.
B. Homogenization- These are then disrupted. Grinding, High pressure, Osmotic shock, and Sonication (vibrations) are some commonly used methods.
C. Centrifugation-It is done in an instrument called preparative centrifugation. It is also called differential centrifugation.

Differential centrifugation is the separation of different components of supernatant that were obtained after homogenization. This is done by subjecting it to a higher centrifugal force that brings about velocity sedimentation or rate zonal centrifugation. The lighter fractions settle down at higher centrifugal force while denser constituents undergo sedimentation at lower centrifugal force.

Various fractions are separated during differential centrifugation. These areas are as under- nuclear, mitochondrial, microsomal fraction, and ribosomal fraction.

Hence, the correct answer is option (B).

Note: Some important points:
- The fractions obtained in velocity centrifugation are purified by equilibrium density-gradient centrifugation.
- This method involves the separation according to their density, not by their size.
- The impure fraction is placed on the top of a gradient solution, e.g., sucrose solution.
- Another use of cellular fractionation involves the production of a good amount of an enriched source of a protein for further purification and helps in the diagnosis of various diseases.