Question

How can organelles be separated from cell homogenate?

Answer 1

Hint: Cell homogenate is the inside constituents of the cell which is obtained by disrupting the cell wall using different molecular methods (mechanical or chemical). The cell homogenate contains various cell organelles including nucleus, cytoplasm, mitochondria, ribosomes, chloroplasts etc. Separation and analysis of cell homogenate is a great technique to learn more about cells and to understand how cells work in healthy and diseased states.

Complete explanation:
The separation of cell organelles from its homogenate is done by a biotechnological device called centrifuge. A centrifuge is a device which uses centrifugal force to separate various components of a fluid. The device contains a metal rotor, a motor to spin the rotor at high speed and cylindrical holes to accommodate the sample tubes. During centrifugation each component of the samples settles down according to its size and shape.
To obtain the cell organelles, first the filtered cell homogenate will be centrifuged in a series of steps at different speeds. After each series of centrifugation, a pellet and a supernatant will be obtained.
Pellet is the solid part that gets sedimented in the bottom. It contains the separated organelle from that step. The supernatant is the liquid lying on top of the pellet which contains the unseparated organelles of the cell. During each step the supernatant should be removed to a fresh tube for further centrifugation. This step should be done until there are no more organelles to separate.
At low speed (\[600\]g for \[10\] minutes) nuclear fraction will sediment, at medium speed (\[15,000\]g for \[5\] minutes) mitochondria fraction sediment and at high speed (\[80,000\]g for \[5\] minutes) microsomal fraction sediment. The final supernatant will be just cytosol.

Note:
There are many types of centrifuge present. They are classified based on the intended use or rotor design. Based on the rotor design, different types of centrifuge are Fixed-angle centrifuge, Swinging-head centrifuge, Continuous tubular centrifuge etc. Based on the intended use they are classified as Laboratory centrifuge, Analytical centrifuge, Haematocrit centrifuge, Gas centrifuge, Industrial centrifuge etc.