Question

If a biochemical analysis of mitochondria has to be done, the best procedure would be
A. Select cells which have a larger number of mitochondria
B. Plasmolyse the cell and filter out the mixture and take the debris
C. Grind the cells and filter out the mixture and take the debris
D. Subject the cell to cell fractionation (centrifuge) and obtain mitochondria

Answer 1

To perform biochemical analysis, the structural integrity of cell organelles should be maintained. By plasmolysis and grinding, the organelles would lose their functional abilities and analysis would not be possible.
So, to conduct a biochemical analysis, the method employed should not degrade the cell organelles. The best method would be the one in which all the organelles can separate out in a differential manner without a loss in function and structure.

Complete answer:
If a biochemical analysis of mitochondria has to be done, the best procedure would be to subject the cell to cell fractionation (centrifuge) and obtain mitochondria. Cell fractionation is a method by which the cellular components are separated while preserving their functions.
Steps of Cellular Fractionation:

Homogenization: The tissue is suspended in an isotonic buffer solution. Homogenization is done by grinding, inducing pressure changes, sonication, and osmotic shock. This leads to the formation of a homogenous mass of cells.

Filtration: This is an optional step and depends on the source of tissue/cells. However, in animal cells, the connective tissue must be removed before the analysis. It is done using either gauze or a suction filter.

Purification: It is done by differential centrifugation. In differential centrifugation, the cellular components like cell organelles are separated by different sedimentation rates.

Hence, the correct answer is option (D).

Note: Initially, the cell debris, fractional organelles, and cytoplasm are removed by centrifugation. Once the nuclei have been sedimented (after centrifuging at a high speed), the supernatant can be centrifuged at a slow speed to separate small organelles like mitochondria.