Question

A piece of liver tissue is homogenized in a laboratory and the homogenate is subjected to sequential centrifugation at increasing speeds (expressed in xg). Centrifugation is used to separate sub-cellular components based on size and density. The steps carried out in the experiment are shown.
Sediments $1,2$ and $3$ would most likely contain.

• A. $1$: Nuclei, $2$: Ribosomes, $3$: Mitochondria
• B. $1$: Nuclei, $2$: Mitochondria, $3$: Lysosomes
• C. $1$: Lysosomes, $2$: Mitochondria, $3$: Nuclei
• D. $1$: Ribosomes, $2$: Nuclei, $3$: Mitochondria

Answer 1

The correct option is B $1$: Nuclei, $2$: Mitochondria, $3$: Lysosomes

Centrifugation is used to separate sub-cellular components based on size and density. The greater the density, the faster it move. Differential centrifugation applies different speed in order to separate different sub-cellular component from the homogenate. When a homogenized liver tissue is centrifuged at 500 xg, the heaviest sub-cellular components will settle first, that is nuclei. When the supernatant is again centrifuged at 10000 xg, the second heavier sub-cellular component will settle, that is mitochondria. When the supernatant is centrifuged at very high speed of 25000 xg, the lightest sub-cellular component will settle, that is lysosomes.

Thus, the correct answer is option B.