Questions 94-96 A tissue or cells can be mashed up in a...

Questions $94-96$ A tissue or cells can be mashed up in a blender to form a liquid homogenate and then spun in an ultracentrifuge at high speeds to separate it into layers based on differences in density. The densest cell organelles settle to the bottom of the tube, forming a pellet. The supernatant, the liquid above the pellet, which contains less-dense organelles, can be poured off and respun. In this way, cell organelles can be isolated. A homogenate of human tissue was processed and spun in this way. See the diagram below. Pellet $\mathrm{C}$ was analyzed and found to consist of the highest concentrations of RNA compared with the other pellets. Which organelles did it contain? (A) Ribosomes (B) Mitochondria (C) Vacuoles (D) Golgi (E) Endoplasmic reticulum

Questions $94-96$ A tissue or cells can be mashed up in a blender to form a liquid homogenate and then spun in an ultracentrifuge at high speeds to separate it into layers based on differences in density. The densest cell organelles settle to the bottom of the tube, forming a pellet. The supernatant, the liquid above the pellet, which contains less-dense organelles, can be poured off and respun. In this way, cell organelles can be isolated. A homogenate of human tissue was processed and spun in this way. See the diagram below.
Pellet $\mathrm{C}$ was analyzed and found to consist of the highest concentrations of RNA compared with the other pellets. Which organelles did it contain?
(A) Ribosomes
(B) Mitochondria
(C) Vacuoles
(D) Golgi
(E) Endoplasmic reticulum

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Key Concepts

Differential Centrifugation

Differential centrifugation is a laboratory technique used to separate cellular components by spinning a homogenized tissue sample at various speeds. Each organelle separates based on its size and density, allowing for the isolation of distinct cellular fractions.

Density-Based Separation

Density-based separation in centrifugation relies on the principle that cellular components settle at different rates according to their density. This technique creates layers in the centrifuge tube, with denser components forming pellets while less dense ones remain in the supernatant.

Ribosomes

Ribosomes are small complexes made up largely of RNA and protein. Their high RNA content makes them prominent in centrifugation fractions where RNA concentration is a key indicator, as they are crucial for protein synthesis.

Cell Fractionation

Cell fractionation is the broader process of disrupting cells and separating their organelles. This technique, often achieved through differential centrifugation, enables researchers to study the structure and function of individual cellular components.

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