cellfractionation

Cell fractionation is a laboratory technique used to separate cellular components based on their physical and chemical properties. This process is crucial for studying the function and composition of individual organelles, such as the nucleus, mitochondria, endoplasmic reticulum, and ribosomes.

The first step in cell fractionation typically involves disrupting the cell membrane to release the intracellular contents. This can be achieved through various methods, including mechanical homogenization, sonication, or osmotic lysis. Once the cells are broken open, a suspension of cellular components is obtained, known as a homogenate.

Following homogenization, the homogenate is subjected to differential centrifugation. This technique utilizes a centrifuge to spin the homogenate at increasing speeds. Heavier and larger cellular components, such as the nucleus, will sediment at lower speeds and can be collected as a pellet. Components of intermediate size and density, like mitochondria and lysosomes, will sediment at higher speeds. Finally, smaller components, such as ribosomes and soluble proteins, remain in the supernatant even at the highest centrifugation speeds.

Further purification of specific organelles can be achieved through density gradient centrifugation. In this method, the homogenate is layered on top of a density gradient medium. Centrifugation separates the components based on their buoyant density, allowing for a more refined isolation of specific cellular structures.

The isolated cellular fractions can then be analyzed using various biochemical and molecular techniques to study their enzymatic activities, protein content, or nucleic acid composition. This information contributes significantly to understanding cellular processes and the roles of individual organelles.