B2.2 Organelles and Compartmentalization

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Organelles

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Specialized structures within a cell that carry out specific functions, such as the mitochondria for cellular respiration or the nucleus for genetic information storage.

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Cell Fractionation

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The process of breaking open cells and then separating the various organelles and cellular components based on their size, shape, and density, typically through a process called differential centrifugation.

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Ultrafiltration

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A process where a liquid is forced through a semipermeable membrane under high pressure, separating solutes based on their size. In biology, this is a key process in the kidney's glomerulus, where blood plasma is filtered to form a filtrate.

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Plasma Membrane

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The semipermeable, flexible boundary that encloses the cytoplasm of a cell, controlling the movement of substances into and out of the cell. It's composed of a phospholipid bilayer with embedded proteins.

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Homogenization

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The process of breaking open cells to release their contents, including organelles, into a solution. This is the first step of cell fractionation.

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Nucleus

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A membrane-bound organelle that contains the cell's genetic material (DNA) organized into chromosomes. It controls the cell's activities and heredity.

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Cytoplasm

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The jelly-like substance enclosed by the cell membrane, but outside the nucleus. It consists of cytosol (the fluid) and the organelles suspended within it.

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Transcription

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The process of synthesizing an RNA molecule (specifically, messenger RNA or mRNA) from a DNA template. This is the first step of gene expression.

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Translation

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The process of synthesizing a polypeptide chain (protein) from the genetic information carried by an mRNA molecule. This occurs on a ribosome.

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Metabolites

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The intermediate and final products of metabolism. They are the small molecules that are reactants, intermediates, and products in a metabolic pathway.