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What is found in the mitochondrial matrix?

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Fluorescent confocal image of HeLa cells with green microtubules outlining cell shapes, red mitochondria, and blue nuclei. — mitochondrion Mitochondria (red) are found throughout the cytoplasm of almost all eukaryotic cells (cell nucleus is shown in blue; cytoskeleton is shown in yellow).

The mitochondrial matrix is the space enclosed by the inner membrane of the mitochondrion. It is filled with a fluid containing a rich mixture of enzymes, metabolic products, and ions.1

Within this matrix, several critical biological processes occur:

Metabolic Reactions: The matrix hosts the series of reactions that convert products from the initial metabolism of sugars, amino acids, and fats into acetyl coenzyme A.2
Tricarboxylic Acid Cycle: The TCA cycle (also known as the Krebs or citric acid cycle) takes place here, where the acetate portion of acetyl coenzyme A is oxidized, producing carbon dioxide and reducing coenzymes like NAD+ and FAD into NADH and FADH2.2
Genetic Material and Protein Synthesis: The matrix contains DNA, which is circular and lacks histones, as well as ribosomes used for synthesizing specific mitochondrial proteins.3