Mitochondrion
Say it: my-tuh-KON-dree-un
A mitochondrion is a double-membraned organelle that makes most of a eukaryotic cell's ATP by breaking down fuel molecules with oxygen.
Also: mitochondria
Definition
What is a mitochondrion?
A mitochondrion is an organelle found in the cytoplasm of most eukaryotic cells, where it carries out the oxygen-using stages of cellular respiration. It has two membranes: a smooth outer one and a heavily folded inner one, whose folds, called cristae, greatly increase its surface area. The fluid-filled space inside the inner membrane is the matrix.
Enzymes in the matrix run the citric acid cycle, while proteins in the inner membrane form the electron transport chain and ATP synthase. Together they produce most of the cell's ATP through oxidative phosphorylation, which is why mitochondria are often called the powerhouses of the cell. Cells that use a lot of energy, such as muscle cells, contain especially many, and a typical body cell has hundreds to thousands.
Mitochondria carry their own small genome, which in humans is about 16,500 base pairs long with 37 genes, and their own ribosomes. These bacteria-like features support the endosymbiotic theory that mitochondria descend from aerobic bacteria taken in by an ancestral cell. In humans, mitochondrial DNA is usually inherited only from the mother.
Word parts
Where does the word “mitochondrion” come from?
- mito-
- threadGreek mitos
- chondr-
- grain, granuleGreek khondrion
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Terms that go with it
- ATPATP (adenosine triphosphate) is the molecule cells use as their main short-term energy carrier, releasing energy when a phosphate group is removed.
- Oxidative phosphorylationOxidative phosphorylation is how cells make most of their ATP, using a proton gradient built by the electron transport chain to drive ATP synthase.
- Electron transport chainThe electron transport chain is a series of membrane proteins that pass electrons to oxygen and use the energy released to pump protons.
- Citric acid cycleThe citric acid cycle is a loop of reactions in mitochondria that breaks down acetyl groups to carbon dioxide, capturing energy as NADH and FADH2.
- OrganelleAn organelle is a specialized structure inside a cell, usually wrapped in its own membrane, that carries out a particular job for the cell.
- ChloroplastA chloroplast is the green organelle in plant and algal cells that captures light energy and uses it to make sugars by photosynthesis.
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Checked against
Written for biofideX in plain words, after checking these references:
- OpenStax Biology 2e, 4.3 Eukaryotic Cells
- NHGRI Talking Glossary: Mitochondria
- MedlinePlus Genetics: Mitochondrial DNA
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