Crista

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Cristae are folds of the inner membrane of a mitochondrion. Their name comes from Latin for crest, and these wrinkles give the membrane more surface area to work with. This extra area helps the mitochondrion produce energy.

Cristae are studded with important proteins, including ATP synthase and various cytochromes. They are connected to the inner membrane by crista junctions, and other proteins (like MICOS and OPA1) help organize and remodel these folds.

Cristae come in different shapes and can be lamellar (flat sheets), tubular (tube-like), or vesicular (sac-like). Different cell types have different crista shapes, and scientists are still learning why.

In the inner membrane, the electron transport chain transfers electrons from NADH and FADH2. As electrons move through the chain, protons are pumped into the space between the membranes, creating a proton gradient. ATP synthase uses this gradient (chemiosmosis) to make ATP from ADP and phosphate, and oxygen accepts electrons at the end of the chain to form water.

Because of their large surface area and organized protein complexes, cristae help mitochondria generate a lot of ATP during aerobic respiration—roughly 30–34 ATP per glucose, far more than glycolysis alone.