Most eukaryotic cells have mitochondria, which produce ATP from products of the citric acid cycle, fatty acid oxidation, and amino acid oxidation. At the mitochondrial inner membrane, electrons from NADH and succinate pass through the electron transport chain to oxygen, which is reduced to water.
The maximum diameter of the lens opening is referred to as its maximum aperture or minimum f-number. The minimum f-number is the smallest f-number that can be selected with the lens. The maximum aperture varies from lens to lens and is included in the lens model name.
In photography and digital photography, aperture is the unit of measurement that defines the size of the opening in the lens that can be adjusted to control the amount of light reaching the film or digital sensor. The size of the aperture is measured in F-stop. See also shutter speed.