More general aspects of the thermodynamics of transport are covered here. Ionophores, and transport of ions and metabolites by mitochondria Early evidence for the chemiosmotic hypothesis came from studies of ion transport by mitochondria. When phosphate is also present, a net uptake of calcium phosphate occurs, which precipitates inside the mitochondria as hydroxyapatite, visible as dense granules in electron micrographs. If a weakly acid anion like acetate is present in the suspending medium, calcium acetate is accumulated, and the mitochondria swell osmotically because of the increased soluble salt inside. Metabolite transport .
Mitochondria have diverse metabolic functions, which vary from tissue to tissue.
In liver mitochondria, a wide variety of externally added substrates can be processed by the mitochondrial metabolic machinery. The enzymes are predominantly in the matrix, requiring that substrates be transported across the mitochondrial inner membrane. The transport is catalysed by a superfamily of proteins, which show strong sequence homology across the whole spectrum of the eukaryote world, but no obvious prokaryote precursor. Transport of metabolites will be covered in greater detail later. Ion transport catalysed by ionophores .