Oxidative phosphorylation

Oxidative phosphorylation is a biological process that occurs in all aerobic organisms. It is part of the energy metabolism and is used for energy in the form of ATP. The energy required for the production of ATP is thereby obtained by means of the respiratory chain and implemented using the chemiosmotic coupling into chemical energy. It brings together more transport proteins.

Enzymes involved

Respiratory chain

Complex V

FoF1 -ATP synthase. Of complex V, finally synthesized ATP, consists of two parts: the F1 part protrudes into the matrix of mitochondria during the Fo - part forms a proton- channel through the inner mitochondrial membrane. With the help of the above -connected four complexes of the respiratory chain, an electrochemical proton gradient is established. According to the laws of thermodynamics is thus towards a driving force of protons in the intermembrane space to the matrix of the mitochondrion. The appropriate channel, the Fo - subunit dar. Similar to a turbine - and indeed could be a rotation of the part are detected Fo - generated by the proton flux energy which is used for the synthesis of ATP by the F1 subunit. (see mechanism of the ATP synthase )

Controversial is the question how many protons required for the synthesis of a molecule ATP from ADP and inorganic phosphate. After Löffler, Petrides: at least three, with in accounting, another proton ( ie a total of at least four) comes up, that was for the transport of phosphate required ( by phosphate / H symport ) in the matrix space.

Depending on, consists of as many C- subunits of the transmembrane ring (Fo C-ring ), a different number of protons to be transported by Fo in the matrix. It may be 10-14 subunits. F1 forms per 120 ° rotation of the gamma unit 1 molecule of ATP - ie when one complete rotation ( 360 °) 3 molecules of ATP. The required number of protons for the formation of an ATP molecule is n = 4 proton for the ATP synthase from E. coli or chloroplast.

Transport proteins

ATP / ADP translocase

The ATP generated by complex V can not pass freely through the inner Mitochondriummembran. Conversely, can not diffuse from the cytosol into the matrix required for the ATP synthase, ADP. However, there is a special transport system to bring ATP in the cytosol and ADP into the matrix, called the ATP / ADP translocase ( see there).

The translocase is a common protein of the inner membrane of the mitochondrion and can constitute up to 14% of all proteins of the inner membrane. Consequently, it is unlikely that the ATP synthesis due to lack of ADP is limited.

Phosphate transporter

For the synthesis of ATP from ADP and phosphate is required. This can be as little diffuse through the inner membrane of the mitochondrion such as ATP and ADP. The transport is possible by a special symporter, the mitochondrial phosphate transporter that is simultaneously a proton and a phosphate molecule from the intermembrane space into the matrix. Its activity can be inhibited by mersalyl.