OXIDATIVE PHOSPHORYLATION
Introduction. Oxidative phosphorylation is a process in which ATP is synthesized coupled to electron transport.
In the respiratory chain the protons are pumped out against a gradient, acidifying the external environment. These will return to the matrix by means of a transport in favor of a gradient, through a transmembrane channel present in the mitochondrial membrane that receives the name of FOF1ATPase or complex V. The return of the protons makes the enzyme complex rotate so that energy is produced , used to synthesize ATP.
For every molecule of NADH that passes into the intermembrane space, 10 protons return, releasing 2.5 molecules of ATP. According to this, one ATP molecule is obtained for every 4 protons, although in reality only three protons are needed to synthesize one ATP molecule
ESPACIO
INTERMEMBRANA
NAD
H.0
MATRIZ
Complex V. It is the enzyme complex of FOF1ATPase, which has been studied for many years. In about 1940 it was known that ATP synthesis took place in the mitochondria. Around 1950, Ochoa, Cori and Lehninger, studying mitochondria, came to the conclusion that this ATP synthesis was coupled to electron transport, taking the name of oxidative phosphorylation.
A series of dehydrogenases are acting in the mitochondria that form reduced coenzymes such as NADH and FADH2, whose reducing potential is going to be used for the synthesis of ATP.
This complex (F0F1ATPase) was studied by Racker in the early 1960s. In the laboratory, they treated the mitochondria with sonation, obtaining small membrane vesicles formed from the inner mitochondrial membrane, which carried out the synthesis of ATP coupled to electron transfer.
1
VESiCULAS EVERTiDAS (Dadas ta vvelta) DiAU'StS
F1
FL
DESNATURAUtALION COUTRiPRNA OURCA
Tronsporte de echrones Fosg.0Yd
eteckonos Fagontaaia ondahva
In this way, it was observed that ATP synthase, also called complex V, has two different components: F1, a peripheral membrane protein, and Fo, which is an integral membrane protein. In this way, an area facing the matrix is obtained, which corresponds to the head (F1); and an intermembrane zone, called the stem (Fo).
It is considered that F1 is where ATP is synthesized, with F0
being an interconnection zone. The combination of both forms the V complex that performs oxidative phosphorylation and electron transport.
This large enzyme complex of the inner mitochondrial membrane catalyzes the formation of ATP from ADP and Pi accompanied by the flow of protons from the positive to the negative side of the membrane.
Experiments carried out in the laboratory show that the activity of oxidative phosphorylation resides in F1, since if complex V is treated with trypsin it is observed that F1 has been eliminated (while part of the F0 is conserved) and it is observed that performs electron transport but not oxidative phosphorylation.
If we then do a dialysis to eliminate the denaturing agent we can return to the previous situation, being able to have both oxidative phosphorylation and electron transport. When we do the sonication, the vesicles are turned over, we say that they are everted vesicles.
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