Biology Times (^19)
March
m 5 types of Cytochromes are involved- a, a 3 , b, c, c 1
Cyt.a, a 3 , b and c 1 are integral protein and Cyt.c is peripheral protein
Table: Comparison between Respiratory complexes of ETS
Mechanism of Electron transport
Each NADH molecule transfers its hydride ion (H+) to FMN of complex I. The electrons are carried
finally to cyt a-a 3 in the sequence.
NADH FMN Fe-S UQ cyt b Fe-S cyt C 1 cyt C cyt a-a 3
FADH 2 by passes FMN and transfer its electrons directly to UQ and finally to cyt a-a 3 in the sequence
FADH 2 UQ cyt b Fe-S cytC 1 cyt C cyt a-a 3
Terminal oxidations involves Complex IV i.e., the cytochrome oxidase. It has two cytochromes a and a 3
containing copper (Cu2+). The a-a 3 complex brings together two electrons (2e-) , two protons ( 2H+) and
one atom of oxygen 1/2O 2 to produce a molecule of water. In this process oxygen becomes the terminal
acceptor, and the process is terminal oxidation. This is the place where cells actually use oxygen.