128. The ultimate electron acceptor in the respiration process is molecular oxyg

Question

128. The ultimate electron acceptor in the respiration process is molecular oxygen. Electron transfer through the respiratory chain takes place through a complex series of oxidation- reduction reactions. Some of the electron transport steps use iron-containing proteins called cytochromes. All cytochromes transport electrons by converting the iron in the cytochromes from the +3 to the +2 oxidation state. Consider the following reduction potentials for three different cytochromes used in the transfer process of electrons to oxygen (the potentials have been corrected for pH and for temperature): cytochrome a(Fe3)ecytochrome a(Fe2) cytochrome b(Fe3ecytochrome b(Fe2) cytochrome c(Fe3ecytochrome c(Fe27) 8-0.385 V & 0.030 V 8-0.254 V In the electron transfer series, electrons are transferred from one cytochrome to another. Using this information, determine

Explanation / Answer

ORDERS ARE : CYTOCHROME B, CYTOCHROME C, CYTOCHROME A

FIRST CTY B, THEN CYT C AND CYT A

LOWER IS THE POTENTIAL GREATER IS THE ABILITY TO DONATE ELECTRONS. THEREFORE CYT B HAS LOWER POTENTIAL VALUE HENCE TRANSFER ELECTRONS FROM CYT B TO CYT C. AFTER THEN, CYT C TRANSFER ELECTRON TO A

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