Which complex of ETC is not associated with liberation of energy –
Correct Answer: ComplexII
Description: Ans. is 'b' i.e., Complex II o During the transfer of electrons through the ETC, energy is produced. This energy is coupled to the formation of ATP molecules by phosphorylation of ADP by an enzyme F0F1, ATPase. The phosphorylation of ADP into ATP is coupled with oxidation of reducing equivalents, therefore the process is called oxidative phosphorylation,o There are three ATP synthesizing sites of electron transport chain : (i) Site I is between NAD and CoQ. i.e., Complex I; (ii) Site II is between CoQ and cytochrome C, i.e., Complex III; and (iii) Site III is between cytochrome C and oxygen, i.e., complex IV. These sites provide energy required to make ATP from ADP by an enzyme F0F1 ATPase.o The energy liberated of site I (complex I) is used to synthesize 1 ATP molecule, at site II (complex III) is used to synthesize 1 ATP molecule and at site III (Complex IV) is used to synthesize Vi ATP molecule. Thus, when 1 NADH molecule enters the respiratory chain, it produce 2.5 molecules of ATP. When 1 molecule of FADH2 enters the respiratory chain only 1.5 molecules of ATP are produced as site 1 of energy liberation is bypassed.Note : Previously it was assumed the NADH produces 3 ATPs and FAD generates 2 ATPs. Recent experiments show that these old values are overestimates and NADH produces 2.5 ATPs and FADH2 produces 1.5 ATPs.
Category:
Biochemistry
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