FADH2 enters at which complex in ETC -
Ans. is 'b' i.e., II o FADH2 enters at complex II, therefore, generates only 1[?]5 molecules of ATP (1 ATP production is bypassed at complex I).o NADH enters at complex I and generates 2[?]5 molecules of ATP.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 phosphorylationo There are three ATP synthesizing sites of electron transport chain:i) Site I is between NAD and CoQ, i.e., Complex Iii) Site II is between CoQ and cytochrome C, i.e., Complex IIIiii) Site III is between cytochrome C and oxygen, i.e., Complex IV.o These sites provide energy required to make ATP from ADP by an enzyme F0F1 ATPase.There is no ATP formation at complex 11.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 1/2 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 I 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.
I
II
III
IV
Respiratory Chain