| 'A' is an inhibitor of chloroplast function. The Production of \[{{o}_{2}}\] and the synthesis of ATP are measured in illuminated chloroplasts before and after addition of' A' as shown below. |
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| Which statement is correct? |
A) 'A' inhibits the reduction of \[NAD{{P}^{+}}\]
B) 'A' inhibits the proton gradient and the reduction of \[NAD{{P}^{+}}\]
C) 'A' inhibits the proton gradient but not the reduction of \[NAD{{P}^{+}}\]
D) 'A' inhibits neither the proton gradient nor the reduction of \[NAD{{P}^{+}}\]
Correct Answer: C
Solution :
The production of oxygen remained unaffected by the addition of 'A' in illuminated chloroplasts as no change is observed from the graph after its addition in the illuminated chloroplast. In contrast, ATP synthesis decreased after addition of 'A'. Since ATP is synthesised by ATP synthase from adenosine diphosphate and inorganic phosphate using a proton gradient created in the thylakoid lumen, ?A? affects ATP synthesis by inhibiting establishment of proton gradient. Also, reduction \[{{\operatorname{NADP}}^{+}}\]into NADPH occurs towards the stromal side of the thylakoid membrane by using high-energy electrons released from PS I thus ?A? does not inhibit this step.
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