2003 AIPMT Photosynthesis in Higher PlantsPhotophosphorylation Easy Question 77 of 91 in Photosynthesis in Higher Plants

Which one of the following concerns photophosphorylation : -

A $ADP + AMP \xrightarrow{light\ energy} ATP$
B $ADP + \text{inorganic } PO_4 \xrightarrow{light\ energy} ATP$
C $ADP + \text{inorganic } PO_4 \rightarrow ATP$
D $AMP + \text{inorganic } PO_4 \xrightarrow{light\ energy} ATP$

The answer is B.

Solution

Photophosphorylation is the synthesis of ATP from ADP and inorganic phosphate in chloroplasts, using the energy of light.
Light drives electron transport in the thylakoid membrane, which builds a proton gradient; ATP synthase uses this gradient to make ATP (chemiosmosis):
$ADP + P_i \xrightarrow{light\ energy} ATP$
The same reaction without light refers to oxidative or substrate-level phosphorylation. AMP is not the substrate of photophosphorylation.
So photophosphorylation is $ADP$ + inorganic $PO_4$ $\xrightarrow{light\ energy}$ ATP.

Concept ATP synthesis using light energy

Photosynthesis in Higher Plants in past papers

91 questions from this chapter have appeared across 26 exam years.