Question

If you expose a photosynthesizing plant to water that contains both radioactive H and radioactive O, in which of the products of photosynthesis will the radioactive H and O show up?
A) H and O both in glucose
B) H in glucose; O in glucose
C) H in water; O in glucose
D) H in glucose and water; O in O2
E) H in glucose and water; O in water and O2

Answer 1

Answer:

D) H in glucose and water; O in O2

Explanation:

In green photosynthesizing plants, photolysis occurs during the light-dependent phase. Photolysis is the splitting of the water molecule in the presence of sunlight. The oxygen atom of water molecules forms oxygen gas that is released as a by-product of photosynthesis. Photolysis also releases electrons and protons from water molecules that finally reduce the NADP into NADPH.

The light-independent phase of photosynthesis fixes reduces CO2 into glucose. NADPH serves as reducing power during the light-independent chemical reactions and therefore, the H atoms from water molecules are incorporated into glucose and water molecules formed during light-independent reactions of photosynthesis.