Question
Question: Synthesis of each molecule of glucose in photosynthesis involves: a) 10 molecules of ATP b) 8 mo...
Synthesis of each molecule of glucose in photosynthesis involves:
a) 10 molecules of ATP
b) 8 molecules of ATP
c) 6 molecules of ATP
d) 18 molecules of ATP
Solution
The formation of glucose occurs in the chlorophyll of chloroplast by the Calvin cycle this cycle rotates 6 times to produce one molecule of glucose. And in each cycle, it required 3ATP and 2 NADPH molecules.
Complete answer:
The formation of glucose occurs in chlorophyll by the Calvin cycle, there are 3 steps in this cycle:
1-Carbon fixation
2-Reduction
3-Regeneration
- In the carbon fixation step, CO2 reacts with RuBISCO (an enzyme) and forms 2 molecules of 3-PGA (3-phosphoglycerate), in this step 2 molecules of ATP are used.
- In the next step reduction, 2 molecules of NADPH are used and form Glyceraldehyde 3-phosphate which ultimately forms glucose.
- In the next step i.e. regeneration, the enzyme which catalyzes the reaction is regenerated and this step uses 1 ATP molecule.
- As we know that for the formation of one molecule of glucose this cycle repeats 6 times and the required amount of ATP is 18 (i.e, 6×3).
The chemical reaction that takes place during photosynthesis is given below:
6CO2+6H2O→ C6H12O6 + 6O2+18ATP + 12NADPH
Hence, the correct option is (d) 18 molecules of ATP.
Note: Photosynthesis involves 2 parts, light reaction, and dark reaction. During light reaction, 18 molecules of ATP formation take place which will be used during the dark reaction to prepare glucose molecules.