Question

question 38 (7 points) identify the labelled structures (a to g) in the diagram of the three cycles of the light independent reactions of photosynthesis. include the number of molecules for a, b, c, e and f only. carbons are shown as red balls. fixation of carbon dioxide regeneration of rubp from g3p reduction of 3 - phosphoglycerate to g3p 1 g3p glucose (2 g3p molecules) question 38 options:

Explanation:

Step1: Identify A

A is carbon - dioxide. In the Calvin cycle, 6 molecules of carbon - dioxide are used for every 1 glucose molecule produced. So, the number of A (CO₂) molecules is 6.

Step2: Identify B

B is ATP. During the reduction phase of the Calvin cycle, 18 ATP are used for every 6 CO₂ molecules fixed to produce 1 glucose. For each turn of the cycle (fixing 1 CO₂), 3 ATP are used. But since we are considering the overall cycle for glucose production, the number of B (ATP) molecules for 6 CO₂ is 18.

Step3: Identify C

C is NADPH. During the reduction phase of the Calvin cycle, 12 NADPH are used for every 6 CO₂ molecules fixed to produce 1 glucose. For each turn of the cycle (fixing 1 CO₂), 2 NADPH are used. So, for 6 CO₂, the number of C (NADPH) molecules is 12.

Step4: Identify E

E is ribulose - 1,5 - bisphosphate (RuBP). At the start of the Calvin cycle, 5 molecules of RuBP are regenerated for every 6 molecules of 3 - phosphoglycerate formed from 6 CO₂. But considering the continuous cycle, for every 6 CO₂ that enter the cycle, 5 molecules of RuBP are regenerated and 1 new RuBP is added to continue the cycle. Overall, for the production of 1 glucose (6 CO₂ fixed), 5 molecules of RuBP are used in the regeneration step and 1 is added, so the number of E (RuBP) molecules is 5.

Step5: Identify F

F is ADP + Pi. As ATP is used in the Calvin cycle to provide energy for reactions, it is hydrolyzed into ADP and Pi. Since 18 ATP are used for the production of 1 glucose (from 6 CO₂), the number of F (ADP + Pi) molecules is 18.

Answer:

A: 6 molecules of carbon - dioxide
B: 18 molecules of ATP
C: 12 molecules of NADPH
E: 5 molecules of RuBP
F: 18 molecules of ADP + Pi