Question

. During dark reaction in plants, CO2 first of all combines with

a) Phosphoenol PO4 (PEP) b) Ribulose 1-PO4 (RMP)

c) Ribulose – 1 – 5 di PO4 (Rubp) d) Phosphoglyceric acid (PGA)​

Answer 1

Explanation:

The carbon-fixing reaction of photosynthesis involves a cyclic series of reactions, often called as the Calvin cycle or C

3

pathway. In carboxylation or fixation, three molecules of CO

2

combine with three molecules of 5C compound called ribulose-1, 5- bisphosphate (RuBP), which is the acceptor molecule of CO

2

, giving rise to an unstable 6- carbon compound. Carboxylation of a molecule of CO

2

to RuBP is catalyzed by the enzyme RuBP carboxylase or Rubisco. The resulting 6C compound is highly unstable. This molecule quickly breaks down to give two molecules of 3-phosphoglycerate (3PG), also called phosphoglyceric acid (PGA).

Answer 2

Answer:

(c)Ribulose -1-5 biphosphate (RuBP)

Explanation: