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Which compound is a metabolic intermediate of the light-independent reactions in photosynthesis?

A. ATP
B. PGA
C. RuBP
D. NADPH

Answer :

Final answer:

The metabolic intermediate of the light-independent reactions in photosynthesis is PGA (3-phosphoglycerate). While ATP and NADPH provide the necessary energy and reducing power, RuBP is also essential but does not serve as a metabolic intermediate. PGA is formed during the Calvin cycle and is subsequently converted into G3P.


Explanation:

Metabolic Intermediates in Light-Independent Reactions

The light-independent reactions of photosynthesis, commonly known as the Calvin cycle, utilize various metabolic intermediates. Among the options listed: ATP and NADPH are products from the light-dependent reactions and are crucial for the energy and reducing power required in the Calvin cycle.

However, the compound that serves as a direct metabolic intermediate during the light-independent reactions is PGA (3-phosphoglycerate). This compound is formed during the initial phase of the Calvin cycle when carbon dioxide is fixed. Subsequently, PGA is converted into glyceraldehyde-3-phosphate (G3P) with the help of ATP and NADPH.

On the other hand, RuBP (ribulose bisphosphate) is another important molecule that must continuously enter the cycle, but it is not a metabolic intermediate; instead, it is a reactant that regenerates.

Key Points:

  1. PGA is a crucial metabolic intermediate in the Calvin cycle.
  2. ATP and NADPH are utilized in the conversion of PGA to G3P.
  3. RuBP is essential for the cycle but is not a product formed during the reactions.

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