Question

Anabolism needs ATP, NADPH and Precursor Metabolites. Describe why each is needed.

Answer 1

Metabolism involves two kinds of reactions.

i. Anabolism = Biosynthesis

ii. Catabolism = Degradation

Anabolic reactions refer to biosynthetic reactions.

Ex: Photosynthesis

They involve the synthesis of macromolecules such as polysaccharides and proteins from their small precursor molecules.

The small precursor metabolites are the starting materials (reactants) in an anabolic reaction.

Ex: CO₂ and H₂O are the reactants in the photosynthetic pathway.

Anabolic reactions are endergonic in nature. They need energy for their completion. Hence, these reactions are driven in the cell by coupling them with ATP hydrolysis.

Most of the anabolic reactions are also reducing reactions. Protons needed for the reduction of precursor molecules are provided by NADPH.

For the production of one glucose molecule by C3 cycle, 12 NADPH and 18 ATP molecules are used.