Question

Explain why NADH and NADPH are almost structurally identical but have distinct metabolic roles?

Answer 1

The difference between NADH and NADPH in terms of their composition and structure is a single phoshphate group. both NADH and NADPH consists of two nucleotides linked by their phosphate groups, where one of the nucleotide contains adenine base and other contains nicotinamide base.

The only difference is that NADPH has phosphate group attached to 2'-carbon while NADH does not.

Both molecules make a huge difference in their functions:

NADH participates in catabolic reactions, that break down molecules to release energy, whereas, NADPH participates in anabolic reactions that consumes energy in order to build up or synthesize large molecules.

NADH is best known for its role in cellular respiration while NADPH is especially important in photosynthesis.