Five Vitamins, Five Coenzyme Forms, Five Reaction Classes | Visual AI Learning Guide

Look at the five rows. Each row is one vitamin, and the middle column is what the body actually uses: the coenzyme form. Thiamine becomes TPP, which handles decarboxylation. Riboflavin becomes FAD and FMN, which move electrons. Niacin becomes NAD and NADP, which carry hydride. Pantothenate becomes part of coenzyme A, which carries acyl groups. Biotin is the carboxylation coenzyme. The right-hand column names the reaction class each one enables. Notice that no two rows share a reaction class — that is why each deficiency blocks a different step.

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Energy-yielding metabolism depends on a small set of recurring reaction types: decarboxylation, redox transfer, acyl transfer, and carboxylation. Each of the five B vitamins supplies one coenzyme that makes one of these reaction types possible.

Thiamine is converted to thiamine pyrophosphate (TPP), the coenzyme for decarboxylation — the removal of a carboxyl group as carbon dioxide — and for the transketolase reactions of the pentose phosphate pathway. Riboflavin becomes flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN), which accept and donate electrons in redox reactions. Niacin becomes nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP), which carry hydride ions (a proton plus two electrons) in dehydrogenase reactions. Pantothenate is part of coenzyme A, which carries acyl groups and delivers acetyl groups to the citric acid cycle. Biotin is the coenzyme for carboxylation, attaching carbon dioxide to a substrate.

The pattern is one vitamin, one coenzyme form, one reaction class. That mapping is what allows a deficiency of any single vitamin to block a specific step rather than shutting down metabolism indiscriminately.