Introduction to Vitamins: Videos & Practice Problems

Because B6 precedes B12 in the discovery timeline, it necessarily participates in earlier metabolic pathways and cannot have similar coenzyme roles as B12 which is restricted to late-life metabolism, making chronological ordering biologically deterministic.

The numeric order reflects discovery chronology and not structural similarity, so B6 and B12 can be chemically and functionally unrelated despite sharing the B designation; students should therefore consult chemical names when comparing function.

The B-numbering system directly encodes chemical formulas such that lower numbers always indicate smaller molecular mass and similar ring structures, meaning students can infer detailed chemistry solely from the vitamin number without additional information.

Vitamin numbers indicate the vitamin's solubility profile (odd numbers for water-soluble and even for fat-soluble), so B6 being an even-numbered B vitamin means it behaves like a fat-soluble vitamin compared with B12, which is odd numbered and therefore water-soluble.