Biochemistry free online lectures for medical students by Biochemistry Club
Riboflavin (Vitamin B2)
- Riboflavin was the first B complex component to be isolated in a pure state.
- This vitamin is synthesized by green plants and microorganisms.
Structure of Riboflavin
- Riboflavin has a dimethyl isoalloxazine ring to which a ribitol is attached.
- Ribitol is the alcohol of ribose sugar.
- Riboflavin is converted to its active co-enzyme forms (FMN and FAD) with the help of ATP.
- Riboflavin is heat stable.
Co-enzyme Activity of Riboflavin
- Riboflavin exists in tissues tightly bound (but not covalently) with enzymes.
- Enzymes containing Riboflavin are called Flavoproteins.
- The two co-enzymes are FMN (Flavin mono nucleotide) and FAD (Flavin adenine dinucleotide).
- During the oxidation process, FAD accepts two hydrogen atoms from substrate.
- In turn, FAD is reduced to FADH2.
- The two nitrogen atoms of isoalloxazine nucleus accept the hydrogen atoms.
- During the amino acid oxidation, FMN is reduced.
- It is re-oxidized by molecular oxygen to produce hydrogen peroxide.
- In the respiratory chain, the NADH dehydrogenase contains FMN.
- The electrons are transported in the following manner:
NAD+ →FMN→ CoQ
- FADH2 when oxidized in the electron transport chain will generate 1.5 ATP molecules.
- Succinate to fumarate by succinate. dehydrogenase
- Acyl CoA to alpha-beta unsaturated acyl CoA by acyl CoA dehydrogenase.
- Xanthine to uric acid by xanthine oxidase.
- Pyruvate to acetyl CoA by pyruvate dehydrogenase.
- Alpha ketoglutarate to succinyl CoA by alpha ketoglutarate dehydrogenase.
For Complete lesson, please visit Vitamins in “Biochemistry I” from the home page