U01.01.075 Vitamin B2

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Learning Objectives

Identify FAD and FMN as the active coenzyme forms of Riboflavin. Explain the role of B2 in redox reactions, specifically within the TCA cycle. Recognize the “2 C’s” of Vitamin B2 deficiency: Cheilosis and Corneal vascularization.

1. Biochemical Function

Vitamin B2 (Riboflavin) is essential for the formation of flavoproteins. It serves as a precursor for two major cofactors involved in oxidation-reduction (redox) reactions.

  • FAD (Flavin Adenine Dinucleotide): A critical cofactor for Succinate Dehydrogenase, which converts succinate to fumarate in the TCA cycle.
  • FMN (Flavin Mononucleotide): A component of Complex I in the electron transport chain.
High-Yield Hook: FAD and FMN are derived from riboFlavin. (B2 yields ~ 2 ATP in the electron transport chain).

Activity

2. Deficiency (Ariboflavinosis)

Deficiency is relatively rare in isolation and often occurs alongside other B-complex deficiencies. It primarily affects the mucosal surfaces and the eyes.

Symptom Clinical Description
Cheilosis Inflammation of the lips, scaling, and painful fissures at the corners of the mouth (angular stomatitis).
Corneal Vascularization Abnormal growth of blood vessels into the clear cornea.
“Magenta” Tongue Glossitis is characterized by a distinct purplish-red discoloration.
Mnemonic: The 2 C’s of B2 deficiency = Cheilosis and Corneal vascularization.

 

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