One-carbon metabolism — Flashcards

Flashcard 1: Vitamin B12 deficiency is characterized by _____ serum methylmalonic acid

Answer: increased

Flashcard 2: S-adenosylmethionine (SAM) donates a CH3 group to anabolic pathways, forming _____

Answer: S-adenosylhomocysteine

Flashcard 3: Tetrahydrofolate (THF) serves as a 1-_____ carrier

Answer: carbon

Flashcard 4: What enzyme converts DHF back to THF?_____

Answer: Dihydrofolate reductase

Flashcard 5: Cystathionine synthase (CBS) deficiency results in high _____ levels, increasing risk for thrombosis

Answer: homocysteine

Flashcard 6: Vitamin B7 (biotin) is a cofactor for the enzyme _____ (propionyl CoA metabolism)

Answer: propionyl-CoA carboxylase

Flashcard 7: What stainable protein is abundant in astrocytes?

Answer: GFAP

Flashcard 8: What enzyme converts pyruvate to alanine?

Answer: alanine aminotransferase (ALT)

Flashcard 9: Role of myeloperoxidase in neutrophils:

Answer: Plays a role in respiratory burst (catalyzes formation of HOCl from H2O2)

Extra: Myeloperoxidase (MPO) is found in the azurophilic granules of neutrophils (PMNs). During the respiratory burst, it converts Hydrogen Peroxide (H2O2) and Chloride ions into Hypochlorous acid (HOCl - bleach), which is a potent bactericidal agent.

Flashcard 10: What reaction is catalyzed by superoxide dismutase during the respiratory burst?

Answer: Conversion of Superoxide ($O_2^-$) to Hydrogen peroxide ($H_2O_2$)

Extra: Superoxide dismutase (SOD) neutralizes superoxide radicals. Reaction: 2O2- + 2H+ -> H2O2 + O2. Clinical Pearl: Mutations in superoxide dismutase 1 (SOD1) are associated with Amyotrophic Lateral Sclerosis (ALS).