Vitamins II

Question 1

Thiamine (B₁)

What is its function?

What are clinical consequences of deficiency?

Answer 1

Function:
Cofactor for pyruvate and alpha-KG dehydrogenase

Beriberi: high output heart failure (wet beriberi) and peripheral neuropathy (dry beriberi)

Wernicke-Korsakoff Syndrome: chronic alcoholics manifest with ataxia, ophthalmoplegia, confusion, and confabulation

Question 2

Riboflavin (B₂)

What is its function?

What are clinical consequences of deficiency?

Answer 2

Function:
Precursor to coenzymes flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD)

Deficiency causes:
atrophy of tongue (glossitis)
fissures in corner of mouth (cheilosis)
dermatitis
corneal ulceration

Rare b/c grains and cereals are fortified w/riboflavin

Question 3

Niacin (B₃)

What is its function?

What are clinical consequences of deficiency?

Answer 3

Function:
Required for production of NAD+ and NADP+ as well as numerous dehydrogenases

Deficiency results in Pellagra:
Diarrhea
Dementia
Dermititis

Question 4

Pyridoxine (B₆)

What is its function?

What are clinical consequences of deficiency?

Answer 4

Function:
Required for several transaminase and decarboxylation reactions

Severe symptoms due to requirement for decarboxylating glutamic acid to the inhibitory GABA causing seizures

Question 5

Biotin

What is its function?

What are clinical consequences of deficiency?

Answer 5

Function: Required for some carboxylation rxns

Deficiency is rare because biotin is synthesized by GI bacteria

Deficiency is associated with the consumption of raw eggs, containing avidin, that binds and inhibits absorption of biotin. Also associated with antibiotic use

Question 6

Cobalamin (B₁₂)

What is its function?

What are clinical consequences of deficiency?

Answer 6

Function:
Required by methylmalonyl CoA mutase
and
Methionine Synthase

Deficiency:
Associated with lack of Intrinsic Factor

Results in:
Block of purine and thymidine biosynthesis, resulting in megaloblastic anemia and subacute combined degeneration of the spinal cord

Question 7

Folate

What is its function?

What are clinical consequences of deficiency?

Answer 7

Function:
Reduced by dihydrofolate reductase to THF, which functions as a one-carbon donor in many biosynthetic pathways

Deficiency:
Impaired thymidine monophosphate synthesis, w/arrest of DNA synthesis
–> results in megaloblastic anemia

Pregnant patients require more folate; deficiency results in neurotubule defects, such as spina bifida

Question 8

Vitamin C

What is its function?

What are clinical consequences of deficiency?

Answer 8

Function:
Hydroxylation of proline residues in collagen and aids in iron absorption

Deficiency:
Scurvy
- easy bruising
- muscular fatigue
- soft, swollen gums
- hemorrhage
- anemia