Biochemistry

Question 1

Vitamin A

Answer 1

Antioxidant.
Visual pigment.
Specialized epithelial differentiation.
Treat AML subtype M3.

Deficiency:
Nyctalopia; xerosis cutis; alopecia; keratomalacia; immune suppression.

Excess:
Arthralgias, skin changes, pseudotumor cerebri, teratogenic.

Question 2

Thiamine

Answer 2

B1
dehydrogenase reactions (alpha-ketoglutarate, transketolase, pyruvate dehydrogenase. 

Deficiency: 
Wernicke-Korsakof (confusion, ophthalmoplegia, ataxia + confabulation, memory loss. Damage to medial dorsal nucleus of thalamus, mammillary bodies). 
Dry beriberi (polyneuritis, symmetrical muscle wasting).
Wet beriberi (high-output cardiac failure, edema).

Question 3

Riboflavin

Answer 3

B2
flavins FAD and FMN in redox reaction.

Deficiency:
Cheilosis, corneal vascularization.

Question 4

Niacin

Answer 4

B3
NAD and NADP in redox. 
From tryptophan (requires B2 and B6 for synthesis). 
Lowers VLDL and raises HDL. 

Deficiency:
Pellagra (diarrhea, dementia, dermatitis) r/o carcinoid syndrome 2/2 increased tryptophan metabolism or isoniazid (2/2 decreased B6).
Glossitis.

Excess:
Facial flushing (2/2/ prostaglandin), hyperglycemia, hyperuricemia.

Question 5

Pantothenate

Answer 5

B5
Co-A + FA synthase.

Deficiency:
Dermatitis, enteritis, alopecia, adrenal insufficiency.

Question 6

Pyridoxine

Answer 6

B6
Transamination (as pyridoxal phosphate), decarboxylation, glycogen phosphorylase.
Synthesis of cystathione, heme, niacin, histamine, and NTs (5-HT, Epi, NE, DA, GABA).

Deficiency:
Convulsions, hyperirritabiliy, peripheral neuropathy, sideroblastic anemias.

Question 7

Biotin

Answer 7

B7
Carboxylation
-Pyruvate to oxaloacetate (Pyruvate carboxylase)
-Acetyl-CoA to malonyl-CoA (acetyl-CoA carboxylase)
-Propionyl-CoA to methylmalonyl-CoA (propionyl-CoA carboxylase).

Deficiency:
Dermatitis, alopecia, enteritis.
2/2 raw egg whites or Abx.

Question 8

Folic acid

Answer 8

B9
Coenzyme for 1-carbon transfer/methylation.
Synthesis of nitrogenous bases in DNA/RNA.

Deficiency:
Macrocytic, magaloblastic anemia . Hypersegmented PMNs; glossitis.

Labs: increased homocysteine, normal methylmalonic acid.

Question 9

Cobalamin

Answer 9

B12
Cofactor for homocyseine methyltransferase and methylmalonyl-CoA mutase.

Deficiency:
Macrocytic, megaloblastic anemia; hypersegmented PMNs; paresthesias, subacute combined degeneration.

Labs: increases serum homocysteine and methylmalonic acid.

Question 10

Vitamin C

Answer 10

Antioxidant. Abosorption of Fe (reduces it to 2+ state).
Hydroxylation of proline/lysine in collagen synthesis.
Dopamine beta-hydroxylase (DA to NE).

Deficiency:
Scurvy (swollen gums, subperiosteal hemorrhages, corkscrew hair), weakened immune response.

Excess:
N/V, diarrhea, fatigue, calcium oxalate nephrolithiasis.
Can increase iron toxicity in predisposed.

Question 11

Vitamin D

Answer 11

D2 = ergocalciferol (from plants)
D3 = cholecalciferol (milk or sun-exposed skin).
25-OH D3 = storage form.
1,25 (OH)2 D3 (calcitriol) = active form.

Increased intestinal absorption of Ca2+ and phosphate. Increase bone mineralization.

Deficiency:
Rickets in children, osteomalacia in adults.
Hypocalcemic tetany.

Excess:
Hypercalcemia, hypercalciuria, loss of appetite, stupor.
Seen in sarcoidosis.

Question 12

Vitamin E

Answer 12

Tocopherol

Antioxidant of membranes.
Can enhance anticoagulant effects of warfarin.

Deficiency:
Hemolytic anemia, acanthocytosis, muscle weakness, posterior column and spinocerebellar tract demyelination (similar to Friedrich ataxia = ataxia, dysarthria, loss of position/vibration sense).
Infertility.

Question 13

Vitamin K

Answer 13

Cofactor for gamma-carboxylation of glutamic acid for blood clotting (factors II, VII, IX, X).

Deficiency:
Neonatal hemorrhage.

Question 14

Zinc

Answer 14

Formation of zinc fingers.

Deficiency:

• Delayed wound healing, hypogonadism, decreased adult hair.
• Dysgeusia, anosmia, acrodermatitis enteropathica.
• May predispose to alcoholic cirrhosis.