Vitamins/Enzymes/Cofactors

Question 1

Vitamin A Function:

Answer 1

Antioxidant, visual pigments (retinal), differentiation of specialized epithelial cells, prevents squamous metaplasia

Treatment for measles and AML, M3 t(15;17)

Question 2

Vitamin A Deficiency:

Answer 2

Night blindness, dry xcaly skin, alopecia, corneal degen (keratomalacia), immune suppression

Question 3

Vitamin A Excess:

Answer 3

Arthralgias, skin changes (scaliness), alopecia, cerebral edema, pseudotumor cerebri, osteoporosis, hepatic abnorm

Teratogenic! cleft palate, cardiac abnormalities

Question 4

Thiamine Cofactor for:

Answer 4

B1

Cofactor for dehydrogenase rxns:
PDH (glycolysis to TCA)
Alpha-ketoglutarate DH (TCA)
Transketolase (HMP shunt nonoxidative)
Branched-chain/alpha-ketoacid DH (Ile, Leu, Val)

Question 5

Thiamine deficiency:

Answer 5

Malnutrition & alcoholism

impaired glucose breakdown –> ATP depletion **worsened by glucose infusion

Wernicke-Korsakoff syndrome - damage to MD thal and MB

Dry beriberi: polyneuritis, symmetric mm wasting

Wet beriberi: high-output HF (DCM), edema

Question 6

Riboflavin Cofactor:

Answer 6

B2
FAD and FMN: cofactors in redox reactions
Succinate DH (TCA)

Question 7

BH4 (tetrahydrobiopterin) is a cofactor in synthesis of:

Answer 7

tyrosine, dopa, serotonin, nitric oxide

Question 8

Most abundant AA in collagen:

Answer 8

Glycine - collagen is 1/3 glycine

Question 9

Collagen synth: triple helix

Answer 9

procollagen, via hydrogen and disulfide bonds, in RER, after hydroxylation and glycosylation
Gets exocytosed into ECS

Problems forming helix –> Osteogenesis imperfecta

Question 10

Steps of collagen synth:

Answer 10

1. synthesis
2. hydroxylation
3. glycosylation
4. exocytosis
5. proteolytic processing
6. cross linking

1-3 in RER of fibroblasts, rest outside fibroblasts in ECS

Question 11

Proteolytic processing of collagen:

Answer 11

in ECS, Cleave disulfide-rich N & C terminal of procollagen (triple helix) by procollagen peptidases –> tropocollagen

Question 12

Cross-linking of collagen

Answer 12

in ECS, reinforce staggered tropcollagen molec by covalent lysine-hydroxylisine cross linkage (by Cu-containing lysyl oxidase)

makes Collagen Fibrils!

Problems cross linking –> Ehlers Danlos