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Flashcards in Biochem: Vitamins Deck (105)
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1

Enzymes that have biotin as a co-factor

- pyruvate carboxylase (gluconeogenesis)
- acetyl CoA carboxylase (FA synthesis)

- propionyl CoA carboxylase (odd-carbon FA, val, Met, Ile, Thr)??

2

Biotin Deficiency:
- MCC
- symptoms

- MCC (rare): excessive consumption of raw eggs (contain avidin, a biotin-binding protein and prevents its absorption)

- Symptoms: alopecia (hair loss), bowel inflammation, muscle pain

3

Thiamine (vitamin B1) deficiency
- MCC
- symptoms

* In thiamine pyrophosphate (TPP) = a cofactor for several dehydrogenase enzyme rxns.*
- MCC: alcoholism (alcohol interferes with absorption)
- Wernicke (ataxia, nystagmus, ophthalmoplegia (wide-eyed, can't follow light)
- korsakoff (confabulation, psychosis)
- wet beri beri (high output cardiac failure)
- dry (early) beri beri (cardiac failure without fluid retention)

*beri beri = heart failure due to Vit B1 deficiency

4

What enzymes require Vitamin B1 (Thiamine) as a cofactor?

* In thiamine pyrophosphate (TPP) = a cofactor for several dehydrogenase enzyme rxns.*
- pyruvate dehydrogenase (PDH?)
- alpha-ketoglutarate dehydrogenase (TCA cycle)
- transketolase (HMP shunt)
- branched chain ketoacid dehydrogenase (metabolism of valine, isoleucine and leucine)

5

Vitamin D Toxicity

- excess Vit D can be stored in liver as 25-hydroxycholecalciferol
- excess Vit D can promote intestinal absorption of calcium and phosphate
- results in hypercalcemia

- direct result of excess Vit D = same as Vit D deficiency
- Hypercalcemia can impair renal function, and early signs include polyuria, polydipsia, and nocturne
- prolonged hypercalcemia can result in calcium deposition in soft tissues (esp kidney), causing irreversible kidney damage

6

Vitamin A (carotene)

- Vit A is converted to several active forms in the body associated with 2 important functions:
1. maintenance of healthy epithelium and 2. vision (retinal)
- important function: retinoid acid and retinol act as growth regulators (bind intracellular receptors (zinc-finger proteins) to regulate transcription), especially in epithelium.
- retinal is important in rod and cone cells for vision

* 3 Vit A structures w different functional groups at C1:
- Retinol: hydroxyl
- retinoid acid: carboxyl
- retinal: aldehyde

7

Vitamin D (cholecalciferol)

important function: in response to hypocalcemia, helps normalize serum calcium levels

8

Vitamin B3

Niacin

- remember, Niacin = NAD(H), NADP(H)
- involved in many pathways, because cofactor for all dehydrogenase (bc NAD)

9

Vitamin K (menaquinone, bacteria; phytoquinone, plants)

Important functions: carboxylation of glutamic acid residues in many Ca2+ binding proteins
- importantly coagulation factors 2, 7, 9 and 10 as well as protein C and protein S

10

Vitamin E (alpha-tocopherol)

antioxidant in the lipid phase. protects membrane lipids from preoccupation

11

What is the cofactor for branched chain ketoacid dehydrogenase?

Thiamine B1

12

Symptoms of Vitamin D deficiency

- bone demineralization
- rickets (children): deformities of legs and other developing bones. muscle weakness common
- osteomalacia (adults, after epiphyseal fusion): less deformity than rickets. may present as bone pain and muscle weakness

13

Causes of Vitamin D Deficiency

- insufficient sunlight
- inadequate fortified foods (milk)
- end-stage renal disease (renal osteodystrophy)

14

What is the cofactor for alpha-ketoglutarate dehydrogenase?

Thiamine (B1)

15

Symptoms of Vitamin A deficiency

- night blindness
- keratinized squamous epithelium
- xerophthalmia, bitot spots
- keratomalacia, blindless
- follicular hyperkeratosis
- alopecia

16

Causes of Vitamin A deficiency

- fat malabsorption
- fat-free diets

17

Vitamin B2

Riboflavin (FAD, FMN)

18

Symptoms of Vitamin E deficiency

- hemolytic anemia
- acanthocytosis
- peripheral neuropathy
- ataxia
- retinitis pigmentosum

19

Causes of Vitamin E deficiency

- fat malabsorption
- premature infants

20

What is the cofactor for propionyl CoA carboxylase

biotin

21

pyruvate carboxylase is involved in what pathway?

gluconeogenesis

22

acetyl CoA carboxylase is involved in what pathway?

Fatty acid synthesis (carboxylation)

23

propionyl CoA carboxylase is involved in what pathway?

(odd-carbon FA, val, Met, Ile, Thr)??

24

What is the cofactor for acetyl CoA carboxylase

biotin

25

transketolase is involved in what pathway?

- HMP shunt
- this is the key enzyme involved in Wernicke Korsakoff syndrome

26

branched chain ketoacid dehydrogenase is involved in what pathway?

metabolism of valine isoleucine and leucine

27

A/e of isotretinoin

Teratogenic (malformation of the craniofacial, cardiac, thymic and CNS structures)

28

What is the cofactor for pyruvate carboxylase?

biotin

29

alpha-ketoglutarate dehydrogenase is involved in what pathway?

TCA cycle, carrier of FA

30

What is the cofactor for pyruvate dehydrogenase?

Thiamine (B1)