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Biochem > Vitamins > Flashcards

Vitamins Flashcards

0
Q

Absorption dependent on (terminal) ileum, bile and pancreas

Toxicity(not readily excredible) more common- ⬆️ intake leads to eventual storage in fatty tissues

Affected by Malabsorption Syndromes:

  • cystic fibrosis
  • celiac sprue
  • mineral oil intake
A

Fat-soluble vitamins

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1
Q

Fat-soluble vitamins

A

Vitamin A

Vitamin D

Vitamin E

Vitamin K

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2
Q

3 forms of VITAMIN A

A

Retinol (vitamin A alcohol) ➡️ gametogenesis

Retinal (vitamin A aldehyde) ➡️ vision

Retinoic acid (vitamin A acid) ➡️ growth regulators in epithelium

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3
Q

Promote epithelial cell proliferation and differentiation

Storage form: retinyl esters

Transport form: retinol-binding protein (RBP)

A

Vitamin A

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4
Q

Vitamin A deficiency

A

Nyctalopia (night blindness) earliest manifestation

Xerophthalmia: eye and corneal dryness

Impotence

Growth retardation

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5
Q

Toxicity of vitamin A (hypervitaminosis A)

A

Hyperkeratosis

Hepatomegaly

Pseudotumor cerebri (h ICP)

Increased fractures

Teratogenic

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6
Q

Derived cholesterol

Precursor: 7-DEHYDROCHOLESTEROL

Storage: 25-(OH) vitamin D3

Active form: 1,25-(OH)2 vitamin D3

Function: responds to hypocalcemia and PTH

End goal: ⬆️ calcium and ⬆️ PO4

  • ⬆️ intestinal absorption of calcium
  • ⬆️ bone resorption
  • ⬆️ kidney reabsorption
A

Vitamin D

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7
Q

3 forms of Vitamin D

A

Ergocalciferol: Vitamin D2, milk, plant sources

Cholecalciferol: Vitamin D3, skin, animal sources

Calcitriol: 1,25-(OH)2 Vitamin D3

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8
Q

Hydroxylations of VITAMIN D

A

Vitamin D3 must be hydroxylated to become the active form. It undergoes a series of 2 hydroxylations:
1st- 25 hydroxylation ➡️ in the liver
2nd- 1 hydroxylation ➡️ in the kidney

(Anticipate vitamin D deficiency in CKD)

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9
Q

Vitamin D deficiency

A

Rickets: in children only, before growth plate closes

Osteomalacia: in adults only, after growth plate closes

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10
Q

Toxicity of Vitamin D (Hypervitaminosis D)

Most toxic vitamin

A

Hypercalcemia

Anorexia and nausea

Thirst

Stupor

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11
Q

Effects of hypocalcemia (vitamin D)

A

Tetany and seizures

Chvostek’s sign

Trosseau’s sign

Long QT

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12
Q

Effects of hypercalcemia (vitamin D)

A

Stones (urolithiasis)

Bones (pain, osteoporosis)

Abdominal groans (constipation, PUD, pancreatitis)

Psychic overtones (depression, anxiety, psc)

Short QT

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13
Q

Antioxidant in the lipid phase

Protects membrane lipids from peroxidation

Prevents oxidation of LDL - ⬇️ atherogenesis

LEAST TOXIC

membrane stabilization prevents atherosclerosis prone to hemolysis - ⬇️ vitamin E

A

Vitamin E

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14
Q

Vitamin E deficiency

A

RBC fragility

Neurological dysfunction (neuropathy)

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15
Q

3 forms of Vitamin K

A

Phylloquinone - Vitamin K1

Menaquinone - Vitamin K2

Menadione - Synthetic

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16
Q

Vitamin K deficiency

A

Rare, because vitamin K can be produced by bacteria in the GIT

Hemorrhagic Disease of the Newborn (HDN)

  • presents as bleeding (including intracranial bleeds)
  • neonates at risk because of sterile GIT and low vitamin K content of breast milk
17
Q

Vitamin K toxicity

A

Jaundice + hemolytic anemia

18
Q

Water-soluble Vitamins

A

Vitamin B1 (thiamine)

Vitamin B2 (riboflavin: FAD, FMN)

Vitamin B3 (niacin: NAD+)

Vitamin B5 (Pantothenic acid: CoA)

Vitamin B6 (Pyridoxine: pyridoxal phosphate)

Vitamin B12 (Cobalamin)

Vitamin C (Ascorbic acid)

Biotin

Folate

19
Q

Generally non-toxic compared to the oil-solubles

  • excesses just wash out of the body in the urine
  • exceptions: VITAMIN B6 and B12
A

Water-soluble Vitamins

20
Q

Active form: THIAMINE PYROPHOSPHATE (TPP)
( used as a cofactor in:
Pyruvate, a-ketoglutarate, and branched chain AA dehydrogenase
Transketolase reactions in the HMP shunt)

A

Vitamin B1 (Thiamine)

21
Q

Vitamin B1 deficiency

A

Beriberi (dry and wet)

  • dry beriberi: dry = no heart failure (Polyneuritis, symmetrical muscle wasting)
  • wet beriberi: wet = with heart failure (High-output cardiac failure ▶️ dilated cardiomyopathy)

Wernicke-Korsakoff syndrome

22
Q

Confusion

Loss of muscle coordination (ataxia)
- leg tremor

Vision changes
- abnormal eye movements (back and forth movement) NYSTAGMUS

double vision

Eye drooping

A

Wernicke’s encephalopathy

23
Q

Inability to form new memories

Loss of memory can be severe

Making up stories (confabulation)

Seeing or hearing things that aren’t really there (hallucinations)

A

Korsakoff syndrome

24
Q

Active form: FLAVIN MONONUCLEOTIDE (FMN), FLAVIN ADENINE DINUCLEOTIDE (FAD)
(used as cofactors in redox reactions, as electron carrier)

A

Vitamin B2 (Riboflavin)

25
Q

Vitamin B2 deficiency

A

No deficiency state but with signs and symptoms

  • stomatitis (inflammation of oral mucosa)
  • cheilosis (inflammation of lips and angle of mouth)
  • dermatitis
  • corneal vascularization
26
Q

Active forms: NICOTINAMIDE ADENINE DINUCLEOTIDE phosphate (NAD+ and NADP+)
(Used as coenzyme in redox reactions, as ➡️ electron carrier; may be derived from tryptophan using Vitamin B6)

A

Vitamin B3 (Niacin)

27
Q

Vitamin B3 deficiency

A

Pellagra = 3Ds (diarrhea, dermatitis, dementia)

  • Hartnup Disease absorption (⬇️ tryptophan)
  • Carcinoid Syndrome metabolism (⬆️ tryptophan)
  • Isoniazid use (⬇️ vitamin B6=⬇️ vitamin B3)
28
Q

Active form: constituent of Coenzyme A (fatty acid)

used as cofactor for acyl transfers; component of fatty acid synthase

A

Vitamin B5 (Pantothenate)

29
Q

Vitamin B5 deficiency

A

No deficiency state but with signs and symptoms:

  • dermatitis
  • enteritis
  • alopecia
  • adrenal insufficiency
30
Q

Active form: PYRIDOXAL PHOSPHATE

  • Used as coenzyme in AA transamination
  • used as coenzyme for: glycogen phosphorylase (glycogenolysis), cystathionine synthase, ALA synthase, synthesis of niacin from tryptophan
A

Vitamin B6 (Pyridoxine)

31
Q

Vitamin B6 deficiency

A

Isoniazid toxicity

  • INH + pyridoxal phosphate = inactive derivative
  • peripheral neuropathy
32
Q

Vitamin B6 toxicity

A

Intake of >2g/day

Gait problems and CNS toxicity

33
Q

Structure: cobalt in center of corrin ring

  • Methylcobalamin ➡️ contains methyl group
  • Cyanocobalamin ➡️ contains CN

Needs intrinsic factor for absorption

  • IF produced by stomach parietal cels
  • absorbed in terminal ileum

Active forms:

  • 5-DEOXYADENOSYLCOBALAMIN: used for methionine synthesis (homocysteine+N-methyl THG -> methionine+THF
  • Methylcobalamin: used for isomerization reactions (methylmalonyl CoA -> succinyl CoA {methylmalonyl mutase}
A

Vitamin B12 (Cobalamin)

34
Q

Vitamin B12 deficiency

A

Pernicious Anemia

  • autoimmune destruction of parietal cells leading to ⬇️ IF secretion and ⬇️ vitamin B12 absorption
  • early SSX: Megaloblastic anemia
  • late SSX: neuropsychiatric

Dx: Schilling Test, Vitamin B12 and anti-IF

Other causes: malabsorption or absence of terminal ileum

35
Q

Structure: PTERIN RING + PARA-AMINOBENZOIC ACID (PABA) + GLUTAMATE RESIDUES

  • humans cannot synthesize PABA and add glutamate, therefore humans cannot synthesize folate
  • should be provided from diet

Active form: TETRAHYDROFOLATE (THF)
PABA ➡️ dihydrofolate (DHF) ➡️ tetrahydrofolate (THF) dihydropteroate synthetase dihydrofolate reductase
- used as coenzyme for 1-carbon transfer
- Methylation reactions, like synthesis of purines and thymine

A

Folic acid

36
Q

Folic acid deficiency

A

Megaloblastic anemia with no neurological symptoms

  • hypersegmentation of neutrophils (earliest manifestation)
  • macrocytic anemia

Neural tube defects
- pregnant mothers must be given 400mcg (x10) folate daily

37
Q

Used a cofactor for carboxylation reactions:
pyruvate carboxylase (pyruvate➡️oxaloacetate)
Acetyl CoA carboxylase (acetyl CoA➡️malonyl CoA)
Propionyl CoA carboxylase (propionyl CoA➡️methylmalonyl CoA)

A

Biotin

38
Q

Biotin deficiency

A

Induced by avidin in egg whites

Dermatitis

Enteritis

39
Q

Used as a cofactor in:

  • Hydroxylation of proline and lysine (collagen synthesis)
  • Dopamine B-hydroxylase (dopamine to norepinephrine)

Reduces Fe3 to Fe2 in stomach to ⬆️Fe absorption (Ferric ➡️ Ferrous)

A

Vitamin C (Ascorbic Acid)

40
Q

Vitamin C deficiency

A

Scurvy

  • loose teeth and sore guns
  • swollen joints
  • fragile vessels
  • anemia

Biochem (28 decks)

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