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Biochem Quiz 4 Winter > Vitamins > Flashcards

Vitamins Flashcards

1
Q

WATER-SOLUBLE VITAMINS

General features

  • Most water-soluble vitamins are precursors of coenzymes involved in intermediary metabolism.
  • All water-soluble vitamins except for vitamin B12 are present in vegetables.
  • Deficiency of all water-soluble vitamins except for vitamin B12 produces clinical symptoms within weeks due to low body stores.
A

WATER-SOLUBLE VITAMINS

General features

  • Most water-soluble vitamins are precursors of coenzymes involved in intermediary metabolism.
  • All water-soluble vitamins except for vitamin B12 are present in vegetables.
  • Deficiency of all water-soluble vitamins except for vitamin B12 produces clinical symptoms within weeks due to low body stores.
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2
Q

What enzymes is Thiamine (B1) pyrophosphate a coenzyme to?

A
  • pyruvate dehydrogenase
  • α-ketoglutarate dehydrogenase
  • transketolase
  • (All carb metabolism)
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3
Q

What does a deficiency in Thiamine cause?

A
  • Korsakoff’s syndrome in alcohol abusers.

* Beriberi- peripheral neuropathy and dilated cardiomyopathy.

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4
Q

What are the requirements of administering Thiamine to alcoholic patients?

A

• always administer Thiamine with glucose to alcohol abusers.

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5
Q

What is B2 Riboflavin are precursor to?

A
  • flavin mononucleotide (FMN)

* flavin adenine dinucleotide (FAD).

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6
Q

What deficiency of B2 Riboflavin causes what?

A
  • fissuring at the angles of the mouth
  • dermatitis
  • purple tongue.
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7
Q

What is B3 Niacin? What is it a precursor for? Why is it not an vitamin, strictly speakin?

A
  • Both nicotinamide or nicotinic acid.
  • Precursors of nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP) coenzymes.
  • We can synthesize niacin from tryptophan.
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8
Q

What does a Niacin deficiency cause?

A

• pellagra (Italian for “sour skin”)- dermatitis, diarrhea, dementia, and death.

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9
Q

What is Hartnup Disease? What is Carcinoid Syndrome?

A
  • Hartnup is diminished tryptophan uptake
  • Carcinoid syndrome is altered tryptophan metabolism
  • Both can result in Niacin B3 deficiencies.
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10
Q

How is Niacin B3 used therapeutically?

A

• Lower LDL and VLDL cholesterol in type IIb hyperlipoproteinemia.

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11
Q

What is Pantothenic Acid B5? Are there deficiencies?

A
  • Component of coenzyme A

* Widely distributed in food; deficiency syndrome has not been characterized.

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12
Q

What is B6? What is B6 a precursor for?

A
  • Collective term for pyridoxine, pyridoxal, and pyridoxamine.
  • Precursors of pyridoxal phosphate, a coenzyme catalyzing reactions involving amino acids.
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13
Q

Why is B6 prescribed together with isoniazid (a tuberculosis drug). What are the symptoms of B6 deficiency?

A
  • B6 binds to isoniazid
  • prevent functional deficiency
  • seizures.
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14
Q

How does Biotin B7 function in the body?

A
  • A coenzyme in carboxylation reactions

* covalently bound to lysine residues

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15
Q

What are the symptoms of Biotin deficiency?

A
  • Dermatitis
  • Glossitis
  • nausea
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16
Q

What dietary practice causes biotin Deficiency?

A
  • eating >20 raw eggs per day

* biotin-binding protein avidin

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17
Q

How is Folate B9 used in the body?

A

• For one-carbon metabolism, including purine and thymidine (DNA) synthesis.

18
Q

What does a deficiency in Folate B9 cause? What efforts have been made to prevent deficiency?

A
  • megaloblastic anemia in adults
  • neural tube defects in fetuses.
  • Given during 1st trimester of pregnancy
  • Supplemented in “enriched” foods since 1998.
19
Q

What is Cobalamin B12 a precursor to?

A
  • methylcobalamin, needed to synthesize methionine from homocysteine in blood cells
  • deoxyadenosylcobalamin, needed for fatty acid metabolism in brain cells.
20
Q

What factor is needed to absorb B12?

A
  • Not produced by plants.

* Requires intrinsic factor for intestinal absorption.

21
Q

When is B12 deficiency common?

A
  • Vegans

* patients with pernicious anemia (lacking intrinsic factor).

22
Q

What does Cobalamin B12 deficiency cause?

A
  • megaloblastic anemia by functionally trapping folate
  • subacute combined degeneration of the spinal cord
  • dementia.
23
Q

What is the Etiology of megaloblastic anemia in vitamin B12 deficiency?

A
  • the folate trap hypothesis
  • During methionine synthesis, N5-methyl-tetrahydrofolate transfers a methyl group to vitamin B12 to form methylcobalamin.
  • This reaction is also required to metabolize N5-methyl-tetrahydrofolate.
  • Lack of vitamin B12 blocks the metabolism of N5-methyl-tetrahydrofolate, which now cannot be used for DNA synthesis.Clinical symptoms become manifest only after years of deficiency due to large body stores.
24
Q

What is the treatment for pernicious anemia?

A
  • intramuscular B12 injections

* circumvents intrinsic factor

25
What is treatment of megablastic anemia?
• Folate supplementation ameliorates deficiencies of either vitamin B12 or folate.
26
Does folate supplementaiont treat subacute combined degeneration of the spinal cord caused by vitamin B12 deficiency?
No
27
What is Ascorbic Acid Vit C necessary for?
• post-translational hydroxylation of proline, especially in collagen.
28
What do deficencies of Vit C cause?
* scurvy- bleeding gums * Hemorrhages around corkscrew hair follicles * bone pain caused by bleeding underneath periosteum * poor wound healing
29
What do mega-doses of Vit C cause?
• oxalic acid kidney stones.
30
FAT-SOLUBLE VITAMINS General features • In the United States, deficiencies of fat-soluble vitamins are often present in patients with fat malabsorption syndromes. * Fat-soluble vitamins are stored in the body and metabolized slowly, and therefore deficiency usually develops only after months of inadequate intake. * Excess consumption of either vitamin A or D leads to toxicity.
FAT-SOLUBLE VITAMINS General features • In the United States, deficiencies of fat-soluble vitamins are often present in patients with fat malabsorption syndromes. * Fat-soluble vitamins are stored in the body and metabolized slowly, and therefore deficiency usually develops only after months of inadequate intake. * Excess consumption of either vitamin A or D leads to toxicity.
31
Vitamin A * Collective term for retinol, retinal, the essential visual pigment, and retinoic acid, which is necessary to maintain differentiation of epithelial cells. * Vitamin A can be obtained from animal sources or derived from β-carotene present in plants. • Deficiency causes 1.2 million cases of permanent blindness each year in the developing world. First symptom is night blindness, which can be rapidly improved with emergency vitamin A therapy.
Vitamin A * Collective term for retinol, retinal, the essential visual pigment, and retinoic acid, which is necessary to maintain differentiation of epithelial cells. * Vitamin A can be obtained from animal sources or derived from β-carotene present in plants. • Deficiency causes 1.2 million cases of permanent blindness each year in the developing world. First symptom is night blindness, which can be rapidly improved with emergency vitamin A therapy.
32
What are important physical signs of vitamin A deficiency?
* corneal epithelial cell dedifferentiation/keratinization | * xeropthalmia and Bitot’s spots.
33
What is vitamin A used to treat?
• Used in treatment of acne and psoriasis
34
What can overuse of vitamin A cause?
* skin rash, liver damage, and raised intracranial pressure | * teratogenic: avoid giving to pregnant patients
35
Vitamin D • Vitamin D can be produced endogenously in the skin by uv irradiation, or obtained from either animal or plant tissues.
Vitamin D • Vitamin D can be produced endogenously in the skin by uv irradiation, or obtained from either animal or plant tissues.
36
What is the active form of Vitamin D? What is its function with regards to Calcium?
* Calcitriol * Formed by two successive hydroxylation reactions: first in the liver, and subsequently in kidney, bone, or placenta. * Calcitriol is a steroid hormone that increases calcium absorption by the intestine epithelium. * In the United states, milk is fortified with vitamin D.
37
What do deficiencies in Vitamin D cause?
* demineralization of formed bone: osteomalacia (bone pain, microfractures and compression fractures) * failure to mineralize developing bones in children, leading to rickets (bowed legs).
38
What are risk factors for Vit D deficiency? What is treatment? What are possible side effects of treatment?
* Risk factors for deficiency = lack of milk consumption (often due to lactose intolerance), dark skin color, low sun exposure. * Calcitriol is given as therapy, but often causes hypercalcaemia: “bones, stones, and abdominal moans.”
39
What is Tocopherol Vitamin E? What do deficiencies cause?
* Antioxidant that protects lipid membranes. | * Deficiency can cause red blood cell fragility.
40
What is Vitamin K used for? Where is it endogenously produced?
* post-translational carboxylation of glutamate, which is required for calcium binding by several blood clotting factors, including prothrombin. * Produced by intestinal bacteria.
41
What do Vitamin K deficiencies cause?
* hemorrhage with a long prothrombin time (PT) | * Decreased clotting
42
Under what clinical circumstances is vitamin K administered to patients? When is Vit K intentionally blocked as a medicine?
* premature infants, who lack the intestinal bacteria that provide vitamin K * adults on long-term antibiotic therapy. * Vitamin K action is intentionally blocked by the drug coumarin, a vitamin K antagonist, to prevent clotting (e.g. in patients with prosthetic heart valves).

Biochem Quiz 4 Winter (6 decks)

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