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Metabolism > Lipids (diseases and vitamins) > Flashcards

Lipids (diseases and vitamins) Flashcards

1
Q

What are the sources of vitamin B12?

A
  • Microbiota
  • Liver
  • Fish
  • Red meat
  • Eggs
  • Dairy
  • Fortified grains
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2
Q

What are the functions of vitamin B12?

A
  1. Participate in β-oxidation of odd-numbered fatty acids
  2. Coenzyme for the methylation of homocysteine to methionine, which also results in the conversion of methyl-H4-folate to methylene-H4-folate for thymidine synthesis
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3
Q

What are the results of vitamin B12 deficiency?

A
  • Branched AAs accumulate, leading to neurologic manifestations
  • Accumulation of homocysteine
  • Pernicious anemia, likely due to immune-mediated destruction of gastric parietal cells and a decrease in intrinsic factor, which is required for absorption of B12 in the intestine
  • Achlorhydria in elderly patients
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4
Q

What are the functions of folate?

A

Transfer of one-carbon units from Ser, Gly, or His during:

  • Synthesis of some AAs
  • Synthesis of purines and TMP
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5
Q

What are the causes of folate deficiency?

A
  • Chemotherapeutic drugs, e.g. methotrexate
  • Increased requirements (e.g. during pregnancy)
  • A folate-free diet
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6
Q

What are the results of folate deficiency?

A
  • Neural tube defects in fetuses (namely spina bifida, anencephaly)
  • Megaloblastic anemia (erythropoietic cells grow but cannot divide due to deficiency in TMP)
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7
Q

What is the minimum daily requirement of folate?

A

400 µg per day

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8
Q

What is the precursor of the vitamin A forms?

A

β-carotene

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9
Q

What is the active form of vitamin A?

A

Retinoic acid, except in spermatogenesis (retinol and retinal) and for vision (11-cis-retinal)

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10
Q

What are the functions of vitamin A?

A

Acts as a transcription factor for several genes, modulating:

  • Reproduction: spermatogenesis and prevention of fetal resorption (retinol and retinal)
  • Growth in children: retinoic acid
  • Maintenance of epithelia: retinoic acid
  • Vision: 11-cis-retinal
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11
Q

What are the sources of vitamin A?

A
  • Preformed vitamin A: liver, kidney, butter, egg yolk
  • As β-carotene: yellow, orange, or dark-green fruits and vegetables
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12
Q

What are the symptoms of vitamin A deficiency?

A
  • Mild: nyctalopia (night blindness)
  • Prolonged: irreversible ophthalmic damage
  • Severe: xerophthalmia (dryness of cornea and conjunctiva, followed by scarring and blindness); acne and psoriasis (treatable with vitamin A administration)
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13
Q

What is the upper limit for vitamin A?

A
  • As vitamin A: >3 mg per day
  • As retinol: >7.5 mg per day
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14
Q

What are the symptoms of vitamin A toxicity?

A
  • Teratogenesis in pregnant women
  • If due to isotretinoin (a drug used for acne) toxicity: increased levels of TAGs and cholesterol, with risk of coronary heart disease
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15
Q

What are the forms of vitamin D?

A
  • Ergocalciferol (D2): from plants
  • Cholecalciferol (D3): from animals or synthesized in skin
  • Calcidiol (25-hydroxycholecalciferol)
  • Calcitriol (1,25-dihydroxycholecalciferol): active form
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16
Q

How is the active form of vitamin D synthesized in the body?

A

(1) ergocalciferol/cholecalciferol → calcidiol (25-hydroxylase)
(2) calcidiol → calcitriol (1-hydroxylase)

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17
Q

What are the functions of vitamin D?

A
  • Regulation of serum levels of phosphate and calcium
  • Low phosphate levels directly upregulate 1-hydroxylase
  • Low calcium levels indirectly upregulate 1-hydroxylase via action of parathyroid hormone
  • Calcitriol acts by negative feedback to decrease parathyroid hormone levels
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18
Q

What are the exogenous sources of vitamin D?

A
  • Fatty fish
  • Liver
  • Egg yolk
  • Fortified milk
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19
Q

What is the daily recommended intake of vitamin D?

A
  • 15 µg (600 IU) per day for ages 1–70
  • 20 µg (800 IU) per day for ages 70 and above
20
Q

What is the upper limit of vitamin D?

A

100 µg (4,000 IU) per day

21
Q

What are the symptoms of vitamin D toxicity?

A
  • Nausea
  • Anorexia
  • Thirst
  • Bone resorption
  • Deposition of calcium in tissues
22
Q

What are the forms of vitamin K?

A
  • Phylloquinone (K1): plants
  • Metaquinone (K2): intestinal microbiota
  • Menadione (K3): synthetic compound
23
Q

What are the natural sources of vitamin K?

A
  • Microbiota
  • Cabbage
  • Spinach
  • Egg yolk
  • Liver
24
Q

What are the functions of vitamin K?

A
  • Carboxylation of Glu residues in coagulation factors, leading to their attachment to platelets
  • Warfarin inhibits the vitamin K epoxide reductase needed for regeneration of vitamin K, acting as an anticoagulant
25
Q

What are the causes of vitamin K deficiency?

A
  • Use of some antibiotics (e.g. cefamandole)
  • In newborns: sterile intestine, breast milk is a poor source
  • Newborns are given an IM shot of vitamin K for prophylaxis against hemorrhagic disease
26
Q

What are the symptoms of vitamin K toxicity?

A
  • Hemolytic anemia
  • Jaundice
27
Q

What is the function of vitamin E?

A

Antioxidant

28
Q

What are the features of type I hyperlipoproteinemia?

A
  • Deficiency in lipoprotein lipase or Apo C-II
  • Leads to increased plasma levels of chylomicron-TAG
29
Q

What are the features of type IIa hyperlipoproteinemia?

A

Deficiency in LDL receptor

30
Q

What are the features of Wolman disease?

A
  • Autosomal recessive
  • Deficiency in lysosomal acid lipase, leading to accumulation of cholesteryl esters and TAGs
31
Q

What are the features of Niemann–Pick disease, type C?

A
  • Autosomal recessive
  • Deficient transport of free cholesterol out of lysosomes
32
Q

What are the features of Tangier disease?

A

Absence of ABCA1

33
Q

What are the features of type III hyperlipoproteinemia?

A

Mutated apoE, leading to decreased binding of chylomicron remnants to receptors

34
Q

What are the isoforms of Apo E?

A
  • Apo E-2: binds poorly, leads to type III hyperlipoproteinemia and premature atherosclerosis
  • Apo E-3: normal
  • Apo E-4: risk of early-onset Alzheimer disease
35
Q

Where does the drug ezetimibe act?

A

Blocks the protein NPC1L1 involved in intestinal uptake of cholesterol

36
Q

What is the result of defects in the protein ABCG5/G8?

A

Decreased pumping of cholesterol out of the intestine, leading to sitosterolemia and increased risk of MI

37
Q

How do statins function?

A

Structural analogs of HMG, competitively inhibit cytosolic HMG CoA reductase

38
Q

What are the features of Tay–Sachs disease?

A
  • Autosomal recessive
  • Deficient β-hexoseaminidase
  • Accumulation of GM2 in lysosomes, leading to rapid neurodegeneration
39
Q

What are the features of Gaucher disease?

A
  • Autosomal recessive
  • Most common lysosomal storage disease
  • Deficient β-galactosidase
  • Treatment: ERT, substrate reduction, or bone marrow transplantation
40
Q

What are the features of Niemann–Pick disease, types A and B?

A
  • Autosomal recessive
  • Deficienct sphingomyelinase
  • Fatty liver, hepatomegaly, mental retardation
41
Q

What are the features of Farber disease?

A
  • Autosomal recessive
  • Deficient ceramidase
  • Joint deformity, nodules of lipid laden cells, hoarse cry
42
Q

What are the features of Fabry disease?

A
  • X-linked
  • ERT available
43
Q

How are sphingolipidoses diagnosed?

A
  • DNA analysis
  • Testing enzyme activity in fibroblasts or leukocytes
44
Q

What are the features of Refsum disease?

A
  • Autosomal recessive
  • Deficiency in phytanoyl CoA hydroxylase (PhyH)
45
Q

What are the features of MCAD deficiency?

A
  • Autosomal recessive
  • Prevalent in Northen Europeans
  • Decreased utilization of MCFAs
  • Severe fasting hypoglycemia and hypoketemia
  • Treated by avoiding fasting
46
Q

What are the features of primary carnitine deficiency?

A
  • Defect in a transporter for uptake of carnitine into skeletal and cardiac muscle
  • Carnitine is excreted in urine
  • Treated by supplementation
47
Q

What are the features of secondary carnitine deficiency?

A
  • Caused by certain drugs (e.g. valproic acid, an antiepileptic), decreased renal resorption, or decreased liver synthesis (due to hepatic disease, for example)
  • Defective β-oxidation, carnitine–LCFA buidls up and is excreted in urine
  • CPT-I deficiency affects the liver, leading to fasting hypoglycemia, coma, and death
  • CPT-II deficiency affects liver, skeletal muscle, and cardiac muscle
  • Treated by avoiding fasting

Metabolism (6 decks)

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