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Biochem Block 3 > Lipoprotein Metabolism > Flashcards

Lipoprotein Metabolism Flashcards

1
Q

What is the composition of a chlyomicron?

A

90% TAG, 2% protein, 3% Phospholipids, 5% cholesterol

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2
Q

What is the composition of VLDL?

A

60% TAG, 5% protein, 15% Phospholipids, 20% cholesterol

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3
Q

What is teh composition of LDL?

A

8% TAG, 20% protein, 22% Phospholipids, 50% cholesterol

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4
Q

What is the composition of HDL?

A

5% TAG, 40% protein, 30% Phospholipids, 25% cholesterol

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5
Q

Where is ApoA-1 synthesized and found?

A

synthesized in the liver and intestine and found on almost all HDL particles.

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6
Q

What is the major structural protein of chylomicrons, VLDLs, IDLs, and LDs?

A

ApoB

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7
Q

(1) autosomal recessive
(2) loss of function mutation in gene encoding microsomal triacylglycerol transfer protein (MTP)
(3) chylomicrons, VLDLs, LDLs and apoB are undetectable in plasma leading to lipid malabsorption
(4) extremely low plasma levels of cholesterol and TAG
(5) Symptoms: early childhood, diarrhea, failure to thrive, deficient of fat soluble vitamins, spinocerebellar degeneration, pigmented retinopathy, acanthocytosis

A

Abetalipoproteinemia

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8
Q

(1) Deficiency of LPL, abnormal LPL, or apo C-II deficiency
(2) slow clearance of chylomicrons and VLDL
(3) fasting plasma is turbid and develops creamy supernatant at 4*C
(4) Symptoms: manifests in childhood, recurrent episodes of severe abdominal pain due to acute pancreatitis, lipemia retinalis, eruptive xanthomas, hepatosplenomegaly

A

Familial Lipoprotein Lipase (LPL) Deficiency

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9
Q

(1) autosomal recessive
(2) mutation in ATP-binding cassette (ABC) transporter family [ABCG5 and ABCG8]
(3) due to increased absorption of plant sterols in intestine and reduced transport of sterols into bile by liver
(4) impaired cholesterol trafficking
(5) elevated levels of LDL cholesterol
(6) Symptoms: tendon xanthomas, premature atherosclerosis
(7) episodes of hemolysis due to incorporation of plant sterols in RBC membranes

A

Sitosterolemia

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10
Q

(1) autosomal codominant
(2) mutations in LDL receptor gene, mostly in ligand binding region on exon 4
(3) high LDL-C levels (200-400 mg/dL in heterozygotes, > 500 mg/dL in homozygotes)
(4) Syqmptoms: cutaneous xanthomas, accelerated atherosclerosis, corneal arcus, tendon xanthomas
(5) High incidence in Afrikaners, Christian Lebanese, and French Canadians

A

Familial Hypercholesterolemia (FH)

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11
Q

(1) autosomal codominant
(2) due to mutation in gene encoding ABCA1
(3) HDL is rapidly cleared from circulation
(4) Low plasma HDL-C levels (

A

Tangier Disease (ABCA1 Deficiency)

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12
Q

(1) autosomal recessive
(2) mutation in gene encoding plasma enzyme LCAT
(3) increased level of free cholesterol in lipoproteins (from 25% to 70% of total plasma C)
(4) lack of normal cholesterol esterification
(5) impairs formation of mature HDL
(6) low plasma concentraions of CE and lysolecithin, abnormal LDL and VLDL in circulation
(7) Symptom: progressive corneal opacification, variable hypertriglyceridemia

A

Familial Lecithin Cholesterol Acyltransferase (LCAT) Deficiency

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13
Q

decreased thyroid function does what to LDL particles and LDL oxidation?

A

it increases the number of LDL particiles and promotes LDL oxidation

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14
Q

what does decreased activity of LPL lead to?

A

hypertracyllycerolemia

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15
Q

thyroid hormones do what:

A

activate LDL receptors
stimulate CETP
stimulate LPL, HL
decreases oxidation of LDL

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16
Q

Are lipids hydrophobic or hydrophillic? soluble or insoluble in blood?

A

hydrophobic and insoluble in blood

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17
Q

how are lipids transported in the bloodstream?

A

packaged as lipoproteins

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18
Q

what determines the density of a lipoprotein?

A

the amount of protein per particle

19
Q

What is the major apolipoprotein for chylomicrons?

A

ApoB-48

20
Q

What is the major apolipoprotein for chylomicron remnants?

A

ApoB-48

21
Q

What is the major apolipoprotein for VLDL?

A

ApoB-100

22
Q

What is the major apolipoprotein for IDL?

A

ApoB-100

23
Q

What is the major apolipoprotein for LDL?

A

ApoB-100

24
Q

What is the major apolipoprotein for HDL?

A

ApoA-1

25
Q

What is the major apolipoprotein for Lp(a)

A

ApoB-100

26
Q

What is the function of Apo C-II?

A

it activates LPL

27
Q

What is the function of Apo A-I?

A

activates LCAT

28
Q

What is the function of Apo A-II and Apo C-III?

A

They inhibit LPL

29
Q

What is the function of Apo C-I?

A

inhibits CETP

30
Q

Where is Apo B48 synthesized?

A

over the RER

31
Q

What does MTP do?

A
  • loads apoB48 with lipds

- loads apoB100 with TAGs, cholesterol, phospohlipids, and Vitamin E

32
Q

What are TAGs degrade into to?

A

FFAs and glycerol

33
Q

In metabolism of VLDL, what are excess carbohydrates converted to?

A

TAGs

34
Q

What do you get if chylomicrons accumulate in the skin?

A

xanthomas

35
Q

What holds on to LPL?

A

heparan sulfate

36
Q

What is Domain 1 of the LDL-receptor?

A

LDL binding site

37
Q

What is Domain 5 of the LDL-receptor?

A

cytoplasmic tail, which is important for attaching the clathrin molecules

38
Q

Where is Apo(a) synthesized?

A

liver

39
Q

What is Apo(a) homologous to?

A

plasminogen

40
Q

What are higher levels of Lp(a) a risk factor for?

A

cardiovascular disease

41
Q

Lp(a) stimulates secretion of what? What does this lead to?

A

Lp(a) stimulates secretion of PaI-1 (plasminogen activator inhibitor-1), which leads to thrombogenesis.

42
Q

Where is LCAT synthesized and secreted?

A

the liver

43
Q

What occurs in the CETP exchange pathway?

A

HDL donates its cholesterole sters to VLDL, IDL, adn LDL in exchange for triaclyglycerol. This is catalyzed by cholesterol ester transfer protein .
-HDL3 is converted to HDL2

Biochem Block 3 (11 decks)

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