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FA - Biochemistry > Biochem - Metabolism (Cholesterol synthesis, Lipid transport, & Familial dyslipidemias) > Flashcards

Biochem - Metabolism (Cholesterol synthesis, Lipid transport, & Familial dyslipidemias) Flashcards

Pg. 117-118 in First Aid 2014 Sections include: -Cholesterol synthesis -Lipid transport, key enzymes -Major apolipoproteins -Lipoprotein functions -Familial dyslipidemias

1
Q

What is the rate-limiting step of cholesterol synthesis, and what enzyme catalyzes it? What substance induces the activity of this enzyme?

A

Rate-limiting step is catalyzed by HMG-CoA reductase (induced by insulin), which converts HMG-CoA to mevaolonate

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2
Q

What is LCAT, and what role does it play in cholesterol synthesis? What portion of cholesterol participates in its role?

A

2/3 of plasma cholesterol is esterified by lecithin-cholesterol acyltransferase (LCAT)

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3
Q

What is the mechanism of Statins? Give an example of a Statin.

A

Statins (e.g., lovastatin) competitively and reversibly inhibit HMG-CoA reductase.

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4
Q

What role does pancreatic lipase play in lipid transport?

A

Degradation of dietary triglycerides (TG) in small intestine

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5
Q

What role does lipoprotein lipase (LPL) play in lipid transport? Where are they found?

A

Degradation of TC circulating in chylomicrons and VLDLs. Found on vascular endothelial surface.

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6
Q

What role does Hepatic TG lipase (HL) play in lipid transport?

A

Degradation of TG remaining in IDL

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7
Q

What role does hormone-sensitive lipase play in lipid transport?

A

Degradation of TG stored in adipocytes

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8
Q

What role does LCAT play in lipid transport?

A

Catalyzes esterification of cholesterol

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9
Q

What role does cholesterol ester transfer protein (CETP) play in lipid transport?

A

Mediates transfer of cholesterol esters to other lipoprotein particles

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10
Q

Draw a diagram demonstrating the interconnections of lipid transport, including and labeling the following involved body parts: (1) Intestine (2) Liver (3) Adipose tissue (4) Capillary (5) Peripheral tissues (with LDL receptors). Also include the lipid transport steps that flow between them.

A

See p. 117 in First Aid 2014 for visual near top/middle of page

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11
Q

What are 2 major kinds of receptors on the liver involved in lipid transport?

A

(1) LDL receptors (2) Remnant (chylomicron remnants) receptors

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12
Q

Draw a diagram depicting the general actions of LCAT & CETP plus the organs involved.

A

See p. 117 in First Aid 2014 for visual near bottom/middle of page

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13
Q

Name 5 major apolipoproteins?

A

(1) E (2) A-1 (3) C-II (4) B-48 (5) B-100

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14
Q

What is the function of apolipoprotein E?

A

Mediates remnant uptake

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15
Q

Which of the following describes apolipoprotein E: (1) Chylomicron (2) Chylomicron remnant (3) VLDL (4) IDL (5) LDL (6) HDL?

A

(1) Yes (2) Yes (3) Yes (4) Yes (5) No (6) Yes

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16
Q

What is the function of apolipoprotein A-I?

A

Activates LCAT

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17
Q

Which of the following describes apolipoprotein A-I: (1) Chylomicron (2) Chylomicron remnant (3) VLDL (4) IDL (5) LDL (6) HDL?

A

(1) Yes (2) No (3) No (4) No (5) No (6) Yes

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18
Q

What is the function of apolipoprotein C-II?

A

Lipoprotein lipase cofactor

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19
Q

Which of the following describes apolipoprotein C-II: (1) Chylomicron (2) Chylomicron remnant (3) VLDL (4) IDL (5) LDL (6) HDL?

A

(1) Yes (2) No (3) Yes (4) No (5) No (6) Yes

20
Q

What is the function of apolipoprotein B-48?

A

Mediates chylomicron secretion

21
Q

Which of the following describes apolipoprotein B-48: (1) Chylomicron (2) Chylomicron remnant (3) VLDL (4) IDL (5) LDL (6) HDL?

A

(1) Yes (2) Yes (3) No (4) No (5) No (6) No

22
Q

What is the function of apolipoprotein B-100?

A

Binds LDL receptor

23
Q

Which of the following describes apolipoprotein B-100: (1) Chylomicron (2) Chylomicron remnant (3) VLDL (4) IDL (5) LDL (6) HDL?

A

(1) No (2) No (3) Yes (4) Yes (5) Yes (6) No

24
Q

What are the components of lipoproteins?

A

Lipoproteins are composed of varying proportions of cholesterol, TGs, and phospholipids

25
Q

Which 2 kinds of lipoproteins carry the most cholesterol?

A

LDL and HDL carry most cholesterol

26
Q

Where does LDL versus HDL transport cholesterol?

A

LDL transports cholesterol from liver to tissues; HDL transports cholesterol from periphery to liver; Think: “LDL is Lousy, HDL is Healthy”

27
Q

What are 2 functions of chylomicrons?

A

Delivers dietary TGs to peripheral tissue. Divers cholesterol to liver in the form of chylomicron remnants, which are mostly depleted of their triaglycerols.

28
Q

What secretes chylomicrons?

A

Secreted by intestinal epithelial cells

29
Q

What is the function of VLDL?

A

Delivers hepatic TGs to peripheral tissue

30
Q

What secretes VLDL?

A

Secreted by liver

31
Q

How is IDL formed?

A

Formed in the degradation of VLDL

32
Q

What is the function of IDL?

A

Delivers TGs and cholesterol to liver

33
Q

What is the function of LDL?

A

Delivers hepatic cholesterol to peripheral tissues

34
Q

What forms LDL? How is LDL taken up by target cells?

A

Formed by hepatic lipase modification of IDL in the peripheral tissue. Taken up by target cells via receptor-mediated endocytosis.

35
Q

What are 2 major functions of HDL?

A

(1) Mediates reverse cholesterol transport from periphery to liver. (2) Acts as a repository for apoC and apoE (which are needed for chylomicron and VLDL metabolism).

36
Q

What secretes HDL? What effect does alcohol have on HDL synthesis?

A

Secreted from both liver and intestine. Alcohol increases synthesis.

37
Q

What is the name of type I familial dyslipidemia? What substances have an increased blood level?

A

I - Hyperchylomicronemia; Chylomicrons, TG, cholesterol

38
Q

What is the name of type IIa familial dyslipidemia? What substances have an increased blood level?

A

IIa - Familial Hypercholesterolemia; LDL, cholesterol

39
Q

What is the name of type IV familial dyslipidemia? What substances have an increased blood level?

A

IV - Hypertriglyceridemia; VLDL, TG

40
Q

What is the mode of inheritance for the following familial dyslipidemias: (1) Type I - Hyperchylomicronemia (2) Type IIa - Familial Hypercholesterolemia (3) Type IV - Hypertriglyceridemia.

A

(1) Autosomal recessive (2) Autosomal dominant (3) Autosomal dominant

41
Q

What defects may cause Type I familial dyslipidemia (Hyperchylomicronemia)?

A

Lipoprotein lipase deficiency or altered apolipoprotein C-II

42
Q

What are 3 clinical findings associated with Type I familial dyslipidemia (Hyperchylomicronemia)? How does this disorder affect the risk for atherosclersois?

A

Causes (1) pancreatitis, (2) hepatosplenomegaly, and (3) eruptive/pruritic xanthomas (no increased risk for atherosclerosis)

43
Q

What is the defect that causes Type IIa familial dyslipidemia - Familial Hypercholesterolemia?

A

Absent or defective LDL receptors

44
Q

For Familial Hypercholesterolemia, what is the cholesterol level for heterozygotes versus homozygotes? Also estimate the incidence of heterozygote versus homozygote.

A

Heterozygotes (1:500) have cholesterol ~ 300 mg/dL; Homozygotes (very rare) have cholesterol ~ 700+ mg/dL.

45
Q

What are 3 clinical findings associated with Type IIa familial dyslipidemia - Familial Hypercholesterolemia?

A

Causes accelerated atherosclerosis (may have MI before age 20), tendon (Achilles) xanthomas, and corneal arcus

46
Q

What is the defect in Type IV familial dyslipidemia - Hypertriglyceridemia?

A

Hepatic overproduction of VLDL

47
Q

What clinical condition can Type IV familial dyslipidemia - Hypertriglyceridemia cause?

A

Causes pancreatitis

FA - Biochemistry (31 decks)

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