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

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

Flashcards in Biochem - Metabolism (Cholesterol synthesis, Lipid transport, & Familial dyslipidemias) Deck (47):
1

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

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

2

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

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

3

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

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

4

What role does pancreatic lipase play in lipid transport?

Degradation of dietary triglycerides (TG) in small intestine

5

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

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

6

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

Degradation of TG remaining in IDL

7

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

Degradation of TG stored in adipocytes

8

What role does LCAT play in lipid transport?

Catalyzes esterification of cholesterol

9

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

Mediates transfer of cholesterol esters to other lipoprotein particles

10

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.

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

11

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

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

12

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

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

13

Name 5 major apolipoproteins?

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

14

What is the function of apolipoprotein E?

Mediates remnant uptake

15

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

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

16

What is the function of apolipoprotein A-I?

Activates LCAT

17

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

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

18

What is the function of apolipoprotein C-II?

Lipoprotein lipase cofactor

19

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

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

20

What is the function of apolipoprotein B-48?

Mediates chylomicron secretion

21

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

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

22

What is the function of apolipoprotein B-100?

Binds LDL receptor

23

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

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

24

What are the components of lipoproteins?

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

25

Which 2 kinds of lipoproteins carry the most cholesterol?

LDL and HDL carry most cholesterol

26

Where does LDL versus HDL transport cholesterol?

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

27

What are 2 functions of chylomicrons?

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

28

What secretes chylomicrons?

Secreted by intestinal epithelial cells

29

What is the function of VLDL?

Delivers hepatic TGs to peripheral tissue

30

What secretes VLDL?

Secreted by liver

31

How is IDL formed?

Formed in the degradation of VLDL

32

What is the function of IDL?

Delivers TGs and cholesterol to liver

33

What is the function of LDL?

Delivers hepatic cholesterol to peripheral tissues

34

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

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

35

What are 2 major functions of HDL?

(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

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

Secreted from both liver and intestine. Alcohol increases synthesis.

37

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

I - Hyperchylomicronemia; Chylomicrons, TG, cholesterol

38

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

IIa - Familial Hypercholesterolemia; LDL, cholesterol

39

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

IV - Hypertriglyceridemia; VLDL, TG

40

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

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

41

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

Lipoprotein lipase deficiency or altered apolipoprotein C-II

42

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

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

43

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

Absent or defective LDL receptors

44

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

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

45

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

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

46

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

Hepatic overproduction of VLDL

47

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

Causes pancreatitis

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