Cholesterol Metabolism and Lipid Transport Flashcards Preview

HMS Chemical Biology and Biochemistry > Cholesterol Metabolism and Lipid Transport > Flashcards

Flashcards in Cholesterol Metabolism and Lipid Transport Deck (74)
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1

Sources of Cholesterol

2

Rate limiting enzyme of cholesterol production

HMG-CoA Reductase

3

Fates of Cholesterol

4

Lipid and cholesterol transport systems make use of the same ____.

Lipid and cholesterol transport systems make use of the same lipoprotein transporters.

5

Chylomicrons deliver dietary fat that is ____; VLDL delivers fat that is ____.

Chylomicrons deliver dietary fat that is absorbed in the intestine; VLDL delivers fat that is produced by the liver.

6

enterohepatic circulation of bile acids

Bile acids are excreted from the gall bladder, used to emulsify fat in the gut, and then many are reabsorbed and delivered back to the liver.

7

Consequences of elevated LDL

8

Cholesterol and Cholesteryl esters

9

Sterol biosynthesis

10

Statins

11

Schematic of LDL

12

Scale of Lipoproteins

13

Apolipoprotein

A lipoprotein stripped of all its lipids.

14

Apo A1

Core protein of HDL. Activates LCAT, the enzyme that triggers reverse cholesterol transport from cells to HDL

15

ApoB48 and B100 relationship

These proteins are both expressed from the same gene, and are made by the small intestine and liver, respectively

16

Apo B100

In the liver, the full length apolipoprotein is made (100% of full length, so it is called ApoB100). This protein acts as a scaffold for the VLDL particle, and thus is also found in the derivative particles IDL and LDL. It acts as the major binding site for the LDL receptor and is thus responsible for uptake of the LDL particle by the liver.

17

Apo B48

In the small intestine, a shorter version (48% of full length) of ApoB is produced (hence ApoB48). This protein acts as the scaffold for a chylomicron. Since it lacks the C-terminal region of ApoB100, it cannot bind the LDL-receptor, and thus chylomicron remnants rely primarily on ApoE for uptake by the liver.

18

Apo CII

Activates lipoprotein lipase

19

Apo E

Triggers clearance of some VLDL particles and all chylomicron remnants.

20

Apo C and E relationship

Secreted by the liver and intestine into the blood stream, where they then bind the nascent lipoprotein particles.

Apo E and C can also be transferred between HDL, VLDL and chylomicrons.

21

Common Pathway for Lipoprotein Production

22

MTP

microsomal triglyceride transfer protein

Responsible for loading VLDL (liver) and chylomicrons (intestine) with triacylglycerides within the ER as the apolipoproteins are being translated.  This step is called lipidation.

23

Enterocytes secrete chylomicrons into ___.  Hepatocytes secrete VLDL into ___.

Enterocytes secrete chylomicrons into lacteals, which then drain into local lymphatics and eventually enter venous circulation via the thoracic duct.  Hepatocytes secrete VLDL into the bloodstream directly.

24

Life of a chylomicron

25

Fatty acid and glycerol absorption and packaging into chylomicrons (within enterocytes)

26

Niemann-Pick C1–like 1 (NPC1L1) protein

A cholesterol transporter located within the apical membrane of an enterocyte.  Responsible for dietary cholesterol absorption.

27

Ezetimibe

Small molecule inhibitor of NPC1L1.  Prevents/lessens dietary cholesterol absorption.

28

Dietary cholesterol absorption diagram

29

Lacteals and Gut Lymphatics

30

Location of the cysterna chyli

Just posterior to the pyloric sphinctre and just right of the abdominal aorta.