Bio 13 - Lipids

Question 1

What does lipoprotein lipase do?

Answer 1

Draws Free Fatty acids (FFA) from chylomicrons and VLDL so cells can use it.

Question 2

What does ApoB-100 do?

Answer 2

The synthesized VLDL, IDL, LDL from the liver are put into the circulation by the protein ApoB-100.

Question 3

What does Apo B-48 do?

Answer 3

Chylomicron secretion from enterocyte to lymphatic system.

Question 4

What does Apo E do?

Answer 4

Mediate extra remnant uptake?

Question 5

What does Apo A-1 do?

Answer 5

Activates LCAT, found on HDL.

Question 6

What does Apo C-II do?

Answer 6

Cofactor for lipoprotein lipase.

Question 7

What is Abetalipoproteinemia?

Answer 7

Autosomal recessive disorder where their is a mutation in the gene for microsomal transfer protein (MTP gene), causes a deficiency of ApoB-48 and ApoB-100. This causes decreased chylomicron, VLDL synthesis and secretion. Clinically causes failure to thrive, steatorrhea, impaired transport of fat-soluble vitamins (D,A,E,K), acanthocytosis on RBCs, ataxiam, night blindness. Biopsy reveals enterocytes swollen with triglicerides.

Question 8

What is the treatment for abetalipoproteinemia>

Answer 8

Give vitamin E.

Question 9

What is Type I Hyperchylomicronemia?

Answer 9

Autosomal recessive disease, caused by deficiency of lipoprotein lipase or defective apolipoprotein C-II (the cofactor for lipoprotein lipase). Causes increased levels of chylomicrons, triglicerides and cholesterols. Presents with pancreatitis, hepatoslenomegaly, pruritic xanthomas. Interestingly, there is no increased risk for atherosclerosis.

Question 10

What is Type IIa familial hypercholesterolemia?

Answer 10

Autosomal dom, either absent or decreased LDL receptors. Causes tendinous xanthomas, corneal arcus, accelerated atherosclerosis. MIs in 20s (double dominant mutation).

Question 11

What is Type-IV hypertriglyceridemia?

Answer 11

Autosomal dom, causes overproduction of VLDL, might cause pancreatitis.

Question 12

What are signs of hypercholesterolemia?

Answer 12

Atheromas (oxidized LDL). Xanthomas (plaques of histiocytes filled with lipids). Xanthelasma (xanthoma in eyelid). Tendinous xanthomas. Corneal arcus (lipid in cornea).

Question 13

What is an important substrate in cholesterol production?

Answer 13

Acetyl-CoA.

Question 14

What is the rate-limiting enzyme in cholesterol synthesis?

Answer 14

HMG-CoA reductase. Not HMG-CoA synthase (rate-limiting enzyme for ketone body production).

Question 15

Which drugs inhibit production of cholesterol?

Answer 15

The statins.

Question 16

What is the precursor molecule for fatty acid synthesis? Where does the synthesis take place?

Answer 16

Acetyl-CoA. Takes place in the hepatocytes.

Question 17

What is the rate-limiting enzyme for Fatty Acid synthesis?

Answer 17

Acetyl-CoA carboxylase.

Question 18

Where does fatty acid degradation take place?

Answer 18

Mitochondria.

Question 19

What is the rate limiting enzyme for Fatty acid degradation?

Answer 19

Carnitine acyltransferase-1 (carnitine palmitoyl tranferase-1).

Question 20

What happens when there is a defect or deficiency of Carnitine acyltransferase-1?

Answer 20

Accumulation of long chain fatty acids in the cytoplasm (because it cannot enter the mitochondria). This causes weakeness, hypotonia, hypoglycemia.

Question 21

What deficiency causes familial hypercholesterolemia?

Answer 21

VLDL receptors.

Question 22

Which apolipoprotein activates LCAT?

Answer 22

Apo A-I.

Question 23

Which apolipoprotein mediates chylomicron secretion?

Answer 23

Apo B-48.

Question 24

Which apolipoprotein Mediates VLDL secretion?

Answer 24

Apo B-100.

Question 25

Which apolipoprotein binds to LDL receptor?

Answer 25

Apo B-100.

Question 26

Which apolipoprotein is Cofactor for lipoprotein lipase?

Answer 26

Apo C-II.

Question 27

Which apolipoprotein mediates uptake of remnant particles.

Answer 27

Apo E.

Question 28

What is the rate-limiting enzyme for Beta-oxidation of fatty acids?

Answer 28

Carnitine acyltransferase-1.

Question 29

How is Lipid transported?

Answer 29

By lipoproteins because fats are insoluble in water (proteins act to emulsify the fat): Triglycerides, Phospholipids, LDL (transports cholesterol from liver to tissues), HDL (Transports cholesterol from periphery to liver), Chylomicrons (Deliver TGs to peripheral tissue, deliver cholesterol to liver), VLDVL (deliver TGs to peripheral tissue), IDL (Deliver TGs and cholesterol to liver).