Lecture 9 - Lipoprotein Metabolism

Question 1

why do fats need to be packaged and kept soluble

Answer 1

so they can be transported in the blood

Question 2

what is the role of O-acyltransferase enzymes

Answer 2

transferring an acyl (fatty) acid group

Question 3

what form is cholesterol most commonly found in

Answer 3

most commonly found in the form of cholesterol ester which is when there is a fatty acid attached

Question 4

what will inhibit the cholesterol synthesis pathway

Answer 4

if there is a lot of cholesterol coming from the diet

Question 5

what enzyme is inhibited to inhibit the cholesterol synthesis pathway

Answer 5

HMG CoA reductase

Question 6

what does HMG CoA reductase do and why is this important

Answer 6

converts HMG CoA to mevalonate = rate limiting step of cholesterol synthesis pathway

Question 7

where is cholesterol found

Answer 7

in the plasma membrane

Question 8

what does cholesterol control in the plasma membrane

Answer 8

the fluidity of the membrane

Question 9

what is the dietary source for cholesterol

Answer 9

animal products

Question 10

what is cholesterol the precursor for

Answer 10

steroid hormones, bile acids and vitamin D

Question 11

what is cholesterol a major constituent of

Answer 11

lipoproteins

Question 12

what is cholesterol important for the transport of

Answer 12

fat soluble vitamins

Question 13

how is cholesterol important for neuronal function

Answer 13

its a part of the myelin sheath

Question 14

what encapsulates lipids in the structure of plasma lipoproteins

Answer 14

proteins and phospholipids encapsulate the lipids to keep the soluble

Question 15

what are the 4 main classes of lipoproteins

Answer 15

• chylomicrons
• very low density lipoprotein
• low density lipoprotein
• high density lipoprotein

Question 16

what is a characteristic of chylomicrons

Answer 16

triglyceride rich

Question 17

what is a characteristic of very low density lipoprotein

Answer 17

triglyceride rich

Question 18

what is a characteristic of low density lipoprotein

Answer 18

cholesterol rich

Question 19

what is a characteristic of high density lipoprotein

Answer 19

• cholesterol rich
• densest because of the high protein content

Question 20

what do ApoB48 (chylomicrons) and ApoB100 (VLDL) and MTP play a crucial role in

Answer 20

lipoprotein assembly

Question 21

in the endoplasmic reticulum what is added to ApoB by MTP as it is being made and what does this form

Answer 21

lipids are added to ApoB and this forms a small lipopotein

Question 22

when a small lipoprotein particle is formed from lipids being added to ApoB, what does MTP add to make the particle bigger

Answer 22

triglycerides

Question 23

what occurs in the golgi before ApoB is secreted

Answer 23

glycosylation

Question 24

lipids combine with what via MTP in the ER to form chylomicrons

Answer 24

ApoB

Question 25

where are chylomicrons secreted from and what do they enter

Answer 25

from intestinal cells entering the bloodstream and lymphatic system

Question 26

what gives plasma a milky appearance after a fat rich meal and what is this due to

Answer 26

chylomicrons can give plasma a milky appearance due to high triacylglycerol content

Question 27

chylomicrons and VLDL are metabolised similarly by what

Answer 27

by lipoprotein lipase

Question 28

what does lipoprotein lipase do and where does this occur

Answer 28

hydrolyses the fatty acids, this occurs at the surface of tissues

Question 29

what does hepatic lipase (HTGL) do

Answer 29

generates LDL

Question 30

what dies LRP bind to

Answer 30

apoE

Question 31

what does LDLR bind to

Answer 31

apoB

Question 32

what receptor family are LRP and LDLP members of

Answer 32

LDL receptor family

Question 33

what do LRP and LDLP do

Answer 33

take up remnant IDl and LDL particles

Question 34

what is the function of lipoproteins

Answer 34

solubilise lipids for transport in blood to tissues

Question 35

what apoprotein is important for assembly

Answer 35

apoB

Question 36

what apoproteins are important for ligand cell surface receptors

Answer 36

apoB and apoE

Question 37

what apoprotein is important for enzyme cofactors

Answer 37

apoCII (for lipoprotein lipase)

Question 38

what are factors that affect lipids levels

Answer 38

• diet = saturated vs unsaturated fats
• drugs = fibrates and statins
• genetics = defects in lipid metabolism
• disease = diabetes

Question 39

diets rich in what are LDL cholesterol lowering

Answer 39

diets rich in plant sterols

Question 40

what are mediterranean diets found to reduce

Answer 40

cardiac mortality

Question 41

eating high amounts of saturated fats can do what

Answer 41

cause LDL levels to increase

Question 42

what do statins do to LDL cholesterol

Answer 42

lower intracellular levels

so the body makes more receptors

meaning there is more LDL uptake

Question 43

what does ezetimibe do to LDL cholesterol

Answer 43

less cholesterol coming into the body as decreased intestinal uptake, so more LDL receptors

Question 44

fibrates and PUFAs both activate a what and what does this bind to and what does this switch on (example)

Answer 44

transcription factor, binds to response element and switching on many genes

one of these is lipoprotein lipase which hydrolyses VLDL and chylomicrons

Question 45

what would a defect in LPL or apoC-II cause

Answer 45

elevated triglyceride levels

Question 46

what would a defect in apoB or MTP cause

Answer 46

low blood cholesterol levels