Lipids and Lipoproteins

Question 1

sources of TAGs

Answer 1

dietary (intestinal cells)
de novo (hepatocytes and adipocytes)

Question 2

what makes up a chylomicron

Answer 2

TAGs
apoproteins
other lipids (cholesterol, phospholipids, fat soluble vit)

Question 3

how do chylomicrons enter the blood

Answer 3

chylomicrons are released into the lymphatic system and then enter blood via the thoracic duct

Question 4

difference between chylomicrons and VLDLs

Answer 4

VLDL transports endogenous products (de novo)

chylomicrons transport exogenous products (dietary)

Question 5

what is the backbone for fa synthesis

Answer 5

g3p (glycerol-3-phosphate)

Question 6

capillary lipoprotein lipase is secreted by which cells

Answer 6

hepatocytes

Question 7

what is lipoprotein lipase associated with

Answer 7

adipocytes (DAG breakdown to MAG)

Question 8

what enzyme is used for TAG breakdown to DAG

Answer 8

HS lipase (hormone sensitive lipase)

Question 9

what are the major enzymes for TAG breakdown

Answer 9

HSL (hormone sensitive lipase)
ATGL? (adipose triglyceride lipase)
LPL (lipoprotein lipase)
MAG Lipase

Question 10

what modulates HSL and which is its active form

Answer 10

phosphorylation (phospho is active)

Question 11

what is the function of perilipin

Answer 11

regulate lipolysis by controlling physical access to HSL

target of obesity treatment

Question 12

what regulates perilipins

Answer 12

PKA (phospho is active; allows association with HSL)

Question 13

5 major types of lipoproteins

Answer 13

chylomicrons
VLDL
LDL
IDL
HDL

Question 14

structure of lipoproteins

Answer 14

outer shell:

• monolayer of phospholipids
• free cholesterol
• apolipoproteins

inner shell:

• hydrophobic TAGs
• cholesterol esters

Question 15

which lipoprotein has the most TAGs and the least protein

Answer 15

chylomicrons

Question 16

which lipoprotein has the least TAGs and the most protein

Answer 16

HDL

Question 17

what is the function of apoB-48

Answer 17

facilitate transportation

Question 18

what is the function of apoC-II

Answer 18

activate LPL

Question 19

what is the function of apoE

Answer 19

facilitate uptake into liver

Question 20

what is the function of apoA-I

Answer 20

activates enzyme that converts cholesterol into cholesterol ester

Question 21

what do nascent chylomicrons need to become mature chylomicrons

Answer 21

apoC-II and apoE (supplied by HDL)

Question 22

what is the function of apoB-100

Answer 22

bind to LDL receptors on target cells

Question 23

what is the function of HDL-C

Answer 23

scavenges and removes LDL from periphery and takes it to the liver to be recycled and processed

Question 24

what is Type I hyperlipoproteinemia (hyperchylomicronemia) caused by and what are the effects

Answer 24

inability to hydrolyze TAGs in chylomicrons and VLDLs

deficiency in apoC-II or defective LPL

effect: increased chylomicrons and TAGs

Question 25

what is Type IIa and IIb hyperlipoproteinemia (familial hypercholesterolemia) caused by and what are the effects

Answer 25

impaired ability to recognize apoB-100 on LDL

LDL receptor is completely (IIa) or partially (IIb) defective

effect: increase cholesterol, LDL
- (IIb) increased TAGs, VLDL
- (IIa) normal TAGs