Lipids and lipoproteins

Question 1

Apolipoprotein definition and functions

Answer 1

Primary protein component of lipoprotein responsible for
1. modulating enzymatic activity on lipoproteins
2. maintaining structural integrity of molecules
3. facilitating uptake of lipoprotein by acting as ligands for cell-surface receptors

Question 2

Apolipoprotein A

Answer 2

major protein found in HDL.

Question 3

Apo-A1 function

Answer 3

plays a role in activation of LCAT with esterifies free cholesterol

Question 4

Apo-A2 function

Answer 4

plays a structural role in HDL and may inhibit LCAT

Question 5

Apolipoprotein B

Answer 5

Major protein of LDL, VLDL and chylomicrons

Question 6

Apo B-100

Answer 6

found in LDL and VLDL and is a ligand for LDL receptor

Question 7

Apo B-48

Answer 7

exclusively in chylomicrons and is structural component and remnant of receptor ligands

Question 8

Chylomicrons appearance, apo content, and function

Answer 8

Contain Apo B-48. Float at the density of normal plasma and would be increased after a meal. Milky appearance dur to exogenous triglycerides. Deliver lipids to hepatic and peripheral cells.

Question 9

VLDL appearance, apo content, function

Answer 9

Apo B-100, apo E, apo C.
Carries triglycerides made by the liver (endogenous) to peripheral tissue
Functions during fasting to provide energy utilization of endogenous lipids
caused milky turbidity in fasting plasma/serum

Question 10

IDL

Answer 10

Transient VLDL remnants produced during conversion of VLDL to LDL

Question 11

LDL appearance, apo content, function

Answer 11

Apo B-100
Formed from lipolysis of VLDL
Forms foam cells leading to fatty streaks and atherosclerotic plaques

Question 12

Lipoprotein A

Answer 12

Like LDL with additional apolipoprotein A. Unknown function but increases are heritable and increase CHD risk. May have clotting impacts.

Question 13

HDL appearance, apo content, function

Answer 13

Apo A-1 ad A-11
Smallest and most dense
synthesized in the liver and intestine
removes access cholesterol from peripheral cells (good cholesterol)

Question 14

Exogenous pathway steps

Answer 14

1. lipids are digested (lumen)
2. lipid assembled with ApoB-48 into chylomicrons
3. HDL donates ApoCII and Apo E (blood)
4. Mature chylomicron activate lipoprotein lipase
5. remnants are endocytosed and hydrolyzed with lysosomes. Releases glycerol and fatty acids in cells

Question 15

Endogenous pathway steps

Answer 15

1. Triacylglycerol and cholesterol are assembled with Apo B-100 to form VLDL (liver)
2. HDL donates Apo CII and E (blood)
3. Apo CII activates LPL > hydrolysis of VLDL > release of glycerol and fatty acids
4. VLDL particles now called IDL and are returned to the liver to be hydrolyzed by hepatic lipase to make LDL

Question 16

Tests done to diagnose lipoprotein disorders

Answer 16

Total cholesterol
triglyceride
HDL
LDL
Medical history and clinical presentation

Question 17

Total cholesterol reference range

Answer 17

140-200mg/dL

Question 18

HDL reference range

Answer 18

40-75 mg/dL

Question 19

LDL

Answer 19

50-130 mg/dL

Question 20

Triglycerides reference range

Answer 20

60-150 mg/dL

Question 21

Does LDL increase result in turbidity?

Answer 21

no

Question 22

Total cholesterol measurement

Answer 22

12 hr fasting with enzymatic methods

Question 23

HDL testing considerations

Answer 23

Must remove or mask non-HDL lipoproteins
remove by precipitating or centrifuging

Question 24

LDL testing considerations

Answer 24

Indirect method, not accurate with trig >400. Direct uses ultracentrifugation or masking.

Question 25

Friedewald calculation

Answer 25

Indirect LDL.
Total chol-HDL-Trig/5