s2m1 biochem – lipoproteins Flashcard



Function & Route?

Apoproteins associated with it?

excess causes what?

secreted by intestinal epithelial cells

Delivers dietary triglycerides to peripheral tissues 

delivers cholesterol in form of chylomicron remnants to liver

B-48, A-IV, C-II, E

pancreatitis, lipemia retinalis, eruptive xanthomas



Function & Route?

Apoproteins associated with it?

excess causes what?


secreted by the liver

Delivers hepatic triglycerides to peripheral tissues

B-100, C-II, E

excess – pancreatitis


how is it formed?


Function & Route?

Apoproteins associated with it?



Formed in the degradation of VLDL

delivers triglycerides & cholesterol to liver (where they are degraded to LDL)

B-100, E







Function & Route?

Apoproteins associated with it?

excess causes what?


Formed by hepatic lipase modification of IDL in the peripheral tissue.

Delivers Hepatic cholesterol to peripheral tissues or liver


excess – atherosclerosis, xanthoma, arcus corneae



Function & Route?

Apoproteins associated with it?



secreted from both the liver & intestine

t/p cholesterol from periphery to the liver

also acts as a repository for ApoC & ApoE




Apoprotein A-I or A-1


structure of what?

Activates LCAT

major structural protein of HDL

Apoprotein B-48


what other Apo is it like, what difference?

mediates chylomicron secretion

derived from B-100

lacks LDL receptor of B-100

Apoprotein B-100

binds to LDL receptor

mediates VLDL secretion

Apoprotein C-II


cofactor/activates for lipoprotein lipase


Apoprotein E


mediates Extra (chylomicron remnant) uptake

Apoprotein (a)



problems associated with it?

very large, resembles LDL particle

forms a complex with LDL

highly atherosclerotic

describe chylomicron metabolism

1. it exits the intestines into the blood with only the B-48 Apo attached.

2. HDL then donates C-II and Apo E to it.

3. LPL (lipoprotein lipase on adipocytes) hydrolyzes fatty acids from the chylomicron into adipose tissue

4. once it’s cut up by LPL it goes to the liver and gets take up via the Apo E into the B/E receptor;

VLDL metabolism

VLDL exits the liver with ApoC attached

the LPL at the adipose tissue cuts it up ; takes it’s triglycerides thus converting the VLDL to IDL

the IDL can further lose triglycerides at the liver to become LDL (hepatic lipase)

now it can carry cholesterol to the liver through the blood

what is the reverse cholesterol pathway?
HDL (synthesized in liver/intestines) carry cholesterol from the periphery to the liver. It doesn’t have the ApoE, thus it t/f it’s contents to VLDL & IDL to get it to the liver
which lipoproteins are involved in the exogenous / endogenous pathways?

exo – chylomicrons

endo – VLDL, IDL, HDL, LDL


what does pancreatic lipase do?
degradation of triglycerides in small intestine
what does LPL (lipoprotein lipase) do?
degradation of triglycerides circulating in chylomicrons and VLDLs
what does HL (hepatic lipase) do?
degradation of triglycerides remaining in IDL
what does LCAT (lecithin-cholesterol acyltransferase) do?
catalyzes esterification of cholesterol 
what does CETP (cholester ester transfer protein) do?
transfer cholesterol esters to other lipoprotein particles

what are two ways of getting cholesterol stored up in the cell?

what enhances / inhibits it?

through HMG-CoA reductase synthesizing cholesterol.

or through LDL & T3 uptake (thyroid hormone needed also)

enhance: insulin, ESREBP

inhibit: glucagon, cortisol, statins


what’s the healthiest state to be in regarding HDL ; LDL levels?
high HDL, low LDL
How are LDL foam cells formed?

LDL get’s oxidized it doesn’t go through the normal metabolism pathway.

instead macrophages engulf them

thus the macrophages become foam cells

what two things induce HDL synthesis?

what about LDL?

HDL – exercise ; regular alcohol consumption


LDL – weight gain, trans fats, diabetes, hypothyroidism


type I – hyperchylomicronemia

what’s increased?

due to what two causes?



increased chylomicrons

elevated blood level of triglycerides & cholesterol

caused by lipoprotein lipase dificiency

or altered Apo C-II

Epigastric pain, turbid retinal vessels


Type II – hypercholesterolemia

increased levels of what?



Increased LDL

Elevated blood levels of cholesterol

due to reduced LDL clearance cuz of reduced amt of LDL receptors

symptoms: CAD/plaques


type IV – hypertriglyceridemia


increased VLDL

elevated blood triglycerides

caused by hepatic VLDL overproduction

Wolman Disease


what is at high levels in the blood?


defect in lysosomal cholesterol ester hydrolase

affects LDL metabolism

reduced LDL clearance – high LDL levels

symptoms: CAD/plaques

Niacin drug

prevents breakdown of VLDL in liver thus less LDL secreted to the blood stream

result in more HDL formation

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