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s2m1 biochem - lipoproteins
Ross University
29
Chemistry
Graduate
01/28/2010

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Cards

Term

Chylomicron

Source?

Function & Route?

Apoproteins associated with it?

excess causes what?

Definition

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

Term

VLDL

Source?

Function & Route?

Apoproteins associated with it?

excess causes what?

 

Definition

secreted by the liver

Delivers hepatic triglycerides to peripheral tissues

B-100, C-II, E

excess - pancreatitis

Term

IDL

how is it formed?

 

Function & Route?

Apoproteins associated with it?

 

 

Definition

Formed in the degradation of VLDL

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

B-100, E

 

 

Term

LDL

 

Source?

 

Function & Route?

Apoproteins associated with it?

excess causes what?

 

Definition

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

Delivers Hepatic cholesterol to peripheral tissues or liver

B-100

excess - atherosclerosis, xanthoma, arcus corneae

Term

HDL

Source?

Function & Route?

Apoproteins associated with it?

 

 

Definition

secreted from both the liver & intestine

t/p cholesterol from periphery to the liver

also acts as a repository for ApoC & ApoE

CETP, A-1

 

 

Term

Apoprotein A-I or A-1

function?

structure of what?

Definition

Activates LCAT

major structural protein of HDL

Term

Apoprotein B-48

function?

what other Apo is it like, what difference?

Definition

mediates chylomicron secretion

derived from B-100

lacks LDL receptor of B-100

Term
Apoprotein B-100
Definition

binds to LDL receptor

mediates VLDL secretion

Term

Apoprotein C-II

function?

Definition

cofactor/activates for lipoprotein lipase

 

Term

Apoprotein E

function

Definition
mediates Extra (chylomicron remnant) uptake
Term

Apoprotein (a)

shape?

function?

problems associated with it?

Definition

very large, resembles LDL particle

forms a complex with LDL

highly atherosclerotic

Term
describe chylomicron metabolism
Definition

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 

Term
VLDL metabolism
Definition

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

Term
what is the reverse cholesterol pathway?
Definition
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
Term
which lipoproteins are involved in the exogenous / endogenous pathways?
Definition

exo - chylomicrons

endo - VLDL, IDL, HDL, LDL

 

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

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

what enhances / inhibits it?

Definition

through HMG-CoA reductase synthesizing cholesterol.

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

enhance: insulin, ESREBP

inhibit: glucagon, cortisol, statins

 

Term
what's the healthiest state to be in regarding HDL & LDL levels?
Definition
high HDL, low LDL
Term
How are LDL foam cells formed?
Definition

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

instead macrophages engulf them

thus the macrophages become foam cells

Term

what two things induce HDL synthesis?

what about LDL?

Definition

HDL - exercise & regular alcohol consumption

 

LDL - weight gain, trans fats, diabetes, hypothyroidism

Term

hyperlipoproteinemias

type I - hyperchylomicronemia

what's increased?

due to what two causes?

symptoms?

 

Definition

increased chylomicrons

elevated blood level of triglycerides & cholesterol

caused by lipoprotein lipase dificiency

or altered Apo C-II

Epigastric pain, turbid retinal vessels

Term

hyperlipoproteinemia

Type II - hypercholesterolemia

increased levels of what?

cause?

symptoms?

Definition

Increased LDL

Elevated blood levels of cholesterol

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

symptoms: CAD/plaques

Term

hyperlipoproteinemia

type IV - hypertriglyceridemia

 

Definition

increased VLDL

elevated blood triglycerides

caused by hepatic VLDL overproduction

Term

Wolman Disease

cause?

what is at high levels in the blood?

symptoms?

Definition

defect in lysosomal cholesterol ester hydrolase

affects LDL metabolism

reduced LDL clearance - high LDL levels

symptoms: CAD/plaques

Term
Niacin drug
Definition

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

result in more HDL formation

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