Lipoprotein Handling Flashcards
what are lipoproteins?
Lipoproteins are transport systems for FATs & CHOLESTEROLS
outercoat:
- phospholipids
- free cholesterol
- proteins (aka apoproteins)
innercore
- cholesterol
- cholesterol esters
- triglycerides
- some vitamines (A & E)
what are the different types of lipoproteins? (5)
- chylomicron: carrier of dietary fats: small intestine -> liver
2. very low density lipoprotein: liver -> rest of body
**3. intermediate denisty lipoprotein
- low density lipoprotein
- high density lipoprotein**
order the different lipoproteins in size order xox
biggest
chylomicron
very low density lipo
intermediate DL
LDL
HDL
smallest
what are the main components of the 5 lipoproteins?
chylomicron: TAG (fats)
very low density lipo: TAG
intermediate DL TAG
LDL: cholesterol
HDL: cholesterol
what are the different lipoprotein apoproteins?
chylomicron
very low density lipo
intermediate DL
LDL
HDL
chylomicron: B48
very low density lipo: B100
intermediate DL: B100
LDL: B100
HDL; All
what are general roles of each? what do they transport and where?
- *chylomicron**: f_at transport from GI tract –> rest of body_
- *very low density lipo:** (similar to chylomicrons) fat transport -> rest of body. VLDL produced in the liver
- *intermediate DL:** left over chylomicrons –> become either LDL or VLDL
LDL: deliver cholesterol to cells
HDL; pick up excess cholesterol and send back to liver
fats (& cholesterol) absorbed from GI tract, turn into chylomicrons and go into lymphatic system:
here they interact with HDLs - how? (2)
fats (& cholesterol) absorbed from GI tract, turn into chylomicrons and go **into lymphatic system:
here they interact with HDLs**
- ApoC2 added: allows chylomicrons to give its triglycerides to peripheral cells
- ApoE added: allows chylomicron remenant to be taken up by the liver to deliver FA & cholesterol
VLDL formation:
how is it the same to chylomicrons?
how different?
VLDLs interact with HDLs
- ApoC2 added: allows VLDLs to give its triglycerides to peripheral cells
- ApoE added: allows VLDLs remenant to be taken up by the liver to deliver FA & cholesterol
= same as chylomicrons
BUT: VLDLs are produced by the liver (chylomicrons come from GI tract)
what is the function of lipoprotein lipase?
what activates ^?
where is lipoprotein lipase most active:
a) during periods of starvation?
b) after a meal
lipoprotein lipase: breaks down fats from inside lipoproteins and carries them into the cells
activated by: Apo C2
where is lipoprotein lipase most active:
a) during periods of starvation: muscle (where FA being used for energy in TCA)
b) after a meal: adipose cells (to form fat)
what is the function of low density liporpotein?
where made?
- *low density lipoprotein:**
- function: deliver cholesterol to peripheral cells of the body
- produced @: liver
- formed by: remains of VLDLS after distribiting most of triglycerides. causes them to be more dense = IDLS. hepatic TAG ligase converts IDL to cholesterol rich LDL, having only Apo B100
why is ApoB100 important for LDLS?
acts as recognition signal for LDL to be taken up by peripheral cells.
LDLs have to be engulfed by the cells to through receptor mediated endocytosis, where gives off the cholesterol inside the cell. yet, the LDLS need ApoB100 to be on them in order to be recognised by the cells
how can ur body create cholesterol?
how does high cholesterol induce negative feedback of cholesetol production? (3)
- acetyl co-A –> cholesterol (via enzyme HMG-coA reductase)
high cholesterol induces negative feedback of cholesetol production
- *- reduces expression of HMG co-A reductase**
- reduced gene expression of LDL (which brings the cholesterol)
- XS stored as cholesterol esters
what is familial hypercholeserolemia ? caused by mutation of which 3 genes?
- autosomal dom disease. mutation of one of three genes:
i) LDLR - receptor for receptor mediated endocytosis
ii) PCSK9: kinase that controls recyclingof LDLRs
iii) APOB: gene for ApoB which binds to LDL
= causes increased levels of cicrulating blood LDL bc not taken up into cells. increases chance of CHD.
causes heart attacks even in children
high density lipoproteins ! :)
function?
- fuse with chylomicrons and VLDLs to get apoproteins they need
2. reverse transport pathway:
i) ApoA1 released by liver -> goes around body and picks up cholesterols from other cells through ABCA1 / G1 receptors
ii) changes the cholesterol -> cholesterol esters
iii) goes back to liver
iv) HDL transfers XS cholesterol ester to liver by binding to scavenger receptors (SR-B1)
the liver can get rid of XS cholesteral esters in WHAT?
the liver can get rid of XS cholesteral esters in bile
explain how having high LDLs leads to the formation of plaque formation & atherosclerosis
- high LDLs stay in blood system become damaged due to ROSs
- damaged LDLs get taken up by macrophages
- but bc there isnt anything really to kill - theyre just cholesterol: macrophages become foam cells (filled with chol)
- foam cells stick to walls of capillaries - fatty streaks -> fatty plaques -> atherosclerosis
