2.4 Lipoproteins and Lipid transport Flashcards
What happens to a chylomicron once its secreted from the mucosal cells?
the chylomicrons circulate through the lymphatic system until it reaches the superior vena cava. During their time in the lymph and continuing in their plasma, chylomicrons undergo a number of physical-chemical and metabolic changes:
1) Gain apoC-II: Activates lipoprotein lipase. Which intitiates core triacylglycerol hydrolysis.
- triacylglycerol is mostly released to adipose, muscle, heart.
- Glycerol will be recycled to liver
- Apo E has receptors in the liver and the remaining chylomicron remnant will be degraded.
Chylomicron is essentially…….???
a fat droplet with triglycerols making up about 90% of its weight.
While chylomicron is getting transferred to its desired location, what else is happening? (regards to lipoproteins)
a number of other lipoproteins are formed to facilitate transport through the aqueous blood system.
Lipoprotein lipase?
breaks down TAGS to fatty acids and glycerol
What’s chylomicron half-life in plasma?
less than a hour.
How is chylomicrons triacylglcerol distributed?
80% Fatty acid: adipose, muscle, heart
20% Glycerol: recycled in liver.
What happens when fatty acids enter the tissue?
They get trapped in cells by conversion to fatty acyl-coA thioesters
What’s the enzyme used to convert fatty acids into fatty acyl-coA thioesters in cells?
fatty acyl-coA synthetase.
What is a chylomicron remnant?
it’s the “shrunken” lipoprotein…. Whatever is left of the chylomicron after Triacylglycerol is released via fatty acid and glycerol.
What happens to the chylomicron remnant?
The liver has receptors specific to APO E, which will take in the chylomicron remnant and gets degraded and recycled
Apo C II and Apo E?
They are picked up from HDL into chylomicrons.
Apo C II + lipoprotein lipase: converts TAG to fatty acid and glycerol.
Apo E: liver has receptor that recognizes it and will degrade chylomicron remnants.
Chylomicron: (composition)
- Largest
- lowers in density due to high lipid/protein ratio
- highest in triacylglycerols as % of weight
VLDL (composition)
- Very low density lipoprotein
- 2nd highest in triacylglycerols as % of weight
IDL (composition)
intermediate density lipoprotein
LDL (composition)
low density lipoprotein
highest in cholesterol/cholesteryl esters as % of weight
HDL (composition)
High density lipoprotein, highest in density due to high protein/lipid ratio
