Skildum: Lipids Flashcards
Which is the most calorically dense food?
Fat
Which particle functions to promote cholesterol homeostasis?
High density lipoprotein (reverse cholesterol transports from tissue to the liver–helps maintain circulating cholesterol levels)
Which lipoprotein activates an extracellular lipase in capillary beds?
ApoCII
What are the important metabolic fates of Fatty acids?
- Oxidized to CO2 and H20
- Triacylglycerol (adipose tissue stores)
- Phospholipids and sphingolipids (membranes)
What forms arachidonic acid (EPA)?
w6fatty acids (linoleic, linolenic acid)
What can arachidonic acid be turned into?
Leukotrienes
PGs
Thromboxanes
*can cause a basal contraction of the LES
What do bile salts do?
TAG enters mouth>
mechanical breakdown>
TAG enters SI>
gall bladder secretes bile salts which act as detergents (derived from cholesterol and synthesized in the liver then stored in the GB)>
makes cholesterol more accessible to the solvents
What does the pancreas do?
Secretes pancreatic lipase>
hydrolyzes two of the FA ester bonds form TAG and makes 2 free FA and 2 MG>
these substances are taken into an enterocyte>
repackaged into TAG>
packaged w/ lipoproteins into a chilomicron then released into the blood stream
What does the bolus of food passing into the stomach do?
Causes secretion of:
secretin> pancreas> pancreatic lipase
cholecystokinin> gall bladder> bile salts
What are the three forms that fat in the diet is consumed as?
triacyglyerol
phospholipids
cholesterol esters
Where does the pancreatic lipase cut triacylglycerol?
At the number 1 and 3 position
Triacylglycerol + pancreatic lipase forms what?
2 fatty acids +
2 monoacylglycerol
What does PLA-2 produced by the pancreas do?
Cuts the number 2 fatty acid from triacyglycerol (not required for digestion)
How is fat metabolized?
TG> digested by bile salts> TG in micelles> pancreatic lipase> 2 FA + 2 monoacylglycerol> uptake by gut epithelial cells> TG in chylomicrons> lymphatic transport> chylomicrons in blood
What happens to short and medium chain Fatty acids?
By pass chylomicron stage and are taken up by gut epithelial cells and then enter the portal blood
Fat that is consumed as a cholesterol ester is broken down by cholesterol esterase to…
Fatty acid and cholesterol (both can be taken up by gut epithelial cells and packaged as lipoproteins)
Fat that is consumed as phospholipids is broken down by PLA2 (cuts number 2 position) to form…
FA and lysophospholipid (taken up by gut epithelial cell and packaged into lipoprotein particle)
The polar head groups of phospholipids can be…
choline
ethanolamine
inositol
How does fat digestion take a different route than normal digestion?
it bypasses the liver and enters the lymphatic system–> blood–> peripheral tissue–> liver
What happens in intestinal epithelial cells?
FA are re-esterified to glycerol to make TG in intestinal epithelial cells
What is the major apoprotein of chylomicrons?
apoB-48–seed crystal to form chylomicron particle
What is ApoB48 encoded by?
same gene as apoB100, the apoprotein of VLDL
How is a nascent chylomicron formed?
TG are absorbed by brush border villae in the intestinal lumen and stored in teh SER. The RER makes ApoB-48. These two products fuse at the golgi complex and form nascent chylomicrons, which then enter the lymph.
What is the hallmark of a chylomicron?
apoB-48–> if a protein contains apo B 48 that particle contains dietary fat
What is the hallmark of a VLDL particle?
apoB-100 (from the liver)
ApoB-48 and ApoB-100 are produced by the same B-apoprotein gene. How RNA editing produce two different products?
intestine> stop codon> apoB48
liver–> C–> unedited full length transcript in hepatocytes
What happens once chylomicrons enter the blood?
They receive ApoCII and ApoE from HDL
What is the function of HDL?
Maintain cholesterol and apoprotein homeostasis
What converts a nascent chylomicron to a mature chylomicron?
ApoCII from HDL
What is the function of ApoCII?
Activates LPL in peripheral tissue (capillary beds of muscle and adipose tissue) which allows the chylomicrons to deliver calories to the peripheral tissue
What happens when the chylomicron interacts w/ the LPL?
Chylomicron/CII interacts w/ LPL>
cuts off free FA from TG>
Free FA are then oxidized for generation of ATP into CO2 and H20 (if work is being done) >
or FA can be re-esterified to glycerol and stored as TG in adipose tissue (no work being done)
What happens when the chylomicron loses CII?
It becomes a chylomicron remnant and is recycled by the liver
What happens to FA and cholesterol taken up by the liver from chylomicron remnants?
They can be repackaged w/ ApoB100 as VLDL
What is the function of VLDLs?
Deliver fatty acid fuels to tissues of the body (similar to chylomicrons)
What activates a nascent VLDL?
apoCII
What is the diff between chylomicrons and VLDL?
chylomicrons are much BIGGER but the relative compositions of each are similar
When can adipose store FA as TG (it can be taken up by chylomicrons or VLDL particles)?
FED STATE!
The glycerol 3 phosphate backbone can ONLY be produced by glycolysis in adipocytes
What is the largest lipoprotein?
chylomicron
What do chylomicrons do?
transfer dietary fat from gut to the tissues
What is the source of chylomicrons?
intestinal epithelial cells
What proteins are associated w/ chylomicrons?
48
CII
E
What do chylomicron remnants do?
return apoproteins to the liver
What proteins are associated w/ chylomicron remnants?
48
E
(lose CII)
What is the function of VLDL?
transfer fat produced by dietary carbs to tissues
What is the source of VLDL
liver
What proteins are associated w/ VLDL?
100 C1 CII CIII E
What is the function of IDL?
deliver lipids, cholesterol to tissues
What is the source of IDL?
remnant of VLDL
What proteins are associated w/ IDL?
100 C1 CII CIII E
(same as VLDL)
What is the function of LDL?
Deliver cholesterol to cells
What is the source of LDL?
remnant of IDL
What protein is associated w/ LDL?
100
What is the fxn of HDL?
cholesterol and apoprotein homeostasis
What is the source of HDL?
liver and intestine
What proteins are associated w/ HDL?
A1 A CI CII LCAT
