BIOL 301 class 20 Flashcards
what is high cholesterol/hyperlipidemia?
excessive amounts of lipids in the blood serum
steps of dietary fat processing
1) bile salts emulsify dietary fats in the small intestine, forming micelles
2) intestinal lipases degrade triacylglycerols (stored form of fat)
3) fatty acids and other breakdown products are taken up by the intestinal mucosa and converted into triacylglycerols (intestinal mucosa repackages it to triacyglycerols)
4) triacylglycerols are incorporated with cholesterol and apolipoproteins into chylomicrons
5) chylomicrons move through the lymphatic system and bloodstream to tissues
6) lipoprotein lipase, activated by apoC-II in the capillary, converts triacylglycerols to fatty acids and glycerol
7) fatty acids enter cells
8) fatty acids are oxidized as fuel or reesterified for storage
What happens to the intestinal epithelium after having a fatty meal?
Fat droplets appear
what are fat droplets?
fats that have been absorbed by the intestine and will be repackaged as TAGs into chylomicrons and sent out to the tissues
The lipid and cholesterol circulatory system
1) starts at the intestine
- intestine produces chylomicrons
2) chylomicrons go into the capillary
- lipoprotein lipase degrades chylomicrons into free fatty acids which then go to the mammary, muscle, or adipose tissue
3) chylomicron remnants can then go to the liver
4) VLDL remnants (IDL) can also go into the liver
- they can also get degraded to LDLs and go into the liver or extrahepatic tissues
5) HDL precursors (from the liver and intestine) can go into extrahepatic tissues
6) from the extrahepatic tissues these HDLs can also go into the liver via reverse cholesterol transport
what is the big role of the liver during the lipid and cholesterol circulatory system?
the liver sends out more proteins to grab more lipids if this is needed via reverse cholesterol transport
what are cholesterol esters?
the storage and transported forms of cholesterol
what are the two types of cholesterol esters?
ACAT & LCAT
what is ACAT?
transfers fatty acids from Fatty AcylCoA to cholesterol in the liver and other cells
what is LCAT?
transfers fatty acids from phosphatidylcholine to cholesterol on HDLs during reverse transport
cholesterol is made by?
a fatty acid esterifying into a cholesterol molecule
what are serum lipids?
- lipoprotein complexes with different lipid/protein ratios
- keep it into a soluble form so they dont form a fat globule in the serum
high LDL = ?
high cholestrol
high HDL = ?
good cholesterol
lipoprotein order from high lipid concentration to low
chylomicrons, VLDL, IDL, LDL, HDL
high protein concentration = ?
low density
low protein concentration = ?
high density
lipoproteins are the delivery vehicles for lipids
at the beginning → they have more lipids so they have a lower density
after delivering lipids to peripheral tissues → they are low on lipids so that means they have a higher density
HDLs are vehicles sent to retrieve excess lipids
→ reverse transport when needed
→ these proteins are recognized by receptors on cell surfaces
→ these receptors then free up fatty acids for import into the cells that need them.
→ the goal is to ultimately deliver fat for storage and energy purposes
apoliproteins
phospholipids, TAGs, and cholesterol circulate in the blood in complexes with apoliproteins
apolipoprotein + lipid = ?
lipoprotein