Lipids Flashcards
What do intestinal enterocytes make from broken down fats
Chylomicrons (90% TG)
Where do chylomicrons go once made
Lymphatic system –> thoracic duct–> blood
What is required for transport of chylomicrons out of the small intestine
Apo B48
What happens if not enough Apo B48
Abetalipoproteinemia
What do cells use to draw free FFA’s from circulating chylomicrons
Lipoprotein Lipase
What does liver do with chylomicron remnat
Makes VLDL
What does Apo B 100 do
Helps secrete VLDL that was made in the liver
What happens if not enough Apo B 100
VLDL cannot leave liver
What is VLDL transformed to as FFA’s are taken up by cells
IDL
What is IDL degraded to and by what?
LDL, by hepatic triglyceride lipase - made in liver
What is LDL rich in
Cholesterol - lost FFA’s
What happens if LDL oxidized
Atheroma
How do cells absorb LDL
By endocytosis, using clathrin coated pit, LDL receptor
What can cells do if they have too much cholesterol
Deposit it in circulating HDL from liver
What is LCAT
HDL uptakes cholesterol from cells this way
What can HDL deposit cholesterol on? By what enzyme?
VLDL or LDL via CETP
What is SRB1
Scavenger receptor - for hepatocyte to pull cholesterol off HDL
Apo B48
Chylomicron secretion from enterocyte to lymphatic system
Apo B100
Found on VLDL, IDL, and LDL that have left the liver
Apo E
Mediate extra remnant uptake
Apo A-1
Activates LCAT, found on HDL
Apo C-II
Cofactor for LPL
What is deficient in Abetalipoproteinemia
AR, deficiency in Apo-B48 and ApoB-10
Mutation in MTP gene
Presentation of abetalipoproteinemia
Presents in first few months of life with FTT, steatorrhea, impaired transport of fat soluble vitamins (ADEK), acanthocytosis (misshapen RBC membrane bc of bad lipids), ataxia, night blindness
Treatment of abetalipoproteinemia
Vitamin E
What is defective in Type 1 Hyperchylomicronemia
AR
Deficiency of LPL
Or, Defective Apolipoprotein CII (LPL cofactor)
Presentation of Type 1 Hyperchylomicronemia
Pancreatitis, HSM, xanthomas
No incr risk of atherosclerosis
What is elevated in the blood in Type 1 Hyperchylomicronemia
Chylomicrons, TG, Cholesterol
What is defective in Type IIa Familial hypercholesterolemia
AD
Absent/decreased LDL receptor - needed for uptake of circulating LDL
Presentation Type IIa Familial hypercholesterolemia
Tendinous xanthomas
Corneal arcus
Accelerated Atherosclerosis
What is defective in Type IV hypertriglyceridemia
AD
Overproduction of VLDL in liver
What is elevated in blood in Type IV hypertriglyceridemia
VLDL and TG
Presentation of type IV hypertriglyceridemia
Pancreatitis
What is increased in blood in type IIa familial hypercholesterolemia?
LDL and cholesterol
What is the substrate for making cholesterol in the body?
Acetyl CoA
Rate limiting enzyme of cholesterol synthesis
HMG-CoA reductase
What is the main precursor in FA synthesis
Acetyl CoA
Where does FA synthesis take place
Cytoplasm of hepatocytes
Rate limiting enzyme of FA synthesis
Acetyl-CoA carboxylase
Where does FA degradation take place
Mitochondria
What is rate-limiting enzyme of FA degradation (beta-oxidation)
Carnitine acyltransferase-1
What happens if deficient in CAT-1?
Can’t get long chain FA into mt –> accum in cytoplasm. And can’t be broken down.
Activates LCAT
Apo A-1
LCAT
Catalyzes esterification of cholesterol
Mediates chylomicron secretion
Apo B-48
Mediates VLDL secretion
Apo B-100
Apoprotein that Binds LDL receptor
Apo B-100
Cofactor for lipoprotein lipase
Apo C-II
Mediates uptake of remnant particles
Apo E
Rate limiting enzyme for ketone body synthesis
HMG-CoA synthase
