Lipoproteins I Flashcards
…………… are spherical macromolecular complexes of lipids and specific proteins
Lipoproteins
…………. are lipoproteins formed in the blood from VLDL (via IDL) and deliver cholesteryl esters to cells that need cholesterol (mainly for cell membranes).
LDL (Beta-Lipoprotein)
……small lipoproteins involved with the reverse cholesterol transport to the liver and are filled in the blood with cholesteryl esters.
HDL (alpha-Lipoprotein)
…………..are lipoproteins released by the liver and contain TAGs and cholesteryl esters that were formed by the liver (endogenous source).
VLDL (pre-Beta Lipoprotein)
………….. are the lipoproteins released by the intestinal mucosal cells which contain dietary lipids (exogenous source) and lipid-soluble vitamins.
Chylomicrons
…….. float on top of the blood sample when separated by ultra-centrifugation
Chylomicrons, then the next layers are:
- Very low density lipoproteins (VLDL)
- Intermediate density lipoproteins (IDL) 4. Low density lipoproteins (LDL)
- High density lipoproteins (HDL)
The purpose of chylomicrons is to………
Transport dietary lipids away from intestinal mucosal cells by the lymph system and later into the blood circulation.
……… cleaves most of the Triacylglycerols (TAGs) of Chylomicron
Lipoprotein Lipases (LPL)
Lipoproteins are anchored in the capillaries of the ………, ………, and ………..
Heart, Muscle, Adipose Tissue
The chylomicron remnants have the function to deliver the dietary cholesteryl esters and other particles to the ……….
Liver
Chylomicrons need ……… and ……… to be released into the lymph.
Apo B-48
MTP- Microsomal TAG transfer protein
Chylomicrons are nascent (functionally incomplete) until they collide with ……. and transfer ……….. and ………
HDL
Apo- E and Apo-CII
……….. Activates Lipoprotein Lipase
Apo C-II
……….. Allows entry of chylomicrons remnants into the liver.
Apo E
Free fatty acids produced by the cleavage action of Liproprotein Lipase are taken up by ………. or …………
Muscle or Fat cells
Cardiac lipoprotein lipase activity is ………….
Insulin-Independent
The heart always takes up fatty acids for its energy metabolism
Adipocyte LPL activity is
Insulin-dependent
When chylomicrons and VLDL are abundant then the generated fatty acids are taken up into fat cells and stored as TAGs.
…………. enhances in adipocytes the synthesis of LPL and its placement in the capillaries.
Insulin
Inside of fat cells, insulin activates the synthesis of …… for storage after uptake of free fatty acid from the blood
TAGs
The chylomicron remnant contains apo E and apo B-48 as …… is returned to HDL
Apo-C
Remnant receptors on the liver recognizes apo E allow the endocytosis of ……..
Chylomicron remnants
……….. released by hepatocytes contains only Apo B-100 until HDL adds during collision Apo C and Apo E
Nascent VLDL
Purposes of VLDL:
- to prevent TAG accumulation in hepatocytes and
- to provide substrates for lipoprotein lipase resulting in fatty acids for other cells.
- to generate eventually LDL which can distribute cholesteryl esters to the cells that require it
Cleavage of TAGs from VLDL creates the VLDL remnant, …….
IDL
IDL is either taken up into the liver via the remnant receptor or …………….
Acts as a substrate for hepatic lipase (hepatic TAG lipase HTGL) which will form LDL in the blood of hepatic capillaries.
Which lipoprotein is absent in blood of fasting healthy individuals?
Chylomicrons
Which lipoprotein has the highest % of cholesterol?
LDL
…….. formed by hepatic lipase in the capillaries of the liver from IDL in the blood
LDL
Purpose of LDL
To transport cholesteryl esters in the blood and deliver cholesterol to cells that need it for their plasma membranes or for steroid hormone synthesis
The LDL receptor in the coated pit on the liver membrane recognizes ………in LDL and the uptake is performed via endocytosis.
Apo B-100
The pH of the endosome allows the separation of LDL from the receptor and the LDL receptor can be…………
Recycled
At high free cholesterol levels the cytosolic enzyme …….. is activated and a reservoir of cholesteryl esters is formed.
(fatty) Acyl CoA cholesterol acyl transferase (ACAT)
If there is still high free cholesterol left in cytosol after the activation of ACAT then ….. is synthesized and also of LDL receptors are down-regulated
HMG CoA reductase (regulated enzyme of cholesterol synthesis)
In the liver after a cholesterol-rich meal the uptake of chylomicron remnants lead to high free cytosol cholesterol levels which ……….. LDL-receptor synthesis.
Reduces.
This leads to temporary increased levels of serum LDL.
Deficient recognition of ……. on chylomicron remnants leads to accumulation of IDL and chylomicron remnants in the blood.
Apo-E
Inactivation of Lipoprotein Lipase due to a deficiency in …… leads to elevated levels of chylomicrons and of VLDL in the blood
Apo C-II
