Lecture 2b-Lipoproteins Flashcards
Where are lipids derived from? and examples
- fatty acids
- e.g. fats, oils, waxes, steroids and sterols, hormones
What is the function of lipids
- energy source
- component of cell membranes
- hormones-cell:cell communication
- insulation for nerves (sphingomyelins)
- Protection of and insulation for organs
- Vit A, D,E,K are lipid soluble
- Buoyancy
why do lipids present a special challenge?
They are hydrophobic
Fatty acids make up….
cholesterol and triacylglycerols (Fats, triglycerides)
Cholesterol makes hormone that we need for _____ _____
dietary needs
Triacylglycerols are used for?
for energy
What transports lipids
lipoproteins
What is the composition of a lipoprotein
- inside: core containing triacylglycerols and cholesteryl esters
- Outside: phospholipids, cholesterols, apolipoproteins (binds lipid to proteins to be transported)
Part two of anatomy of lipoprotein
Core: nonpolar lipids
* cholesterol ester
* triglyceride
Outside: amphipathic lipids
* phopholipid
* cholesterol
What does cholesterol do?
Prevents it from collapsing
name the lipoproteins from highest to lowest density
HDL, LDL,IDL, VLDL, chylomicrons
Which lipoprotein has the most triacylglyerols
chylomicron which also has the least cholesterol
Which lipoprotein has the most cholesterol
LDL
The more triacylglycerols, what happens to size of lipoprotein
it gets bigger
As density increases, the size
decreases
what are apoprotiens
are on the surface, providing structure and function (binding and enzyme activation
Apo A-I is associated with what lipoprotein and what is the function
- HDL
- Structural protein for HDL and activator of LCAT
Apo B-100 is associated with what lipoprotein and what is the function
- VLDL, IDL, LDL
- structural protein for VLDL and LDL and ligand for binding to LDL receptor
Apo B-48 is associated with what lipoprotein and what is the function
- Chylomicrons
- Structural proteins for chylomicrons
ApoA-1 is unique to what
to HDL–> structural and enzyme activator
ApoB is unique to what?
to non-HDL particles–> structural and ligand for receptor binding
how do we change apolipoproteins B?
mRNA editing
What happens to the apolipoprotein B in the intestine
- There is cytidine demainase editing complex (active) which changes CAA to UAA (stop codon) so we get 48
What happens to the apolipoprotein B in the liver
The codon stays as a Gln (CAA) and becomes a apoB100 proteins
apoB 48 is expressed in what and involved in what ?
Expressed mucosal cells and involved in receptor mediated chylomicron by the liver
apoB 100 is expressed in what and involved in what ?
expressed in the liver and involved in receptor mediated LDL uptake by the liver
explain the process of chylomicrons
Lipoprotein lipase (LPL) reaction
lipoprotein lipase present in:
- adipocytes
- striated mucsles
- prancreatic islets
- macrophages
What is the fuction of lipoprotein lipase
Hydrolysis of TG presents hydrolysis of TG present in chylomicrons and very-low density lipoproteins
what is the substrate for LPL reaction
triacylglycerol
What are the products of the lipoprotein lipase reaction
1,2-diacylglycerol and fatty acid
explain how VLDL and LDL are interconnected
What is the subtrate for lipoprotein
triglycerol
What is the LCAT reaction
What substrate can be used besides lecitin ?
Acyl-coenzyme:cholesterol actltransferases (ACAT)
what lipoprotein does reverse cholesterol transport?
HDL particles
What does HDL do
What is the function of HDL and LDL
- HDL: reverse cholesterol transport back to the liver for excretion
- LDL: takes cholesterol to all different organs
Explain the interconnecions of CETP (cholesterol ester transfer protein
Overview of HDL particles-reverse cholesterol transport
- HDL removes cholesterol from tissue and transports it to liver
- liver disposes cholesterol as bile acids
- HDL is called “good” cholesterol
What happens when cholesterol is taken up via LDL receptors
- LDL is internalized, then lysomoal hydrolysis to relaease cholesterol
- Once you have enough cholesterol in the cell regulatory actions:
1. decrease HMG CoA reductase (enzyme that makes cholesterol
2. increase ACAT or LCAT (makes cholesterol esters
3. decrease LDL receptors (no more cholesterol taken up
Where are chylomicrons synthesis in, secreted into, contains, rich in and function
- Synthesis in: The small intestines in the fed state
- Secreted into: the lymph vessels, then—> moves into the blood
- Contains apo B48
- Rich in:TGs
- Function: deliver TG’s to body cells to be used as fuel
Where are VLDL synthesis in, secreted into, contains, rich in and function
- Synthesis in the liver from excess dietary carbohydrate and protein along with the Chylomicron remnant
- Secreted into: the bloodstream
- Rich in: TGs
- Function: Deliver TGs to body cells
- Contains apo B100
Where are LDL synthesis in, secreted into, results from, rich in and function
- Synthesis in the Liver as VLDL
-
Results from: VLDL once it has lost a lot of its TG’s and
C–>CE - Secreted into: the bloodstream
- Rich in: Cholesterol
- Function: Deliver cholesterol to all body cells
Where are HDL synthesis in, secreted into, results from, rich in and function
- Synthesis in : the Liver and Small Intestine
- Secreted into: the bloodstream
- Function: Pick up cholesterol from body cells and take it back to the liver = “reverse cholesterol transport”
- Potential to help reverse heart disease
What does hyperlipidemia/hyperlipoproteinemia cause
Increase risk of atherosclerosis and cardiovascular diseases
What is familial hypercholesterolemia
- FH patients have high LDL and plasma cholesterol levels
- Lack LDL receptors: decrease degradation of LDL
- Mutations in LDL receptor gene
What is are the souces of cholesterol
found in aminal food only
Where is cholesterol synthesized ?
Liver
What is the atherosclerosis: LDL hypthesis?
- Elevated levels of LDL cholesterol and apoB100 directly contribute to atherosclerosis
- Oxygen radicals in endothelial lining of the arteries oxidize LDL and retain them
- Activated endothelial cells have increased inflammation
- Macrophages take up LDL and are saturated with cholesterol thus forming foam cells
What are the major enzymes of lipoprotein metabolism:
- Lipase (LPL)
- Lecithin:Cholesterol Acyl Transferase (LCAT)
- Cholesterol ester transfer Protein (CETP)
