Lipid Transport Flashcards
What lipids are present in blood plasma?
Lipoproteins are most abundant
Fatty Acids
What is blood plasma?
All of the blood minus the cells
Blood serum is ________.
Blood plasma without clotting factors
What is used to transport lipids?
Lipoproteins
What is a lipoprotein?
A triglyceride, cholesterol, cholesterol ester, phospholipids form NON-COVALENT aggregates with proteins forming a complex known as lipoproteins
Hydrophobic lipids form the _____ of the lipoprotein
Core
Triglycerides
Cholesterol Esters
Amphipathic Lipids are a at the _______-
interface between aqueous medium and hydrophobic core
Apoproteins are _______.
Amphipathic
Chylomicrons and VLDL contain a high amount of _________.
What is the difference?
Triacylglycerols
Triacylgycerols carried by chylomicrons are obtained from the diet.
VLDLs carry triacylglycerols synthesized in the liver.
HDL has a lot of ________.
Proteins
Order the major human plasma lipoproteins from least dense to most.
Chylomicron
VLDL
IDL
LDL
HDL- LOTS of proteins
What makes up over 50% of lipids in LDL ?
Cholesterol and cholesterol esters
Where are the following produced?
Chylomicrons
VLDL
IDL
LDL
HDL
Chylomicrons - Intestinal epithelial cells from dietary fats
VLDL- Liver from dietary carbs
IDL- Blood
LDL- Blood
HDL- Liver and Intestine
What are the functions of the following?
Chylomicrons
VLDL
IDL
LDL
HDL
Chylomicrons - Carries TG in blood
VLDL - Carries TG in blood
IDL - Endocytosed by liver or converted to LDL
LDL- Endocytosed by liver and peripheral tissues
HDL- Returns cholesterol from peripheral tissues to liver, exchanges proteins and lipids with other lipoproteins
Which two lipoproteins carry lipids in blood?
Chylomicron
VLDL
Which is the only lipoprotein that returns cholesterol from tissues to the liver ?
What is one other function of this lipoprotein?
HDL
Exchanges proteins and lipids with other lipoproteins
Apoproteins are ________.
Proteins associated with lipoproteins.
Which apoprotein is the ligand for the LDL receptor?
B100 and E
What is the activator of LCAT?
Apoprotein A-1
What is the activator of lipoprotein lipase?
Apoprotein C-II
What is a chylomicron remnant receptor and also a ________ for LDL?
Ligand
Apoprotein E
What are the 4 enzymes involved in lipoprotein metabolism?
- Lipoprotein Lipase (LPL)
- Hepatic Lipase
- Lecithin-Cholesterol Acyltransferase(LCAT)
- AcylCoA :Cholesterol Acyltransferase (ACAT)
What is the function of LPL?
Processing of chylomicrons and VLDL
MOST IMPORTANT
What is the function of hepatic lipase?
What is another name?
Hepatic triglyceride lipase
IDL to LDL
What is the function of LCAT
Catalyze transfer of LCFA to cholesterol to make cholesterol esters
What is the function of ACAT?
Intracellular enzyme that makes cholesterol esters
Describe the formation of chylomicrons
- FA and 2MG are incorporated into micelles with the help of bile salts.
- Micelles enter epithelial cells of the intestine and regenerate TGs from FA and 2MG on the surface of SER
- TG combine with apoproteins from RER and phospholipids to migrate to the Golgi Body
- The Golgi pinches off vesciles to make chylomicrons and then exit into the lymph and then into the blood via exocytosis.
__________ breaks down triacylglycerols (TAGs) so that bile salts can __________
Pancreatic lipase breaks down triacylglycerols (TAGs) so that bile salts can incorporate them into micelles
Triacylglycerols are resynthesized by _________ in __________ using ______ and _______.
SER
Intestinal Epithelial Cells
FA and 2-monoglycerol
Chylomicrons start as _____________ and end as ________.
Mixed Micelles, Nascent Chylomicrons
When nascent chylomicrons enter the blood they will encounter ________ which will donate _____ and ______ which _____________.
HDL
Apoprotein E and CII which make the chylomicrons mature and become very large
What tissues are related to LPL (lipoprotein lipase)?
Muscle and Adipose Tissue
These secrete LPL into the capillary tubes of the blood vessels. It is not incorporated fully into the blood.
What does LPL do?
Once the Chylomicron TG has been matured by HDL donated Apoprotein E and CII, LPL will hydrolyze TAGs in chylomicrons to produce FATTY ACIDS AND GLYCEROL.
The lack of Apoprotein CII will inhibit _______.
LPL activation.
What are the products of lipoprotein lipase on mature Chylomicron TAG?
Create Fatty Acid and Glycerol
Chylomicrons ________ in size by 50% after LPL activity and are called _______.
These bind to receptors on ______ and enter through ________. ______ enzyme degrades __________ to generate _______.
reduce
Remnants
Plasma membrane of liver and other cells and enter through endocytosis. Lysosomal enzyme degrades chylomicron remnants to generate
FA
Cholesterol
AA
Glycerol
Chylomicrons are produced in ______ cells and end up in ________.
Intestinal Epithelial Cells
Liver Cells or other cells
How is VLDL made?
Protein synthesized on the rough endoplasmic reticulum are packaged with triacylglycerol in the ER and Golgi complex to form VLDL.
VLDL are transported to the cell membrane in secretary vesicles, and secreted by exocytosis.
VLDL is synthesized in the _______ and transported to the ________. It is in an __________. _______ transfers ______________ to make VLDL ________.
Liver, Blood
Immature state
HDL, Apoprotein E, CII, CE (Cholesterol Esters)
Mature
What degrades TAGs in VLDL?
Lipoprotein Lipase
IDL is produced in the ________. What is its precursor?
Blood
VLDL
What is the difference between LPL and HTGL?
LPL is produced by muscle & adipose tissue and deals with larger particles such VLDL and Chylomicrons
HTGL is produced by liver tissue and deals with small particles such as IDL
HTGL can hydrolyze _______ to ________.
IDL TG to Fatty acid and Glycerol
OR
LDL
LDL is produced in the _____
blood
IDL and LDL will get take up by _______.
Liver and Peripheral Cells
What is the similarity between LPL and HTGL/
They both hydrolyze TGs to fatty acids and glycerols.
VLDL when hydrolyzed by ______ is the precursor of _______ which is the precursor of ________ when hydrodlyzed by _____.
LPL , IDL
LDL, HTGL
LDL consists of lots of cholesterols and ________.
Why is this bad for us?
Cholesterol esters
Humans do not have the enzymes to change the heterocyclic ring structure of cholesterol.
Cholesterol esters can be ________ creating ________.
oxidized
oxidized LDL
What does oxidized LDL do?
Cause damage to endothelial layer of blood vessel.
Macrophages will come to the site of injury and take out oxidized LDL without much regulation and form FOAM cells due to the buildup of LDL within themselves.
These foam cells form fatty streaks and eventually cause further endothelial damage.
Damaged endothelial cells release TXA2 and now macrophages and platelets will release growth factors.
These growth factors will cause proliferation and migration of smooth muscle cells to the intimal layer of arterial wall
Fibrous material will also create a thick collagen cap.
FOAM cells are believed to be the starting point for atherosclerosis.
LPL from _______ cells is stimulated by _________.
Adipose Cells
Apoprotein CII and Insulin
As long as either Apoprotein CII OR Insulin are available, LPL will function.
True or False
FALSE
Insulin must be available!
Diabetic patients who have trouble controlling insulin may have a build up of ___________ because _________.
Chylomicrons and VLDL
LPL
Hyperchylomicronemia
Treatment
Familial LPL or Apoprotein CII deficiency resulting in
Increased chylomicrons, VLDL, TGs and cholesterol in blood
Fat restriction
Describe how the LDL Receptor works
Location
Surface of ER
LDL protein is synthesized and transported to Golgi Body via lipid vesicles and then to the plasma membrane.
These receptors must aggregate in order for LDL to bind and initiate endocytosis.
The receptor will bring in the LDL via a lipid vesicle which will get broken down by Lysosomes.
The receptor can be recycled
LDL receptor is only on the liver cells.
True or False
FALSE
LDL-receptor binds LDL only.
True or False
FALSE
LDL
VLDL
IDL
Chylomicron remnants
IDL
A problem in LDL receptor will cause ________.
An accumulation of LDL in the blood
Cholesterol regulates what enzyme?
HMG-CoA Reductase
What can the cell do if cholesterol gets too high in cell?
- Insert cholesterol into plasma membrane
- Reduce HMG COoA reductase
- Use ACAT to convert cholesterol to cholesterol ester
- Reduce LDL receptors
ACAT is located _______ the _____cell.
inside the liver
HDL is produced by the _____.
Liver
HDL becomes mature by _______.
Donating Apoproteins to VLDLs and chylomicrons
This makes HDL change shape from disc to spherical
Mature HDL can pick up ________ from _____ using a protein called ______.
Cholesterol in peripheral tissues is now moved to the surface of HDL
______ in HDL will convert _________ to ______.
In the blood, _______ from VLDL will migrate to _____ while the _________ from HDL will migrate to _____.
cholesterol from peripheral tissue, ABC1
LCAT in HDL will convert cholesterol to cholesterol esters.
In the blood, TAGs from VLDL will migrate to HDL while the Cholesterol Ester from HDL will migrate to VLDL.
VLDL can be metabolized to IDL and then LDL which can be taken up by LDL receptors in the liver
Liver is the only place we can synthesize cholesterol because _________.
It can produce bile salts
What is reverse cholesterol transport?
The transfer of TG from VLDL to HDL and the Cholesterol Ester from HDL to VLDL
LCAT converts _______ to _______.
Cholesterol to cholesterol esters
LCAT is in the ______ and associated with ____.
Blood, HDL
What is the best level of cholesterol?
Less than 200mg/dL
How does Statin inhibit cholesterol synthesis?
Inhibit HMG CoA reductase
Cell will respond by increasing LDL receptors thus reducing blood cholesterol
What is cholestyramine?
A drug that binds to bile salts making them unabsorabable by human bodies and thus being excreted through feces
