Lipid Transport Flashcards
What factors affect the concentration of lipid in the blood?
- the nutritional status of the organism
- individual constitution
Why are lipids not able to be transported free in the circulation?
As they have a hydrophobic nature.
What is the differences between unesterified fatty acids and the following: triglycerides, phospholipids and cholesterol esters?
Unesterified esters are transported in association with albumin whereas the others form large covalent aggregates with proteins which are also known as lipoproteins.
Where are lipids transported from?
- The gut to the liver.
- The liver to non-hepatic tissue including adipocytes.
- Non-hepatic tissue back to the liver.
What are the different functions for fatty acids?
- polyunsaturated fatty acids can act as ligands for transcription factors involved in energy metabolism e.g. they can play a role in insulin regulation.
- they regulate lipid oxidation in the liver and muscle
- down regulate genes involved in lipogenesis in the liver and adipose tissue.
- increase the expression of UCP-2 and 3 in mitochondria to increase thermogenesis.
What are the percentages of different fats in blood?
- triglycerols = 45%
- cholesterol esters = 15%
- phospholipids = 35%
- free fatty acids = 5%
- NOTE: the percentages above can vary due to the nutritional state and they are all insoluble in water.
What is the composition that lipids can be transported as other than lipoproteins?
They can be transported as free fatty acids which are formed from triglycerides and are stored in adipose tissue. However they are also actually bound to a proteins such as albumin as Na+ salt as if they would act as a detergent causing damage to the cell membrane if it were transported as a fatty acid alone.
What is the amount of fatty acids needed to achieve saturation?
2mM
How do fatty acids move in and out of the cell?
Through simple diffusion
*Note: the concentrations of fatty acids within the cell are kept low.
How are lipoproteins carried into the blood as?
As plasma lipoproteins
What are the five major types of lipoproteins?
- chylomicrons- a little different as they are synthesised from dietary fats in the gut lining.
- very low density lipoproteins (VLDL)
- low density lipoproteins (LDL)
- intermediate density lipoprotein (IDL)
- high density lipoproteins (HDL)
- Note: each type has a different function
What is the structure of a lipoprotein?
LOOK AT NOTES FOR DIAGRAM
- each lipoprotein contains one very large protein called apolipoprotein.
- contains phospholipids, cholesterol and triglycerides.
What is the composition of chylomicron?
Protein= 1-2% Cholesterol= 3-7% Phospholipid= 3-8% Triglyceride= 90-95%
What is the composition of a VLDL?
Protein= 10% Cholesterol= 19% Phospholipid= 15% Triglyceride= 53%
What is the composition of a LDL?
Protein= 18% Cholesterol= 11% Phospholipid= 22% Triglyceride= 31%
What is the composition of a IDL?
Protein= 25% Cholesterol= 50% Phospholipid= 21 Triglyceride= 4%
What is the composition of a HDL?
Protein= 49% Cholesterol= 22% Phospholipid= 28% Triglyceride= 2%
What is the apolipoprotein associated with a chylomicrons?
B48, Apo C2, C3 and E
What is the apolipoprotein associated with a VLDL?
B100, Apo C1, C2, C3 and E
*Note: VDLD acquires the Apo C1,C2,C3 and E from HDLs when it circulates in the blood- it starts off only with B100
What is the apolipoprotein associated with a LDL?
B100 and Apo E
What is the apolipoprotein associated with a IDL?
B100
What is the apolipoprotein associated with a HDL?
Apo A1, A2, C1, C3, D and E
Are the different types of lipoproteins able to interact with each other?
Yes they are able to interact and can exchange apolipoproteins.
What are the functions of the apolipoprotein?
-Structural- they are the backbone of lipoproteins
-To solubilize lipids- they allow the lipids to become soluble in aqueous environments
-Act as enzymes or enzyme cofactors
*Apo C2 activates lipoprotein lipases
*Apo A1 for lecithin: activates cholesterol
acyltransferase
-Targeting lipoproteins to different tissues
*Apo B100 and Apo E bind to the LDL receptor
*Apo E binds to the HDL receptor