Lipid Transport Flashcards
What are the structural roles of apoproteins?
Package non-water soluble lipid molecules into soluble forms known as multi-molecular particles.
What are two ways that lipids can be transported in the blood plasma?
Lipoprotein particles
Bound non-covalently to albumin (fatty acids only)
What are the functional roles of apoproteins?
Activate enzymes
Recognise cell surface receptors
What is the structure of a lipoprotein particle?
Hydrophobic core made up of triacylglycerols and cholesterol esters
Surface coat made up of phospholipids, cholesterol and apoproteins.
What keeps lipoproteins stable?
Need to maintain their spherical shape and this depends on the ration of surface lipids to core.
What are core components of a lipoprotein removed by?
Lipases and transfer proteins.
How do lipoproteins differ and what differences in properties does this give them?
Apoprotein composition and the different types of lipids they contain.
Properties
- net electrical charge
- size
- molecular weight
- density
How can different lipoproteins be separated?
Electrophoresis
Ultracentrifugation
How are chylomicron remnants and VLDL remnants formed?
Removal of lipids (mostly TAGs) from chylomicrons and VLDLs.
What do chylomicrons do?
Transport triacylglycerols from the small intestine to tissues such as adipose tissue.
What must happen to dietary triacylglycerols before they are absorbed in the small intestine?
Must be hydrolysed by pancreatic lipase into fatty acids and glycerol.
What does lipoprotein lipase do?
Hydrolyses triacylglycerols carried by chylomicrons to release fatty acids that enter cells of adipose tissue.
What do VLDLs do?
Transports triacylglycerols synthesised in the liver to adipose tissue for storage.
What do LDLs do?
Transport cholesterol synthesised in the liver to tissues.
What do HDLs do?
Transport excess tissue cholesterol to the liver for disposal as bile salts.
What is a dyslipoproteinaemia?
Any defect in the metabolism of plasma lipoproteins.
How can secondary dyslipoproteinaemia occur?
It is acquired from diet, drugs or an underlying disease such as diabetes.
Which types of dyslipoproteinaemias are NOT associated with coronary artery disease?
Type I
How can dyslipoproteinaemia be treated?
Aim is to reduce cholesterol level in blood
Lifestyle modifications
Statins
Bile salt sequestrants
How do statins work?
They reduce synthesis of cholesterol in the liver by inhibiting the enzyme HMG-CoA reductase.
How is cholesterol disposed of in the body?
Converted to bile salts that are excreted in the bile.
How do bile salt sequestrants work?
Bind to bile salts in the GI tract.
Prevents them from being re-absorbed into the hepatic-portal circulation.
Excreted in the faeces.
Where is lipoprotein lipase found?
Attached to inner surface of capillaries in tissues such as adipose tissue and skeletal muscle.
What increases the production of lipoprotein lipase?
Insulin
