4. Lipid Transport Flashcards
How are lipids transported round the body?
2% carried bound to albumin but has limited capacity
98% carried as lipoprotein particles (phospholipid, cholesterol, cholesterol esters, proteins, TAG)
How are phospholipids classified?
According to their polar head group
What are the 3 shapes phospholipids can form?
Liposome
Micelle
Bilayer sheet
Where does cholesterol come from?
Some obtained from diet
Most synthesised in liver
What is the role of cholesterol?
Essential component of membranes
Precursor of steroid hormones
Precursor of bile acids
How is cholesterol transported round the body?
Cholesterol ester
What are lipoproteins made up of?
Phospholipid monolayer with small amount of cholesterol
Peripheral apolipoproteins
Integral apolipoproteins
Cargo consisting of triacylglycerol, cholesterol ester, fat soluble vitamins
What are the 5 distinct classes of lipoproteins?
Chylomicrons (largest) VLDL IDL LDL HDL (smallest) Each contains variable content of apolipoproteins, triglyceride, cholesterol, cholesterol ester
How many major classes of apolipoproteins are there?
6
A, B, C, D, E, F, G, H
What are the 2 important apolipoproteins?
apoB (VLDL, IDL, LDL)
apoAI
What are the 2 roles of apolipoproteins?
Structural - packaging water insoluble lipid
Functional - co-factor for enzymes, ligands for cell surface receptors
Chylomicron metabolism
Look at notability
VLDL metabolism
Look at notability
IDL and LDL metabolism
Look at notability
What is the function of LDL metabolism?
Provide cholesterol from liver to peripheral tissues
Peripheral cells express LDL receptor and take up LDL via process of receptor mediated endocytosis
What is the clinical relevance of LDL?
Half life of LDL in blood much longer than VLDL or IDL so it’s more susceptible to oxidative damage
Oxidised LDL taken up my macrophages that transform to foam cells and contribute to formation of atherosclerotic plaques
What is the function of chylomicrons?
Transport dietary triacylglycerol from the intestine to tissues such as adipose tissue
What is the function of VLDL?
Transport fo triacylglycerol synthesised in live to adipose tissue for storage
What is the function of IDL?
Short loved precursor of LDL
Transport of cholesterol synthesised in live to tissues
What is the function of LDL?
Transport of cholesterol synthesised in liver to tissues
What is the function of HDL?
Transport of excess cholesterol from cells to liver for disposal as bile salt and to cells requiring additional cholesterol
What are hyperlipoproteinaemias?
Raised plasma level of one or more lipoprotein classes (6 main classes)
Caused either by over production or under removal
Defects in enzymes, receptors or apoproteins
All but one associated with coronary artery disease
What are the clinical signs of hyperholesterolaemia?
High levels of cholesterol in blood Cholesterol depositions in various areas of body Xanthelasma - yellow patches on eyelids Tendon xanthoma - nodules on tendon Corneal arcus - white circle around eye
What is raised serum LDL associated with?
Atherosclerosis
