L4: Lipid Transport Flashcards
What are lipids?
Structurally diverse, insoluble molecules
What are the different types of lipids?
Triacylglycerol (di and mono too) Fatty acids Cholesterol (cholesterol esters) Phospholipids Vitamins A, D, E and K
What is the problem with transport?
Insoluble cant transport in blood
Solution–> carrier molecules
2% lipids (mainly FA) bound to albumin
98% –> lipoprotein particles
What is the structure of a phospholipid?
Polar head (hydrophilic) –> classified according to this
Phosphate
Glycerol backbone
Non Polar tails (hydrophobic)- Fatty acids X2
How can phospholipids arrange themselves?
Bilayer sheet
Liposome–> bilayer in a sphere shape
Micelle
Where does cholesterol come from? What is it for?
Synthesised in liver
Component of membranes
Precursor steroid hormones –> cortisol, aldosterone, testosterone, oestrogen
Precursor bile acids
How is cholesterol transported around the body?
Cholesterol esters
Esterification –> Lecithin Cholesterol Acyltransferase (LCAT) or Acyl-coenzyme A cholesterol acyltransferase
What is the function of lipoproteins?
Transport lipids around the body Consist of phospholipid, cholesterol, cholesterol esters, proteins, TAG Cargo: - TAG - Cholesterol esters - Fat soluble vitamins A, D, E and K
What is the structure of a lipoprotein?
Phospholipid monolayer –> spherical
Small amount of cholesterol and apolipoproteins
–> Intergral (apoA and apoB) and peripheral (apoC and apoE)
What are the different classes of lipoproteins?
Chylomicrons –> Chylomicron remnants (lipid removed)
Very Low Density Lipoproteins (VLDL)
Intermediate Density Lipoproteins (IDL)
Low Density Lipoproteins (LDL)
High Density Lipoproteins (HDL)
Variable amounts of apolipoproteins, triacylglycrides, cholesterol and cholesterol esters in each
How was the density off lipoproteins discovered?
Flotation Ultracentrifugation –> separated
Particle diameter inversely proportional to density
What are apoplipoproteins?
Associated proteins
Lipoprotein specific
How many classes of apoplipoproteins are there?
6 major –> A, B, C, D, E and H
What are the most important apoplipoproteins?
apoB (VLDL, IDL, LDL) and apoAI (HDL)
What is the function of apoplipoproteins?
Structural role–> packaging of water insoluble lipids
Functional role–> Co-factor for enzymes
–> ligands for cell surface receptors