Lipid transport an function Flashcards
What does a triglyceride contain?
Glycerol and 3 fatty acid chains
What does it mean when a fatty acid is saturated?
No double bond
Why do we need lipids?
Lipids are good for you
-Energy and energy store
-Vitamins antioxidants (transport)
-Insulation
-Protects organs
-Structure (brain)
-Phospholipids - bilayer cell membrane integrity
-Hormones prostaglandins
-Gene expression
-Essential fatty acids (hormones and cell membrane)
How is fat absorbed into the body?
1) Droplet
2) Bile emulsifies in the intestine into smaller droplets *increase in SA is good for enzyme activity
3) Monoglycerides and pre fatty acids formed
4) These enter the epithelial of the small intestine as micelles
5) Triglyceride again
6) Aggregate into protein
What is the name of lipids and cholesterol which are transported into the blood as complexes of lipids and proteins?
Lipoproteins
What part of a lipoprotein is hydrophobic?
Core with triglycerides
What part of the lipoprotein is hydrophilic and why?
Coating - to help facilitate in cell uptake. Cholesterol/Polar phospholipids
What are the FIVE classes of lipoproteins?
-Chylomicrons
-Very low density lipoproteins (VLDL)
-Low density lipoproteins (LDL)
-Intermediate density lipoproteins (IDL)
-High density lipoproteins (HDL)
What does HDL do?
‘GOOD’
Reverse cholesterol transport, takes free cholesterol to the liver to prevent build up of plaques
What does LDL do?
‘BAD’
Tries to deposit in cells and tissues and then drops into arteries and a plaque is formed (atherosclerosis) = stroke / mi
What is ApoB100?
Apolipoprotein
-In VLDL, IDL, LDL, main physiological ligand for LDL receptor and made in the liver.
LDL - which interacts with the LDL receptors, and is highly expressed in the liver, peripheral and is uptaken into cells
What is HDL like?
More dense, has a higher amount of protein
What is the pathway for exogenous lipids?
1) Cholesterol and TG from the diet are absorbed in the ileum, transports in the chylomicrons to the lymph, blood then capillaries to the muscle and adipose tissue.
2) TG is hydrolysed by lipoprotein lipase, glycerol and free fatty acids are released which are taken up into tissues
3) Remaining chylomicrons remnants with cholesteryl esters travel to the liver, bind to receptors and are endocytosed
4) Cholesterol is stored, oxidised to bile acids or enters the endogenous pathway
What is the pathway for endogenous lipids?
1) Cholesterol from diet and newly made TG in liver travels as VLDL to muscle and adipose tissue
2) TG is hydrolysed in tissues by lipoprotein lipase, then glycerol and FFA is liberated
3) Lipoprotein partciles become smaller but retain cholesterol esters and become LDL, which binds to LDL receptors on cells - (LDL receptors recognise apopB100 on LDL particles)
4) Cholesterol deposited in tissues for cell membranes and other functions
5) Cholesterol can return to plasma and liver for tissues via HDL (reverse cholesterol transport) - Plasma -> Liver -> excretion
6) Cholesterol is esterified with LCFA in HDL and transferred to VLDL or LDL in plasma by cholesteryl ester transfer protein (CETP)
What is the LDL receptor pathway?
1) LDL attached to the liver
2) pH is less than 5, –> LDL dissociates from the receptor
3) Vescile pinches apart = 2 vesciles
1= LDL which fuses with lysozyme - cholesterol release in cytosol - cell membrane formation
2= receptors, recycle to cell surface –>fuses to cell membrane, –> turns inside out (exocytosis) –> return cell surface process begins again!
How does the reverse cholesterol transport system work?
HDL is made in the liver and small intestine,
1) Taken up and esterfies
2) HDL more spherical
3) Transfer to liver cells
4) Excretion