Lipid metabolism Flashcards
What is the major form of metabolic energy storage in humans
TAG’S (triacylglycerides), they are hydrophobic and is constitutes 90% of dietary lipids.
What are the two major metabolic pathways for TAG’s
Beta oxidation: in the MTC to release energy in the form of ATP.
Synthesis of TAG’s from acetyl-CoA (for storage)
What are the 3 stages of oxidation of TAG’s
1) Beta oxidation of long-chain fatty acids to acetyl-CoA fragments.
2) Oxidation of acetyl-CoA to C02 in the citric acid cycle
3) transfer of electrons from reduced electron carriers f to Mt respiratory chain.
Where does fatty acid synthesis take place
Occurs mainly in the liver and adipocytes, occurs in the cytosol so acetyl-CoA has to be extracted from the mitochondria (via citrate-malate cycle)
Outline fatty acid biosynthesis
Citrate—>acetyl-CoA—>malonyl CoA (Rate limiting)
malonyl CoA and acetyl CoA both bind to fatty acid synthase and a series of condensation reactions where water is lost
Describe the nature of cholesterol
Amphipathic (hydrophobic and hydrophilic properties
made from acetyl-CoA and is eliminated as Wbile acids.
What is the role of cholesterol and bile
An important component of biological membranes
the precursor of steroid hormones
source of bile acids
the bile acids aid in lipid digestion and absorption along with cholesterol excretion.
How is cholesterol synthesised
Acetyl-CoA—>HMG-CoA—> mevalonate—>squalene—>cholesterol.
What do chylomicrons transport
Delivers dietary TAG’s to muscle and adipose tissue + dietary cholesterol to the liver
What do VLDL transport
Transports endogenous TAG’s and cholesterol
What do LDL’s transport
transport cholesterol from the liver to tissues
What do HDL’s transport
transports cholesterol from tissues to liver e.g. remove cholesterol from tissues.
