Lipids 2 Flashcards
How and where are fatty acids released from triacylglycerol to begin breaking down?
Hormone sensitive lipase (HSL) activates kinase which phosphorylates triacylglycerol Enzyme to be active to begin to break down triacylglycerol.
Where does beta oxidation occur and what are the products of breaking down fatty acids two carbons at a time?
It occurs in the mitochondrial matrix. The products are acetyl CoA and NADH and FADH2.
What are the three stages of beta oxidation?
Activation of the fatty acids in the cytosol.
Transportation of these into the mitochondria.
Degradation to acetyl coA in the mitochondrial matrix.
What is fatty acid activated to in the cytoplasm?
It is activated to fatty acyl coA.
How does the long chain fatty acyl get into the mitochondria?
It does this via a carnitine shuttle which transports the fatty acyl part of the molecule across the membrane and the CoA is seperate. They rejoin when they’re in the mitochondria.
What are the two carnitine enzymes and what are they inhibited by?
Carnitine fatty acyl transferase (CAT 1)
Carnitine Palmitoyl transferase.
These are inhibited by malonyl CoA which is needed for fatty acid synthesis.
What can occur in carnitine palymitoyl transferase deficiencies?
This means that there is no beta oxidation so the patient becomes hypoglycaemic. It can be improved with IV glucose and a therapy can be giving them medium chain fatty acids that don’t need transportation via carnitine.
Can be deficient in liver and muscles which impairs their function.
What are the four steps of degradation?
Dehydrogenation (Oxidation) to produce FADH2.
Hydration of intermediate.
Dehydrogenation to produce NADH.
Thiolysis to cleave the intermediate to make acetyl CoA that feeds into the CAC cycle.
How many beta oxidation cycles and how many products do you get from one 16 carbon palmitate?
Seven beta oxidations to produce eight acetyl CoA, 7 FADH2 and 7 NADH. 129 molecules of ATP are formed from these. (131 made but 2 lost in production of palmitoyl CoA)
How are very long chain fatty acids degradated ?
Fatty acids over 22 carbons long must undergo preliminary beta oxidation in the peroxisomes. This is not energy efficient as no FADH2 is produced from these first steps. The shortened fatty acid links to carnitine and diffuses out of the peroxisome and into the mitochondria for further oxidation. Defects in this pathway result in a build up of long chain fatty acids in blood and tissue.
What happens when someone is starving and they have an excess in acetyl CoA?
Their usual pathway of feeding the acetyl CoA into the CAC is halted and instead it gets turned into ketone bodies.
Name three ketone bodies and describe what they are
Acetone
Acetoacetyl
Beta hydroxybutyrate
These are formed in the liver (mitochondrial matrix) but they can’t be used by the liver. Excess acetyl CoA gets converted to ketone bodies from which cardiac and skeletal muscles get energy. They are soluble in blood.
What happens to ketone bodies when the body is starving or diabetes is uncontrolled?
Ketone bodies will be made in excess due to an abundance of acetyl CoA. Oxaloacetate will not be made due to a lack of glucose so Acetyl CoA cannot be processed. The blood pH will drop (acidemia) and ketonaemia and ketonuria will occur. This can cause fruity breath as well.
