7. Energy Production - Lipids Flashcards
Who are the most common elements in lipids and phophsolipids?
Lipids: C, N and O.
Phophsolipids: C, N, O, P and N.
Are carbohydrates or lipids more reduced?
Lipids so they release more energy when oxidised but require more oxygen for oxidation.
What are the three classes of lipids?
Fatty acid derivatives, hydroxy-methyl-glutaric acid derivative and vitamins.
What do triacylglycerols consist of?
Glycerol backbone and fatty acid side chain.
Where are triacylglycerides stored?
In adipose tissues.
When are triacylglycerides utilised for energy?
In prolonged exercise and pregnancy.
How are TAGs metabolised in the GI tract?
By pancreatic lipases.
What happens to fatty acids in the GI tract?
They’re converted to TAGs and packaged in lipoprotein particles, chylomicrons, then released into circulation via lymphatics. They’re carried to adipose tissue and stored as TAGs and release as fatty acids again when required.
What happens in low glucose levels with TAG metabolism?
Fatty acids are released as an alternative fuel.
What is the general formula for fatty acids?
CH3(CH2)nCOOH
n= 14-18.
Where does stage two of fatty acid metabolism occur?
In the mitochondria.
What happens in stage two of fatty acid metabolism?
FA activated outside the mitochondrion. It’s then transported across the inner mitochondrial membrane using a carnitine shuttle. FA cycles through a sequence of oxidative reactions with C2 removed each cycle.
How are fatty acids activated?
CH3(CH2)nCOOH + ATP + CoA –> CH3(CH2)nCO~CoA + AMP + 2Pi
Catalysed by fatty acyl CoA synthase.
What regulates the rate of fatty acid oxidation?
The carnitine shuttle transporting fatty acyl~CoA across the mitochondrial membrane.
What happens in exercise intolerance?
There’s a defect in the transport system of fatty acyl~CoA across the mitochondrial membrane so lipid droplets end up in the muscle.
Where is fatty acid metabolism inappropriate?
In the brain, red blood cells and white bloody cells due to their lack of mitochondria.
Where is glycerol metabolised?
In the liver.
Briefly describe the metabolism of glycerol.
Glycerol + ATP —-> glycerol phosphate + ADP
Glycerol kinase
Glycerol phosphate —-> triacylglycerol synthesis.
OR glycerol phosphate + NAD+ —-> DHAP + NADH
DHAP —-> glycolysis.
What is the most important intermediate in both catabolic and anabolic pathways?
Acetyl~CoA.
What are the three ketone bodies produced in the body and whereabouts are they produced?
Acetoacetate, acetone and B-hydroxybutyrate. All made in the liver.
What is physiological ketosis?
When plasma ketone body concentration is 2-10mM
What condition can lead to pathological ketosis?
Type I diabetes.
How is ketone body production controlled?
If NADH/NAD+ ratio increases, there is product inhibition.
What happens with ketone body synthesis when the insulin/glucagon ratio is high?
HMG-CoA reductase makes mevalonate that goes to cholesterol.
Give a diagrammatic summary of the regulation of ketone body synthesis by the insulin/glucagon ratio.
Acetyl CoA
|
>
HMG-CoA
Insulin | | Glucagon
> >
Cholesterol Ketone bodies
What happens when ketone body levels go above the renal threshold level?
Ketouria.
Are lipids generally hydrophobic or hydrophilic?
Hydrophobic, they’re insoluble.
