Fatty Acid Oxidation Flashcards
What are Lipases secreted by and what do they hydrolyse ?
Lipases are secreted by the pancreas into the gut. They hydolyse triacylglycerols to release two fatty acids, leaving monoacylglycerol
These breakdown products can be taken up into ?
Intestinal cells (often referred to as absorption)
What happens to the fatty acids once they have crossed the membrane to be absorbed into the intestinal cells ?
The fatty acids recombine with the monoacylaglycerol to re-form triacylglycerols
These are then packaged up with other lipids and proteins to form greasy particles called ?
Chylomicrons
Chylomicrons are released via ?
The lymph system to the blood and transported to the tissues mainly:
Adipose Tissue - To be stored until required for energy production
Heart and Skeletal muscle - For immediate oxidation
What enzyme is activated by response to metabolic need ?
An enzyme called triglyceride lipase is activated by hormones in response to metabolic need – starvation or stress (fight or flight)
The fatty acids are released into the blood. They bind to ?
The most abundant protein in the plasma, serum albumin
Why is the brain so dependent on blood glucose for energy and so sensitive to hypoglycaemia?
They cannot pass through the blood-brain barrier, so are NOT available for oxidation by brain cells.
What happens when glycerol is transported to the liver ?
It is converted in two steps into dihydroxyacetone-P, which links it into the glycolysis/gluconegenesis pathway
Why is fat a more efficient energy storage than Glycogen ?
- Fatty acids are more reduced than glucose, so yield more ATP per carbon atom when they are oxidised.
- Triacylglycerols are nonpolar so are stored with no associated water.
- In contrast 1g of dry glycogen binds about 2g of water, greatly increasing its mass.
Why can acetyl coA not make more glucose directly ?
This is because for each two carbon atoms entering the citric acid cycle as acetyl CoA, two carbon atoms are released as CO2
What happens during prolonged starvation ?
Fatty acid oxidation in liver can exceed the capacity of the citric acid cycle to dispose of the acetyl CoA formed.
What are excess ketone bodies degraded to ?
Acetone. This can be detected on the breath of untreated diabetics
What may explain the loss of weight on a low carbohydrate-high-fat diet?
The energy cost of producing glucose by gluconeogenesis
