Energy Release from Fat Flashcards
What are 3 main functions of lipids biologically?
- Components of cell membrane
- Precursors of hormones
- Long term fuels
How are triglycerides stored?
As large fat droplets in fat cells of adipose tissue
How are stored triglyceride fats broken down in adipose tissue?
Lipase is activated by adrenaline and glucagon. This removes the fatty acids chains from the glycerol. The free fatty acids travel in the plasma and bind to albumin.
Glycerol diffuses in the blood stream to all tissues
What happens to glycerol when metabolised?
It is water soluble so is taken up by all tissues. In most tissues, it enters glycolysis and then the Krebs cycle. In the liver, it enters glycolysis and is converted to glucose via gluconeogenesis.
Give some details on fatty acid metabolism by the beta oxidation pathway
- where do the reactions occur?
- what are intermediates present as?
- how is the biological energy of fatty acids conserved?
- how many enzyme reactions occur and what does this result in?
- all reactions occur in the mitochondrial matrix
- intermediates present as CoA thioesters
- biological energy of fatty acid molecule is conserved as the transfer of 2H atoms to the cofactors NAD+ and FAD+ to form NADH and FADH2
- 4 enzyme reactions that result in the removal of acetyl CoA
What is the difference between Acyl CoA and Acetyl CoA?
Acyl is made from fats where as acetyl is made from glucose.
What happens to fatty acid chains to activate them?
ATP is added and so is acyl coA synthetase. The OH group on the end is removes and the CoA group is added
What forms thioester bonds with carboxylic acids?
Coenzyme A
Explain the 2 stages that transport the fatty acids into the mitochondria
Stage 1 - Fatty acyl CoA is passed through the membrane and to the inter membrane space. Here, the acyl group and the coenzymes split up
Stage 2 - The acyl group is handed back to a different coenzyme
Give details on the 4 steps of fatty acid energy release
- Removal of 2 H atoms. This causes the formation of a double bond. The hydrogen atoms reduce FAD+
- Addition of water occurs across the double bond forming hydroxacyl-CoA
- Removal of 2H atoms again, this forms NADH and H+. OH group to =O
- Removal of 2 C units when adding coenzyme A. This forms fatty acyl - CoA and acetyl - CoA which is used in the Links reaction
What then happens to the carbon chain thats made 2 carbons shorter?
It goes back into the reaction and becomes 2 carbons shorter again.
If a fatty acid with 16C atoms is used, how many repeats of the pathway will there be?
How many NADH and FADH2 will be formed?
How many acetly CoA will be produced?
7 repeats
7 of each
8
What has to occur with metabolism of odd number fatty acid carbons?
What is produced in this reaction?
Need to add another carbon and undergo isomerisation.
Succinyl C.
Explain what ketogenesis is and why it occurs
It occurs when fat metabolism is the main source of energy. (starvation and type 1 diabetes)
Fatty acid oxidation leads to high concentration of acetyl CoA. This excess is converted to ketone bodies in the liver.
Ketone bodies can be used in most but not all tissues. Why is this?
In most cells, they can be converted back into the TCA cycle intermediates.
