Lecture 28 Flashcards
When do anaerobic reactions occur and what do they recycle for the aerobic?
Anaerobic reactions of pyruvate are typically done when there is not enough oxygen, though it could also occur due to the citric acid cycle working to capacity. They recycle NADH back into NAD+ for aerobic respiration.
What does beta oxidation produce?
The beta oxidation pathway prouces no ATP directly, but does produce acetyl-Coa, NAD+ And FAD which will allow us to make ATP. Fatty acids are the substrate used in beta oxidation to produce acetyl CoA.
What is the preferred fuel for most tissues? Why? Why can carbohydrates become fatty acids but not vice versa?
Fatty acids are the preferred fuel for most tissues (fat is the primary energy reserve), this is because they are light to store relative to energy (due to ease of reduction and carbs being stored in 2/3rds water). Acetyl CoA can be used to produce fatty acids but cannot go back to being pyruvate, hence carbohydrates can become fatty acids but not vice versa.
What is the pathway for fatty acids in the blood? Starting from the adipose tissues.
triacylglycerol is broken up by lipases into free fatty acids and glycerol in the adipose tissues, these then move passively into the blood via a downwards concentration gradient. The glycerol goes into the liver for further processing and the free fatty acids travel via an albumin-ffa complex which then transports the free fatty acids to the tissues passively. Inside the cell fatty acid binding proteins will bind to the fatty acids to keep them solubilised.
How does fatty acid activation for oxidation occur?
Fatty acid activation occurs before the fatty acid enters the mitochondria, they are activated by attachment to CoA, forming fatty acyl-CoA, this uses energy from hydrolysis of ATP (all the way to AMP, without adding phosphate to the molecule, this is a cost of two ATP).
Where does fatty acid oxidation occur and how does it get there?
Fatty acid oxidation occurs in the mitochondria matrix (hence it needs to get across the inner and outer membrane). To do this is travels through the fatty acyl-CoA carrier on the outer membrane and then the CoA is swapped for Carnitine by carnitine acyltransferase, then a carrier protein on the inner membrane lets the fatty acyl-carnitine through into the matrix and then carnitine acyltransferase II swaps the carniting for CoA.
What fatty acids does beta oxidation use?
Beta oxidation uses fatty acids with an even number of carbons which are saturated.
What steps occur in beta oxidation?
Beta oxidation starts with fatty acyl-CoA, it is then oxidised to trans-delta2-enoyl-CoA a small distance from the CoA group (while reducing FAD to FADH2, this forms a double bond on the molecule and removes two hydrogens). This is then hydrated to L-B-hydroxyacyl-CoA which adds an OH group and an H group to saturate the bond. Oxidation then occurs (NAD+ to NADH + H+), changing it to Beta-ketoacyl CoA. This is then cleaved to acetyl CoA which is then cleaved to fatty acyl CoA (shorter by two carbons than the starter molecule).
