Question

Which of the following enzymes are stimulated to support the use of fat (lipids) to fuel ATP synthesis during exercise.

Answer 1

During the time of exercise,

Fat (triglyceride) storred in the adipose tissue are broken down in to Fatty acid and glycerol b y the help of LIPASE enzyme.

This fattyacid are bound to the albumin in the blooad and carried to the muscle.

In the muscle , the fattyacid is oxidised to produce ATP

Once inside a long-fat-fat-acid cell the CoA ligase elicits a reaction between the fatty molecule with ATP (broken AMP and inorganic pyrophosphate) to give acyl-adenylate, and then combines with the free coenzyme A to give the fat molecule acyl-CoA.
For acyl-CoA to enter mitochondrion using shuttle carnitine:

Acyl-CoA is transferred to the hydroxyl group of carnitine by the carnitine Palmitoyltransferase I, which is the cytosolic face of the outer and inner mitochondrial junctions.
Acyl-carnitine is blocked internally by carnitine-acylcarnitine translocase, as carnitine is shut off.
Acyl-carnitine is converted to acyl-CoA by carnitine Palmitoyltransferase II, which is located on the inner surface of the inner mitochondrial membrane. The released carnitine is locked back into the cytosol, as acyl-CoA is locked inside the matochondrial matrix.

Beta oxidation, in the mitochondrial matrix, then cuts long carbon chains of fatty acids (in the form of acyl-CoA cells) in a series of two carbon units (acetate), which, in combination with enzyme A, form the acetyl CoA, coupled with oxaloacetate to form citrate at the beginning of the citric acid cycle.It is appropriate to think of this reaction as marking the starting point of the cycle, as this is where the fuel - acetyl-CoA is added to the cycle, which will be dissolved as CO2 and H2O by extracting the maximum energy gained in the form of ATP, during each cycle.

In short, the steps of beta oxidation (the initial separation of free acids into acetyl-CoA) are as follows:

Dehydrogenation by acyl-CoA dehydrogenase, yields 1 FADH2
Injection of water with enoyl-CoA hydratase
Dehydrogenation is a 3-hydroxyacyl-CoA dehydrogenase, yielding 1 NADH + H +
Cleavage is thiolase, yielding 1 acetyl-CoA and fatty acid now reduced by 2 carbons (forms new acyl-CoA, shortened)

This beta oxidation reaction is repeated until the fatty acid is completely reduced to acetyl-CoA or, internally, in the case of fatty acids having abnormal amounts of carbon atoms, acetyl-CoA and 1 molecule of propionyl- CoA with one fatty acid molecule. Each beta oxidative cut of an acyl-CoA molecule produces 5 ATP molecules.

The acetyl-CoA produced by beta oxidation enters the krebs cycle in the mitochondrion by combining with oxaloacetate to form citrate. GTP,NADH,FADH2 are synthesized which are further converted in to ATP by the help of Electron transpot chain