Answer:
C. Aerobic Respiration / Carbohydrates and Fats
Explanation:
The energy system used to make ATP in our body is known as aerobic respiration which uses carbohydrates and fats as it's primary fuel.
GLUCOSE/CARBOHYDRATE
Aerobic respiration which uses carbohydrate (glucose) as fuel comprises below mentioned processes:
(1) Glycolysis
(2) TCA cycle (Kreb's cycle)
(3) Electron transport chain (ETC)
(1) Glycolysis
During glycolysis, glucose which is a 6 carbon compound is converted into pyruvate which is a 3 carbon compound. Pyruvate subsequently enters PDH complex wherein it is oxidatively decarboxylated so as to produce a 2 carbon compound known as Acetyl-CoA (acetyl coenzyme A).
(2) TCA cycle (Kreb's cycle)
The Acetyl-CoA (acetyl coenzyme A) hence produced then enters TCA cycle in mitochondria wherein very high energy producing molecules like NADH, FADH2 etc. are produced.
(3) Electron transport chain (ETC)
The high energy molecules like NADH, FADH2 etc. cannot be used by our body to do day to day activities so these molecules then enter ETC within mitochondria itself to undergo oxidative phosphorylation so as to produce ATPs. These ATPs can be used by our body directly to do day to day activities.
FATS
Fats are able to produce the 2 carbon compound Acetyl-CoA (acetyl coenzyme A) by the process of beta oxidation (β oxidation) not through glycolysis and PDH complex. Once Acetyl-CoA (acetyl coenzyme A) molecules are produced they enter TCA and then undergo ETC as described above.
Note: Fats require more oxygen (through heavy exercise) to undergo beta oxidation and aerobic respiration but they produce more energy/ATP as compared to carbohydrates.
