Question

Which of the following biomolecules is common to respiration-mediated breakdown of fats, carbohydrates and proteins?
A. Pyruvic acid
B. Acetyl CoA
C. Glucose-6-phosphate
D. Fructose 1,6-bisphosphate

Answer 1

Hint: Respiration: It is the breakdown of carbon bonds of a complex carbon compound through the process of oxidation that occurs within the cells, leading to release of the required amount of energy.
Respiratory substrates: they are the compounds that are oxidized during the process of respiration.

Complete step-by-step answer:
Aerobic respiration: It is a type of respiration in which breakdown of products takes place in enough or ample amounts of oxygen.
Aerobic respiration takes place in the mitochondria of a cell.
The crucial events in aerobic respiration are:
1. The complete oxidation of pyruvate by the stepwise removal of all the hydrogen atoms, further leads to three molecules of carbon dioxide.
2. The passing on of the electrons removed as part of the hydrogen atoms to molecular oxygen with the simultaneous synthesis of ATP.
During the breakdown of glucose, it firstly enters into the glycolytic pathway in which it is first broken down into pyruvic acid by glycolysis in the cytoplasm.
It then enters into the mitochondria where pyruvic acid is broken and converted into acetyl CoA.
Fats are stored in our body in the form of triglycerides which are made up of fatty acids.
These triglycerides or fatty acids undergo a series of reactions called beta oxidation to form keto acids which get converted into acetyl CoA and can enter Krebs cycle.
 Amino acids which form the breakdown product of proteins form one or the other intermediates of Krebs cycle and enter into it. For example, amino acid isoleucine gets converted into acetyl CoA and enters Krebs cycle.

So, the correct option is option B. Acetyl CoA.

Note: Pyruvate which is formed by the glycolytic catabolism of carbohydrates in the cytosol after this it enters into the mitochondrial matrix and undergoes oxidative carboxylation by a series of reaction which is catalyzed by pyruvate dehydrogenase.