Question

Energy extraction and the complete oxidation of foodstuffs requires three stages. The energy extracted from fuels is converted to ATP. Select the statements that are true for the different stages required for energy extraction and complete oxidation of foodstuffs.
A. In the first stage, macromolecules are converted to monomers, and a small amount of ATP is produced.
B. In the first and second stages the majority of ATP needed for cellular processes is produced.
C. In the third stage, fuel molecules are completely oxidized to CO2 , and most of the ATP needed for cellular processes is produced.
D. In the third stage, fuel molecules are completely oxidized to CO2 , and a small amount of ATP is produced.
E. In the second stage, monomers are broken down, and a small amount of ATP is produced.
F. In the third stage, fuel molecules are completely oxidized to CO2 , and no ATP is produced.

Answer 1

Answer:

C. In the third stage, fuel molecules are completely oxidized to CO2 , and most of the ATP needed for cellular processes is produced.

Explanation:

The three stages in the generation of energy from the oxidation of foodstuffs are given below:

First stage - This stage is the preparation stage and no useful energy is produced in this stage. In this stage, large molecules in food are broken down into smaller units. Proteins are broken down to amino acids, polysaccharides to simple sugars such as glucose, and fats are broken down to glycerol and fatty acids.

Second stage - In this stage, the various small molecules from the first stage are degraded to simple units (mostly acetyl-CoA) that are useful in metabolic activities of the body. Few ATP molecules are generated in this stage.

Third stage - In this final stage, most of the ATP required for cellular processes is produced from the complete oxidation of the acetyl unit of acetyl CoA to CO₂ in the citric acid cycle as well the oxidation of the electron carriers NADH and FADH₂ in oxidative phosphorylation.