Question

Energy released by the oxidation of one molecule of glucose is-
A. 800 Kcal
B. 695 Kcal
C. 686 Kcal
D. 700 Kcal

Answer 1

Hint: We eat food to get energy. The food we eat is in the form of a complex substance. Our digestive system converts the complex substance into a simpler form and this simpler substance oxidizes and gives energy.

Complete answer:
Respiration involve two process are-
1. Breathing- In breathing, we inhale oxygen-rich air and exhale carbon dioxide-rich air.
2. Cellular oxidation- It is processed in which a simpler form of food that blood carries from the villi of the intestine after the digestion process gets oxidized in the presence of oxygen. Oxidation of a simpler form of food takes place in the cell. Hence, this process is called cellular respiration.
The complete oxidation of glucose-
a. Glycolysis- Glucose is split into pyruvic acid.
b. Complete oxidation of pyruvate-Removal of all hydrogen atoms, leaving three molecules of carbon. In this step pyruvic acid converts into Acetyl CoA.
c. Synthesis of ATP- transfer of electrons removed as part of the hydrogen atoms to oxygen molecules for the synthesis of ATP.
This stepwise oxidation of glucose is required to release more energy.
One glucose molecule releases thirty-eight ATP molecule, 686 K.cal energy released by 38ATP molecule
Hence, the correct option (C).

Additional Information:
At the end of digestion process-
1. Fats convert into fatty acids and glycerol.
2. Protein converts into amino acids.
3. Carbohydrate into glucose.
4. All the simpler forms of food undergo the oxidation process but take a different path.
5. Fatty acids and glycerol directly convert into Acetyl CoA and then into ATP.
6. Amino acids convert into pyruvic acid then Acetyl CoA and then into ATP.

Note: Respiratory pathway known as amphibolic pathway because it involves both mechanisms anabolism and catabolism. Anabolism is the formation of the compound and catabolism is the breakdown of the compound. Citric acid cycle and glycolysis are examples of the amphibolic pathway.