Question

One mole of glucose in metabolism liberates how many kilocalories of energy?
A. 180
B. 80
C. 160
D. 380

Answer 1

Hint: Glucose is the carbohydrate molecule having 6 carbon molecules. During the process of respiration, one glucose molecule yields a certain amount of energy in the form of ATP (adenosine triphosphate) with carbon dioxide and water as an end product.

Complete Answer:
On complete combustion of one glucose molecule into carbon dioxide and water, the great amount of energy is released i.e. about 686 kilocalories. On the metabolism of the glucose molecule, it can take place by the process of respiration in which energy is released in the form of ATP.

Respiration can takes place by two mechanisms:
(I) Aerobic respiration: This is the process in which the metabolism takes place in the presence of oxygen.
(II) Anaerobic respiration: This process takes place in the absence of oxygen.
The ATP production rate changes with the type of respiration. In aerobic respiration the net ATP produced is 38. One ATP yields approximately 10 kilocalories of energy. Thus, the energy liberated during the metabolism of one mole of glucose is 380 kilocalories.

The correct option is D i.e. 380.

Additional information: The respiration mainly involves 3 processes that are:
- Glycolysis: In this process the glucose (6C) molecule gets converted into the two molecules of pyruvate (3C). The pyruvate formed is converted into Acetyl coA in presence of ions and pyruvate dehydrogenase enzyme.
- Kreb’s cycle: It is also known as Tricarboxylic acid cycle (TCA) or citric acid cycle. In this process Acetyl coA is entered into the TCA cycle which is the cyclic process. It is responsible for the production of ATP in large amounts. It takes place in a mitochondrial matrix.
- Electron transport system: In this system, the NADH and FADH formed in the krebs cycle are utilized and produce 3 molecules of ATP and 2 molecules of ATP respectively.

Note: During the process of fermentation, only 2 ATP molecules are produced from one glucose metabolism and the rate of oxidation of $NADH$ to $NAD^+$ takes place at a slower rate than that of aerobic respiration. Since the ATP are produced basically in the mitochondria of the cell thus mitochondria is considered as the Powerhouse of the Cell.