Question

How many ATPs are gained by complete oxidation of glucose?

Answer 1

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 energy liberated is 380 kilocalories. One ATP yields approximately 10 kilocalories of energy. Thus, the net ATP produced during the complete oxidation of one mole of glucose is 38 ATP.

Additional information: The respiration mainly involves 3 processes that are:
(I) Glycolysis: In this process the glucose (6C) molecule gets converted into the two molecules of pyruvate (3C). The pyruvate formed is converted into Acetyl coenzyme A in presence of $Mg^{2+}$ ions and pyruvate dehydrogenase enzyme.
(II) Kreb’s cycle: it is also known as Tricarboxylic acid cycle (TCA) or citric acid cycle. In this process Acetyl coenzyme A 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.
(III) 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.