Question

Most of the energy from the carbohydrates is released by oxidation when
(a) Pyruvic acid is converted into ${ C{ O }_{ 2 } }$ and ${ H }_{ 2 }{ O }$.
(b) Pyruvic acid is converted into acetyl coA
(c)Sugar is converted into pyruvic acid.
(d) Glucose is converted into alcohol and ${ C{ O }_{ 2 } }$.

Answer 1

From the carbohydrates, most of the energy is released at the end of glycolysis when ${ C{ O }_{ 2 } }$ and ${ H }_{ 2 }{ O }$ are formed. This process of energy conversion occurs in the cytoplasm of the cell.

Complete answer:
When pyruvic acid is converted into ${ C{ O }_{ 2 } }$ and ${ H }_{ 2 }{ O }$ most of the energy from the carbohydrates are released by oxidation. Glycolysis converts one molecule of glucose into two molecules of pyruvic acid. A carboxyl group is removed from pyruvate and carbon dioxide is released and ${ N{ A{ D }^{ + } } }$ is reduced to NADH, also an acetyl group is transferred to coenzyme A resulting in acetyl CoA.

Additional Information: -The respiration involves the movement of oxygen from the outside environment to the cell and also the movement of carbon dioxide from the cell to the outside environment within the tissues.
-The respiration can be aerobic or anaerobic. In both the processes glycolysis is common which occurs in absence of oxygen.
-During glycolysis one molecule of glucose is converted into two molecules of pyruvic acid, this pyruvate oxidation is a key connector that links glycolysis to the rest of cellular respiration.
-By the glycolysis process pyruvate is produced in the cytoplasm but oxidation takes place in the mitochondrial matrix in eukaryotes.
-In the matrix A carboxyl group is removed from pyruvate and carbon dioxide is released and ${ N{ A{ D }^{ + } } }$ is reduced to NADH, also an acetyl group is transferred to coenzyme A resulting in acetyl CoA.
-This acetyl CoA serves as fuel for the citric acid or Krebs cycle in the next stage of cellular respiration. Here it helps in activating the acetyl group for preparing it to undergo the necessary reactions to enter the Krebs cycle.
-The pyruvate molecules after glycolysis still contain lots of extractable energy. Then pyruvate enters the Krebs cycle and generates a lot of energy in the form of NADH, ${ F{ A{ D{ H }_{ 2 } } } }$ and ATP also produce carbon dioxide and water as the by-product through various steps.
-In aerobic respiration pyruvic acid is completely metabolized to carbon dioxide and water releasing a lot of energy.
-But in anaerobic respiration, the pyruvic acid is incompletely metabolized to ethanol or lactate releasing very less amount of energy as compared to aerobic respiration.
So, the correct answer is, 'pyruvic acid is converted into ${ C{ O }_{ 2 } }$ and ${ H }_{ 2 }{ O }$'.

Note: -Glycolysis occurs in both aerobic and anaerobic respiration.
-The glycolysis process converts one molecule of glucose into two molecules of pyruvic acid.
-After glycolysis, the pyruvate molecules enter the Krebs cycle and generate a lot of energy.
-Pyruvic acid is completely metabolized in aerobic respiration and releases a lot of energy.
-Pyruvic acid is incompletely metabolized in anaerobic respiration so it releases a less amount of energy.