Question

Redraw the flow-chart with corrections. Explain in brief the process of obtaining energy through oxidation of carbohydrates, lipids & proteins.

How energy is formed from oxidation of carbohydrates, fats and proteins? Correct the diagram given below.

Answer 1

Corrected flow-chart:

Process of obtaining the energy:

1. Carbohydrates: Carbohydrates like glucose are oxidized to pyruvic acid. Pyruvic acid is converted to acetyl-co-enzyme-A which is oxidized through Kreb’s cycle. The molecules of NADH₂ produced during this are oxidized through electron transfer chain reaction and finally, energy is obtained.
2. Proteins: Proteins are digested to amino acids and amino acids are converted into acetyl-co-enzyme-A. Acetyl-co-enzyme-A is oxidized through Kreb’s cycle. The molecules of NADH₂ produced during this are oxidized through electron transfer chain reaction and finally, energy is obtained.
3. Lipids: Lipids are converted to fatty acids and fatty acids to acetyl-co-enzyme-A. Acetyl-co-enzyme-A is oxidized through Kreb’s cycle. The molecules of NADH₂ produced during this are oxidized through electron transfer chain reaction and finally, energy is obtained.

Answer 2

1. Dietary carbohydrates are digested by enzymes and transformed to glucose. Proteins and lipids are metabolised into amino acids and glycerol, respectively.
2. Carbohydrates are oxidised during cellular respiration. Aerobic respiration involves three processes for glucose oxidation: glycolysis, tricarboxylic acid cycle (Kreb's cycle), and electron transfer chain.
3. During glycolysis, one molecule of glucose yields two molecules of pyruvic acid, ATP NADH₂, and water. The process converts pyruvic acid into Acetyl-Coenzyme-A, releasing two molecules of NADH₂ and CO₂.
4. In the TCA cycle, molecules of Acetyl-Co-A enter mitochondria and undergo a series of cyclic events. The acetyl portion of Acetyl-Co-A is totally oxidised throughout this cyclical phase. This reaction releases chemicals such as CO₂, H₂O, NADH₂, and FADH₂.
5. In the third step of the ETC reaction, NADH₂ and FADH₂ from the first two steps are used to produce ATP molecules. Each NADH₂ molecule yields 3 ATP molecules, while FADH₂ yields 2 ATP molecules.
6. When one molecule of glucose is completely oxidised in the presence of oxygen, it produces 38 molecules of ATP, which is how carbohydrates are converted into energy.
7. Insufficient carbohydrates in the diet might lead to energy generation from proteins or lipids. Acetyl-Co-A is produced by the conversion of fatty acids from lipids and amino acids from proteins. Acetyl-Co-A can produce energy through the TCA cycle.