CBSE Class 9 Answered

namasthe . explain the process RESPIRATION.

Asked by aninadathoorsridharan | 16 Nov, 2015, 12:33: PM

Expert Answer

Respiration is the catabolic process of releasing energy from simple sugar glucose for carrying out various life processes.

The breakdown of glucose in the presence of oxygen is called aerobic respiration.

The breakdown of glucose in the absence of oxygen is called anaerobic respiration.

The mechanism of respiration involves the following four stages:

Breathing: It is a physical process in which oxygen rich air is taken inside the body (inspiration) and carbon dioxide rich air is forced out of the lungs (expiration).
Gaseous transport: Oxygen absorbed by the blood in the lungs is transported by Red Blood Cells (RBCs) as oxyhaemoglobin throughout the body by means of arteries. Carbon dioxide from the tissues is transported to the lungs by the blood.
Tissue respiration: The terminal blood vessels or the capillaries transport oxygen to the body cells or tissues, where oxygen diffuses through their thin walls. Likewise, the capillaries pick up carbon dioxide released by them.
Cellular respiration: The complex chemical changes which occur inside the cells to release energy from glucose. Cellular respiration consists of three main stages - glycolysis, Krebs cycle and electron transport.
- Glycolysis: It is the process of breakdown of a six-carbon compound glucose into two molecules of a three-carbon compound called pyruvic acid or pyruvate. This further breaks down into ethanol (in plants) and lactic acid (in animals). The energy released during glycolysis is used for the production of high-energy compounds such as Adenosine Triphosphate or ATP and Nicotinamide Adenine Dinucleotide or NADH.
- Krebs Cycle: The Krebs cycle involves step-by-step breakdown of pyruvic acid/lactic acid to produce ATP and CO₂. H⁺ions released in the cycle are removed through the oxygen supplied by forming H₂O. The process yields a large amount of energy.
- Electron Transport: The energy-rich compounds formed during the Krebs cycle are oxidised through an electron transport chain for the release of energy. This energy is released in the form of ATP. There is a net gain of 38 ATP molecules on complete oxidation of glucose.