The cells in our body perform functions like growth, excretion, reproduction, etc. A cell needs energy to perform these functions. The food we take in is converted into glucose by the digestive system.
- Glucose reaches the cells through the blood.
In the presence of oxygen, glucose is broken down into energy, water and carbon dioxide. Anaerobic respiration takes place in the muscle cells if enough oxygen is not present in the cell.
Glucose is converted into lactic acid and carbon dioxide in the absence of oxygen. Accumulation of lactic acid inside the cells leads to muscle cramps. Oxygen will break down lactic acid into carbon dioxide and water.
- Yeast respires in the absence of oxygen.
Glucose is converted into alcohol and carbon dioxide by yeast in the absence of oxygen. Yeast is used in beverage industries to produce beer and wine.
During day time, plants utilise oxygen to perform photosynthesis. During the night, plants release carbon dioxide and take in oxygen for respiration. In plants, the exchange of gases takes place through a special structure, called the stomata. The process of respiration in plants breaks down glucose and releases energy.