Respiration in Organism : NCERT /CBSE Notes

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.

Respiration in Organism , NCERT / CBSE Notes, CTET Exam Notes
  • 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.
  • The energy released from food is useful in activities like growth, excretion, reproduction, running, reading and sleeping.
  • The food we eat has to be converted into glucose for releasing energy. Digestive juices convert complex carbohydrates into glucose.
  • The breakdown of glucose in a cell to release energy is called cellular respiration. Blood absorbs glucose and transports it to the cells. In the cells, this glucose is broken down to release energy.
  • The breakdown of glucose in the presence of oxygen is called aerobic respiration.
  • Cells use oxygen to break down glucose and release energy.
  • When we inhale air, oxygen goes into the lungs. From the lungs, the oxygen is absorbed by the red blood cells and supplied to all the cells in the body. Our cells use this oxygen to break down glucose to release energy. Carbon dioxide and water are also formed.
  • The breakdown of glucose in the cell in the absence of oxygen is called anaerobic respiration.
  • Muscle cells require a lot of energy to perform exercisesMuscle cramps occur when strenuous exercises like cycling, running, speed walking, etc. are done for a long time. The accumulation of lactic acid in the muscles causes muscle cramps.
  • During anaerobic respiration, lactic acid is formed in the muscles.
  • massage or a hot bath can ease a muscle cramp by improving the circulation of blood in the affected muscles.
  • Anaerobic respiration can be seen in yeast.
  • The breakdown of glucose in the absence of oxygen in yeast forms alcohol, energy and carbon dioxide. Yeasts and other organisms that respire in the absence of oxygen are also known as anaerobes.
  • Plants utilise oxygen for respiration released through photosynthesis during the day, and at night, they take in oxygen from the atmosphere and give out carbon dioxide and water vapour.
  • The stomata are involved in the entry and exit of gases in plants.
Must Read: Breathing In Humans, Animals and Insects

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