notes prepared by subhankar Karmakar
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The assimilated food is used as a fuel to get energy for various life processes and as a material for the growth and repair of the body.
BREATHING
The mechanism by which organisms obtain oxygen from the air and release carbon dioxide is called breathing.
RESPIRATION
The process of releasing energy from food is called respiration. The process of respiration involves taking in oxygen into the cells, using it for releasing energy by burning food, and then eliminating the waste products (carbon dioxide and water) from the body. The process of respiration which releases energy takes place inside the cell of the body. Respiration is essential for life because it provides energy for carrying out all the life processes which are necessary to keep the organisms alive. Respiration is opposite process of photosynthesis.
Difference between Breathing and Respiration
• Respiration includes breathing as well as the oxydation of the food in the cells of the organism to release energy.
• Breathing is a physical process whereas respiration also includes biochemical process of oxidation of food.
• The process of breathing involves lungs of the organism whereas the process of respiration also involves the mitochondria in the cells where food is oxidized to release energy.
STORAGE OF ENERGY RELEASED DURING RESPIRATION
The energy produced during respiration is stored in the form of ATP molecules in the cells of the body.
ADP is a substance called Adenosine Di-phosphate and ATP is a substance called Adenosine Tri-phosphate. Both the molecules are present inside a cell. ATP has a high energy content.
(i) the energy release during respiration is used to make ATP molecules from ADP and inorganic phosphate.
ADP (low energy) + Phosphate + Energy (from respiration) → ATP (high energy content)
Thus, energy is stored in the cells in the form of ATP.
(ii) When the cell needs energy then ATP can be broken down using water to release energy.
ATP → ADP + Phosphate + Energy
The energy equivalent to 30.5 kJ/mole is released in this process. This released energy by ATP is used to carry out all the endothermic reactions taking place in the cells.
The energy stored in ATP is used by the body cells for various purposes like contraction of muscles, conduction of nerve impulses, synthesis of proteins and other activities related to the functioning of cells.
"ATP is known as the energy currency of cells."
TYPES OF RESPIRATION
The respiration which uses oxygen is known as aerobic respiration and the respiration which takes place with out using oxygen is known as anaerobic respiration.
The key compounds that we takes part in respiration are:
1. Glucose C₆H₁₂O₆
2. Pyruvic Acid or Pyruvate CH₃(CO)COOH
GLYCOLYSIS
The oxidation of glucose to pyruvic acid or pyruvate is called Glycolysis. It occurs in cytoplasm. It does not require oxygen to complete. One molecule of glucose produces two molecules of pyruvic acid.
In presence of oxygen, pyruvate is completely oxidised and produces carbon dioxide, water and a lots of energy. But if oxygen is not present, Pyruvate is converted to either ethanol and carbon dioxide (in plant cell) or lactic acid (in animal cell). Energy release is less.
LACTIC ACID
Lactic acid is also called as Lactate. It is a hydroxy carboxylic acid.
AEROBIC RESPIRATION
1. The respiration which uses oxygen is called aerobic respiration.
2. Here, glucose is completely broken down into carbon dioxide and water by oxidation.
3. It produces lots of energy and stored it in the form of ATP molecules.
4. Glucose first undergoes glycolysis to produce pyruvate in cytoplasm then pyruvate is broken down into carbon dioxide and water in the presence of oxygen in mitochondria and produces lots of energy.
5. Mitochondria are the sites for aerobic respiration.
6. Most of the living organisms uses aerobic respiration and hence can not live without oxygen.
ANAEROBIC RESPIRATION
Anaerobic Respiration in Plants:
1. The respiration which takes place without oxygen is known as anaerobic respiration.
2. Yeast and some bacteria obtain energy through anaerobic respiration.
3. Glucose is broken down to pyruvate by glycolysis in cytoplasm. Then, Pyruvate produces ethanol (C₂H₅OH) , carbon dioxide by fermentation and energy is stored in ATP molecules.
4. The whole process of anaerobic respiration takes place in cytoplasm.
5. Although human beings obtain energy through aerobic respiration but in certain cases we use anaerobic respiration too. During vigorous physical exercise, oxygen is used up faster in the muscle cell in that case when oxygen supply becomes less our cells use anaerobic respiration.
6. Glucose is first gets converted into pyruvate by glycolysis and next it is converted to lactic acid and small amount of energy.
Anaerobic Respiration in Animals:
LACTIC ACID FORMATION AND MUSCLE CRAMPS
During heavy physical activities our body uses anaerobic respiration and glucose gets converted into lactic acid. The accumulation of lactic acid in our muscle cell causes muscle cramps. We can get relief from cramps in muscles caused by heavy exercises and production of lactic acid by taking a hot water bath or massage.
DIFFERENCES BETWEEN AEROBIC AND ANAEROBIC RESPIRATION
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AEROBIC RESPIRATION |
ANAEROBIC RESPIRATION |
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1. Aerobic respiration takes place in the presence of Oxygen. |
Anaerobic respiration takes place In the absence of Oxygen. |
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2. Complete breakdown of the food occurs in aerobic respiration. |
Partial breakdown of foods occurs in anaerobic respiration |
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3. The end products in aerobic respiration are carbon dioxide and water. |
The end products in anaerobic respiration may be ethanol and carbon dioxide (in yeasts) or lactic acid (in animals). |
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4. Aerobic respiration produces a considerable amount of energy. |
Much less energy is produced in anaerobic respiration. |
