Since the amount of oxygen dissolved in water is comparatively lower than that in air, the acquatic animals have to breath rapidly to take in sufficient oxygen. The energy released during the process of respiration is used up to synthesize the ATP (adenosine triphosphate) which is used to fuel all other activities in the cell.Īquatic animals breathe faster than the terrestrial animals It is also called fermentation.Īerobic respiration: The breakdown of pyruvate into carbon-dioxide and water in presence of oxygen it is known as aerobic respiration. This process takes place in the cytoplasm.Īnaerobic respiration: The breakdown of pyruvate into ethanol and carbon-dioxide is absence of oxygen is known as anaerobic respiration. ➡ The first step in all three cases is the break-down of glucose into a three-carbon molecule called pyruvate. ➡ Respiration may take place in different conditions like presence of oxygen, lack of oxygen and absence of oxygen. Respiration: It is a metabolic process which involves breakdown of food to release energy. ➡ The rest of the material is then removed from the body via the anus. ➡ The unabsorbed food is then transferred to large intestine where water is absorbed from it. ➡ The villi are richly supplied with blood vessels which take the absorbed food to each and every cell of the body to meet their energy requirements. ➡ The inner lining of the small intestine has numerous finger-like projections called villi which increase the surface area for absorption of food. ➡ Digested food is then absorbed by the walls of the small intestine. It finally convert the proteins to amino acids, complex carbohydrates into glucose and fats into fatty acids and glycerol. ➡ The walls of the small intestine contain glands which secrete intestinal juice. ➡ Pancreas secrete enzymes such as trypsin for the digestion of proteins. ➡ Bile juice from liver helps in emulsification of fats. It receives the secretions of the liver and pancreas for this purpose. ➡ Complete digestion of carbohydrates, proteins and fats occurs in small intestine. Meat is easier to digest, hence carnivores like tigers have a shorter small intestine.) (Note - Herbivores eating grass need a longer small intestine to allow the cellulose to be digested. ➡ From the stomach, the food now enters the small intestine (the longest part of the alimentary canal). It also kills bacteria entered through food and prevents infection. ➡ Hydrochloric acid creates an acidic medium which facilitates the action of the enzyme pepsin. ➡ The gastric glands present in the wall of the stomach release hydrochloric acid, a protein digesting enzyme called pepsin, and mucus. ➡ The muscular walls of the stomach help in mixing the food with more digestive juices. ➡ The food is taken to the stomach through the food-pipe called oesophagus. ➡ The lining of canal has muscles that contract rhythmically in order to push the food forward. ➡ The food is chewed in mouth by the muscular tongue. ➡ Saliva contains an enzyme called salivary amylase that breaks down complex starch (present in food) into simple sugar. ➡ Food is taken in through mouth where it is moistened by saliva. Process of digestion of food in human beings
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