Respiration
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Respiration  It is the process by which chemical energy stored in the food is released in the form of ATP along with carbon dioxide and water.   Respiration begins with breathing, a combined process of inhaling oxygen and exhaling carbon dioxide.   Types of respiration  Respiration can be of two types – Aerobic and Anaerobic.  Both of these respirations take place inside the cell. Aerobic respiration involves breakdown of glucose into carbon dioxide and water in the presence of oxygen. In aerobic organisms, the pyruvate molecule is further broken down in the mitochondria of a cell. The pyruvate molecule that contains three carbon atoms is broken down into three molecules of carbon dioxide and three molecules of water by the action of mitochondrial enzymes. Anaerobic respiration involves the breakdown of food into alcohol and carbon dioxide in the absence of oxygen.   The breakdown of glucose to release energy from the cells in anaerobic conditions is fermentation. Under anaerobic conditions prevailing in our muscle cells, the insufficiency of oxygen converts the pyruvate molecules into lactic acid and energy.   Accumulation of lactic acid in our muscle cells causes cramps. Process of respiration  During respiration, a glucose molecule that contains six carbon atoms is broken down into pyruvate. Pyruvate is a molecule that contains three carbon atoms. 1) In aerobic organisms, the pyruvate molecule is further broken down in the mitochondria of a cell. The pyruvate molecule that contains three carbon atoms is broken down into three molecules of carbon dioxide and three molecules of water by the action of mitochondrial enzymes. Glycolysis is the process which involves breakdown of glucose molecule to release two molecules of pyruvate. It is  multi-step procedure occurring in the cytoplasm of the cells. The process is same for plant cells and animal cells. This process results in the formation of pyruvate molecules along with some ATP molecules. Pyruvate molecules act as substrate molecules for the Krebs cycle which occurs in the mitochondria of both animal and plant cells. Krebs cycle also finally releases ATP molecules, energy coins of the cell.Glycolysis is made up of preparatory phase and pay-off phase. The net gain of glycolysis is 2 ATP and 2 NADH2. Pyruvate can be utilised in Kreb's cycle, lactic acid or alcohol fermentation, based on the availability of oxygen.  Krebs' cycle involves a set of enzymatic reactions taking part in mitochondria in the presence of oxygen to yield energy rich molecules. It is also called as Tricarboxylic acid cycle. The net gain of aerobic respiration at the end of Krebs' cycle is 2 ATP molecules, 8 molecules of NADH+H+  and 2 molecules of FADH2. As we know, ATP is the energy rich coin of the cell utilised for different purposes. Electron Transport Chain is a step wise process which generates energy in the form of ATP molecule from NADH and FADH2 produced during glycolysis, Krebs cycle and other catabolic processes. Electron Transport Chain is an important step of cellular respiration. The mechanism by which Electron Transport Chain generates ATP is called as chemiosmotic phosphorylation. Electron Transport Chain is made up of different complexes and enzymes which participate in ATP synthesis. ETS comprises of several energy carriers which include NADH dehydrogenase complex (Complex I), Ubiquinone (Complex Q), Succinate dehydrogenase complex (complex II), Cytochrome bc1 complex (Complex III), Cytochrome c, Cytochrome c oxidase (Complex IV) 2) Under anaerobic conditions prevailing in our muscle cells, the insufficiency of oxygen converts the pyruvate molecules into lactic acid and energy.  Accumulation of lactic acid in our muscle cells causes cramps. Fermentation is an anaerobic process which takes place in the absence of oxygen. It converts sugar substrates into alcohol and carbon dioxide. Fermentation process also releases certain amount of energy Both aerobic and anaerobic respiration release energy in the form of ATP.  The energy released in the aerobic process is 19 times greater than the energy released in anaerobic process. The energy in the form of ATP is used for many activities such as the contraction of muscles, protein synthesis and conduction of nervous impulses etc. Respiration in plants Respiration in plants is just opposite to that of photosynthesis. Exchange of gases takes place in plants through special structures called as stomata. Stomata are small pores present on the surface of leaves and green parts of plant. Opening and closing of stomata are controlled by guard cells. Dark respiration taking place in plants is independent of the presence of light. Plant cells after synthesizing sugar molecules through photosynthesis, undergo cellular respiration to break down food molecules to obtain energy in the form of ATP molecules. Dark respiration is a form of respiration where carbon dioxide is released without the aid of sunlight. Light phase or photorespiration is an inevitable process which occurs in C3 plants. There is a decreased output of photosynthesis. ATP is not synthesized in photorespiration and carbon is released in the form of carbon dioxide. Nitrogen is also released in the form of ammonia. Respiration in aquatic forms  The rate of breathing in aquatic organisms is much faster than in terrestrial organisms. Respiration in aquatic animals is performed by diffusion through body surface and special respiratory organs called as gills. Fish are the aquatic vertebrates which respire through structures called as gills. This is called as branchial respiration. Gills are present on either side of the head and are supplied by rich blood vessels. Fish obtain oxygen dissolved in water. During respiration, water enters the body through mouth, passes through gills and comes out of the operculum. Exchange of gases takes place in the gills of fish supplied by numerous blood vessels. They accept oxygen into the body and expel out carbon dioxide. Respiration in terrestrial forms  Terrestrial animals have special organs for taking in oxygen from the atmosphere. For instance, cockroaches respire through the trachea, and scorpions through the book lungs. Breathing is the physical act of inhaling and exhaling. Breathing involves taking in oxygen from the environment and removal of carbon dioxide from the body. The diaphragm is a thin thin sheet of muscle separating the thorax and the abdomen, and helps in respiration. Path taken by air Air enters a human body through the nostrils. It passes through nasal cavity and  then enters trachea. From the trachea, air enters the bronchi and then goes into the lungs. The bronchi form a network of bronchioles. Each bronchiole has alveoli at the end in the lungs. The thin membranes of alveoli allow the exchange of gases. Alveoli are richly supplied with blood vessels. Haemoglobin present in RBCs is a metallo-globulin which is made up of 2 alpha chains and 2 beta chains. The respiratory pigment, haemoglobin present in blood absorbs oxygen from the lungs and carries it to tissues all over the body. In return it carries carbon dioxide from the tissues to the lungs.

#### Summary

Respiration  It is the process by which chemical energy stored in the food is released in the form of ATP along with carbon dioxide and water.   Respiration begins with breathing, a combined process of inhaling oxygen and exhaling carbon dioxide.   Types of respiration  Respiration can be of two types – Aerobic and Anaerobic.  Both of these respirations take place inside the cell. Aerobic respiration involves breakdown of glucose into carbon dioxide and water in the presence of oxygen. In aerobic organisms, the pyruvate molecule is further broken down in the mitochondria of a cell. The pyruvate molecule that contains three carbon atoms is broken down into three molecules of carbon dioxide and three molecules of water by the action of mitochondrial enzymes. Anaerobic respiration involves the breakdown of food into alcohol and carbon dioxide in the absence of oxygen.   The breakdown of glucose to release energy from the cells in anaerobic conditions is fermentation. Under anaerobic conditions prevailing in our muscle cells, the insufficiency of oxygen converts the pyruvate molecules into lactic acid and energy.   Accumulation of lactic acid in our muscle cells causes cramps. Process of respiration  During respiration, a glucose molecule that contains six carbon atoms is broken down into pyruvate. Pyruvate is a molecule that contains three carbon atoms. 1) In aerobic organisms, the pyruvate molecule is further broken down in the mitochondria of a cell. The pyruvate molecule that contains three carbon atoms is broken down into three molecules of carbon dioxide and three molecules of water by the action of mitochondrial enzymes. Glycolysis is the process which involves breakdown of glucose molecule to release two molecules of pyruvate. It is  multi-step procedure occurring in the cytoplasm of the cells. The process is same for plant cells and animal cells. This process results in the formation of pyruvate molecules along with some ATP molecules. Pyruvate molecules act as substrate molecules for the Krebs cycle which occurs in the mitochondria of both animal and plant cells. Krebs cycle also finally releases ATP molecules, energy coins of the cell.Glycolysis is made up of preparatory phase and pay-off phase. The net gain of glycolysis is 2 ATP and 2 NADH2. Pyruvate can be utilised in Kreb's cycle, lactic acid or alcohol fermentation, based on the availability of oxygen.  Krebs' cycle involves a set of enzymatic reactions taking part in mitochondria in the presence of oxygen to yield energy rich molecules. It is also called as Tricarboxylic acid cycle. The net gain of aerobic respiration at the end of Krebs' cycle is 2 ATP molecules, 8 molecules of NADH+H+  and 2 molecules of FADH2. As we know, ATP is the energy rich coin of the cell utilised for different purposes. Electron Transport Chain is a step wise process which generates energy in the form of ATP molecule from NADH and FADH2 produced during glycolysis, Krebs cycle and other catabolic processes. Electron Transport Chain is an important step of cellular respiration. The mechanism by which Electron Transport Chain generates ATP is called as chemiosmotic phosphorylation. Electron Transport Chain is made up of different complexes and enzymes which participate in ATP synthesis. ETS comprises of several energy carriers which include NADH dehydrogenase complex (Complex I), Ubiquinone (Complex Q), Succinate dehydrogenase complex (complex II), Cytochrome bc1 complex (Complex III), Cytochrome c, Cytochrome c oxidase (Complex IV) 2) Under anaerobic conditions prevailing in our muscle cells, the insufficiency of oxygen converts the pyruvate molecules into lactic acid and energy.  Accumulation of lactic acid in our muscle cells causes cramps. Fermentation is an anaerobic process which takes place in the absence of oxygen. It converts sugar substrates into alcohol and carbon dioxide. Fermentation process also releases certain amount of energy Both aerobic and anaerobic respiration release energy in the form of ATP.  The energy released in the aerobic process is 19 times greater than the energy released in anaerobic process. The energy in the form of ATP is used for many activities such as the contraction of muscles, protein synthesis and conduction of nervous impulses etc. Respiration in plants Respiration in plants is just opposite to that of photosynthesis. Exchange of gases takes place in plants through special structures called as stomata. Stomata are small pores present on the surface of leaves and green parts of plant. Opening and closing of stomata are controlled by guard cells. Dark respiration taking place in plants is independent of the presence of light. Plant cells after synthesizing sugar molecules through photosynthesis, undergo cellular respiration to break down food molecules to obtain energy in the form of ATP molecules. Dark respiration is a form of respiration where carbon dioxide is released without the aid of sunlight. Light phase or photorespiration is an inevitable process which occurs in C3 plants. There is a decreased output of photosynthesis. ATP is not synthesized in photorespiration and carbon is released in the form of carbon dioxide. Nitrogen is also released in the form of ammonia. Respiration in aquatic forms  The rate of breathing in aquatic organisms is much faster than in terrestrial organisms. Respiration in aquatic animals is performed by diffusion through body surface and special respiratory organs called as gills. Fish are the aquatic vertebrates which respire through structures called as gills. This is called as branchial respiration. Gills are present on either side of the head and are supplied by rich blood vessels. Fish obtain oxygen dissolved in water. During respiration, water enters the body through mouth, passes through gills and comes out of the operculum. Exchange of gases takes place in the gills of fish supplied by numerous blood vessels. They accept oxygen into the body and expel out carbon dioxide. Respiration in terrestrial forms  Terrestrial animals have special organs for taking in oxygen from the atmosphere. For instance, cockroaches respire through the trachea, and scorpions through the book lungs. Breathing is the physical act of inhaling and exhaling. Breathing involves taking in oxygen from the environment and removal of carbon dioxide from the body. The diaphragm is a thin thin sheet of muscle separating the thorax and the abdomen, and helps in respiration. Path taken by air Air enters a human body through the nostrils. It passes through nasal cavity and  then enters trachea. From the trachea, air enters the bronchi and then goes into the lungs. The bronchi form a network of bronchioles. Each bronchiole has alveoli at the end in the lungs. The thin membranes of alveoli allow the exchange of gases. Alveoli are richly supplied with blood vessels. Haemoglobin present in RBCs is a metallo-globulin which is made up of 2 alpha chains and 2 beta chains. The respiratory pigment, haemoglobin present in blood absorbs oxygen from the lungs and carries it to tissues all over the body. In return it carries carbon dioxide from the tissues to the lungs.

#### Activities

Activity 1 School.ie has created an interesting and interactive animation to cover almost all the topics related to respiration. This is devised as a comprehensive study involving respiratory syetm, mechanism of breathing, gaseous exchange, transport of respiratory gases and aerobic respiration. It has aslo added a note on the dangers of smoking to insist on the ill-effects of smoking. Glossary is informative on specifying all the terms related to respiration. There are progressive tests ot the end of every topic which help students in their self-analysis. Go to Activity Activity 2 Biomanbio.com has constructed a small game to make students familiar with equation for respiration. Just by using audio and video format one can know the reactants and products taking part in photosynthesis. The game is devised in such a way that it shows different type of organisms which perform respiration in single frame. It allows the user to know the facts about respiration. Finally it also differentiates respiration from that of photosynthesis. Go to Activity

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