Respiration in Organisms (Science Test - Jan 2024 PDF)

# RESPIRATION IN ORGANISMS Each cell of an organism performs functions like nutrition, transport, excretion and reproduction - for this purpose, it needs energy. Our food is stored energy which is released during respiration. Breathing is the process during which, we breathe in air having oxygen an...

# RESPIRATION IN ORGANISMS Each cell of an organism performs functions like nutrition, transport, excretion and reproduction - for this purpose, it needs energy. Our food is stored energy which is released during respiration. Breathing is the process during which, we breathe in air having oxygen and we breathe out air rich in carbon dioxide. The air rich in oxygen is transported to all parts of the body and ultimately to each cell. This oxygen is utilised by the cell for respiration. The process of breakdown of food in the cells of an organism with the release of energy is called cellular respiration. ## Types of Respiration On the basis of the presence or absence of oxygen, respiration is classified into two types: 1. **Aerobic Respiration** When the breakdown of glucose occurs with the use of oxygen, it is called aerobic respiration. During aerobic respiration, glucose is completely broken down into carbon dioxide and water and energy is released. Aerobic respiration takes place in mitochondria. It can be shown by the following equation: Glucose(food) + Oxygen -> Carbon dioxide + Water + Energy Aerobic respiration is seen in most of the organisms such as humans (man), dogs, cats, lions, elephants, cows, buffaloes, goats, snakes, earthworms, frogs, fishes, etc. 2. **Anaerobic Respiration** When a breakdown of glucose takes place without using oxygen, it is called anaerobic respiration. The glucose is not completely broken down into carbon dioxide and water. An intermediate compound is formed with the release of less amount of energy during this process. It can be shown as follows: Glucose + No oxygen or air -> Alcohol + Carbon dioxide + Energy Yeasts such as *Saccharomyces cerevisiae* and certain bacteria carry out anaerobic respiration. These organisms that carry out respiration in the absence of oxygen are called anaerobes. Yeast is a single-celled organism. During anaerobic respiration (also called fermentation), yeast produces ethanol or alcohol as a byproduct which is used in making wine and beer. The carbon dioxide produced by yeast is used in the bread making industry. The CO2 gas released during this process causes the bread dough to rise. ## Anaerobic Respiration in Muscles Usually, aerobic respiration takes place in humans, but under certain conditions, anaerobic respiration may also occur in our muscles for a short time, due to temporary deficiency of oxygen. When we perform a heavy exercise like running, cycling, walking, weight lifting, etc., we require a large amount of energy. To meet the energy requirement our muscle cells perform anaerobically respiration. During this process, the glucose or food in the muscle cells is partially broken down in the absence of oxygen to form lactic acid and some extra energy is released. The following equation shows the production of lactic acid: Glucose(Food) -> Lactic acid + Energy This occurs because during vigorous physical activity, the utilisation of oxygen occurs at a faster rate in the muscles that can be supplied by the blood. When the lactic acid produced during anaerobic respiration, gets accumulated in the muscles, it causes muscle cramps. The muscle cramps can be relieved by taking a hot water bath or a massage. This improves the circulation of blood and oxygen supply to the muscle cells increases. The increased supply of oxygen results in the complete breakdown of lactic acid into carbon dioxide and water, thereby giving relief from cramps. ## Differences between aerobic and anaerobic respiration | | Aerobic respiration | Anaerobic respiration | |----------|------------------------------|---------------------------------| | Oxygen | It occurs in the presence of oxygen. | It takes place in the absence of oxygen. | | Breakdown | The complete breakdown of food takes place in aerobic respiration. | Partial breakdown of food occurs in anaerobic respiration. | | Products | End products of aerobic respiration are CO₂ and water. | End products of anaerobic respiration are alcohol and CO₂ or lactic acid (in muscles). | | Energy | A large amount of energy is produced during aerobic respiration. | Less amount of energy is produced during anaerobic respiration. | ## Breathing It is the process in which air rich in oxygen is taken inside and air rich in CO₂ is given out, with the help of respiratory organs. Thus, breathing involves two steps which take place alternately. * **Inhalation:** Taking in of air rich in oxygen into our body is called inhalation. * **Exhalation:** Giving out air rich in carbon dioxide from our body to the external environment is called exhalation. This activity must be performed under the supervision of your teacher or parent. Close your nostrils and mouth tightly and look at a watch. Note down the time for which you could hold your breath. We will soon start feeling uneasy and cannot hold our breath for even one minute. ## Breathing Rate The number of times a person breathes in a minute is termed as breathing rate. An adult human being can inhale and exhale 15-18 times in a minute. It is the average breathing rate of an adult human being. The breathing rate of a person is not always constant. It changes according to the oxygen requirement of the body. Breathing rate is somewhat faster in women than in men and in children, it is higher (20-30 times/min) than adults. Breathing rate is slowest while sleeping (as less energy is required) while maximum during heavy exercise like running, weight lifting, etc. (much energy is required). Increased breathing rate provides a greater amount of air entry into the lungs, hence blood can absorb oxygen at a faster rate. Faster breathing supplies more oxygen to the body cell for producing more energy, required for heavy exercises. During heavy exercise, the breathing rate can increase to 25 times per minute. Because of this, food gets broken down at a faster rate and thus make us feel hungry. When we feel drowsy, sleepy or tired, we yawn (i.e. open our mouth wide to take a long and deep breath, of air), because our breathing rate slows down and the body does not receive sufficient oxygen. ## Mechanism of Breathing The mechanism of breathing can be understood by the following points: * Normally, we take in air through our nostrils. When we inhale air, it passes through our nostrils into the nasal cavity. * From the nasal cavity, the air reaches our lungs through the windpipe. * Lungs are present in the chest cavity. This cavity is surrounded by ribs on the sides. * A large, muscular sheet called diaphragm forms the floor of the chest cavity. ## DRAW A NEAT LABELLED DIAGRAM OF HUMAN RESPIRATORY SYSTEM A diagram of the human respiratory system is presented with the following labels: * Nostrils * Pharynx * Trachea * Alveoli * Right lung * Left lung * Diaphragm