IGCSE BIOLOGY RESPIRATION GAS EXCHANGE Dr. Mohamed Sameh What is respiration? Respiration is the release of energy from the breakdown of glucose, by combining it with oxygen inside living cells. What is gaseous exchange? Gaseous exchange is the movement of gases (oxygen and carbon dioxide) into and out of an organism. Aerobic v Anaerobic AEROBIC ANAEROBIC A very efficient method of producing energy. Inefficient (incomplete breakdown of glucose) – releases 1/20th energy compared to aerobic. Occurs during normal daily activity. Produces energy much faster over a short time period. Eg. sprinting Produces energy more slowly Build-up of waste products eventually stops the muscle than anaerobic. from working Gaseous exchange is the movement of gases (oxygen and carbon dioxide) into and out of an organism. Gaseous exchange is brought about by the actions of the breathing system (the respiratory system) The Breathing System Ribs these protect the contents of the thorax. There are 12 pairs of ribs in both men and women. Rib muscles the intercostals. Raise and lower the rib cage Right bronchus – a branch of the trachea Diaphragm a sheet of muscle used in the mechanism of breathing Trachea surrounded by rings of cartilage to stop it collapsing Left lung Bronchiole a smaller branch of the bronchus Alveoli clusters of grape-like air sacs where gas exchange takes place Bronchiole 1 Alveolus 1. Deoxygenated blood flow from the tissues, rich in carbon dioxide Bronchiole Alveolus 2 2. Carbon dioxide diffuses out of the blood stream into the alveoli, and then into the bronchiole Bronchiole Alveolus 3 3. Oxygen diffuses from the bronchiole into the alveoli and then into the red blood cells. Bronchiole Alveolus 4. Oxygenated blood now leaves the alveoli and carries oxygen to the tissues. 4 Features of the alveoli: 1. A very large, moist surface area. 2. An excellent capillary blood supply 3. Very thin cell membrane separating blood and lung Ventilation INHALATION = taking air into the lungs EXHALATION = removing air from the lungs IN OUT Nitrogen 79% Nitrogen 79% Oxygen 21% Oxygen 16% Carbon dioxide 0.04% Carbon dioxide 4% Ventilation BREATHING IN Rib cage moves upwards and outwards. Diaphragm moves downwards and becomes flatter. Overall effect: volume of the thorax increases, pressure decreases, so air is drawn IN BREATHING OUT Rib cage moves downwards and inwards. Diaphragm moves upwards and becomes dome shaped. Overall effect: volume of the thorax decreases, pressure increases, so air is pushed OUT PHOTOSYNTHESIS 6CO2 + 6H2O à C6H12O6 + 6O2 RESPIRATION C6H12O6 + 6O2 à 6CO2 + 6H2O The compensation point is where light intensity is at the point where the rate of photosynthesis is equal to the rate of respiration. At light intensities below this point, more respiration occurs. At higher light intensities, more photosynthesis occurs. Carbon dioxide and oxygen move into and out of the leaf via diffusion. These gases move through pores on the underside of the leaf called stomata. O2 CO2 Carbon dioxide is needed for photosynthesis and oxygen is needed for respiration. Leaf adaptations for gas exchange Leaf structure Adaptation Spongy mesophyll Contain air spaces for gas exchange to occur. They provide a large surface area for gas exchange. The spongy mesophyll cell membranes are also thin, moist and permeable, aiding gas exchange further. Lower epidermis Contains the stomata. Stomata Are pores found in the underside of the leaf but can be found in the upper epidermis. They open in light and close in the dark. They allow gases such as oxygen (out) and carbon dioxide (in) to leave and enter the cell. They also allow water to escape. Their opening and closing is controlled by guard cells. Glucose In the light, the guard cells produce glucose which lowers the water concentration in them, drawing water into the cells by osmosis. The guard cells become turgid, and the stomata opens. Pa p e r In the dark, the glucose produced during the 2 day will be used in respiration. As no new glucose is made, this increases the concentration of water inside the cell (as solute o concentration falls), causing water to be drawn n out by osmosis. The guard cells lose water, becoming flaccid, and the stomata closes. l y 1) 2) 3) 4) 5) 6) Air enters via the mouth and nose. It will then enter the trachea. The trachea branches into two bronchi one going into each lung. The bronchus branches into small tubes called bronchioles. At the end of each bronchiole are millions of alveoli where gaseous exchange takes place. Here oxygen will enter the blood and carbon dioxide will leave the blood. Structure Function Trachea Supported by rings of cartilage that prevent it from collapsing. Brings air into the lungs. Bronchus They are supported by rings of cartilage. It branches off the trachea to bring air into the lungs. Bronchiole Branch off the bronchi. Alveoli Small air sacs that are the site of gas exchange. Lung The organ where gas exchange occurs. Ribs Protect internal organs of the thorax. Intercostal muscles Muscles between the ribs that aid breathing by moving the ribs. Diaphragm Sheet of muscle below the ribs that aid breathing. Its movements increase and decrease the thorax. Pleural membranes Thin layers that reduce friction between the lungs and the inside of the chest wall during breathing. Ventilation Aerobic respiration Anaerobic respiration in the presence of oxygen. in the absence of oxygen. Involves the complete breakdown of glucose. Involves the incomplete breakdown of glucose. Provides more energy. Provides less energy. End products in animals and plants: carbon dioxide and water End product in animals – lactic acid. End product in plants - ethanol Glucose + oxygen C6H12O6 + 6O2 carbon dioxide + water + energy 6CO2 + 6H2O + energy. Veniole Arteriole Energy Glucose + Oxygen Glucose and oxygen diffuse from the blood into the muscle cell à Carbon dioxide + Water Muscle cell Energy is used for muscle contraction Carbon dioxide and water diffuse from the muscle cell into the blood Why anaerobic respiration? If it is so inefficient compared with aerobic respiration, why do cells bother? Sometimes our muscles are working so hard that the lungs and bloodstream cannot deliver oxygen fast enough, so the muscles must respire anaerobically. This can lead to a build up of lactic acid in the muscle. A lactic acid build-up in muscles can result in cramp, an unpleasant and often painful sensation caused by muscle contraction or over-shortening. In order to break down the lactic acid the body needs more oxygen à OXYGEN DEBT Glucose + oxygen C6H12O6 + 6O2 carbon dioxide + water + energy 6CO2 + 6H2O + energy. Veniole Arteriole Energy Glucose + Oxygen Glucose and oxygen diffuse from the blood into the muscle cell à Carbon dioxide + Water Muscle cell Energy is used for muscle contraction Carbon dioxide and water diffuse from the muscle cell into the blood Why anaerobic respiration? If it is so inefficient compared with aerobic respiration, why do cells bother? Sometimes our muscles are working so hard that the lungs and bloodstream cannot deliver oxygen fast enough, so the muscles must respire anaerobically. This can lead to a build up of lactic acid in the muscle. A lactic acid build-up in muscles can result in cramp, an unpleasant and often painful sensation caused by muscle contraction or over-shortening. In order to break down the lactic acid the body needs more oxygen à OXYGEN DEBT Aerobic respiration Anaerobic respiration in the presence of oxygen. in the absence of oxygen. Involves the complete breakdown of glucose. Involves the incomplete breakdown of glucose. Provides more energy. Provides less energy. End products in animals and plants: carbon dioxide and water End product in animals – lactic acid. End product in plants - ethanol Anaerobic respiration in plants Glucose à ethanol + carbon dioxide + energy C6H12O6 à 2C2H5OH + 2CO2 In plants, anaerobic respiration (respiration without oxygen) is known as fermentation. This process is commonly used to our advantage in the production of beer and ales, and wine. Anaerobic respiration in plants Glucose à ethanol + carbon dioxide + energy C6H12O6 à 2C2H5OH + 2CO2 In plants, anaerobic respiration (respiration without oxygen) is known as fermentation. This process is commonly used to our advantage in the production of beer and ales, and wine. Smoking can damage the lungs and the cardiovascular system causing disease Investigate breathing in humans A. The release of carbon dioxide 1)Set up your apparatus, as shown in the picture. Labelling the conical flasks as X and Y. 2)Add 20cm3 of hydrogencarbonate indicator into each conical flask. 3)Breath in and out gentle for three minutes. 4) Record the The results show us that there is a greater amount of carbon dioxide in the air that we breathe out. Then the air left when we breathe in. The breathing rate increases during exercise as your body requires more oxygen for aerobic respiration. After exercise, your breathing rate remains high because of an oxygen debt which occurs when your body switches from aerobic respiration to anaerobic respiration during vigorous exercise. Anaerobic respiration produces lactic acid, which must be broken down by oxygen.
