2 Chapter 10Respiration in Humans10.1 Why Do Living Things Respire?10.2 Studying Respiration10.3 Gas Exchange in Humans10.4 How Does Inspired Air Differ from Expired Air?10.5 Effects of Tobacco Smoke on Human Health
3 Why Do Living Things Respire? 10.1Why Do Living Things Respire?Learning OutcomesAfter this section, you should be able to:define and state the equations in words for aerobic and anaerobic respiration in humans;describe the effect of lactic acid in muscles during exercise.
4 Why Do Living Things Respire? 10.1Why Do Living Things Respire?Energy that is needed for organisms to move, grow, excrete and reproduce, is obtained through the consumption of food.To use the energy available in food, living organisms need to break down the food molecules through a process called oxidation.The oxidation of food molecules to produce energy is called respiration.Respiration occurs in the cell and although it involves the breakdown of food molecules, it is not digestion.Digestion is the process in which food is broken down into simpler substances for absorption into the cells.In respiration, organic compounds (food molecules) are converted into inorganic compounds (e.g. carbon dioxide and water) to produce energy.
5 Why Do Living Things Respire? What is aerobic respiration? 10.1Why Do Living Things Respire?What is aerobic respiration?The oxidation of glucose in the presence of oxygenResults in the production of a large amount of energy by giving off carbon dioxide and water as waste productsThe word equation for aerobic respiration:Notes:Organic molecules other than glucose (e.g. amino acids and fatty acids) can be used in respiration. Glucose, however, is the most commonly used food molecule in respiration. The chemical energy stored in glucose cannot be used directly by cells and has to be broken down via cellular respiration to release energy in a form that can be used by the cells (i.e. adenosine triphosphate, ATP).+glucoseoxygenenergycarbondioxidewater
6 Why Do Living Things Respire? 10.1Why Do Living Things Respire?Aerobic respiration occurs in the mitochondria of all cells.mitochondriaNote:Mitochondria are like little factories which produces energy from the respiration of glucose.
7 What is anaerobic respiration? 10.1Why Do Living Things Respire?What is anaerobic respiration?The oxidation of glucose in the absence of oxygenReleases less energy than aerobic respirationThe word equation for anaerobic respiration in humans:glucose+energylactic acidNotes:The waste products of anaerobic respiration differs from species to species depending on what is used as an electron acceptor. (oxygen is used as an electron acceptor in aerobic respiration)In humans, the waste product produced in anaerobic respiration is lactic acid.In yeast, the waste product produced in anaerobic respiration is ethanol and carbon dioxide.Equation for anaerobic respiration by yeast: glucose ethanol + carbon dioxide + energy
8 What happens during exercise? 10.1Why Do Living Things Respire?What happens during exercise?Muscles contract vigorously to enable movement.Respiratory rate and heart rate increase to enable more oxygen to reach the muscles.If the increased oxygen intake is not able to meet the oxygen demand, anaerobic respiration will take place to provide the energy required.Start by asking a student to describe how he/she feels before, during and after running the 2.4km fitness test.Notes:By increasing the respiratory rate, the oxygen intake increases. Increased oxygen demand of the body can be met.By increasing the heart rate, inhaled oxygen can be transported quickly to the relevant parts of the body (e.g. muscles).
9 What happens during exercise? 10.1Why Do Living Things Respire?What happens during exercise?When anaerobic respiration occurs, lactic acid accumulates and the muscles incur an oxygen debt.Lactic acid accumulation causes the soreness and tiredness in muscles.Note:An oxygen debt is the volume of oxygen required to remove the lactic acid that has been built up.
10 Chapter 10Respiration in Humans10.1 Why Do Living Things Respire?10.2 Studying Respiration10.3 Gas Exchange in Humans10.4 How Does Inspired Air Differ from Expired Air10.5 Effects of Tobacco Smoke on Human Health
11 10.2 Studying Respiration Learning Outcome After this section, you should be able to:carry out simple experiments to determine the products of respiration.
12 Carbon dioxide is a product of aerobic respiration 10.2Studying RespirationCarbon dioxide is a product of aerobic respirationThe potassium hydroxide solution in flask A removes carbon dioxide from the air.The air entering flask B and C does not contain carbon dioxide. Hence, any carbon dioxide detected in flask D would be due to respiration by the snails.Limewater turns chalky when carbon dioxide is dissolved into it.The limewater in flask B should not turn chalky because the carbon dioxide in the air entering flask B should have been removed in flask A.Carbon dioxide is released during respiration. Therefore, the limewater in D should turn chalky.potassium hydroxide solutionlimewaterABlimewatersnailsCD
13 Carbon dioxide is a product of anaerobic respiration 10.2Studying RespirationCarbon dioxide is a product of anaerobic respirationThe glucose solution is first boiled and cooled to:remove dissolved oxygenkill microorganismsDue to limited oxygen availability, the yeast undergoes anaerobic respiration.If carbon dioxide is released during the anaerobic respiration of yeast, the limewater will turn chalky.The limewater should turn chalky as anaerobic respiration of yeast produces ethanol and carbon dioxide.Highlight to students that carbon dioxide is not always released in anaerobic respiration. (e.g. Anaerobic respiration in muscle cells does not produce carbon dioxide.)Note:Yeast suspension is prepared using distilled water and dry yeast.glucose and yeast suspensionlimewater
14 Heat is a product of respiration 10.2Studying RespirationHeat is a product of respirationThe vacuum flask insulates the experimental set-up.The cotton wool plug allows gaseous exchange between the seeds and the environment.The antiseptic solution prevents growth of microorganisms.If heat is produced during respiration, the thermometer would register a temperature higher than the surrounding temperature.vacuum flaskpea seedsin antisepticsolutioncotton wool plugthermometerThe thermometer should register a higher temperature than the surrounding temperature as respiration releases heat energy.Note:Germinating (actively growing) seeds are used because they have higher rate of respiration as compared to dormant seeds.
15 Chapter 10Respiration in Humans10.1 Why Do Living Things Respire?10.2 Studying Respiration10.3 Gas Exchange in Humans10.4 How Does Inspired Air Differ from Expired Air10.5 Effects of Tobacco Smoke on Human Health
16 10.3 Gas Exchange in Humans Learning Outcomes After this section, you should be able to:identify the organs involved in the human gaseous exchange system;describe the role of the alveoli in gaseous exchange.
17 Why the need for a respiratory system? 10.3Gas Exchange in HumansWhy the need for a respiratory system?Humans are large organisms that are made up of millions of cells.We have a small surface area to volume ratio, unlike unicellular microorganisms.This mechanism of exchange is called external respiration and it involves a process called breathing.Emphasise to students the difference between external respiration and cellular respiration.External respiration refers to the breathing process. It is the process where oxygen is taken into and carbon dioxide is removed from the body.Cellular respiration refers to the oxidation of glucose to release energy in cells. Aerobic respiration requires oxygen which is obtained through breathing (external respiration).
18 Gas exchange system in humans 10.3Gas Exchange in HumansGas exchange system in humansnasal cavitylarynxpharynxThe fringe of hair and the mucous layer on the walls of the nasal cavity trap dust and foreign particles.The air is warmed and moistened as it passes through the nasal passages.
19 Gas exchange system in humans 10.3Gas Exchange in HumansGas exchange system in humansC-shaped rings of cartilage support the trachea.They keep the lumen of the trachea open.nasal cavitylarynxpharynxtracheabronchusC-shaped ring of cartilageTransverse section of a tracheaHighlight to students that the trachea branches out into two bronchi (singular: bronchus).
20 Gas exchange system in humans 10.3Gas Exchange in HumansGas exchange system in humansOn the inner walls of the trachea and bronchi are:gland cellepithelial cellciliamucus produced by gland cellgland cellsepithelial cellsGland cells secrete mucus that trap dust particles and bacteria in the air that is channelled to the lungs.Epithelial cells have cilia that sweep trapped particles and bacteria up the bronchi and trachea, to the pharynx.
21 Gas exchange system in humans 10.3Gas Exchange in HumansGas exchange system in humansnasal cavitylarynxpharynxtrachealungThe lungs lie in the thoracic cavity.Within the lungs, the bronchial tubes divide repeatedly to form bronchioles.Bronchioles end in clusters of air sacs called alveoli.bronchiolea cluster of alveolibronchusURLBronchial tubes refer to the tubes of the bronchi (singular: bronchus)Highlight to students that each bronchiole ends in a cluster of grape-like structures called alveoli (singular: alveolus). The alveoli are the site of gaseous exchange.Click on the Video-URL button to be directed to a website where a video summary (length = 1:46 minutes) on the human gaseous exchange system can be found. This video introduces the passage of air into the trachea, bronchi, bronchiole and alveoli. It also covers the features of the trachea (C-shaped cartilage) and explains how the large surface area to volume ratio is achieved for efficient gaseous exchange.
22 How are the alveoli adapted for efficient gaseous exchange? 10.3Gas Exchange in HumansHow are the alveoli adapted for efficient gaseous exchange?capillary networkThe numerous alveoli in the lungs increase the surface area for gaseous exchange.The alveoli are well-supplied with blood capillaries to maintain a steep concentration gradient of gases.
23 How are the alveoli adapted for efficient gaseous exchange? 10.3Gas Exchange in HumansHow are the alveoli adapted for efficient gaseous exchange?The alveolar surface is coated with a thin film of moisture to allow oxygen to dissolve.The wall of each alveolus and its surrounding capillaries are one-cell thick, ensuring faster rate of diffusion.capillary wallthin film of wateralveolar wall
24 Gaseous exchange in the alveolus 10.3Gas Exchange in HumansCO2O2inhaled oxygencarbon dioxide to be exhaledcapillaryalveolusGaseous exchange in the alveolusdeoxygenated blood (carbon dioxide rich)oxygenated blood (transported to the heart)URLHighlight to students that the alveolus is the site of gaseous exchange and that this gaseous exchange occurs via diffusion.Blood entering the lungs has lower concentration of oxygen and higher concentration of carbon dioxide than the air in the alveolus (the inhaled air).Carbon dioxide from the blood diffuses into the alveolus and this carbon dioxide will be channelled out of the lungs via expiration.The air in the alveolus contains a higher concentration of oxygen than the blood entering the lungs.The oxygen in the alveolus diffuses into the blood in the capillary vessels and is transported to the heart where it is pumped throughout the body.Click on the Video-URL button to be directed to a website with a video (length = 1:22 minutes) that shows how gaseous exchange occurs at the alveoli.
25 How is oxygen transported? 10.3Gas Exchange in HumansHow is oxygen transported?Oxygen molecules bind to haemoglobin in red blood cells to form oxyhaemoglobin.This process is reversible.Notes:Oxygen is transported by haemoglobin in red blood cells. When haemoglobin binds to oxygen, it becomes bright red in colour and when it loses oxygen, it becomes purplish-red in color. The binding of oxygen is a reversible reaction.The binding of oxygen to haemoglobin (Hb) molecules is dependent on the concentration of oxygen in the surroundings. In oxygen-rich areas (such as in the lungs), oxygen binds to Hb to form oxyhaemoglobin. In places where oxygen concentration is low (e.g. muscles), the process is reversed and oxygen molecules are released. This allows efficient transportation and distribution of oxygen.+ oxygen moleculeshaemoglobinoxyhaemoglobin- oxygen molecules
26 How is carbon dioxide transported? 10.3Gas Exchange in HumansHow is carbon dioxide transported?Carbon dioxide molecules produced by tissue cells are converted to hydrogen carbonate ions which diffuse into the blood plasma.In the lungs, the hydrogen carbonate ions are converted back into carbon dioxide.In blood, converted toHydrogen carbonate ionsCarbon dioxideIn the lungs, converted to
27 Chapter 10Respiration in Humans10.1 Why Do Living Things Respire?10.2 Studying Respiration10.3 Gas Exchange in Humans10.4 How Does Inspired Air Differ from Expired Air?10.5 Effects of Tobacco Smoke on Human Health
28 How Does Inspired Air Differ from Expired Air? 10.4Learning OutcomeAfter this section, you should be able to:state the difference in composition between inspired air and expired air.
29 How Does Inspired Air Differ from Expired Air? 10.4Breathing is the muscular contractions and movements of the ribs, which result in air moving in and out of the lungs.The taking in of air is called inspiration (or inhalation). The giving out of air is called expiration (or exhalation).
30 How Does Inspired Air Differ from Expired Air? 10.4
31 Chapter 10Respiration in Humans10.1 Why Do Living Things Respire?10.2 Studying Respiration10.3 Gas Exchange in Humans10.4 How Does Inspired Air Differ from Expired Air10.5 Effects of Tobacco Smoke on Human Health
32 Effects of Tobacco Smoke on Human Health 10.5Learning OutcomeAfter this section, you should be able to:describe the effects of the major toxic components of tobacco smoke on human health.
33 Effects of Tobacco Smoke on Human Health 10.5Carbon monoxideNicotineaddictiveincreases risk of blood clot in blood vesselsincreases the risk of heart diseasesdecreases the ability of red blood cells to transport oxygenincreases the rate at which fats are deposited on the inner arterial walls (leads to artherosclerosis)Irritants(e.g. formaldehyde, hydrogen cyanide)Tarparalyse the cilia lining in air passagesincrease the risk of chronic bronchitis and emphysemacarcinogenicparalyses the cilia lining in air passagesreduces the efficiency of gaseous exchange
34 Effects of Tobacco Smoke on Human Health 10.5Chronic bronchitisIn chronic bronchitis,the epithelium lining the airways is inflamedthere is excessive mucus secretionthe cilia lining the airways are paralysedSymptoms:Breathing difficulties due to blocked airwaysPersistent cough (body’s response to clear the blocked airways)over secretion of mucusNotes:Tobacco smoking is the most common cause of chronic bronchitis. The components of tobacco smoke that contribute to the development of this disease are the irritants and tar.Persistent and prolonged coughing can lead to emphysema.cilia paralysed and unable to remove mucus
35 Effects of Tobacco Smoke on Human Health 10.5EmphysemaIn emphysema,the partition walls between alveoli break down due to violent coughs. (This reduces the surface area available for gaseous exchange.)the lungs lose their elasticity and become inflated with airSymptomsBreathing difficultiesWheezinghealthy lungspartition walls between alveolidiseased lungsdamaged partition wallsA person that suffers from both chronic bronchitis and emphysema, has chronic (meaning recurrent, persistent) obstructive (due to the blockage in the airways) lung disease.Note:Tobacco smoking is also the most common cause of emphysema.