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KEY STAGE 4 RESPIRATION © Boardworks Ltd 2003 So far, we have considered both the structure of the breathing system and how it is adapted for breathing in and out. BUT... We have not talked about why the body needs to breathe. If you remember, we know that we breathe constantly throughout life. Also, we know that if we stopped breathing we would eventually die. So, breathing in Oxygen (O2) must be linked to something that we need constantly and without it our bodies would die. The answer is ENERGY making. © Boardworks Ltd 2003 The energy making process depends on the breathing system and the digestive system. Imagine a fire... This will produce energy in the form of heat but only if it is supplied with 2 main ingredients. FUEL OXYGEN © Boardworks Ltd 2003 Well, the bodies energy making reaction needs similar things to the energy making process of fire. Like the fire, the body needs Oxygen and a Fuel. The Oxygen is supplied by the breathing system + And the fuel (in the form of digested food) comes courtesy of the digestive system 2 © Boardworks Ltd 2003 If we now think back over the journey of oxygen and digested food through the human body, we will realise that they both end up in the same place. Food Oxygen Breathing system These substances eventually arrive at the body cells Digestive system BLOOD © Boardworks Ltd 2003 Therefore, the raw materials for the energy making process eventually arrive at the body cells. This energy making process is known as... RESPIRATION Each living cells is supplied with food and oxygen in order to generate energy. capillary Blood Oxygen + Food muscle cell © Boardworks Ltd 2003 No chemical reaction is 100% efficient. Therefore, as well as producing the useful energy, respiration also produces waste products. These waste products must be removed from the body If the process of breathing in is used to obtain the O2 for respiration, it would make sense for the body to use the process of breathing out to remove these waste products of this reaction. This is exactly what happens!! © Boardworks Ltd 2003 If we study the composition of the air that is breathed out, we will identify the waste products of respiration. Two tests help us identify these waste products. Before you start exhaling, the lime water is a clear liquid Test One Blow gently through a straw into a test tube filled with lime water. straw After a short while, the lime water becomes cloudy. lime water © Boardworks Ltd 2003 If a gas is bubbles through lime water and the liquid becomes cloudy, the gas is identified as…. Carbon Dioxide (CO2) This is the first of our waste products of respiration. Test Two On a freezing cold day, watch what happens when you breathe out. The air you breathe out is visible because the mystery waste product condenses back into a liquid. © Boardworks Ltd 2003 This waste product is water vapour and so our final waste product of the process of respiration is... Water Using this information, we can now write out the full equation for respiration FOOD (GLUCOSE) from digestive system + OXYGEN CARBON DIOXIDE from breathing system waste product exhaled + WATER waste product exhaled + ENERGY USEFUL! © Boardworks Ltd 2003 However, to call this reaction just ‘respiration’ is not quite correct. Let us try to understand why….. Think about what you do in an average day Sometimes you are resting Low energy requirements Sometimes you are active High energy requirements © Boardworks Ltd 2003 Your body requires different amounts of energy at different times. This is exactly what happens Our rate of breathing will change The blood will have to flow at different speeds according to demand The process of respiration must be able to ‘speed up’ and ‘slow down’ Therefore... This will mean that we need different amounts of food to feed the reaction It will also mean that we need different amounts of oxygen to feed the reaction © Boardworks Ltd 2003 It seems that the process of respiration changes during the course of the day. Let’s take two extreme examples human activity and see how the process of respiration change... 1. Sleeping 2. Running a marathon This may not represent the daily activities of an average human, but this scenario will help us understand this process of respiration in more depth. © Boardworks Ltd 2003 What happens to the process of respiration when the body is performing these different activities. Let’s deal with each one in turn. SLEEPING When we sleep, our body is at rest. There is a low demand for energy. Low energy demand Low demand for food and oxygen Blood flow does not have to be rapid The breathing rate remains normal In other words, the body has plenty of time to inhale the oxygen that it needs. It also has time to completely digest the food to release the important chemicals (e.g glucose). The blood can efficiently transport these substances to the cells without increasing its rate of flow. © Boardworks Ltd 2003 When the body is performing respiration in such as way, it is given a special name. When the body… O2 • has plenty of oxygen • is able to completely digest food • can supply the cells with the oxygen and food that they need We say it is performing AEROBIC respiration. © Boardworks Ltd 2003 So our original equation for the process of respiration is actually the equation for aerobic respiration. Glucose + Oxygen Carbon Dioxide + Water + Energy This is an efficient process... Our bodies perform aerobic respiration for much of the day. In fact, as long as the supply of Oxygen remains high enough, we will continue to perform aerobic respiration. Enough energy is made to supply the whole body Of course, the amount of energy we produce will drop if the level of oxygen drops. © Boardworks Ltd 2003 So, now we know that there is a form of respiration which is performed when there is a supply of oxygen to the body. But, what happens in situation 2? remember the runners? Are they performing aerobic respiration? Well, in order to answer that question, we have to think about what their bodies are doing during the race. before during after © Boardworks Ltd 2003 What’s happening? before Energy Demands Oxygen available Low High Aerobic Low / Aerobic (but slowing) High during after None Dropping None / Low Form or respiration ? © Boardworks Ltd 2003 ? How can the body perform aerobic respiration in this situation? Aerobic respiration requires oxygen but when you have been running a race or doing strenuous exercise, you cannot inhale enough oxygen for this reaction. Glucose + Oxygen Carbon Dioxide + Water + Energy This process fails! But, if this process fails when the oxygen levels drop, the body would be left with absolutely no energy. © Boardworks Ltd 2003 No energy would lead to stop working! ? The problem is that we often do exercise and our bodies continue working. ? What must be happening when our oxygen levels drop to zero? ? ? ? ? ? This would mean that the body would stop working whenever it became short of oxygen. ? The body must be able to keep working through short periods of low/no oxygen. ? HOW? © Boardworks Ltd 2003 Well, it is quite a remarkable process….let’s examine it. With aerobic respiration, the cells supply of oxygen and food is relatively constant Oxygen When this supply is cut off, the cell is left with excess food and lacks energy. Food blood cell It solves this problem by making energy from just the food alone! © Boardworks Ltd 2003 Now because it is releasing energy from food, it is still performing respiration. But... It is not aerobic respiration because there is no oxygen present. (aero- means of air) Therefore we call it ANAEROBIC respiration The energy being made by breaking down the food without oxygen. This seems a better process! To be able to make energy without needing oxygen would be very beneficial. However, there is a problem. © Boardworks Ltd 2003 Remember the last time you ran a race, carried a heavy weight or swam under water for too long and ran short of breath. It probably felt uncomfortable. Well, if anaerobic respiration was as efficient as it sounds, this lack of comfort would not happen. So, what is the problem with anaerobic respiration? When the cell breaks down the food to release the energy, it also makes a potentially harmful waste product. The breakdown of the food is also incomplete. It is not an efficient process. © Boardworks Ltd 2003 This waste product is known as LACTIC ACID. Therefore the equation for Anaerobic respiration is… Glucose from the digestive system Lactic Acid + (some) Energy waste product not as much energy as with aerobic respiration You will notice that this reaction is only an option for short periods of time. This is because the waste product is harmful and not enough energy is made to satisfy the body. © Boardworks Ltd 2003 Why is Lactic Acid so harmful? Well, this chemical can stop muscles within the body, from contracting and relaxing. The Lactic acid soaks the muscle cells and prevents the muscle cell from doing its job. Relaxation Contraction If the muscles in your body stop contracting and relaxing they are said to be fatigued. They eventually seize and you experience cramp. © Boardworks Ltd 2003 If you want to consider the full impact of damage caused by the presence of Lactic Acid, just remember that the heart is made of muscle cells! This leaves us with a problem... If we want to do exercise YES We want the energy that anaerobic respiration produces NO But we don’t want the Lactic Acid waste product So the answer is for anaerobic respiration to be a ‘gap-fill’ during periods of very low / no oxygen availability. © Boardworks Ltd 2003 In other words…. rest exercise stops Aerobic Anaerobic oxygen levels exercise time Anaerobic respiration keeps our bodies going until we can breathe in more oxygen again. Whilst we are performing anaerobic respiration, our bodies are building up a ‘debt’ of oxygen. © Boardworks Ltd 2003 This is rather like owing the bank some money. Once you get some money, you have to pay off that debt. We can think of that debt as being the presence of lactic acid in the body. When our bodies convert from aerobic to anaerobic respiration, we start making lactic acid. As soon as this begins, the body starts building an oxygen debt. This is equivalent to the amount of oxygen it would have used if aerobic respiration had continued. © Boardworks Ltd 2003 This oxygen debt will have to be repaid when the exercise stops. Oxygen will be used to break down the lactic acid that is present in the body. The oxygen ‘oxidises’ the lactic acid. In fact, the lactic acid is oxidised into carbon dioxide and water. In this way, the process of aerobic respiration can be converted into The process of anaerobic respiration which can then turn back into... © Boardworks Ltd 2003 Glucose Glucose Glucose + + Oxygen Oxygen Carbon Dioxide Carbon Dioxide + Lactic Acid water + water + + + Lots of energy little energy Lots of energy before exercise after exercise at rest again © Boardworks Ltd 2003 So, in summary, the body has the ability to produce energy, despite changes in the supply of oxygen. Here are the two forms of respiration. Aerobic respiration (complete breakdown of food) Glucose + Oxygen Carbon Dioxide + Water + Energy oxidised Anaerobic respiration Lactic Acid + Little Energy (incomplete breakdown of food) Aerobic respiration is performed when oxygen is present Anaerobic respiration is performed when oxygen is absent © Boardworks Ltd 2003 Now that we know how the energy is made, we need to consider what it is used for? Remember, cellular respiration occurs all over the body. Energy Therefore this energy is used for the many processes that sustain life. Amongst all these, there are a few important uses that we can examine. © Boardworks Ltd 2003 What is energy used for? 1 To allow muscles to contract 2 To build up large molecules from smaller ones 3 To help maintain a steady body temperature 4 To power the active transport of substances within the body © Boardworks Ltd 2003 We can consider each one in turn. 1 To allow muscles to contract and relax. In order for muscles to have an effect, they must move something in the body. Often this tends to be a bone. © Boardworks Ltd 2003 By moving the bone, they create a lever which does some work. muscle bone Using energy generated within the muscle, it contracts and alters the position of the bones. In doing so, work can be done e.g. something can be lifted. Muscle relaxed energy Muscle contracted © Boardworks Ltd 2003 2 To build up large molecules from smaller ones. In order for the human body to stay healthy, it must obtain nutrients from the 7 food groups. These are: Fats Proteins Minerals Vitamins Water Fibre Carbohydrates A balanced diet should contain elements from all 7 groups. © Boardworks Ltd 2003 Once we have digested the food from our diet, we release many useful substances. DIET Respiration digestion Useful raw materials ENERGY The body uses the energy from respiration to turn these raw materials into useful substances. © Boardworks Ltd 2003 A simple example of this use of energy can be seen when the body builds new proteins from amino acids. Step 1 Proteins are eaten as part of our food (e.g. protein in eggs) Step 2 These proteins are made of amino acid chains. The order of the amino acids is specific to the protein. amino acids © Boardworks Ltd 2003 Step 3 This protein may not be the one that the body requires. Therefore, the digestive system uses protease enzymes to break up the amino acid chain. Step 4 This process of digestion releases the individual amino acids. © Boardworks Ltd 2003 Step 5 Now that the raw materials are free, the body then uses the energy from respiration to assemble them into new proteins. A new protein will have a different order of amino acids. Energy respiration new protein (old) © Boardworks Ltd 2003 Step 6 This new protein, and others like it, will now be used in different ways by the body. The energy from respiration has made this possible. © Boardworks Ltd 2003 3 To help maintain a steady body temperature. The conditions outside our body are constantly changing. One minute they can be hot, the next cold. Despite this, our bodies must be kept at a constant temperature. © Boardworks Ltd 2003 This constant temperature is 37oC. The reason why our bodies must remain at 37oC is because this is the temperature at which enzymes work most effectively. You may remember that enzymes are chemicals that control many of the chemical reactions within our bodies. Therefore... colder 37oC hotter Enzymes working slowly and the body is suffering. Enzymes working well and body is fine. Enzymes damaged and body can become ill. © Boardworks Ltd 2003 The temperature of the body is controlled by a region of the brain. As blood flows around the body, it also visits this ‘thermo-regulatory’ centre in the brain. The brain senses the bodies temperature by sensing the temperature of blood. REST OF BODY Once it knows what the body temperature is, it can act accordingly. In order to understand what happens, think about what your body does when it is hot or cold outside. How do you react? © Boardworks Ltd 2003 On a hot day… You sweat. Blood is pumped to the surface of your skin. If we consider the second of these effects, we can see where the energy from respiration is used. Remember that blood flows through vessels which are lined with muscle cells. blood artery outer wall © Boardworks Ltd 2003 These muscle cells contract and relax using energy from respiration. The contraction and relaxation of these muscles can affect the blood flow through the vessel. E.g. if the muscle runs in a circular direction around the vessel, when it contracts, it could constrict the blood flow If a blood vessel is constricted in this way, blood flow is reduced and this in turn, will affect the direction of blood flow through the body. The opposite is also true. If the muscles relax, the blood vessel could become wider and the blood flow increases. © Boardworks Ltd 2003 Now, if we consider the blood vessels within the skin, we see how the contraction and relaxation of blood vessel muscles affects the flow of blood. surface of the skin skin Blood vessels Direction of blood flow We can see that blood can flow in different directions within the skin. When the brain senses that the body is too hot, it takes steps to redirect the blood flow to the skin surface. © Boardworks Ltd 2003 The brain can cause the contraction and relaxation of muscles within the walls of these blood vessels. Energy from respiration is used to power the contraction of these muscle cells. Brain B L O O D > 37oC makes the blood flow to the surface of the skin this vessel widens this vessel constricts © Boardworks Ltd 2003 When the blood flows to the surface, it comes into close contact with the air surrounding the body. This air is much cooler than the temperature of the blood. HEAT HEAT HEAT air skin blood The heat within the blood escapes to the cool air and the result is that the body’s temperature drops. Remember, respiration produces the energy that is needed by the muscle cells within the walls of the blood vessels. © Boardworks Ltd 2003 4 To power the active transport of substances within the body. This is our final use of the energy generated during respiration. In order to understand how active transport works, we must firstly consider the concept of diffusion. Diffusion is the movement of a substance from an area of high concentration to an area of low concentration. © Boardworks Ltd 2003 The particles would move from left to right. High Concentration Low Concentration This particle could be an oxygen molecule that is moving from the alveolus to the blood capillaries within the lungs. © Boardworks Ltd 2003 The diffusion of oxygen into the blood will eventually mean that the body cells can perform respiration. But what if the supply of oxygen (or another molecule) was not fast enough? This is when active transport comes into play. Active transport requires energy. This energy comes from respiration. Active transport uses energy to speed up the process of diffusion. © Boardworks Ltd 2003 Active transport gives this process an extra ‘push’. High Concentration Low Concentration This completes our study of the breathing system and the processes of aerobic and anaerobic respiration. © Boardworks Ltd 2003 Respiration….do I really need oxygen? Work through the following tasks, filling the missing words or crossing out the wrong words where necessary. A The body can perform two types of respiration. These are: 1. ____________ respiration (performed in plenty of O2) 2. ____________ respiration (performed in little or no O2) © Boardworks Ltd 2003 B Aerobic Respiration _______ + ______ _______ _______ + ______ + ______ C Aerobic respiration is performed when the supply of oxygen to the cells is HIGH / LOW. It is the COMPLETE / INCOMPLETE breakdown of food and so is very INEFFICIENT / EFFICIENT. It is a method of respiration that produces LOTS / LITTLE energy for the body. If the body does not get enough oxygen to the cells it CAN / CAN’T perform aerobic respiration. Instead it has to perform __________ respiration for a LONG / SHORT period of time. © Boardworks Ltd 2003 Why would the body be short of oxygen? Two common reasons for the body being short of energy would be if a human was performing… D 1. HEAVY / LIGHT exercise for LONG / SHORT periods of time. 2. HEAVY / LIGHT exercise for LONG / SHORT periods of time. E Anaerobic Respiration _______ + ______ _______ _______ + ______ waste product useful © Boardworks Ltd 2003 F Anaerobic respiration is performed when the supply of oxygen of the cells is HIGH / LOW. It is the COMPLETE / INCOMPLETE break down of food and so is very INEFFICENT / EFFICIENT. It is a method of respiration that produces LOTS / LITTLE energy for the body. © Boardworks Ltd 2003 Use the words below to answer the next section. fatigued aerobic oxygen muscle contracting anaerobic broken Lactic Acid This is poisonous. It can build up in _________ cells and stop them ___________ and relaxing. We say the cell is tired or __________. If we then relax and breathe again the body recovers. The supply of ___________ increases and the lactic acid is ___________ down. The body can now stop performing ___________ respiration and go back to performing __________ respiration. © Boardworks Ltd 2003 Multiple choice Questions © Boardworks Ltd 2003 1. Which of the following is a definition of respiration? A breathing B the release of energy from food C obtaining oxygen and releasing carbon dioxide D exchanging gases © Boardworks Ltd 2003 2. Aerobic respiration is a type of respiration that uses up… A oxygen. B energy. C carbon dioxide. D water. © Boardworks Ltd 2003 3. Which of the following are the raw materials for the process of aerobic respiration? A carbon dioxide, water and glucose B glucose and carbon dioxide C oxygen, water and energy D oxygen and glucose © Boardworks Ltd 2003 4. Which of the following are the waste products of aerobic respiration? A oxygen and carbon dioxide B glucose and energy C carbon dioxide and water D oxygen, water and energy © Boardworks Ltd 2003 5. Which of the following is a useful product of aerobic respiration? A oxygen B energy C carbon dioxide D glucose © Boardworks Ltd 2003 6. Which of the following is an accurate equation for this process of aerobic respiration? A Glucose + Carbon Dioxide Water + Energy + Oxygen B Oxygen + Carbon Dioxide Glucose + Sugar + Energy C Water + Energy + Sugar Carbon Dioxide + Oxygen D Glucose + Oxygen Carbon Dioxide + Water + Energy © Boardworks Ltd 2003 7. Animals perform anaerobic respiration when the body is short of… A energy. B carbon dioxide. C food. D oxygen. © Boardworks Ltd 2003 8. The main waste product from the process of anaerobic respiration is… A lactic acid. B carbon dioxide. C urea. D water. © Boardworks Ltd 2003 9. Which of the following statements accurately describes one use of the energy released during respiration? A The breakdown of protein into muscle from which amino acids are made. B The building of amino acids from proteins. C The building of protein from amino acids, with these proteins then being used to make muscle. D The building of carbohydrates from fatty acids to make organs. © Boardworks Ltd 2003 10. One further use of the energy that is generated by respiration is in… A the lowering of the body temperature on a cold day. B the raising of the body temperature on a hot day. C allowing the body temperature to change to match the air temperature. D maintaining a steady body temperature despite changes in the air temperature. © Boardworks Ltd 2003 11. What is the term used to describe the inefficient contraction of muscles that can occur during anaerobic respiration? A tiredness B exhaustion C fatigue D hyperventilation © Boardworks Ltd 2003 12. What causes the inefficient contraction of muscle that can occur during anaerobic respiration? A The complete breakdown of glucose (releasing more energy than aerobic respiration) and the build up of lactic acid. B The incomplete breakdown of glucose (releasing less energy than aerobic respiration) and the build up of lactic acid. C The incomplete breakdown of glucose (releasing more energy than aerobic respiration) and the breakdown of lactic acid. D The complete breakdown of glucose (releasing more energy than aerobic respiration) and the breakdown of lactic acid. © Boardworks Ltd 2003 13. If muscle cells become short of oxygen then the rate of aerobic respiration… A stops. B speeds up. C slow down. D remain constant . © Boardworks Ltd 2003 14. If muscle cells are deprived of oxygen then aerobic respiration will… A stop. B speed up. C slows down. D remains constant. © Boardworks Ltd 2003 15. David Beckham has just come off the pitch at Old Trafford after a tiring game. He is breathing heavily in order to… A carry out a series of chemical reactions that result in the complete oxidation of lactic acid to carbon dioxide and water. B slow down anaerobic respiration. C speed up anaerobic respiration. D increase the “oxygen debt”. © Boardworks Ltd 2003