1. Contents Respiration Waste products Aerobic respiration Anaerobic respiration What is respiration? An energy-making process Summary quiz

2. We know that we breathe constantly throughout life. Also, we know that if we stopped breathing we would eventually die. something So, breathing in oxygen (O 2 ) must be linked to something that we need constantly and without it our bodies would die. The answer is ENERGY making. An energy-making process

3. Ingredients to make energy The energy-making process depends on the breathing system and the digestive system. This will produce energy in the form of heat but only if it is supplied with 2 main ingredients. FUELOXYGEN Imagine a fire...

4. 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. + fuel and the fuel (in the form of digested food) comes courtesy of the digestive system. 2 oxygen the oxygen is supplied by the breathing system Our fuel

5. 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. these substances eventually arrive at the body cells foodoxygen breathing system digestive system BLOOD Our pipelines to the cells

6. Every living cell needs to respire Therefore, the raw materials for the energy-making process eventually arrive at the body cells. This energy-making process is known as... R E S P I R A T I O N Each living cell is supplied with food and oxygen in order to generate energy. oxygen blood food + capillary muscle cell

7. Contents Respiration Waste products Aerobic respiration Anaerobic respiration What is respiration? An energy-making process Summary quiz

8. Waste products 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. This is exactly what happens! If the process of breathing in is used to obtain the O 2 for respiration, it would make sense for the body to use the process of breathing out to remove these waste products of this reaction.

9. 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 After a short while, the lime water becomes cloudy. Test One Blow gently through a straw into a test tube filled with lime water. lime water straw What’s the waste?

10. Identification of the first waste product If a gas is bubbles through lime water and the liquid becomes cloudy, the gas is identified as…. This is the first of our waste products of respiration. carbon dioxide (CO 2 )

11. 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. Seeing your breath This waste product is water vapour and so our final waste product of the process of respiration is... water

12. Using this information, we can now write out the full equation for respiration. WATER CARBON DIOXIDE ++ ENERGY FOOD (GLUCOSE) OXYGEN + from digestive system from breathing system USEFUL! waste product exhaled The equation for respiration

13. Contents Respiration Waste products Aerobic respiration Anaerobic respiration What is respiration? An energy-making process Summary quiz

14. 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. resting sometimes you are resting low energy requirements When is energy needed?

15. A busy day! active sometimes you are active high energy requirements

16. Food and fuel flexibility Your body requires different amounts of energy at different times. Therefore… the process of respiration must be able to ‘speed up’ and ‘slow down’ 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 the blood will have to flow at different speeds according to demand our rate of breathing will change this is exactly what happens

17. Throughout the day… Let’s take two extreme examples human activity and see how the process of respiration change... It seems that the process of respiration changes during the course of the day. This is not the daily activities of an average human, but this scenario will help us understand the process of respiration in more depth. 1. sleeping 2. running a marathon

18. SLEEPING When we sleep, our body is at rest. There is a low demand for energy. low energy demand blood flow does not have to be rapid low demand for food and oxygen 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 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. Sleeping

19. Contents Respiration Waste products Aerobic respiration Anaerobic respiration What is respiration? An energy-making process Summary quiz

20. Aerobic respiration When the body is performing respiration in such a way, it is given a special name. When the body… We say it is performing AEROBIC respiration. O2O2O2O2 has plenty of oxygen is able to completely digest food can supply the cells with the oxygen and food that they need

21. So our original equation for the process of respiration is actually the equation for aerobic respiration. This is an efficient process... enough energy is made to supply the whole body. 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. Of course, the amount of energy we produce will drop if the level of oxygen drops. Glucose + OxygenCarbon Dioxide + Water + Energy Equation for aerobic respiration

22. Exercise: before - during - after 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? 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. duringbeforeafter Remember the runners?

23. Energy demands Oxygen available Form of respiration What’s happening? before lowhighaerobic during high low / none aerobic (but slowing) after droppingnone / low ? Physical activity dictates energy demands

24. ? 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 + OxygenCarbon 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. Running out of the good stuff

25. No energy would lead the body to stop working! The body would stop working whenever it became short of oxygen. The problem is that we often do exercise and our bodies continue working. What must be happening when our oxygen levels drop to zero? The body must be able to keep working through short periods of low/no oxygen. But how? Oxygen levels at zero

26. With aerobic respiration, the cells supply of oxygen and food is relatively constant. oxygen food cellblood When this supply is cut off, the cell is left with excess food and lacks energy. It solves this problem by making energy from just the food alone! Oxygen shortage at the cellular level

27. Contents Respiration Waste products Aerobic respiration Anaerobic respiration What is respiration? An energy-making process Summary quiz

28. Now because it is releasing energy from food, it is still performing respiration. no But it is not aerobic respiration because there is no oxygen present. (aero- means of air) ANAEROBIC 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. Anaerobic respiration

29. 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. Hitting the wall

30. 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. So, what is the problem with anaerobic respiration? What’s wrong with anaerobic respiration?

31. GlucoseLactic Acid + (some) Energy This waste product is known as LACTIC ACID. Therefore the equation for anaerobic respiration is… from the digestive system 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. The anaerobic equation

32. 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. relaxationcontraction If the muscles in your body stop contracting and relaxing they are said to be fatigued. They eventually seize and you experience cramp. Why is lactic acid so harmful?

33. 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 We want the energy that anaerobic respiration produces YESNO So the answer is for anaerobic respiration to be a ‘gap-fill’ during periods of very low / no oxygen availability. But we don’t want the lactic acid waste product Striking the right balance

34. time oxygen levels rest exercise exercise stops aerobic anaerobic 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. Oxygen debt

35. 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. Paying it off

36. 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. Doing the sums

37. Dealing with the lactic acid build-up 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...

38. The body has the ability to produce energy, despite changes in the supply of oxygen. Here are the two forms of respiration. glucose + oxygencarbon dioxide + water + energy Aerobic respiration (complete breakdown of food) Anaerobic respiration (incomplete breakdown of food) Aerobic respiration is performed when oxygen is present. Anaerobic respiration is performed when oxygen is absent. glucose + oxygen carbon dioxide + water + lactic acid + little energy Respiration summary

39. Work through the following tasks, filling the missing words or crossing out the wrong words where necessary. The body can perform two types of respiration. These are: 1. ____________ respiration (performed in plenty of O 2 ) 2. ____________ respiration (performed in little or no O 2 ) A Aerobic Respiration _______ + ______ _______ _______ + ______ + ______ B Respiration…do I really need oxygen?

40. 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. C Respiration…do I really need oxygen?

41. Two common reasons for the body being short of energy would be if a human was performing… 1.HEAVY / LIGHT exercise for LONG / SHORT periods of time. 2. HEAVY / LIGHT exercise for LONG / SHORT periods of time. D Anaerobic Respiration _______ + ______ _______ _______ + ______ waste productuseful E Why would the body be short of oxygen?

42. 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. F Why would the body be short of oxygen?

43. The acid test fatigued oxygen muscle contracting anaerobicaerobic broken 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. This is poisonous. It can build up in _________ cells and stop them ___________ and relaxing. We say the cell is tired or __________.

44. Contents Respiration Waste products Aerobic respiration Anaerobic respiration What is respiration? An energy-making process Summary quiz

45. Multiple-choice quiz