Unit 8 B: Respiration Respiration: Respiration is a chemical reaction that happens in all living cells. It is the way that energy is released from glucose, for our cells to use to keep us functioning. Remember that respiration is not the same as breathing (which is properly called ventilation). Aerobic respiration: The glucose and oxygen react together in the cells to produce carbon dioxide and water. The reaction is called aerobic respiration because oxygen from the air is needed for it to work. Here is the word equation for aerobic respiration: glucose + oxygen carbon dioxide + water (+ energy) (Energy is released in the reaction. We show it in brackets in the equation because energy is not a substance.) Now we will look at how glucose and oxygen get to the cells so that respiration can take place and how we get rid of the carbon dioxide. Glucose from food to cells: Glucose is a type of carbohydrate, obtained through digestion of the food we eat. Digestion breaks food down into small molecules. These can be absorbed across the wall of the small intestine into the bloodstream. Glucose is carried round the body dissolved in blood plasma, the pale yellow liquid part of our blood. The dissolved glucose can diffuse into the cells of the body from the capillaries. Once in the cell glucose can be used in respiration. Oxygen from the air to cells: When we breathe in oxygen enters the small air sacs, called alveoli, in the lungs. Oxygen diffuses from there into the bloodstream. Oxygen is not carried in the plasma, but is carried by the red blood cells. These contain a red substance called haemoglobin, which joins onto oxygen and carries it around the body in the blood, then lets it go when necessary. Like glucose, oxygen can diffuse into cells from the capillaries. Red blood cells carry oxygen around the body. Carbon dioxide from cells to the air: The carbon dioxide produced during respiration diffuses out of the cells and into the blood plasma. The blood carries it to the lungs. It then diffuses across the walls of the alveoli and into the air, ready to be exhaled. 1
The respiratory system and ventilation: The respiratory system: The human respiratory system contains the organs that allow us to get the oxygen we need and to remove the waste carbon dioxide we don't need. It contains these parts: Lungs Tubes leading from the lungs to the mouth and nose Various structures in the chest that allow air to move in and out of the lungs. Ventilation: Movements of the ribs, rib muscles and diaphragm allow air into and out of the lungs. Take care - this is called breathing or ventilation, not respiration. When we breathe in, we inhale. When we breathe out, we exhale. Air passes between the lungs and the outside of the body through the windpipe, called the trachea. The trachea divides into two bronchi, with one bronchus for each lung. Each bronchus divides further in the lungs into smaller tubes called bronchioles. At the end of each bronchiole, there is a group of tiny air sacs. These air sacs have bulges called alveoli to increase their surface area. 2
Inhaled air and exhaled air: Gas Inhaled air (air entering lungs) Exhaled air (air leaving lungs) Oxygen 21% 17% Carbon dioxide 0.04% 4% Nitrogen 78% 78% Water vapour Varies Saturated Compared to the air we breathe in, the air we breathe out has: Less oxygen More carbon dioxide. The amount of nitrogen stays the same, but there is more water vapour in exhaled air. We can test for the presence of the extra carbon dioxide in exhaled air using limewater. If we exhale into limewater, it turns cloudy white. Gas exchange: We need to get oxygen from the air into the blood, and we need to remove waste carbon dioxide from the blood into the air. Moving gases like this is called gas exchange. The alveoli are adapted to make gas exchange in lungs happen easily and efficiently. Here are some features of the alveoli that allow this: They give the lungs a really big surface area They have moist, thin walls (just one cell thick) They have a lot of tiny blood vessels called capillaries. The gases move by diffusion from where they have a high concentration to where they have a low concentration: Oxygen diffuses from the air in the alveoli into the blood. Carbon dioxide diffuses from the blood into the air in the alveoli. 3
Some water vapour is also lost from the surface of the alveoli into the lungs - we can see this condensing when we breathe out on cold days. The circulatory system: The circulatory system is the body s transport system. Oxygen and nutrients including glucose travel around the body in the blood. Blood: Blood is a mixture of different types of cells in a liquid. Red blood cells carry oxygen from the lungs to the cells and take carbon dioxide back to the lungs. White blood cells help fight disease. Plasma is a straw coloured liquid that carries nutrients, as well as hormones which control your body, and antibodies which help fight disease. Platelets help blood to clot when you have a wound. Circulation of blood: Blood circulates around the body, pumped by the heart. It travels in a network of tubes called blood vessels. There are three main types: Arteries carry blood away from the heart. Veins carry blood back to the heart. Capillaries are tiny vessels that join arteries to veins. 4
Capillaries branch deep inside the body s tissues. Here substances such as oxygen, glucose and carbon dioxide can be exchanged between the blood and the cells. Pumping faster and harder: 1- The heart pumps blood to the lungs. Here, it picks up oxygen, and carbon dioxide leaves it. 2- Oxygenated blood goes back to the heart. 3- The heart pumps oxygenated blood around the body to organs such as the gut, the muscles and the brain. 4- Deep in the tissues oxygen, glucose and other nutrients pass from the blood to the cells for respiration. Waste material such as carbon dioxide passes from the cells to the blood to be carried away. 5- The deoxygenated blood travels back to the heart to be pumped back to the lungs again. If you run a race, your muscle cells are respiring fast so they need lots of oxygen and glucose. They are producing more carbon dioxide and water, as well as releasing lots of energy to win the race. To supply the cells, your heart pumps faster and harder, circulating the blood faster and you breathe faster too. What if you tried to sprint hard for an hour? Your lungs would not be able to pick up enough oxygen, and your heart would not be able to circulate the blood fast enough. Your muscle cells would run short of oxygen. When this happens you get cramp and feel exhausted. You have to stop! But if you jog slowly, your body can supply enough oxygen and glucose for a long time. 5
Smoking : One serious smoking experiment: 1- Some of the disgusting grot that comes out of cigarettes can be observed by drawing the cigarette smoke through clean glass wool. 2- The results show the wool quickly get stained with horrible black ink. The thermometer shows a rapid increase in temperature as well. 3- One of the great unsolved mysteries of our time is why there are still so many people who take up smoking and destroy their lungs with disgusting black grot. Smoking destroys your lungs with three kinds of grot: 1- Nicotine: This is an addictive drug that makes the heart beat faster, narrows the arteries and so causes high blood pressure. This leads to heart disease. 2- Tar: This coats the lining of the lungs making them less able to take in oxygen. It also contains carcinogens which cause cancer. 3- Carbon monoxide: This is a poisonous gas which joins up with red blood cells, making them incapable of transporting oxygen around the body. Eight reasons not to start smoking: 6
Q1: 1- Complete the sentences: Food gives us the raw for making new cells. We need new cells so that we can and damage. Food also gives us the that we need for growing, and keeping. 2- Complete the table. What we use when we respire What we release when we respire 3- a)use the information in the table to complete the equation. Glucose + carbon dioxide + + ( ) b) Write the symbol equation for the reaction above. 7
c) Name the reactants and the products. What else is produced? Q2: Complete the following. is the body s transport system. It carries nutrients including and oxygen around the body to the cells and tissues. Here they are used for. Q3: Do an internet or library search on how people first found out about the human blood circulation. Try entering these names: Galen, Vesalius, Harvey, Ibn -Al- Nafis. Q4: Label the following parts of the diagram: Kidneys intestines heart cells in the body lungs Then match each of the following descriptions to the correct part. Blood collects digested food here: Blood drops off waste chemicals here: Blood collects oxygen and drops off carbon dioxide here: The heart keeps the blood moving round the body: Blood takes carbon dioxide and waste chemicals away from here: Blood drops off oxygen and food here: 8
Q5: Complete the following table: Arteries Capillaries Veins Carry blood from the heart Connect to Carry blood the heart Carry blood Carry both oxygenated and deoxygenated blood Carry blood Have valves to stop the back flow of blood Have a layer of Walls are very Thin layer of muscle muscle space inside Tiny vessels in close contact to space inside cells Blood flows at Pressure due to the action of the heart Low blood pressure and slow speed to allow exchange of materials Blood flows at pressure Q6: 1- Use the bold words around the diagram to complete the sentences. Small blood vessels called take substances to the cells in your body. Blood carries and to the cells. These substances pass into the. Waste and pass from the cells in to the. 2- The cells in your body need oxygen and glucose. 9
a) Complete the flow diagram. b) Why do the cells in your big toe need oxygen and glucose? Q7: The diagram below shows the blood circulation. Use arrows to show how blood circulates through the blood vessels and heart. (use red arrows to show oxygenated blood and blue arrows to show de-oxygenated blood) Q8: Sometimes your cells don t have enough oxygen to release all the energy that they need. But they can respire for a short time without oxygen. Respiration without oxygen is called anaerobic repiration. It releases less energy from glucose than aerobic respiration. The waste products of aerobic and anaerobic respiration are also different. Anaerobic respiration produces lactic acid, which is poisonous to cells. It is what makes your muscles sore when you do more exercise than usual. It can also give you cramp. 1- What does anaerobic respiration mean? 10
2- This is the word equation for aerobic respiration: glucose + oxygen carbon dioxide + water + energy This is the word equation for anaerobic respiration: glucose lactic acid + carbon dioxide + some energy Write down three differences between these equations. 3- Find out how you get rid of lactic acid. 4- Find out what oxygen debt is. Q 9: At sea level there is twice as much oxygen than at 6000m high on a mountain. People who climb mountains therefore need to take a supply of oxygen. The summit of Mount Everest is about 9000m above sea level. People who live at high altitudes breathe more quickly and more deeply than people who live at sea level. Also, their number of red blood cells is different. Altitude (m) Number of red blood cells per cm 3 of blood Sea level 5000 1000 6000 3000 7500 5000 8000 1- Look at the table. Use the information in the table to plot a bar chart. 11
2- What do the results show us about the relationship between altitude and the number of red blood cells? 3- Why do people who live at high altitudes breathe more quickly and more deeply? 4- The 1968 the Olympic Games were held in Mexico City, which is 2000m above sea level. How do you think this affected athletes from lowland countries? 5- Give a possible explanation why so many African runners are so successful in long distance and marathon races. Q10: Fire officer Allen has to use breathing apparatus to go into burning buildings. His breathing apparatus is connected to an oxygen tank on his back. 1- Complete the flow diagram with the followings: Alveoli blood fine tubes in lungs mouth Our lungs can be damaged by things that we breathe in. Dust, smoke from fires and cigarette smoke can all harm our lungs. 12
How well our lungs can take oxygen into our blood is called our lung function. The graph shows how cigarette smoke affects lung function. 2- How does the lung function of a smoker compare with that of a non- smoker? 3- What is the difference in lung function between a 65-year-old smoker and a 65-year-old who quit smoking at the age of 45? Q11: Look at the diagram to answer the following questions. 1- Complete these sentences: The gas moves from X to Y. The gas moves from V to W. 2- The wall around the alveolus is very thin. Why is it useful for the alveolus to have a very thin wall? Q12: Sometimes, patients in hospitals have to be fed by injecting liquid food directly into the blood vessels known as veins. This is called intravenous feeding. It happens when there is a problem with a person s digestive system. 1- Find out some other examples of when a person might need to be fed in this way. 13
2- Intravenous feeding has to provide a balance of nutrients. a) What do you think intravenous food contains? b) Why does the intravenous fluid contain only soluble foods? c) What parts of the intravenous food provide a patient with energy? 3- Doctors can use the intravenous feeding method to get other things into the patient s body. Write down one example. Q13: List the parts of the blood. Underline the part that carries oxygen, and in another colour the part that carries glucose. Q14: Mrs Daniel, the science teacher, set up three gas jars and timed how long it took for each candle to go out. The diagram shows us what she did. 1- For each gas jar, write down the percentage of oxygen in the air. 2- Predict the order that the candle go out. Explain your prediction. 3- What should Mrs Daniel do to make this experiment a fair test? 14
4- Mrs Daniel did a similar experiment again using inhaled air. This time, she grew a small pot of cress plants in the jar under a lamp for one week, before putting the burning candle in the jar (carefully, so as not to let the gases in the jar escape). The candle burnt for longer. Find out why this happened. Activity: Using a respirometer This is a diagram of apparatus that you can use to measure the rate of respiration. It is used to measure the amount of oxygen removed or carbon dioxide added to the air in the test tube. The maggots take in oxygen and give out carbon dioxide. Any carbon dioxide in the test tube is absorbed by the soda lime. So as oxygen is taken out of the air in the test tube and carbon dioxide is added, the coloured liquid moves towards the maggots. You can use the scale to measure how much the liquid moves. Planning your investigation Your task is to plan an investigation to find out the effect of temperature on the volume of oxygen and carbon dioxide exchanged by the maggots. For your plan, you must do the following: 1- Decide on a heading for your investigation. The heading might start like this: The effect of temperature on the... 2- Make a prediction. We normally make a prediction about what will happen and we say why we think it will happen. Fanoulla; As it gets hotter, the air will expand and the coloured liquid will move away from the test tube. Christopher: As it gets hotter, the maggots become more active and they take up more oxygen. This causes the coloured liquid to move towards the test tube. Maliwan: 15
As it gets hotter, the maggots produce more carbon dioxide. This pushes the coloured liquid away from the test tube. a) Discuss Fanoulla s, Christopher s and Maliwan s ideas with other pupils. b) Write down your prediction. 3- Decide the temperatures that you will use. Ideally you need a range of at least five temperatures (ranging from 0 C to 40 C). 4- Decide how you will measure the temperature. (Whether you will use a temperature sensor or a thermometer). 5- How you will keep each experiment at a constant temperature. You could use: Ice Hot water from a kettle A Bunsen burner to heat water An electronic water bath 6- The number of times that you will repeat each experiment, and why. 7- What things (factors) you will keep the same and how you will make this a fair test. You could consider: The number of maggots The kind of maggots (species, size, age) The glassware The time it is left before taking a reading 8- What safety precautions you will take. When we handle living material, we always wash our hands and wipe the bench with disinfectant. Remember, you will be handling glassware, hot water and living things. 9- What results you will take from the experiment. You will need to produce a table for your results. In this experiment, you will be measuring: Different temperatures The volume of oxygen taken up by maggots, or The volume of carbon dioxide released by the maggots 16
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