IGCSE Biology Edexcel - Section 4 Respiration

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Respiration	Respiration is the process of releasing energy from glucose which happens constantly in every living cell.
Respiration Key Points	1. Respiration occurs in every cell in your body. 2. It's the process of releasing energy from glucose. 3. Energy is released as chemical energy and heat. - Chemical energy is used to do things such as create large molecules from smaller ones (proteins from amino acids) and heat energy helps to maintain a constant body temperature. 4. There are two types of respiration - aerobic and anaerobic.
Aerobic Respiration	Plentiful supply of oxygen available. Aerobic means 'with oxygen' and is the most EFFICIENT way to release energy from glucose.
Equation for Aerobic Respiration	Glucose + Oxygen --> Carbon Dioxide + Water (Reverse of photosynthesis equation)
Anaerobic Respiration	Takes place without oxygen and doesn't use oxygen. For example when you do vigorous EXERCISE your body cannot supply enough oxygen to your muscles for aerobic respiration even though your heart rate and breathing rate increase as much as they can. Your muscles have to start respiring anaerobically. Anaerobic means without oxygen. NOT the best way to convert glucose into energy because it releases much LESS ENERGY. In anaerobic respiration the glucose is only partially broken down and lactic acid is also produced. The lactic acid builds up in the muscles and it gets painful and leads to cramp.
Anaerobic Respiration Equation 1	Glucose --> Lactic acid (+Energy)
Anaerobic Respiration In Plants	Plants can respire without oxygen but they produce ethanol (alcohol) and CO2 instead of Lactic acid. Fungi such as YEAST also do anaerobic respiration like this e.g. yeast in the production of beer.
Anaerobic Respiration Equation 2	Glucose --> Ethanol + Carbon Dioxide
Investigating Respiration	Carbon Dioxide production can be detected using an indicator. Hydrogen-Carbonate solution to show that living organisms produce C02 as they respire. Normally Solution = ORANGE Turns YELLOW in presence of CO2
Experiment 1: Germinating Beans demonstrating CO2 Production	-First soak some dried beans in water for a day or two. They will start to GERMINATE. Germinating beans will Respire. -Boil a similar sized second bunch of dried beans. Kills the beans ensuring they cannot respire and these dead beans will act as your control. -Place some hydrogen-carbonate indicator into two test tubes. -Place a platform made of gauze into each test tube and place the beans on this. -Seal the test tube with a rubber bung. -Leave the apparatus for a set period of time e.g. 1 hour -During that time CO2 produced by germinating beans should have effected the hydrogen-carbonate indicator - it will have turned yellow. -Repeat experiment to increase reliability. (Can also use woodlice or maggots however the control would be glass beads.)
Experiment: Investigating Heat	-Prepare two sets of beans. Water one set and allow them to germinate. Boil the other set to kill the beans and act as your control. -Add each set of beans to a VACUUM FlASK making sure there is some AIR in the flasks so the beans can respire aerobically. -Place a thermometer into each flask and seal with cotton wool. -Record the temperature for each flask daily for a week. -The beans are well insulated in the flasks so when the beans respire and produce heat, the test flasks temperature will increase compared to the control flask.
Gas Exchange - Flowering Plants	Plants exchange gases by DIFFUSION. When plants carry out photosynthesis they USE UP CO2 from the atmosphere and PRODUCE 02 as a waste product. When plants Respire they use up O2 and produce CO2 as a waste product. (Same as humans.) 1. Photosynthesis - uses lots of CO2 so hardly any inside the leaf. Makes more CO2 move into the leaf by diffusion (from an area of high concentration to an area of low concentration.) 2. At the same time lots of O2 is being made as a waste product. Some is used in respiration and the rest diffuses out through the stomata. (Area of higher concentration to an area of lower concentration.)
Light Intensity	The net exchange of gases depends on light intensity. Photosynthesis only happens during the day (when there is light available.) Plants must respire all the time to get the energy they need to live. During the day when Light intensity is high. Plants make more oxygen by photosynthesis than they use in respiration. So in daylight release oxygen. Use up more CO2 then they produce so take in CO2. At night (low light intensity) - plants only respire as not enough light for photosynthesis. So take in oxygen and release CO2 (like us.)
Adaptation of the leaf for efficient gas exchange...	- Broad: Large surface area for diffusion - Thin: Gases only have to travel a short distance to reach the cells where they are needed. Short diffusion distance. - Air spaces: Allows gases such as CO2 and O2 to move easily between cells. Also increases the surface area for gas exchange. - Lower surface full of little wholes called Stomata. They allow gases to diffuse directly into and out of the leaf. Also allow water to escape known as TRANSPIRATION. - Stomata close as it gets too dark. Photosynthesis cannot happen in the dark so don't need to be open to let CO2 in. Stomata are closed water cannot escape so stops the plant from drying out. - Stomata also close when supplies of water from the roots start to dry up. Stops photosynthesis from occurring but if they didn't close plant may dry out and die which is worse. - Opening and closing of Stomata is controlled by the cells that surround them (called guard cells.)
Gas Exchange - Flowering Plants Experiments...	Hydrogen-carbonate indicator shows CO2 concentration. Normal = Orange Increase = Yellow Decrease = Purple Experiment to show how light intensity affects gas exchange. - Add the same volume of hydrogen-carbonate indicator to four boiling tubes. -Place a smilar sized leaf in each (same species and size) and seal with rubber bung. Trap leaf stem with rubber bung to stop it falling down into the solution if you need to. Keep the fourth tube empty as a control. -Completely wrap one tube in aluminium foil, a second tube in gauze. Place all tubes in bight light of the same intensity. -Leave tubes for an hour and then check the colour of the indicator.
Results of each tube...	Tube 1: Control so no change. Tube 2: Aluminium foil, no light could access the leaf thus photosynthesis couldn't occur so respires taking in oxygen and giving out carbon dioxide leading to an increase in CO2 concentration so YELLOW. Tube 3: Gauze some light some darkness both fairly constant so no change. Tube 4: Light directly hitting leaf. Photosynthesis taking in CO2 giving out O2 so decrease in CO2 concentration so PURPLE.
The Respiratory System and Ventilation....	Thorax is the top part of the body. Separated from lower part of the body by the diaphragm. Lungs protected by rib cage which are surrounded by pleural membranes. Air you breathe goes through the trachea. Splits into two tubes called the bronchi. Each one is a bronchus. Bronchi split into smaller tubes called bronchioles which end at small bags of air/air sacs called alveoli where gas exchange takes place.
Breathing In...	1) Intercostal muscles and diaphragm CONTRACT. 2) Thorax volume INCREASES. 3) DECREASES the pressure thus drawing air in.
Breathing Out...	Intercostal Muscles and Diaphragm relax. Thorax Volume Decreases. Pressure Increase thus forcing air out.
Investigating the Effect of Exercise on Breathing Rate...	- Record heart rate at rest by counting the number of breaths you take for one minute. Do this 3 times and find the average. - Choose a range of exercises to complete e.g. jogging and skipping. - Set a time for how long you complete each exercise e.g. 2 minutes running. - Immediately after exercise record heart rate by COUNTING THE NUMBER OF BREATHS PER MINUTE. - Get a couple other people to do the same to obtain a range of results to compare. - Repeat the experiment to ensure accurate results and reliability. - Results should show that exercise increases breathing rate. This is because your muscles respire more during exercise and need to be supplied with more O2 and have more CO2 removed so your breathing rate increases. - Ensure you control all variables. -Time spent exercising using a stopwatch. Temperature of room using air conditioning or thermostat.
Gas Exchange - Humans	Alveoli carry out gas exchange in the body. The lungs contain millions of alveoli where gas exchange happens. Blood passing next to the alveoli has just returned to the lungs from the rest of the body so lots of CO2 and very little oxygen. Oxygen diffuses out of the alveolus (high C.) and into the blood. (low C.) Carbon dioxide diffuses out of the blood (high C.) and into the alveolus (low C.) to be breathed out. When the blood reaches body cells O2 is released from the red blood cells and diffuses into body cells. At the same time CO2 diffuses out of the body cells into the blood and is carried back to the lungs.
Alveoli are specialised for gas exchange...	- huge number of microscopic alveoli gives the lungs an enormous surface area. - moist lining for gases to dissolve in. - Alveoli have thin walls only one cell thick so the gases don't have to diffuse that far. - Great blood supply to maintain a high concentration gradient. - Walls are permeable so gases can diffuse across easily.
Smoking Tobacco - problems	- Smoking damages walls inside the alveoli, reducing surface area and leading to diseases such as emphysema. - Tar in cigarettes damages the cilia in your lungs and trachea. These hairs along with mucus catch a load of dust and bacteria before they reach the lungs. Cilia also help to keep the trachea clear by sweeping mucus back towards the mouth. Chest infections more likely. - Tar also irritates the brooch and bronchioles encouraging mucus to be produced which can't be cleared due to damaged cilia causing smokers cough and bronchitis. - Carbon monoxide in cigarette smoke reduces amount of oxygen the blood can carry. Heart rate increases which leads to an increase in blood pressure. High blood pressure damages artery walls making the formation of blood clots more likely. Increases risk of coronary heart disease e.g. heart attacks. Tobacco also contains carcinogens - chemicals that lead to cancer.

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IGCSE Biology Edexcel - Section 4 Respiration

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