Investigating cells Aerobic Respiration Mr G Davidson

19 May, 2015G Davidson2 Energy Energy cannot be created. Energy cannot be destroyed. Energy exists in a number of different forms, e.g. heat, light, sound, electrical, etc…

19 May, 2015G Davidson3 Chemical Energy This is stored energy. When one chemical substance is changed into another during a chemical reaction, this stored energy is often released. It may be released as heat, light, sound, etc..

19 May, 2015G Davidson4 Chemical Energy The sun is the primary source of energy for this planet. It is possible to trace the path of this energy from the sun to the cells in organisms.

19 May, 2015G Davidson5 Chemical Energy Not all the energy released by the sun arrives in the cells. Each time an energy conversion takes place some energy is “lost”. This lost energy is not destroyed – it simply passes out of the pathway in another form and is therefore, wasted energy.

19 May, 2015G Davidson6 Energy Changes in Organisms Energy is always associated with changes. Energy is continually being converted from one form to another. Animal and plant tissues contain chemical energy in the form of carbohydrates and fats.

19 May, 2015G Davidson7 Energy Changes in Organisms This energy can be converted into a variety of forms. Organisms consist of vast numbers of different kinds of cells. All cells need energy. Each cell or group of cells has a particular function to carry out. Individual cells are capable of carrying out several different energy conversions.

19 May, 2015G Davidson8 Energy from Foods All cells need a supply of food. Food contains chemical energy. The foods eaten by animals contain carbohydrates, proteins and fats.

19 May, 2015G Davidson9 Energy from Foods Foods can be analysed to find out the proportions of carbohydrate, protein and fat. These proportions are often given as percentages. It is also possible to find out how much energy a particular food contains. This is measured in kilojoules per gram. (kJg -1 )

19 May, 2015G Davidson10 Energy from Foods Food % Carbohydrate % Fat% Protein Energy Content (kJ/g) Olive oil Gelatin (dried) Almonds Sugar Sausages Pastry If the numbers of the percentages don’t total 100, then the food also contains water.

19 May, 2015G Davidson11 food calorimeter The energy content of food is measured using a food calorimeter. Energy from Foods Thermometer Known volume of water Known mass of food The food is set alight and the rise in temperature of the water is calculated.

19 May, 2015G Davidson12 Food Calorimeter

19 May, 2015G Davidson13 Respiration Carbohydrate in the form of glucose is transported to each cell in an organism. CELLULAR RESPIRATION. The process by which cells release the energy stored in glucose molecules is called CELLULAR RESPIRATION. There are 2 types: Aerobic respiration Aerobic respiration – this occurs when there is a plentiful supply of oxygen to the cell. Anaerobic respiration Anaerobic respiration – this occurs when there is no oxygen available to the cell.

19 May, 2015G Davidson14 Oxygen Uptake It is possible to measure changes in oxygen content using a RESPIROMETER. Each type of respirometer contains a chemical to absorb and therefore remove carbon dioxide given out by the organism. The respirometer measures both the volume of oxygen taken up by a respiring organism, and the volume of CO 2 released. They are equal. GLUCOSE + OXYGEN ENERGY + CO 2 + WATER

19 May, 2015G Davidson15

19 May, 2015G Davidson16 Carbon dioxide Release Before a gas can be identified, it must be collected or located. Once this is done an identification test can be carried out.

19 May, 2015G Davidson17 Carbon dioxide Release Bicarbonate indicator solution changes colour from red to yellow when carbon dioxide is present. In order to prove that any CO 2 detected around a respiring organism, has come from that organism, we have firstly to remove the CO 2 from the organism’s air supply.

19 May, 2015G Davidson18 Burning Sugar If glucose is burned it releases carbon dioxide. It also releases water. Glucose Bicarbonate indicator

19 May, 2015G Davidson19 Burning Sugar The carbon dioxide causes the bicarbonate indicator to turn yellow. Glucose Bicarbonate indicator

19 May, 2015G Davidson20 Burning Sugar Yeast is a fungus which can respire aerobically or anaerobically. If it has a goes supply of glucose and oxygen then CO2 is also released. This would seem to indicate that respiration and burning are quite similar in that the waste products are the same.

19 May, 2015G Davidson21 Energy Release Warm blooded animals maintain their body temperature above that of their surroundings. This means the animal is losing its heat to its surroundings. This heat energy must be coming from energy locked up in food. The heat energy is released as part of respiration. Plants also give off heat because they are respiring also.

19 May, 2015G Davidson22 Why Cells Need Energy Energy in cells is continually being converted from chemical energy to other forms according to the needs of the cell. All living cells respire. When a cell or entire organism ceases to respire it dies. Metabolism is a word used to describe what happens inside cells or whole organisms.