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Investigating cells

Investigating cells. Aerobic Respiration. Mr G Davidson. Energy. Energy cannot be created. Energy cannot be destroyed. Energy exists in a number of different forms, e.g. heat, light, sound, electrical, etc…. Chemical Energy. This is stored energy.

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Investigating cells

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  1. Investigating cells Aerobic Respiration Mr G Davidson

  2. Energy • Energy cannot be created. • Energy cannot be destroyed. • Energy exists in a number of different forms, e.g. heat, light, sound, electrical, etc… G Davidson

  3. 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.. G Davidson

  4. 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. G Davidson

  5. 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. G Davidson

  6. 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. G Davidson

  7. 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. G Davidson

  8. Energy from Foods • All cells need a supply of food. • Food contains chemical energy. • The foods eaten by animals contain carbohydrates, proteins and fats. G Davidson

  9. 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) G Davidson

  10. Energy from Foods If the numbers of the percentages don’t total 100, then the food also contains water. G Davidson

  11. Thermometer Known volume of water Known mass of food Energy from Foods • The energy content of food is measured using a food calorimeter. The food is set alight and the rise in temperature of the water is calculated. G Davidson

  12. Food Calorimeter G Davidson

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

  14. GLUCOSE + OXYGEN ENERGY + CO2 + WATER 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 CO2 released. • They are equal. G Davidson

  15. G Davidson

  16. 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. G Davidson

  17. Carbon dioxide Release • Bicarbonate indicator solution changes colour from red to yellow when carbon dioxide is present. • In order to prove that any CO2 detected around a respiring organism, has come from that organism, we have firstly to remove the CO2 from the organism’s air supply. G Davidson

  18. Burning Sugar If glucose is burned it releases carbon dioxide. It also releases water. Glucose Bicarbonate indicator G Davidson

  19. Burning Sugar The carbon dioxide causes the bicarbonate indicator to turn yellow. Glucose Bicarbonate indicator G Davidson

  20. 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. G Davidson

  21. 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. G Davidson

  22. 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. G Davidson

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