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Quick Quiz Recap

Quick Quiz Recap. What is the definition of osmosis? What is the difference between osmosis and diffusion? How is a red blood cell adapted for its job? Where does protein synthesis occur? Where does respiration occur? What is respiration? What is the job of the cell wall?

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Quick Quiz Recap

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  1. Quick Quiz Recap • What is the definition of osmosis? • What is the difference between osmosis and diffusion? • How is a red blood cell adapted for its job? • Where does protein synthesis occur? • Where does respiration occur? • What is respiration? • What is the job of the cell wall? • Name 3 organelles you find in a plant cell but not an animal cell

  2. Enzymes

  3. Respiration • Summarise respiration • What is it? • Where does it occur? • Why is it needed?

  4. Enzymes • What are they?

  5. Amylase and Starch • How do you test for STARCH? • How do you test for GLUCOSE?

  6. Amylase and Starch • EQUIPMENT- for 30 students • Boiling tubes • Thermometers • Iodine • Benedict’s Solution • Starch solution • Amylase

  7. Amylase and Starch • Set up 2 water baths. One will be for the Benedict’s test, the other should be maintained at roughly 350. • Add some amylase to starch. Wait 5 minutes. • Split the solution between 2 test tubes. Test one for starch and test one for glucose. Write your results for room temperature. • Next, place a volume of amylase in a test tube and put it in a water bath at 350. Do the same for a small volume of starch. • After 10 minutes of being in the water bath, mix the two solutions together. Place back in the 350 water for 10 minutes. • After 10 minutes test the solution for starch and for glucose like you did before. • Write up the experiment

  8. Amylase and Starch • Results and conclusion –What should have happened and why? • Evaluation

  9. Enzymes

  10. What is an enzyme? What type of molecules are enzymes? How do enzymes work?

  11. Enzymes as Catalysts A catalyst causes reactions to occur more easily and more quickly by reducing the activation energy needed to start the reaction. They also allow reactions to occur at lower temperatures.

  12. High energy intermediate Activation energy Energy Substrates Products Progress of reaction

  13. Active site Enzyme molecule Substrate molecules (complementary shape to active site) Reaction occurs Enzyme remains unchanged The Active Site - The Lock and Key Model Substrate and enzyme molecules react together...Substrate molecules bind with enzyme molecules at the activesite because of their complementary shapes. Product molecules diffuse away from the active site The enzyme converts the substrate into products. This is the ‘lock and key model’ of enzyme activity.

  14. Substrate molecule in the active site Enzymemolecule Amylase, although a relatively simpleenzyme is still a complex molecule Active Sites Enzymes have a special site on their surface called an active site into which the reacting substrate molecules fit. Enzymes are highly specific and each enzyme has a different shaped active site. An amylase enzyme will accept starch molecules but not the molecules of other carbohydrates, proteins or lipids.

  15. Conditions effecting enzyme activity

  16. What effects an enzyme? Name 2 things that will effect how well an enzyme works? Think about human digestion and thermoregulation

  17. Conditions effecting enzyme activity practical • EQUIPMENT • Hydrogen Peroxide • Potatoes • Knives • Potato borers • Boiling tube and bungs • Ice • Thermometers

  18. The Effect of Temperature on the volume of oxygen produced by the enzyme catalase when reacted with Hydrogen Peroxide • Variables • Dependent= • Independent= • Control= • Results Table

  19. METHOD • Measure out a 4cm strip of potato. Place in a boiling tube. • Measure out 30 cm3 of Hydrogen Peroxide using a measuring cylinder and then transfer to a boiling tube • Place the boiling tubes in the water bath/ice, depending on the temperature you are measuring. • Leave them in the water bath/ ice until the Hydrogen Peroxide has reached the correct temperature • When your hydrogen peroxide solution has reached the temperature you are investigating, transfer it to the boiling tube with the potato in and place the bung on as quickly as possible. • Record the volume of oxygen produced in 5 minutes • Repeat the experiment for different temperatures

  20. Results and Conclusions • Draw a graph of the results • Describe and explain for 5 marks the graph • Include the term kinetic energy • Include collisions • Include denature • Include active site

  21. The Effect of Temperature on Enzyme Activity At low temperatures the reacting molecules do not have much kinetic energy, so the collisions are fewer and the rate of reaction is slow. As the temperature rises, the reacting molecules gain kinetic energy, so the number of substrate/enzyme collisions increases, and consequently the rate of reaction is much higher.

  22. Special bonds stabilise an enzyme’s 3D shape Special Bonds If the special bonds are broken the 3D shape is lost The Effect of Temperature on Enzyme Activity Eventually a temperature is reached where the rate of reaction is greatest - this is called the optimum temperature. However, as the temperature is increased beyond the optimum temperature, special bonds that stabilise the enzyme’s three dimensional structure are broken, and the physical shape of the enzyme’s active site starts to change.

  23. Substrate moleculeno longer fits in the active site Enzymemolecule The Effect of Temperature on Enzyme Activity Substrate molecules no longer fit properly, and at a critical temperature, the substrate will not fit into the active site at all - at this point the enzyme is said to have been denatured. Denatured enzymes will not be able to catalyse a reaction and hence the products are not formed. Denaturing is permanent and reducing the temperature will not undo the damage to the active sites.

  24. For many enzymes, the maximum rate of reaction is reached at atemperature between 37°C to 40°C.This is the optimum temperature. The enzyme has been denatured. Rapid increasein reaction rate. Temperature and Enzyme Activity As the temperature increases, molecules move more quickly and collide more often - the reaction rate increases. The reaction rate doubles for every 10°C rise in temperature.

  25. The Effect of pH on Enzyme Activity Each enzyme has an optimum pH (fastest reaction rate) and pH can alter the shape of the active site. The shape change may be temporary or permanent, in which case the enzyme is denatured.

  26. Summary • What is the job of an enzyme? • Explain 2 conditions that effect enzyme activity • Name 3 places where enzymes are required in the human body.

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