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Cell metabolism and Enzymes

Cell metabolism and Enzymes. Metabolism (all of the chemical reactions in a living thing). Anabolic reactions. Catabolic reactions. Small molecules are combined to make larger molecules. Energy is needed. Large molecules are broken down into smaller molecules. Energy is given out.

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Cell metabolism and Enzymes

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  1. Cell metabolism and Enzymes

  2. Metabolism(all of the chemical reactions in a living thing) Anabolic reactions Catabolic reactions Small molecules arecombined to make larger molecules. Energyis needed Large molecules arebroken downinto smaller molecules.Energyis given out.

  3. Sources of energy in cells for anabolic reactions • Solar energy Sunlight is a source of energy capable of being absorbed by cellular pigments e.g. chlorophyll. 2. Cellular energy Catabolic reactions in cells release energy

  4. Enzymes

  5. Enzymes – the key to it all Almost all chemical reactions that take place inside living things are controlled by enzymes. Enzymes are biological catalysts – they change the rate of reactions without getting used up themselves. Every enzyme is a protein and has a specific 3D shape.

  6. Enzyme Action The substance that an enzyme acts on is its substrate The substance(s) that the enzyme forms is called the product(s)

  7. Catabolic enzyme Catalyse is an enzyme that converts hydrogen peroxide into water and oxygen • Catabolic = breaks a big molecule into smaller ones

  8. Anabolic Enzyme DNA Polymerase is an enzyme that builds DNA nucleotides from tiny nucleotide units in our cells Anabolic = makes small molecules into bigger ones

  9. Consider This • Amylase is an enzyme found in saliva. It breaks starch molecules into smaller maltose molecules • What is the substrate? • What is the product? • Will amylase break fats into fatty acids + glycerol? Why? • Is this an example of a catabolic or an anabolic reaction? Why?

  10. And This • DNA Polymerase is an enzyme that builds DNA using tiny molecules in our cells • What is the substrate? • What is the product? • Do you think DNA polymerase could do the reverse reaction? Why?

  11. Learning Check • What is meant by a substrate? • What is the unit formed when an enzyme combines with its substrate called? • Give an example of an anabolic reaction • Give an example of a catabolic reaction

  12. Enzymes and Temperature

  13. Mandatory experiment Investigation 1 • How does temperature effect the rate of reaction of an enzyme?

  14. Step A • 5g of chopped up celery • 1 drop of washing up liquid • 10mls of Buffer solution ALL INTO A GRADUATED CYLINDER

  15. 5ml of Hydorgen peroxide • The graduated cylinder and contents • ALL IN A WATER BATH UNTILL THEY ARE THE SAME TEMPERATURE AS THE WATER BATH Step B

  16. Step C Add the hydrogen peroxide to the graduated cylinder.Time for 1 minute and see the volume of oxygen made

  17. Temperature and enzymes • At very low temperatures molecules are moving slowly and enzymes work slower because of less collisions with substrate • As temperature increases molecules start to move and bump into each other causing the rate of reaction to increase

  18. Rate of reaction 37 Temp (oC) Temperature and enzymes • Above certain temperatures enzymes start to lose their shape the rate of reaction falls. • When the shape is fully lost the enzyme is said to be denatured this is usually a permanent condition • Human enzymes work best at body temperature (37°C) • Plant Enzymes work best at 20-30 °C

  19. Check your learning • Why does temperature have an effect on the rate of reaction? • Why do enzymes not work well at low temperatures? • As temperature increases what happens to enzyme activity? • What is the optimum temp for enzymes in plants and humans? • What happens when an enzyme loses its shape?

  20. Enzymes and pH

  21. Mandatoryexperiment • Investigation 2 - To investigate the effect of pH on the rate of enzyme action

  22. pH • pH scale goes from 0 -14 • Less than 7 is acidic • 7 is neutral • More than 7 is basic (or alkaline)

  23. To investigate the effect of pH on catalase activity

  24. Finely chop the celery. Weigh 5 g of the chopped celery. Step 1

  25. Step 2 Add 10 ml of your pH buffer 4, one drop of washing-up liquid and 5 g of celery into a graduated cylinder.

  26. Step 3 Add 5 ml of hydrogen peroxide to a boiling tube.

  27. Step 4 Place the graduated cylinder and the boiling tube in a water bath at 25 °C – until they reach the required temperature

  28. Step 5 Add the hydrogen peroxide into the graduated cylinder and record the volume immediately.

  29. Step 6 Time for 2 minutes and record the final volume.

  30. Rate of reaction 0 pH 14 Enzymes and pH • pH is important for enzymes as it can make enzymes change their shape! • The best ph (optimum pH) is usually pH 7 • Outside this they lose their shape and get denatured

  31. Check your learning.. • What is an enzyme? Why are they needed for our metabolism? • What does rate of reaction of an enzyme mean? • What does an enzyme act on? • What effect does temperature have on the rate of activity of an enzyme? • What effect does pH have on the rate of activity of an enzyme?

  32. Higher level – The active site theory of enzymes

  33. How enzymes work Enzymes are not flat they have a 3D structure The active site is the specific part of the enzyme which combines with the substrate.

  34. Enzymes – active site theory Because of the special shape of the active site enzymes are very specific about the reactions they catalyse. If the shape of the active site changes then the enzyme cannot work and is denatured.

  35. products enzyme reactant active site 2. Enzyme- substrate complex is formed. The enzyme changes the structure of the substrate 3. Products leave the active site The enzyme changes back to original shape 1. Substrate fits into the active site

  36. What conditions could denature an enzyme?

  37. Mandatory experiment • Investigation 4: the effect of heat denaturation of the activity of an enzyme

  38. Put 5g of chopped celery into two boiling tubes in water baths at 100OC and 20OC for 10 minutes. Remove and cool.

  39. Make up 2 graduated cylinders with.. 10cm3 of pH buffer 9 1 drop of washing up liquid Add boiled celery to A Add unboiled celery to B

  40. Step 3 In a water bath at 20oC add 5 cm3 of hydrogen peroxide to both graduated cylinders Measure the volume of oxygen gas produced in two minutes

  41. Check your learning… • What is meant by the specificity of an enzyme? • How can the Active Site Theory explain the specificity of enzymes? • How can an enzyme be denatured? • Give two features of a denatured enzyme?

  42. Immobilising enzymes

  43. Bioprocessing • Bio-processing is the use of enzyme controlled reactions to produce a product • Traditionally micro-organisms such as bacteria and yeast were used but since the 1950’s enzymes are being used

  44. Immobilising enzymes • Enzymes are often immobilised or fixed (attached to each other or an inert substance) so that they can be used repeatedly in a bioreactor

  45. How to immobilise enzymes • The enzyme can be trapped in beads using sodium alginate and calcium chloride

  46. Mandatory experiment • Investigation 4: To prepare an immobilised enzyme and examine its application

  47. Step 1 Making up the solutions

  48. In one beaker – make up a sodium alginate solution

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