Bacteria & viruses


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Bacteria & viruses

  2. 2. Bacteria belong to the Kingdom: MONERA Plant Animal Fungi Protist or PROKARYOTA Monera
  3. 3. BACTERIA  are among the smallest organisms  about 1/1000 mm  occur in the:  soil  air  water  inside organisms
  4. 4. Bacteria have different shapes Staphilococcus (cluster)
  5. 5. Flagella are used for locomotion
  6. 6. Structure of a bacterium [learn to draw] Slime capsule Cell wall Cell membrane Chromosome /DNA Food store/glycogen granule Cytoplasm Flagella
  7. 7. Two types of cells: Plant Animal Fungi EUKARYOTIC all other cells Protist PROKARYOTIC bacterial cells Monera
  8. 8. Differences between prokaryotic and eukaryotic cells PROKARYOTES EUKARYOTES 1. No proper nucleus is 1. Have a proper nucleus, present, that is their that is their genetic DNA is NOT enclosed in material is enclosed a nuclear membrane within a nuclear but lies free in the membrane cytoplasm
  9. 9. PROKARYOTES 2. Smaller cells EUKARYOTES 2. Larger cells 3. Their organelles are 3. Their organelles are NOT membrane-bound membrane-bound A eukaryotic cell is generally 10x greater.
  10. 10. SPORE FORMATION  bacteria produce a thick protective wall around them in adverse conditions e.g.  heat  drought  presence of poisons  they are now known as SPORES: can survive for many years [anthrax spores, 1,300 years old can cause disease]  the wall breaks when favourable conditions return
  11. 11. ASEXUAL REPRODUCTION  bacteria reproduce by BINARY FISSION
  12. 12. A single bacterial cell inside the human body can reproduce every 20 minutes. Mention three conditions inside the human body that provide bacteria with the ideal environment.
  13. 13. 1.Temperature is warm 2.Food 3.Water 4.pH is ideal
  14. 14. Question: SEP, 2009 Why are bacteria classified as prokaryotic organisms? (2) Lack a proper nucleus i.e. chromosomes are nor enclosed in a nuclear membrane. There are no membrane-bound organelles. Name the type of reproduction that takes place in bacteria. (2) Asexual reproduction by binary fission.
  15. 15. A group of bacteria is called a colony
  16. 16. How can bacteria respire?  AEROBICALLY  use oxygen  e.g. nitrogen fixing bacteria  ANAEROBICALLY  do not use oxygen  e.g. denitrifying bacteria
  17. 17. FEEDING 1) PHOTOSYNTHETIC  build up their food by a chemical like chlorophyll 2) SAPROTROPHIC  decay dead material 3) PARASITIC  get food from living organisms, causing them harm
  18. 18. Bacteria and other organisms which cause disease are called: PATHOGENIC
  19. 19. 1) Decay bacteria (in soil)  saprophytic bacteria break down dead organisms to return essential nutrients to the soil
  20. 20. 2) Decay bacteria (in sewage)  bacteria decompose sewage before it is thrown into the sea
  21. 21. 3) Genetic engineering  bacteria can be used to produce useful chemicals such as insulin
  22. 22. Question: MAY, 2009 Give the biological explanation of each of the following statements. Most bacteria are saprophytes but some are mutualistic bacteria. (3) Saprophytes feed on dead and decaying material and live freely. Some live in a close association with another organism where both benefit. E.g. bacteria in rumen of cow.
  23. 23. Most bacteria feed on dead and decaying matter and so are saprophytes. Help in recycling nutrients. Mutualistic bacteria:  Some bacteria form a relationship within intestines of mammals where both help each other. Digest cellulose in herbivores. Produce vitamins B and K in humans.  Nitrogen-fixing bacteria in root nodules of leguminous plants get food and shelter from plant and give the plant ammonium compounds.
  24. 24. 4) Vinegar production  bacteria are used to convert: ethanol to ethanoic acid Acetobacter aceti
  25. 25. 5) Making silage silage is:  undecayed grass  used for feeding livestock in winter
  26. 26. the newly cut grass:  is allowed to wilt (to remove water and so concentrate the sugar in grass)  but is not dried before conversion to silage newly cut grass
  27. 27.  the grass:  is prevented from decaying by lactic acid produced by anaerobic bacteria  is covered by plastic sheeting to exclude oxygen and rain A silo in which silage is made and then stored.
  28. 28. 6) Biogas formation Biogas is produced when anaerobic bacteria breakdown: Biogas is a mixture of:  methane  carbon dioxide  sewage  manure  plant material Anaerobic bacteria Effluent
  29. 29. A biogas plant is built underground:  to keep a constantly cool temperature – overheats if above ground A biogas plant as used by a family in China.
  30. 30. What can biogas be used for? When biogas is burnt, it can be used for:  heating the home  cooking  to generate electricity
  31. 31. Question: SEP, 2003 A major concern for most people these days is the use and availability of energy. Fossil fuels are nonrenewable forms of energy. One excellent source of energy is Biogas. This is a mixture of methane (CH4) and carbon dioxide (CO2). This can be produced in a laboratory using the simple set-up shown below.
  32. 32. a) Name: i) One suitable material which can be placed in the flask to generate Biogas; Plant material/animal manure ii) The organisms that must be present in the flask together with this material to produce Biogas; Bacteria iii) The process occurring within the flask Anaerobic respiration
  33. 33. 7) Cheese, butter & yoghurt making all require: lactic acid bacteria Bacteria convert LACTOSE [sugar in milk] LACTIC ACID
  34. 34. Lactic acid is:  made by the process called lactic acid fermentation : lactose  lactic acid
  35. 35. The manufacture of cheese, butter & yoghurt depend on the curdling (coagulation) of milk.  lactic acid is needed to make the milk curdle
  36. 36. 4 Cheese making 1 Milk pasteurised at 73C for 15 sec to kill most microbes 2 Curds cut into blocks and piled up Huge vat Special strain of cheese-making bacteria added to convert sugar in milk to lactic acid 5 Blocks chopped and mixed with salt to slow down bacterial growth 6 Cheese packed into 3 Enzyme (rennin) added to moulds and left to ripen separate into curds & whey 6 Flavour gradually develops and bacterial action makes cheese more digestible
  37. 37. Rennet for cheese making can be made by: animals Huge vat bacteria
  38. 38. Whey poured off Curds cut into blocks Ripening
  39. 39. Moulds in press [seen better in this picture]
  40. 40. Yoghurt production
  41. 41. Yoghurt production Lactic acid is produced during fermentation by special strains of bacteria added to the milk Spherical Streptococcus Rod-shaped Lactobacillus
  42. 42. The following list gives five of the steps involved in the commercial production of a well known brand of yoghurt. A)Milk heated to 73C for at least 30 seconds to make it virtually sterile. B)‘Sterilised’ milk is cooled to 44C. C) Special ‘yoghurt’ bacteria added to ‘sterilised’ milk. D)Milk kept at 44C for four hours to allow bacteria to convert it to yoghurt by making lactic acid. E) Yoghurt stored in cartons at 4C to slow down further bacterial action.
  43. 43. Question: MAY, 2012 Humans use different micro-organisms including bacteria to produce useful substances and food stuffs. Bacteria are added to pasteurised milk to produce yoghurt. Explain why milk is pasteurised before producing yoghurt. (2) To kill living microbes so that yoghurt can have a longer shelf-life.
  44. 44. Butter making Fermentation Churning
  45. 45. Butter-making machine
  46. 46. Bacteria are added to cream This culture has 4 bacteria — 2 which seem to primarily drive the acidification and 2 which drive the flavour.
  47. 47. The cream is beaten/churned Churning the milk Butter can be made at home. What forms after 5 minutes beating the cream?
  48. 48. Soft butter and a liquid called buttermilk form.
  49. 49. The buttermilk is strained out. The butter is squeezed to remove the remaining liquid.
  50. 50. Question: SEP, 2008 Milk is used in the production of butter and cheese. Below is a simplified flow diagram which describes the production of butter: Fermentation Churning
  51. 51. i) Why is bacteria added to the cream? (2) Bacteria produce lactic acid which makes milk curdle. Also to add flavour. ii) Write a word equation to show the fermentation process in which cream is converted to sour cream. (3) Lactose Lactic acid
  52. 52. Question: [MAY, 2010] Give a biological explanation for each of the following statements: In cheese making when the enzyme rennin is added to milk, the temperature of the curding (clotting) milk is kept in the region of 40C. (3) Enzymes must be kept at their optimum temperature to work fast. Increasing the temperature above the optimum denatures the enzyme and the reaction slows down or even stops.
  53. 53. Question: [SEP, 2009] A group of biology students investigated a type of yoghurt. Some yoghurt samples were taken. The pH of yoghurt samples was tested. Would you expect the pH to be acidic, neutral or alkaline? Give a reason for your answer. (3) Acidic. Bacteria change the sugar in milk called lactose into lactic acid.
  54. 54. Question: [MAY, 2010] Give a biological explanation for the following statement: Bacteria are involved in making yoghurt. (5) Certain types of bacteria are needed to make yoghurt. Bacteria change lactose into lactic acid by fermentation. The lactic acid makes the milk curdle. Flavour , colouring & fruit may be added.
  55. 55. 1) Cause diseases in animals and plants, e.g. Tuberculosis in man, cause tooth decay 2) Spoil food 3) Denitrifying bacteria reduce the nitrate content in the soil
  56. 56. Question: MAY, 2004 a) i) Name one organism that has a mutually beneficial symbiotic relationship with a bacterium. ii) Explain what each organism benefits from the symbiotic relationship. (1, 2) e) Describe one saprophytic activity of bacteria that is: i) useful to humans; ii) harmful to humans. (2)
  57. 57. Question: MAY, 2007 Explain how bacteria inside the body may have both beneficial and harmful effects. (4) Beneficial effects:  digest cellulose in herbivores as they produce cellulase  produce vitamins B and K in intestines of humans Harmful effects:  cause disease
  58. 58. RESISTANCE TO DISEASE 1) The skin forms a barrier to bacteria. 2) Chemicals e.g.  hydrochloric acid in the stomach  lysozyme in tear fluid destroy bacteria
  59. 59. 3) Body fluids such as saliva, contain antibodies. 4) White blood cells can: i) engulf bacteria ii) produce antibodies to kill bacteria
  60. 60. FOOD PRESERVATION [this section acts as background knowledge about bacteria]. 1) COLD TREATMENT  freezing does not kill microbes, but stops them multiplying and slows their action
  61. 61. 2) DRYING  microbes need moisture and if the food is dried, they become dormant  dried food lasts indefinitely  food is dried by blowing air over it Grapes soon go bad BUT raisons can be stored for a long time.
  62. 62. 3) HEAT TREATMENT  heat:  kills many of the microbes  can STERILISE food
  63. 63. Question: MAY, 2012 Explain the following statement: In food preparation, a clean sterile surface is necessary. (2) To avoid contamination of food with harmful microbes.
  64. 64. Method used to find out which is the most effective antibiotic to kill microbes
  65. 65. Viruses consist of:  a strand of DNA or RNA surrounded by a protein coat (capsid) Protein coat (made of capsomeres) Genetic material (DNA or RNA) Viruses are NOT cells as they lack the usual cell components
  66. 66. Different shapes of viruses AIDS virus Tobacco mosaic virus which causes tobacco mosaic disease in tomato plants.
  67. 67. Different shapes of viruses Virus that attacks bacteria. Influenza virus Bacterium attacked by viruses.
  68. 68. Viruses:  are smaller than bacteria (measured in nm, 1nm = 1/1000 000 mm)  reproduce only when inside living organisms virus bacterium
  69. 69. Viruses are borderline between living & non-living things Living Carry out all 7 vital functions Made of cells Non-living Can be crystallised Viruses: REPRODUCE and CAN BE CRYSTALLISED
  70. 70. Question: MAY, 2007 Explain why viruses are always considered parasitic. (2) Always cause harm to the cell in which they have reproduced. Cell bursts and dies.
  71. 71. Question: SEP, 2008 a) The diagram below shows the generalized structure of a virus. Label the parts A and B. (2)
  72. 72. Question: SEP, 2008 a) The diagram below shows the generalized structure of a virus. Label the parts A and B. (2) Protein coat / capsid DNA or RNA / genetic material
  73. 73. Question: SEP, 2008 b)Viruses are not usually considered to be living organisms. Why? (2) Are not composed of cells. Do not carry out all of the seven vital functions.
  74. 74. Question: SEP, 2008 The diagram below shows the reproductive stages of a virus in an incorrect order. Fill in the table to indicate the correct order in which these events take place. (3) Step Letter 1 2 3 4 5 6
  75. 75. Step 1 2 3 4 5 6 Letter B F D E A C
  76. 76. Question: June, 1998 Explain clearly, how viruses differ from bacteria in their structure and in their mode of life. (Present your answer in the form of a table.) (8)
  77. 77. Viruses 1. No cell membrane 2. No organelles 3. Never present 4. Never present 5. No food stores 6. Do not respire 7. Do not excrete 8. Do not grow Bacteria 1. Cell membrane present 2. Organelles present 3. May have flagella 4. May have a slime capsule 5. Store food granules 6. Respire 7. Excrete 8. Grow
  78. 78. THE END