2. N 2 Nitrogen fixing bacteria in soil and nodules of plants Nitrates are made into proteins in plants NO 3 - Animals get their protein by eating Death and decay Bacteria break down the protein into nitrates NO 3 - Which can be taken back up by plants and made into proteins Denitrifying bacteria use nitrates and release nitrogen into the air Lightning and the addition of fertlisers also adds nitrates to soil

3. 80 % of the atmosphere is made up of nitrogen gas N 2

4. nitrogen gas is very unreactive and very few organisms can extract it from the air

5. Nitrogen is essential for all organisms as it is needed to make proteins

6. Some terms you need to know first: N 2 Nitrogen NH 4 + Ammonium NH 3 Ammonia NO 2 -Nitrite NO 3 -Nitrate NO 2 Nitrogen oxide

8. Plants can easily make carbohydrates like sugars and starches

9. +

10. NO 3 - + nitrate ions need to be added to carbohydrates to make amino-acids

11. NO 3 - + nitrate ions need to be added to carbohydrates to make amino-acids Amino acid

12. Amino acid

13. Amino acid Amino acid

14. Amino acid Amino acid Amino acid

15. Amino acid Amino acid Amino acid Amino acid

16. Amino acid Amino acid Amino acid Amino acid Amino acid

17. Amino acid Amino acid Amino acid Amino acid Amino acid The amino-acids are joined together in chains to make polypeptides

18. But where does the nitrate come from?

20. Certain bacteria are able to take atmospheric nitrogen and “fix” it into nitrate ions

21. N2N2

22. N2N2

23. N2N2

24. N2N2 NO 3 -

25. N2N2 These nitrogen fixing bacteria are either free living in the soil... NO 3 -

26. These nitrogen fixing bacteria are either free living in the soil... Or live in special nodules in the roots of plants

28. These nitrogen fixing bacteria are either free living in the soil... Or live in special nodules in the roots of plants

29. These nitrogen fixing bacteria are either free living in the soil... Or live in special nodules in the roots of plants

30. These nitrogen fixing bacteria are either free living in the soil... Or live in special nodules in the roots of plants

31. These nitrogen fixing bacteria are either free living in the soil... Or live in special nodules in the roots of plants

32. NO 3 -

33. The nitrate in the soil or in the root nodules can then be used by the plant to make proteins

34. Bacteria also help to recycle the nitrogen that has been made into protein

36. After death...

38. And of course the production of waste compounds containing nitrogen

40. Bacteria break down these proteins and waste products to release ammonia NH 3

42. protein

43. Bacteria break down these proteins and waste products to release ammonia NH 3 protein

44. Bacteria break down these proteins and waste products to release ammonia NH 3 protein

45. Bacteria break down these proteins and waste products to release ammonia NH 3 protein NH 3

46. The ammonia is further broken down by Nitrifying bacteria to release nitrates NH 3

47. The ammonia is further broken down by Nitrifying bacteria to release nitrates NH 3 NO 3 -

48. Unfortunately some of the nitrates in the soil end up back as nitrogen in the atmosophere...

49. Nitrates

51. N 2 Nitrates Denitrifying bacteria use nitrates and release nitrogen into the air

52. Putting it all together into a cycle...

53. N 2

56. Nitrogen fixing bacteria in soil and nodules of plants Nitrates

57. N 2 Nitrogen fixing bacteria in soil and nodules of plants Nitrates

58. N 2 Nitrogen fixing bacteria in soil and nodules of plants NO 3 -

59. N 2 Nitrogen fixing bacteria in soil and nodules of plants Nitrates are made into proteins in plants NO 3 -

60. N 2 Nitrogen fixing bacteria in soil and nodules of plants Nitrates are made into proteins in plants NO 3 -

61. N 2 Nitrogen fixing bacteria in soil and nodules of plants Nitrates are made into proteins in plants NO 3 -

62. N 2 Nitrogen fixing bacteria in soil and nodules of plants Nitrates are made into proteins in plants NO 3 - Animals get their protein by eating

63. N 2 Nitrogen fixing bacteria in soil and nodules of plants Nitrates are made into proteins in plants NO 3 - Animals get their protein by eating

64. N 2 Nitrogen fixing bacteria in soil and nodules of plants Nitrates are made into proteins in plants NO 3 - Animals get their protein by eating Death and decay

65. N 2 Nitrogen fixing bacteria in soil and nodules of plants Nitrates are made into proteins in plants NO 3 - Animals get their protein by eating Death and decay

66. N 2 Nitrogen fixing bacteria in soil and nodules of plants Nitrates are made into proteins in plants NO 3 - Animals get their protein by eating Death and decay

67. N 2 Nitrogen fixing bacteria in soil and nodules of plants Nitrates are made into proteins in plants NO 3 - Animals get their protein by eating Death and decay Bacteria break down the protein into nitrates NO 3 -

68. N 2 Nitrogen fixing bacteria in soil and nodules of plants Nitrates are made into proteins in plants NO 3 - Animals get their protein by eating Death and decay Bacteria break down the protein into nitrates NO 3 -

69. N 2 Nitrogen fixing bacteria in soil and nodules of plants Nitrates are made into proteins in plants NO 3 - Animals get their protein by eating Death and decay Bacteria break down the protein into nitrates NO 3 - Which can be taken back up by plants and made into proteins

70. N 2 Nitrogen fixing bacteria in soil and nodules of plants Nitrates are made into proteins in plants NO 3 - Animals get their protein by eating Death and decay Bacteria break down the protein into nitrates NO 3 - Which can be taken back up by plants and made into proteins

71. N 2 Nitrogen fixing bacteria in soil and nodules of plants Nitrates are made into proteins in plants NO 3 - Animals get their protein by eating Death and decay Bacteria break down the protein into nitrates NO 3 - Which can be taken back up by plants and made into proteins

72. N 2 Nitrogen fixing bacteria in soil and nodules of plants Nitrates are made into proteins in plants NO 3 - Animals get their protein by eating Death and decay Bacteria break down the protein into nitrates NO 3 - Which can be taken back up by plants and made into proteins Denitrifying bacteria use nitrates and release nitrogen into the air Lightning and the addition of fertlisers also adds nitrates to soil

73. Stages in N cycle Nitrogen fixation Use of Nitrates by plants Assimilation by animals Decomposition and ammonification Nitrification Denitrification

74. NITROGEN from the air is converted into NITRATES by NITROGEN FIXATION 4 ways: 1.Free living NITROGEN FIXING BACTERIA (Rhizobium) found in the soil. 2.NITROGEN FIXING BACTERIA (Rhizobium) found in the roots of some plants (leguminous). The rhizobium use an enzyme called nitrogenase which converts N 2 gas into ammonium ions NH 4 +. They can only do this if they have 1). a supply of N 2, 2). A supply of ATP 3).anaerobic conditions (no oxygen). 3.Fixation in the atmosphere -lightning. The energy from lightning causes the N 2 and O 2 to react to form nitrogen oxides. These dissolve in the rain and fall onto the ground. 4.Fixation by Harber process. This is when N 2 and H 2 gases are reacted together to produce ammonia. This ammonia is converted into ammonium nitrate, which is the most widely used inorganic fertiliser.

75. Use of fixed nitrogen by plants In legumes the fixed nitrogen produced by the Rhizobium in their root nodules is used to make amino acids. This is distributed to all areas of the plant to make proteins. Some plants take up nitrate ions (NO 3 -) from the soil by active transport. This is then converted to nitrite (NO 2 -), then ammonia, and then amino acids e.g. NO 3 - NO 2 - NH 3 amino acids (Nitrate)(nitrite)(ammonia)(amino acids) So plants use nitrates to make amino acids.

76. Assimilation of nitrogen Animals get their nitrogen from the proteins they eat. Proteins are broken down into amino acids during digestion. The amino acids are then built up again into proteins in cells during protein synthesis. Protein amino acidsproteins Excess amino acids (any surplus protein in our diet) is deaminated in the liver and is excreted in urea as urine. Excess amino acids urea urine

77. Decomposition and Ammonification Decomposers gradually break down the protein in dead plants and animals into amino acids – decomposition. Decomposers include bacteria and fungi which produce protease enzymes. They use some of the amino acids for their own growth. The rest is broken down into ammonia. Ammonia is also produced from the urea in animal urine. The production of ammonia is called ammonification.

78. Nitrification The ammonia in the soil is then converted into nitrite ions (NO 2 -) and then nitrate (NO 3 -) ions by nitrifying bacteria. (Nitrosomanus and Nitrobacter).

79. Denitrification Dentrifying bacteria reverse the nitrogen fixation process. They convert nitrates back into nitrogen gas. Found in sewage treatment, compost heaps and wet soils.

80. What is the role of these bacteria in the N cycle? 1. Nitrogen fixing (Rhizobium). 2. Nitrifying bacteria - Nitrosomanus 3. Nitrifying bacteria - Nitrobacter. 4. Dentrifying.

81. What is the role of these bacteria in the N cycle? 1. Nitrogen fixing (Rhizobium). Convert Nitrogen gas into organic nitrates in soil and plants. 2. Nitrifying bacteria - Nitrosomanus Convert ammonium into nitrites 3. Nitrifying bacteria - Nitrobacter. Convert nitrites into nitrates 4. Dentrifying. Convert nitrates into Nitrogen gas.

82. Stages in N cycle – breifly summarise each one: 1.Nitrogen fixation 2.Use of Nitrates by plants 3.Assimilation by animals 4.Decomposition and Ammonification 5.Nitrification 6.Denitrification

83. Nitrogen Fixation: converts gaseous nitrogen (N2) into ammonia (NH3). Certain bacterial species, both aerobic and anaerobic, carry out this conversion. Nitrification: only certain bacteria, the nitrifying bacteria, can use NH3 as an energy source. The reaction occurs in two steps: –Nitrosomonas bacteria convert ammonia (NH3) to nitrite (NO2-) –Nitrobacter bacteria convert nitrite (NO2-) to nitrate (NO3-) Denitrification: bacteria that can respire anaerobically will convert nitrate (NO3-) to nitrite (NO2-). Note that nitrate is now serving as an electron acceptor. Some anaerobic respirers can also use nitrite (NO2-), converting it further into nitrous oxide (NO), nitrogen dioxide (N2O), and ultimately nitrogen gas (N2). Assimilation: ammonia can be directly assimilated into organic compounds inside cells, producing amino groups (-NH2). Excretion: during excretion, fermentation, and other catabolic processes, excess amino groups (-NH2) are released, ultimately producing ammonia (NH3). Assimilatory Nitrate Reduction: since nitrate (NO3-) is far more common than ammonia, many organisms can only acquire nitrogen in the form of nitrate. They must reduce nitrate to form the amino groups needed for metabolism. This process, which superficially resembles nitrate reduction by anaerobic respiration, is entirely different. Reference: http://www.slideshare.net/shabeelpn/nitrogen-cycle-3614281