42. Biogeochemical cycling I

Question 1

what are biogeochemical cycles?

Answer 1

• cyclin atoms
  – movement of element between living and non-living forms
• most common elements in organic molecules
  – C; N; H; O; P; S

Question 2

how do key elements work in organisms?

Answer 2

• C
  – organic macromolecules
  – fossil fuels
• N
  – DNA
  – RNA
  – proteins
  – agriculture
• P
  – DNA
  – RNA
  – agriculture
• S
  – protein structure

Question 3

what is the sulphur used for?

Answer 3

• sulphhuric acid
• non-ferrous metals
• pigments
• fibres
• pharmaceuticals
• plant nutrients

Question 4

how does sulphur affect plant nutrients?

Answer 4

• contributes to increased crop yields
  – similar functions in plant growth and nutrition as N
• catalyst in chlorophyll production
  – deficienty = yellow leaves
• vitamins / oils in plants
• nodule formation

Question 5

what are SRB?

Answer 5

• suphate reducing bacteria
• strict anaerobes
• anaerobic respiration utilising sulphate as terminal electron acceptor
  – reducing H2S
• assimilatory sulphate reduction
  – reduce small amounts of sulphate in order to synthesis sulphur-containing cell components (eg. cysteine - an AA)
• dissimilatory suphate reduction
  – sulphate-reducing microorganisms reduce sulphate in large amounts to obtain energy and expel resulting sulphide waste

Question 6

how is sulphate biologically reduced?

Answer 6

• chemolithotropic growth
  – H2 + SO4- = HS- + H2O
  – hydrogen electron donor
• chemoorganotrophic growth, incomplete oxidation
  – lactate incompletely oxidised to acetate
  – lactate + SO4- = acetate + H2O + HS-
• chemoorganotrophic growth, complete oxidation
  – acetate completely oxidised to CO2
  – acetate + SO4- = HS- + 2 CO2
• sulphide oxidised to sulphur

Question 7

how is biological sulphate reduction applied?

Answer 7

• bioremediation
  – suphur-rich waste streams converted to sulphide
  – acid mine drainage treatment
  – wastewater treatment
  – removal of heavy metals
• sulphide oxidised to sulphur
  – THIOPAQ process

Question 8

what is nitrogen fixation?

Answer 8

• conversion of atmospheric N2 to usable forms

Question 9

what are the processess of N2 fixation?

Answer 9

• atmospheric fixation
• industrial fixation
• biological fixation

Question 10

what is atmospheric fixation?

Answer 10

• energy of lightning breaks N2 molecules
  – enables atoms to combine with O forming nitrogen oxides
• dissolve in rain
  – forming nitrates carries to earth

Question 11

what is industrial fixation/

Answer 11

• great pressure at 600 Celcius T, with use of catalyst
  – atmospheric N2 and H2 combined to form NH3
• ammonia directly used as fertiliser
  – further processed to urea and ammonium nitrate

Question 12

what is biological fixation?

Answer 12

• bacteria in nitrogen cycle
  – N enters living world by bacteria and other single-celled porkaryotes
• convert atmospheric N2 to biologically usable forms
  – nitrogen fixation
• some nitrogen-fixing bacteria are free-living soil/water
  – others beneficial symbionts live inside plants
• capture atmoshperic N2 and convert to ammonia
  – N2 + 8H+ + 8e- + 16 ATP = 2 NH3 + H2 + 16 ADP + 16 Pi

Question 13

what is an example of nitrogen-fixing prokaryotes?

Answer 13

• photosynthetic cyanobacteria in most aquatic ecosystems that get sunlight
  – maintain fertility of semi-aquatic environments through nitrogen fixation
• rhizobium bacteriua
  – symbiotic living in roots of non-/legume plants
  – provide with fixed nitrogen
• free-living bacteria geus Azotobacter
  – key N fixers in terrestrial ecosystems