Clockie 4 Cycles

Question 1

Abiotic:

Answer 1

(e.g., air, water, minerals) inorganic

Question 2

Biotic:

Answer 2

(e.g., predators, decomposers)

Question 3

Biogeochemical cycles include:
•	Biological components 
•	Geological components 
•	 reservoir 
•	source

Answer 3

• phototrophs & heterotrophs
• volcanoes & oceans
• part of biosphere contains significant amounts of element.
• for element for living organisms & sink to it returns to

Question 4

elements cycle:

Answer 4

sources to sinks, microbial metabolism generates a series of redox changes.

Question 5

Macroelements flow in …

Answer 5

biogeochemical cycles

Question 6

Aerobic carbon cycling

carbon cycles between CO2 & various reduced forms of carbon, including biomass.

Answer 6

• Photosynthesis fixes CO2=> biomass. => O2 &organic compounds
• Lithotrophs reduce CO2 => biomass.
• Respiration => CO2 to atmosphere.
• Net gain O2, loss CO2 => photic zone

Question 7

ANEROBIC C CYCLE

Answer 7

• Less iron, & less redox potential than O2
• Occurs in subsurface in environment = Soil, benthos, rock
• fermentation & lithotrophic (chemoautorophic) respiration
• Incomplete breakdown of biomass carbon
• Formation of peat, oil, gas

Question 8

• Sulphur & iron & some nitrifying oxidising chemoautotrophs use

Answer 8

use the Calvin cycle to fix CO2

• Thiobacillus, leptospirillum

Question 9

METHANOTROPHY

methanotrophs & methylotrophs

Answer 9

= Methylosinus, Methylococcus capsulatus

Question 10

Methanogenesis:

equation

Answer 10

• CO2 + 4 H2 → CH4 + 2H2O

Question 11

Methanogenesis:
organism:
Terminal electron acceptor:
Electron acceptors:

Answer 11

• Archaea only
• carbon
• such as O2, S, NO3) depleted, H2 & CO2 increase

Question 12

Methanogenesis:

Answer 12

final step in decay of organic matter

Question 13

profoundly anaerobic conditions:

Answer 13

–	Rumen
–	Termite guts
–	Anoxic sediments
–	Paddy fields
–	Anaerobic digesters

Question 14

ACETOGENESIS

Answer 14

• grp uses CO2 as electron acceptor
• convert CO2 => acetate (by Acetyl-CoA pathway)
• most gram-+/ve in genus Clostridium

Question 15

NITROGEN CYCLE

Answer 15

• more oxidation states than any other elements
• cannot exist without prokaryotes.
• Atmosphere = N2 79%, major accessible
• Artificial nitrogen fixation => Haber process = fertilizers for agriculture
• Reservoir: air (nitrogen gas)
• Key constituent of protoplasm
• Exists in a number of oxidation states
• Availability limits life

Question 16

3 major processes of microbial nitrogen transformation:

Answer 16

– Nitrogen fixation
– Nitrification
– Denitrification

Question 17

DIAZOTROPHS

Answer 17

-only prokaryotes
-nitrogenase enzyme complex
molybdenum protein, iron protein
8H+ +8e + N2 -> 2NH3 + H2 => 18-24ATP

Question 18

N2 FIXATION

equation

Answer 18

• N2 → NH3 → NH4+

Question 19

N2 FIXATION
Catalyzed by
conditions:

Answer 19

nitrogenase
• Only works anaerobically
• tremendous input of energy

Question 20

N2 FIXATION

Organisms x3

Answer 20

• Klebsiella, Clostridium, Pseudomonas in soil
• Rhizobium within legumes
• Cyanobacteria in oceans and freshwater

Question 21

NITRIFICATION

Equation

Answer 21

NH4+ → NO2– → NO3–

Question 22

NITRIFICATION organisms

Answer 22

Soil: Nitrosomonas oxidizes NH4+ to NO2–

• Nitrobacter oxidizes NO2– to NO3–

Question 23

assimilatory nitrate reduction:

Answer 23

Nitrate assimilation to biomass

Question 24

DENITRIFICATION

equation

Answer 24

NO3– → NO2– → NO → N2O → N2

Question 25

DENITRIFICATION

- Nitrate & nitrite reduction =

Answer 25

dissimilatory nitrate reduction.

Question 26

ANEROBIC AMMONIUM OXIDATION

equation

Answer 26

NH4+ + NO2– → N2 + 2 H2O

major source of N2 anaerobic ammonium oxidation by nitrite
(the anammox reaction).

Question 27

ANEROBIC AMMONIUM OXIDATION

organism

Answer 27

planctomycete genera

Question 28

SULPHUR CYCLE

Answer 28

• Competing assimilatory & dissimilatory sulphur reactions in biosphere => “sulphur triangle” H2S, S0, & SO42–.
• Oxygen: H2S oxidized => sulphur dioxide => sulphate.
• Anaerobically: H2S = photolyzed => sulphur.
• Sulphate is electron acceptor for anaerobic respiration, or may be assimilated into biomass, with reduced sulfur groups.
• Elemental sulphur may be oxidized => sulfate by lithotrophs.

Question 29

Chemolithotroph

Reduced Sulphur oxidizers x3

Answer 29

• Thiobacillus, Thiomicrospira, Thiothrix

* H2S So SO32- -> SO42-