L16: Carbon Cycle Pathways

Question 1

Draw the global C cycle

Answer 1

draw it

Question 2

List key carbon cycle pathways

Answer 2

1. methanotrophy
2. methanogenesis
3. respiration (aerobic / anerobic)
4. photosynthesis
5. fermentation

Question 3

What is carbon fixation

Answer 3

carbon dioxide from the atmosphere is converted into organic molecules, primarily carbohydrates

by autotrophs (CO2 energy source)

Question 4

What is calvin cycle

Answer 4

• aerobic autotrophs

*RUBISCO condensces RUBP and CO2

*high energy input via 12NADPH + 18ATP which reduces 6CO2 => 1 glucose

• prevent wasteful photorespiration, cells performing the Calvin cycle often have carboxysomes that let in carbon dioxide and keep out oxygen.

Question 5

Who participates in aerobic methanol methyl metabolism

Answer 5

1. methanogens
2. methanotrophs
3. methyltrophs

Question 6

describe methanogens, c source, energy source

Answer 6

• archaea, obligatory anaerobes
• reduces compounds as energy-yielding CH4
  *live in areas of high H2/CH2

*Source: CO2, methylated compounds
*e- acceptor: CO2
CO2+H2=CH4+H2O

Question 7

Methanotrophs

Answer 7

aerobic
*CH4 oxidised to CH3OH (methanol)
Csource: CH3OH
energy source: CO2 (oxidides CH3OH)

• After methane is oxidized (requires
  energy and oxygen), it can be either…
• Incorporated as biomass
  (requires energy) or
• Carbon can be further oxidized and the electrons can be used for the ETC and NADH production (produces energy and CO2)

Question 8

Methyltrophs

Answer 8

*most diverse
*C source: consueme CH3OH + methyl products
*methanotrophs that use methan but cannot oxidise CH4

Question 9

Who foes anaeorbic methan oxidation

Answer 9

ANME (aneorbic methantrophic bacteria and archea)

Methane oxidation without oxygen

Question 10

ANME archea

Answer 10

how: catalysed by ANME archa + SRBs

where: aneorbic marine sediments

mechs: methanogens catayse reverse methanogensis

helphers: SRB, denitrifiers

Question 11

methylmoribilis oxifera

Answer 11

ANME
oxides CH4 (using O2 from NO2/NO) as TEA draw

Question 12

chemically breakdown and draw and list microbial methane metabolism

Answer 12

1. methylmirabilism oxyfera AOM
2. methognesis
3. aeaobic oxidation of methane
4. reverse methanogenesis

Question 13

Temperature-dependent microbial proce

Answer 13

Photosynthesis rates increase with higher temperatures, up to a maximum
* Respiration rates increase with higher temperatures, and continue increasing
* At temperatures where respiration exceeds photosynthesis, soil carbon gets
released to the atmosphere, and soils become a carbon source rather than sink

Question 14

What do these prefixes mean: photo + chemo, organo + litho, hetero + auto

Answer 14

energy: sunlight + breaking chem compounds e-: organic compounds + inorganic compounds carbon: organic or CO2

Question 15

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Answer 15

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