4.3 Carbon Cycling

Question 1

how is carbon dioxide removed from the atmosphere?

Answer 1

autotrophs absorb co2 and convert it into other carbon compounds

carbon dioxide is soluble in water so it dissolves or forms carbonic acid and disosciates to form hydrogen carbonate ions which are both used by autotrophs to form carbon compounsd

Question 2

how is carbon dioxide released

Answer 2

by respiration by non-photosynthetic plant cells, animal cells, sophotrophs (so all cells that respire aerobically)

Question 3

how is methane produced

Answer 3

methane is produced from organic matter in anaerobic conditions by methanogenic archaeans

the anaerobic prokaryotes and pathway

1. bacteria that convert matter inot organic acid,alcohol and hydrogen and carbon dioxide
2. bacteria use organic acids and alcohol to produce acetate and carbon dioxide and hydrogen
3. archaeans produce methane from carbon dioxide hydrogen and acetate

CO2 + 4H2 –> CH4 + 2H20

CH3COOH –> CH4 + CO2

this happens in anaerobic environments

• mud along shores
• swamps mires wetlands with water logged soil
• guts of termits and ruminant mammal e.g. cattle and sheep
• landfill sites where organic waste is buried

Question 4

explain why methane conc levels are low

Answer 4

methane is oxidised to co2 and h2o naturally

therefore low levels despite high levels of release

Question 5

how does peat form

Answer 5

if organic matter is not fully decomposed because of anaerobic conditons in waterlogged soil

this is becasue saphotrophs cannot thrive in these conditons so acidic conditions tend to develop further inhibiting the saphotrophs and mathanogens may break down teh matter

this material can become compressed to form peat

Question 6

how does organic matter fossilize

Answer 6

partially decomposed organic mattter from pastgeological era was converted into oil and gas in porous rocks or into coal

coal is formed when peat is buried under sediment compressed, heated

oil and gas form in the mud at teh bottom of the sea and lakes due to anaerobic conditions so decomposition is incompleted

partially decomposed matter is compressed, heated and chemical changes occur which prodcue complex mixtures of oil and gas

methane form the largest part of natural gas, deposits are found when porous rocks can hold this gas with impervious rocks to prevent gas to escape

Question 7

combustion of organic matter

Question 8

what is limestone

Answer 8

animals such as reef building corals and molluscs have hard parts that are calcum carbonate and have become fossilized

in acidic conditions when these animals die teh calicum carbonate dissolves away but if neutral or alkaline the parts form part of the sea bed which results in limestone

Question 9

draw the carbon cycle

Answer 9

we can only estimate global fluxes in carbon through the cycle

humans affect this by

• deforestation
• combustion of fossil fuels
• agriculutre (methane production)