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I/GCSE Biology: The carbon cycle

The carbon cycle

October 10, 2022

Do you guys still remember the carbon cycle in I/GCSE Biology?

Capturing carbon dioxide

  • Fixing – Absorbing carbon dioxide from the air and converting it into complex carbon compounds. Plants fix carbon dioxide during photosynthesis
  • CO2 molecule taken into leaf – during photosynthesis changed into organic carbon compound = glucose (carbohydrate) = fixing
  • Removes carbon from physical environment
  • Refer to I/GCSE Biology,  Glucose used for respiration = converted to CO2 + released back into air
  • Glucose may be changed into complex carbon compounds e.g. carbs, proteins & fats in plant tissue

Carbon compounds in animals

In I/GCSE Biology,

  • If plant eaten by animal – plant tissue broken down during digestion
  • Some carbon compounds
    • absorbed through animals gut + made into carbs, proteins, fats etc. rest = faeces
    • converted to glucose for respiration then transformed to CO2 – released into atmosphere
    • become part of animals body tissues or excreted in urine – animal eaten = same processes happen in that animal n
  • Plant or animal not eaten = die and detritus feeders will feed on dead body
  • Detritus feeder = an organism that feeds on detritus (decomposing organic waste)
    • Break down complex carbon compounds + use them to make more carbon compounds in their bodies – release carbon as CO2 to air from respiration
  • Decomposer organism e.g. fungi + B continue process of decay – do the same as arrow above

The full cycle

  • Heat + pressure turns large quantities if organisms e.g. trees into fossil fuels
  • Combustion of fossil releases CO2 into air
  • When carbon returned, leaf captures it and fixes it in photosynthesis – cycle starts again
  • Constant cycling of carbon through carbon compounds in living organisms + CO2 in air = carbon cycle
  • Carbon cycle = the way in which carbon atoms circulate between living organisms and the physical environment
  • Only nutrients and CO2 continuously cycled – energy is captured by plants then transferred as heat to environment – energy can't be used by living organisms = no energy cycle
  • Plants photosynthesise during day, take CO2 from atmosphere. Plants respire all the time releasing CO2 back into atmosphere

That's all~