4.3 Carbon cycling

Carbon cycle

A biogeochemical cycle where carbon is exchanged between 4 spheres of earth.

Things carbon is exchanged in

• Atmospheric gases – mainly carbon dioxide (CO₂), but also methane (CH₄)

• Oceanic carbonates – including bicarbonates dissolved in the water and calcium carbonate in corals and shells

• As organic materials – including the carbohydrates, lipids and proteins found in all living things

• As non-living remains – such as detritus and fossil fuels

Carbon concentration gradient

The process by which the concentration of carbon dioxide is greater outside the cells of plants which allows for passive diffusion into the plant.

Compensation point

The point that the net carbon dioxide is 0 due to an offset between cellular respiration and photosynthesis.

Carbonic acid

A product of when atmospheric carbon dioxide dissolves in water, creating carbonic acid. Creates hydrogen ions causing ocean acidification.

• Created carbonate ions (H₂CO₃  ⇄  HCO₃^– + H⁺) which acquires metal ions

Calcium carbonate

Formed by the combination of hydrogen carbonate ions from with calcium which allows for shelled organisms to create their exoskeletons.

Methane

A gas formed typically in the digestive tract of animals, wetlands, and marine sediments.

Coal formation

When peat is compressed under sediment, the heat and pressure produces coal which can be burned to release heat and carbon dioxide.

Combustion

The burning of organic compounds in the presence of oxygen.

• Produces exergonic reaction

Carbon sink

A forest, ocean, or other natural environment viewed in terms of its ability to absorb carbon dioxide from the atmosphere.

Gigaton

1 billion metric tons. Typically used to talk about carbon