Biogeochemical cycles

 Carbon cycle

1)      Reduced form of carbon: CH₄, Organic matter [ presence of H]

       Oxidized form of carbon: CO, CO₂ [To ease my memorising, there is presence of O]

 

 

 2) Organic matter undergo respiration to release CO₂.

      Organic matter undergo fermentation to become CH₄, CO₂, H₂.

 

3) Carbon dioxide will be fixed into organic matter again by plants and photosynthetic bacteria such as cyanobacteria and green algae.

 

4) Organic matter includes cellulose, lignin, hemicellulose from plant cell wall, starch, hydrocarbon and lipids from animals.

 

 

Nitrogen cycle

 

3 major process:

1) Nitrification (Oxidation)

Ammonium ion (NH₄⁺)     -------------->   Nitrite (NO₂⁻) --------------> Nitrate (NO₃⁻)

2) Denitrification

 

Nitrate (NO₃⁻) -----------> Nitrogen gas (N₂) / Nitrite (NO₂⁻)

 

Reduction of nitrate to ammonium ion by several bacteria such as Geobacter sp. , Clostridium sp. , Desulfovibrio sp.

 

Nitrate (NO₃⁻) -----------> Ammonium ion (NH₄⁺)

 

3) Nitrogen fixation (Reduction)

 

Nitrogen gas (N₂) ----------> Ammonium ion (NH₄⁺)

 

Sulfur Cycle

1) Mineralization of organic sulphur to the inorganic form, hydrogen sulphide (H₂S is toxic)
2) Oxidation of sulphide (H₂S)  and elemental sulphur (S) to sulphate (SO₄⁻)
3) Reduction of  elemental sulphur (S) /sulphate (SO₄⁻) to sulphide (H₂S) (dissimilatory)
4) Reduction of sulphate (SO₄⁻) to organic sulphur. (assimilatory)

 Iron cycle

Oxidation (Aerobic condition)

Ferrous ion (Fe²⁺) --------> Ferric ion ( Fe ᶟ⁺)

Reduction (Anaerobic condition)

Ferrous ion (Fe²⁺) <-------- Ferric ion ( Fe ᶟ⁺)

Ferric ion ( Fe ᶟ⁺) --------> Fe₃O ₄by magnetotactic bacteria

Manganase cycle

Oxidation
Mangnase ion (Mn²⁺)-------->  Manganic ion (MnO₂)(Mn ⁴⁺ )

Reduction
Mangnase ion (Mn²⁺) <--------  Manganic ion (MnO₂)(Mn ⁴⁺ )