The Carbon Cycle

The Carbon Cycle

Processes

• Photosynthesis- Fixation of atmospheric CO2 by plants using sunlight energy and its conversion to carbohydrates, releasing oxygen as its product.
• Feeding- Organic compounds passed along food chains.
• Sedimentation- Deposition of skeletons of marine animals on sea bed.
• Carbon Resovoirs- Places where carbon atoms exist, Atmosphere, living things, organic matter, fossil fuels, rocks, oceans.
• Combustion- Release of C02 when organic substances are burned.
• Decomposition- Breakdown of organic matter, releasing CO2 in anaerobic conditions, CH4 in anaerobic conditions.
• Fossilisation- Incomplete decomposition leading to the formation of fossil fuels.
• Respiration- Release of energy from high energy substances releasing CO2 into the atmosphere.

Human Impacts

• Combustion of fossil fuels has released CO2.
• Intensive agriculture, cattle (CH4)
• Deforestation, reduces carbon fixation.
• Mining & Processing coal oil and gas releasing methane.
• Ploughing increases decomposition (CO2)
• Padi fields flood the spill, increases anaerobic respiration.

The Greenhouse Effect

• The natural ‘trapping in’ of heat by greenhouse gases in the troposphere.
• Occurs in the lower atmosphere.
• CO2→ Respiration, decomposition, Combustion of fossil fuels.
• Oxides of Nitrogen → Volcanoes, Combustion of fossil fuels.
• Methane → Decomposition, anaerobic respiration, Marshes, intensive Farming, Rice Fields, Landfill sites.

Consequences of Climate Change

• Sea level rise → Ice melting, thermal expansion
• Change in Climate Pattern → Hurricanes, Wind patterns, Precipitation.
• Ocean Current → ‘El Nino’, hot water spreads to South America, collapses food chains, Changes to gulf stream.
• Ocean pH → CO2 dissolves into water, oceans become more acidic, algal blooms, coral bleaching.

The Nitrogen Cycle

• Nitrogen is found in all amino acids and nitrogenous bases.
• Nitrogen is taken up by roots as ammonium and nitrate ions. The uptakes are linked with protein synthesis of nucleic acids.
• Nitrogen Fixaton → Nitrogen fixing bacteria in the soil convert Nitrogen gas into ammonium ions and in symbiotic bacteria, organic acids and amino acids. Live in root nodules of legumes.
• N2 → NH4 → Organic Acids → Amino Acids.
• Reaction is catalysed by nitrogenase enzymes, will not work under oxidation.
• SOme ammonium ions and amino acids are converted into the vascular tissues of the hosts plants and roots.
• Rhizobium → Legumes. Uses nitrogenase to fix N2. Nitrogenase is inhibited by oxygen so it is surrounded by leghaemoglobin.
• Ammonification → Bacteria and fungi decompose dead organisms and animal products leaving Nitrogen into the plants.

Processes

• Denitrification → NO3 → N2
• Nitrification → NH3 → NO2.
• NO2 → NO3
• N2 Fixation→ Rhizobium in plant nodules, Azobacter in the soil.
• Ammonification → Bacteria and fungi.
• Rhizobium → Symbiotic relationship with legumes, inhibited by oxygen, plant produces leghaemoglobin so N2 fixation can happen.
• Ammonification → break down proteins into ammonium ions.
• Nitrification → aerobic bacteria add nitrites and nitrates to the soil in oxidation reaction. Nitrobacter and Nitrosomonas.
• Denitrification → Anaerobic bacteria convert nitrates om the soil to nitrogen in reduction reactions.