Nitrogencomprises 78.08 % of the atmosphere making it the largest constituent of the gaseous envelope that surrounds the Earth. Nitrogenis important in the make up of organic molecules like proteins and DNA. Mostorganisms cannot use nitrogen in this form, i.e N2
Plantssecure their nitrogen in “fixed” forms i.e incooperated in compounds such as: Nitrate ions NO3 Ammonia NH3 Urea (NH2)2CO Animalssecure their nitrogen (and all other compounds from plants (or animals that have eaten plants).
Four processes participate in the cycling of nitrogen in the biospere: • Nitrogen fixation • Decay • Nitrification • Denitrification *microorganisms play major roles in all processes*
Thenitrogen molecule is quite inert. To break it apart so that its atoms can combine with other atoms requires the input of substantial amounts of energy. inert-nonreactive gas during chemical synthesis, analysis or preservation of reactive materials
Three processes are responsible for most of the nitrogen fixation: 1. Atmospheric fixation 2. Biological fixation 3. Industrial fixation
Theenormous energy of lightening breaks nitrogen molecules and enables then to combine with oxygen in the air forming nitrogen oxides. These dissolve in rain forming nitrates that are carried to the earth. *contributes 5-8% of total fixed*
Made synthetically via Haber Process. Nitrogenand hydrogen reacted under great pressure and temperature in the presence of a catalyst to make ammonia. Ammonia applied directly to farm fields as fertilizers or further processed with oxygen to make nitric acid.
Theability to fix nitrogen is found only in certain bacteria and archaea. Some live in symbiotic relationship with plants of the legume family Rhizobium Some establish symbiotic relationships with animals Some live free in soil
Biological nitrogen fixation requires a complex set of enzymes and a huge expenditure of ATP
Protein made by plants enter and pass through food webs at each level. Ateach trophic level metabolism produces nitrogen compounds that return to the environment in excretions. Microorganisms break down the molecules in excretion and dead organisms into ammonia, NH3.
Most of the ammonia produced by decay is converted into nitrates. Bacteria of the genus Nitrosomonas oxidize NH3 nitrites NO2 Bacteria of the genus Nitrobacter oxidize nitrites nitrates NO3
Thisis the reduction of nitrates to nitrogen gas, thus replenishing the atmosphere Anaerobic bacteria use nitrates as an alternative to oxygen in their respiratory process. Closing the nitrogen cycle
A side product of this reaction is known as nitrous oxide N2O, more commonly known as “laughing gas”A mild anesthetic, also a greenhouse gas that contributes to global warming,
Carbon, C is one of the most common elements on Earth. Its found:4. in the tissues of living organisms5. in the atmosphere6. dissolved in ocean water and7. locked up in limestone deposits that line the ocean floor
Living organisms provide two important steps in the carbon cycle.r Plants absorb CO2 from the atmosphere to use during photosynthesis2 Other organisms release CO2 into the air during respiration
In addition there are several important non-organic storage areas of carbon in the environment:a A large portion is stored in rocksi Oceans hold a large amount of CO2 because it dissolves easily in waterl Coal, oil and limestone store carbon that once form ancient organisms**burning fossil fuels will release CO2 into the atmosphere**
Photoautotrophsconstantly remove carbon dioxide through the process photosynthesis. Certainbacteria known as chemoautotrophs use carbon dioxide to synthesize the organic compounds they need.
Thecarbon present in food made by plants reaches animals through the food chain. Carnivorousanimals receive this carbon when they eats animals.
Carbon dioxide is continuously dissolved in water bodies by diffusion. Once dissolved it either remains in the waters or gets converted into carbonates -2 CO3 and bicarbonates HCO3
Thedissolved carbon dioxide is used by plants for photosynthesis. Thecarbonates are converted into calcium carbonate by certain marine organisms. Thecalcium carbonate is used by corals and oysters to make their shells. When these organisms die their shell deposit to the sea floor and eventually turn into sedimentary rocks.
When plants and animals die and get buried under the ground, after millions of years they change into fossil fuels due to high pressure and other physical and chemical changes.
Carbon dioxide is regularly returned to the atmosphere by the process of respiration in plants and animals. Burningof wood and fossil fuels in industry and automobiles also releases carbon dioxide.
Itabsorbs infrared light. The atmosphere absorbs more heat than i