Presentation on theme: "Nitrogen Fixation: Nitrogen fixation is one process by which molecular nitrogen is reduced to form ammonia. Ammonification: The chemical transformation."— Presentation transcript:
1 Nitrogen Fixation: Nitrogen fixation is one process by which molecular nitrogen is reduced to form ammonia. Ammonification: The chemical transformation of organic nitrogen into ammonia by the metabolic breakdown of proteins and amino acids. Nitrification: The oxidation (loss of electrons) of ammonia by specialized bacteria Draw and label a graphic showing your understanding of the carbon cycle.
6 Nitrogen CycleLightning discharges convert some of the molecular nitrogen into forms that plants can useMost nitrogen in the atmosphere enters the biological pathways of the nitrogen cycle through nitrogen fixation
7 Nitrogen FixationBiological absorption of atmospheric nitrogen to form organic nitrogen containing compoundsNitrogen fixation is one process by which molecular nitrogen is reduced to form ammonia
8 AmmonificationPlants obtain nitrogen from the soil either as ammonium or as nitrateWith an input of energy, plants reduce nitrogen to an organic form such as ammoniumOrganic nitrogen is the most reduced form of the nitrogen atom, with the highest potential chemical energyOrganic nitrogen is used to construct proteins
9 AmmonificationProteins are eventually metabolized (broken down to yield energy)Excess nitrogen is excreted into the environment as wasteHydrolysis: A chemical process that splits molecules by the addition of waterOxidation: The loss of elections from a substance involved in a redox reactionRedox Reaction: A chemical reaction involving the transfer of one or more elections from one reactant to another
10 AmmonificationAmmonification occurs through the breakdown of proteins into amino acids by hydrolysis and oxidation of the carbon in those amino acidsThis process results in the production of ammoniaAmmonia is usually transformed to ammonium
11 NitrificationNitrification: The oxidation (loss of electrons) of ammonia by specialized bacteriaNitrification yields nitrite and nitrateOxidation steps release much of the potential chemical energy of organic nitrogenEach step is carried out by specialized bacteria
12 DenitrificationIn water-logged anaerobic soils and in oxygen depleted bottom waters, organic matter is broken down through denitrificationNitrate is converted back to atmospheric nitrogen
13 Nitrogen FixationThe loss of readily available nitrogen through denitrification is offset by nitrogen fixationNitrogen fixation is accomplished by specialized bacteria (prokaryotes)Azobacter: a free living speciesRhizobium: occurs in a symbiotic relationship with the roots of some legumes
14 Nitrogen FixationConvert atmospheric nitrogen to minerals that can be used to synthesize nitrogenous organic compoundsSome cyanobacteria fix nitrogen in aquatic ecosystemsOrganisms that fix nitrogen are fulfilling their own metabolic requirements, but the excess ammonia they release becomes available to other organisms
15 Nitrogen Fixation The direct product of nitrogen fixation is ammonia Most soils are at least slightly acidic, and ammonia released into the soil picks up a hydrogen ion to form ammoniumAmmonium can be used directly by plants
16 Nitrogen FixationAmmonia is a gas and can evaporate back into the atmosphereAmmonia lost from the soil may then form ammonium in the atmosphereAs a result, ammonium concentrations in rainfall are correlated with soil pH over large regionsMost of the ammonium in the soil is used by certain aerobic bacteria as an energy source (nitrification)
17 What must happen to nitrogen before plants and animals can use it? Nitrogen must be converted, or “fixed”, into forms that are useable by plants (ammonium or nitrate ions). Then, animals eat the plants and assimilate the nitrogen from the plants.
18 What organisms are able to “fix”, or convert, nitrogen to be usable by plants? How else might nitrogen be “fixed” or converted?Symbiotic and free-living bacteria are able to fix nitrogen to be usable by plants. Nitrogen can also be fixed by lightning strikes, fires, or through industrial methods. However, it is mostly done by bacteria.
19 Important Concepts of the nitrogen cycle nitrogen in the atmospherenitrogen in decaying matter and wastenitrogen assimilating to animalsnitrogen fixation by bacteriadecomposition by bacteria and fungidenitrification and nitrification.