University of Bath International Foundation Year

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University of Bath International Foundation Year SEMESTER 2 2012/13 BIOLOGY PRESENTATION BY: HUI SAAN LIM

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University of Bath International Foundation Year. SEMESTER 2 2012/13 BIOLOGY PRESENTATION BY: HUI SAAN LIM. The Nitrogen C ycle. T h e N i t r o g e n - PowerPoint PPT Presentation

Transcript of University of Bath International Foundation Year

University of Bath International Foundation Year

University of Bath International Foundation YearSEMESTER 22012/13BIOLOGY PRESENTATION

BY: HUI SAAN LIM

The Nitrogen CycleT h e N i t r o g e n

C y c l e

NitrogenNitrogen is important to all life.There is an abundant supply of nitrogen in the earth's atmosphere, nearly 79% of the air is nitrogen.Nitrogen belongs to the 7th element in the periodic table.It is found in plants and animals.Nitrogen is essential for the formation ofamino acidsin proteins.

How do plants and animals obtain nitrogen?Nitrogen is sounreactive, it cannot be used directly by plants to make protein.

Most of the plants and animals cannot get the nitrogen they need directly from the air, it must first be fixed to a usable form. We depend on a special kind of bacteria that can absorb N2 gas and use it, which involves the conversion of nitrogen gas to nitrates.

Nitrogen fixationNitrogen can be fixed in three ways:Atmospheric fixation This occurs spontaneously due to lightning; only a small amount is fixed this way. Industrial fixation The Haber process is used to make nitrogen fertilizers. Biological fixation Nitrogen-fixing bacteria fix 60% of nitrogen gas.Atmospheric fixationThe enormous energy from lightning breaks the nitrogen molecules and enables their atoms to combine with oxygen in the air, forming nitrates. Precipitation carries nitrates to the ground, where they can be assimilated by plants.

Industrial fixation (Habers process)Ammonia is produced in industry :Under a high pressure of 200 atmospheres (atm)Extremely high temperature of 600CThe use of an iron catalyst

Atmospheric nitrogen and hydrogen can be combined to form ammonia (NH3).

How the Haber Process works

Biological fixationAbout 60% of nitrogen fixation is done by bacteria.There are two types of nitrogen fixing bacteria:Free living bacteriaFix significant levels of nitrogen without the direct interaction with other organismsSymbiotic bacteria

Aztobacter

Symbiotic BacteriaThe plant provides sugars that are used by nitrogen-fixing microorganism. The microbe provides nitrogen to the host plant. Mutualism Rhizobium inhabit the roots of leguminous plants, forming lumps or nodules where the nitrogen fixation takes place.Rhizobium uses enzyme nitrogenase to convert N2 to NH4+ using H + and ATP

AssimilationUptake of nitrogen by plants

The nitrates (NO3-) and ammonia (NH3) resulting from nitrogen fixation are used to produce amino acids.

Animals then ingest these algae and plants, converting them into body organic compounds (eg. Protein)AmmonificationThe initial form of nitrogen is organic. Soil fungi and bacteria, convert the organic nitrogen back into ammonium (NH4+).Ammonification classically occurs in the soil, in an aerobic environment.Once ammonification has been accomplished, the next stage, nitrification, can occur.

NitrificationMost plants cannot utilize ammonium effectively, and they require nitrate as their essential source of nitrogen nutrition.Nitrification is aprocessconducted by a specialized group of bacteria.Oxidation of ammonium compounds to nitrites and then to nitrates by the nitrifying bacteria.

Nitrification..Nitrification is a two stage process and each stage is performed by a different group of bacteria.

Oxidation of ammonium to nitrite is a function carried out by ammonium oxidizing bacteria.Nitrosococcus nitrosus, Nitrosospira briensis, Nitrosovibrio and Nitrococcus

NitrificationOnce nitrite is formed, it is rapidly oxidized further to nitrate, by nitrite- oxidizing bacteria.

Nitrospira gracilis, Nirosococcus mobilisetc, and several fungi(e.g. Penicillium, Aspergillus)The nitrates can then be taken in by plants.

Nitrification Process

DenitrificationNitrates are reduced to nitrites and then to nitrogen gas, completing the nitrogen cycle and replenishing the atmosphere.

Denitrifying bacteria:Thiobacillus denitrificans, Micrococcus denitrificans, Pseudomonas aeruginosa, etc.Conditions areanaerobic. Bacteria get the oxygen they need for respiration from the breakdown of nitrates.Denitrification can be a harmful process as fixed nitrogen is removed from the soil, making it less fertile.

Nitrogen Cycle Overview

Videohttps://www.classzone.com/books/ml_science_share/vis_sim/em05_pg20_nitrogen/em05_pg20_nitrogen.swf

QuestionsThe relationship between Rhizobium and Legumes is

A. Competitive B. Parasitic C. Predator/ Prey D. Mutualistic

2. The industrial process by which ammonia is made from nitrogen gas is called

A. The Ammonia process B. The Haber process C. Electrolysis

3. The conversion of nitrogen gas to nitrates by bacteria is called

A. NitrificationB. Nitrogen fixationC. DecayD. DenitrificationE. Excretion

Figure 4 shows the stages in biological nitrification.

8 (c) (i) Give two ways in which ammonium ions can be produced.1 ......................2 ............................ (2 marks)

BibliographyGlenn Toole(2008) ,AQA Biology A2 (Chapter 6) Cheltenham p.95-97

http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway_pre_2011/greenworld/recyclingrev2.shtml

http://www.tutorvista.com/content/biology/biology-iv/ecosystem/nitrogen-cycle.php##close_iframe

http://chemistry.about.com/od/geochemistry/ss/nitrogencycle.htm