Overview Of Amino Acid Metabolism

INTRODUCTION:

Amino acid are nitrogen containing biomolecules that perform a variety of function apart from serving as Building blocks of protein .all biomolecules incorporate nitrogen in the reduced state which organisms Acquire directly or indirectly .the de navo fixation of nitrogen to ammonia is restricted to few prokaryotes.

In this unit we shall study the biological nitrogen cycle and how nitrogen is made available  to different Group of organisms. the amino acid ,glutamate and glutamine are the first to assimilate ammonia which is The major nitrogen donor for the synthesis  of other nitrogenous biomolecules .

 An overview of biologically active substance derived from amino acid will also be covered .the unit ends with a discussion on protein energy malnutrition (PEM)

NITROGEN CYCLE

Nitrogen cycle is one of the important cycles in the biosphere .nitrogen is the most abundant gas in the atmosphere(>76%)but react with difficult .the transformation undergone by nitrogen through the agency of living organisms constitute the global nitrogen cycle. during the various stages of the nitrogen cycle it interconverts between  different oxidation  states ranking from (+5to-3).the major player in the de navo  fixation of reduced nitrogen and recycling are microbes . it is important to recognise at the point that all biomolecules  incorporate nitrogen only in the reduced from ,which they acquire directly or indirectly .

The fixation of atmospheric nitrogen to ammonia is restricted to few prokaryotes which are either photosynthetic or non photosynthetic and vary in their oxygen dependence. nitrogen fixed by soil microbes can partly be converted to nitrate by the process of nitrification involving sequential transformation by nitrosomonas and nitrobactor species. 

 

Most plant readily absorb nitrate than ammonium from the soil ;other prefer ammonia. in any case nitrate is incorporated into biomolecules (amino acid)

only after reduction ti ammonia (nitrate assimilation ) some can obtain fixed bacterial symbiont. the assimilation of ammonia to organic compounds is ammonia assimilation.

This in turn generates nitrogen donors to support the synthesis of a variety of nitrogen containing  biomolecules  including proteins and nucleic acid polymers .animal are incapable of both  nitrogen fixation and nitrate assimilation so they are totally  dependent on plant and microorganism for the synthesis of organic nitrogenous compound which they obtain from diet.

The cycle completes with the return  of gaseous nitrogen back to the biosphere. the decomposition of organic material after death of the plant and animal or their excreta releases ammonia (ammonification ) ,which is either assimilated by plant or is acted upon by denitrifying bacteria. most of these microbes are  anaerobic in place of oxygen (anaerobic respiration ). they produce gaseous oxides of nitrogen such as NO and nitrous oxide before ending up with nitrogen 

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