Chapter 30 and 31 (Amino acid Metabolism) Chapter Objectives -ZOOM + 1. How is a

Question

Chapter 30 and 31 (Amino acid Metabolism) Chapter Objectives -ZOOM + 1. How is atmospheric nitrogen converted into a biologically useful form of nitrogen. 2. Define nitrogen fixation, what organisms are capable of nitrogen fixation. Why do farmers rotate their crops with legumes? 3. Why are certain amino acids defined as essential for human beings. 4. What are the sources of carbon atoms for amino acid synthesis. 5. How many biosynthetic families are know for amino acid biosynthesis. What is the transamination reaction? What is the cofactor required for the 6. transamination reaction? 7. 8. What is the fate of amino acids released after protein digestion or turnover. Describe the steps in the urea cycle. Is it linked to the citric acid cycle? Explain. Important Terms and Comparisons Nitrogen fixation Essential and non essential amino acids Pyridoxal phosphate Feedback inhibition Transamination Urea cycle Ketogenic and glucogenic amino acids

Explanation / Answer

1. nitrogen is converted from atmospheric nitrogen (N2) into usable forms in four steps. they are fixation,nitrification,ammonification,de-nitrification.

fixation:

here at first N2 must be fixed or converted in to ammonia(NH3).This can happen occasionally through a lightning strike, but the bulk of nitrogen fixation is done by free living or symbiotic bacteria. These bacteria have the nitrogenase enzyme that combines gaseous nitrogen with hydrogen to produce ammonia.

nitrification:

nitrification converts ammonia to nitrate.  It is usually performed by soil living bacteria, such as nitrobacter.

ammonification:

ammonification is also called mineralization. here bacteria or fungi convertthe organic nitrogen from dead organisms back into ammonium (NH4+). Nitrification can be worked on ammonium too.

De-nitrification:

nitrate is finally converted to nitrogen on this step. it occurs by the help of bacterial species Pseudomonas and Clostridium, usually in anaerobic conditions.

2. nitrogen fixation:

in nitrogen fixation N2 is converted in to ammonia(NH3).This can happen occasionally through a lightning strike, but the bulk of nitrogen fixation is done by free living or symbiotic bacteria. These bacteria have the nitrogenase enzyme that combines gaseous nitrogen with hydrogen to produce ammonia.

farmers use crop rotation to:

-reduce the build-up of pests & diseases
-crop rotation allows crops such as brassicas to used Nitrogen fixed by legumes
-crop rotation allows specific fertilisers to be used for the next crop.

3. Human beings do not have the biochemical pathways to synthesize essential amino acids from simpler precursors.`the human body uses amino acids to produce proteins, perform critical metabolic functions in the formation of other molecules and to produce energy.

4. the carbon skeletons for biosynthesis of amino acids come from the intermediates of glycolysis, the citric acid cycle, or the pentose phosphate pathway, CAC (Aspartate, Methionine, Threonine, Isoleucine, Lysine, Glutamate),Glycolysis (Valine, Leucine, Serine),Glycolysis + PPP ( Pehnylalanine, Tryptophan, Tyrosine), PPP ( Histidine).

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