Ch22-Biosynthesis_AA_Nucleotides_10_posted

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Unformatted text preview: Click to edit Master subtitle style 11 Biosynthesis of Amino acids and Nucleotides Chapter 22 Click to edit Master subtitle style 22 Most of Nitrogen in biological system is bound in - Amino Acids- Nucleic Acids Biosynthesis of both these class of molecules have lot in common:- Intermediates- Precursors- common reactions Biosynthesis of Amino acids and Nucleotides Click to edit Master subtitle style 33 v Rare use of metals: molybdenum, selenium, vanadium. v Many genetic diseases due to defects in the enzymes of these pathways. v Regulation is very important because each amino acid is needed in small amounts. v Both amino acids & nucleotides are charged molecules: - cannot be accumulated in large amounts in a cell. Importance of studying of these biosynthetic pathways Click to edit Master subtitle style 44 Generally, control of metabolic pathways is by:- amount of enzyme?- activity of enzyme? Here its the activity of enzymes. Control 55 Nitrogen metabolism Soluble and biologically active Nitrogen is in scarce supply. Strict balance is needed in use of: ammonia, amino acids, and nucleic acids. Lots of salvaging takes place to conserve Nitrogen. 66 Nitrogen Cycle Fixation: Atmospheric Nitrogen is fixed (reduced) to Ammonia (NH3 or NH4+) by Ammonia Ammonia can be used by most organisms. Nitrification: It can be converted by soil bacteria to nitrite (NO2-) & nitrate (NO3-) (nearly all ammonia reaching soil is converted to nitrate) Plants and bacteria can take up & reduce nitrate and nitrite through the action of: Nitrate Reductase enzymes Ammonia is incorporated into amino acids by plants. Animals use plants as a source of amino acid. - Upon death, proteins are converted to _ammonia_ then to nitrate.- via denitrification, nitrate is converted to _N2__. Nitrogen Cycle 88 Only _prokaryotes_ can fix atmospheric Nitrogen:- Cyanobacteria (__in soil, water__),- Azotobacter _free living_ and- Rhizobacteria (symbionts) in roots of legumes. N l N triple bond is very _stable (with bond energy of 930kJ/mol) High energy needed: Industrial production of ammonia at 400 500 celsius+ _high_ pressure. They create situation where nitrogen is adjusted How is it done biologically at normal temperature & pressure?- Nitrogen Fixation 99 Nitrogen Fixation Catalyzed by Nitrogenase Complex: 1. Dinitrogenase reductase (iron 4Fe-4S center) 1. Dinitrogenase (iron & molybdenum) Fixation by highly reduced _dinitrogenase_ , - needs 8 electrons (6 for N2, 2 for H2) Dinitrogenase in turn is reduced by _dinitrogenase reductase__ . 1010 N2 + 10H+ + 8e- + 16 ATP & 2NH4+ + 16 ADP + 16 Pi + H2 Required 8 e- are transferred:- one by one and - each passing needs 2 ATP .-Nitrogenase complex is highly sensitive to _oxygen__....
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This note was uploaded on 11/16/2010 for the course BIOL 2010 taught by Professor Kumar during the Winter '07 term at East Texas Baptist University.

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Ch22-Biosynthesis_AA_Nucleotides_10_posted - Click to edit...

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