Topic 3-L6 - Biosynthesis Flashcards
Nitrogen fixation
Some organisms (rare, bact. and archaea) produce nitrogenase –enzyme that converts N2 to NH3
Bact. And archaea that can do nitrogen fixation are known as
“diazotrophs”. E.g. - cyanobacteria,
rhizobia, some archaea methanotrophs
Why convert NH2 to NH3 during nitrogen fixation
NH3 is a much more metabolically useful form of nitrogen – can be used by cells as a nitrogen source for building nitrogen containing molecules (e.g., nucleic acids, protein, etc)
Nitrogenase is comprised of two
proteins
dinitrogenase & dinitrogenase reductase - use Fe/Mo
cofactors
In nitrogen fixation, Electrons come from
Fe/S proteins such as flavodoxin – transferred to dinitrogen reductase – to dinitrogenase – to N2.
Activation/reduction of triple bond
very energetically demanding –requires adding
6 electrons (8 electrons consumed) - 2 ATP per electron…16 ATP per 2 NH3 produced!
Building the cell’s molecules: gluconeogenesis
Producing glucose (for carbon/energy storage or as a precursor for biosynthesis) done using gluconeogenesis
gluconeogenesis is basically the reversal of
Glycolysis
In gluconeogenesis, what’s produced
Glucose-6-P produced which is the activated to produce other mol.
Producing sugar-containing molecules
By activating glucose
Glucose can be “activated” by the
addition of
nucleotide diphosphates
such as ADP-glucose, UDP-glucose
(using ATP, UTP)
Activated form used to produce
polysaccharides for:
- LPS (Gram negative outermembrane)
- NAM/NAG (peptidoglycan)
- Storage molecules like glycogen/starch – later used for carbon/ energy
Amino acids needed to produce
proteins and more (e.g. peptidoglycan)
In the formation of amino acids, Carbon skeletons come mainly from
intermediates of the citric acid cycle,
glycolysis
inorganic nitrogen sources such as NH3 used to build
nitrogen-containing molecules (e.g. amino acids)
