5-5: Biosynthesis Flashcards
Is N2 metabolically useful for most organisms? Why or why not?
No, it is too stable (triple bond)
What is nitrogenase?
An enzyme that converts N2 to NH3
Bacteria and archaea that can convert N2 to NH3 are called what? Give an example.
Diazotrophs
e.g. cyanobacteria, rhizobia, archaeal methanotrophs
Why do organisms convert N2 to NH3?
NH3 more metabolically useful form of nitrogen, can be used to build nucleic acids and proteins
What two proteins is nitrogenase made of? What cofactors do they use?
dinitrogenase and dinitrogenase reductase that use Fe/Mo cofactors
Explain electron flow in nitrogenase.
Electrons come from pyruvate, passed to flavodoxin, to dinitrogen reductase, to dinitrogenase to N2, producing NH3.
How much ATP does dinitrogenase require? Why?
16 ATP per 2 NH3 produced.
Reduction of triple bond of N2 very energetically demanding
What are two key enzymes needed for nitrogen assimilation?
Glutamate dehydrogenase and Glutamine synthase, which act as nitrogen donors
How is Glu and Gln made?
Adding NH3 and alpha-ketogluarate to make gluatamate. A second amine is added to make glutamine.
What is gluconeogenesis
Producing glucose for carbon/energy storage or as biosynthesis precursor
Gluconeogenesis is basically what?
reversal of glycolysis
How is glucose-6-phosphate activated
Addition of nucleotide diphosphate such as ADP-glucose, UDP-glucose which us ATP or UTP.
Activated form of glucose-6-phosphate can be used to produce what?
LPS (gram (-) OM)
NAM/NAG (peptidoglycan)
Storage molecules (glycogen/starch)
Where do the carbon skeletons of AA come from?
Intermediates of CAC or glycolysis
What is a parent amino acid?
Precursors to producing amino acids (eg. Asp)
What are ACP
Acyl carrier proteins, “holder” of substrate for f.a. synthesis
How are fatty acids built?
2 carbons at a time by adding malonyl-CoA (3C) to growing chain, releasing CO2 as byproduct
How is malonyl-ACP made?
Acetyl-CoA is used to maky malonyl-CoA, which is used to make malonyl-ACP>
What are the basic building blocks for nucleotides
Pentoses (5C sugar, ribose)
Nucleobases
What does pentose phosphate pathway do
Generates NADPH, carbon skeletons and ribose-5-P from glucose-6-phosphate, which can then be used to make nucleotides and other key metabolites.
What is ribose-5-P used for
Make ribonucleotides
Are purines and pyrimidines built using the same pathway?
No, seperate pathways
What are the key intermediates of purine and pyrimidine synthesis?
Purines = IMP
Pyrimidines = orotate
What does ribonucleotide reductase do
Converts ribonucleotides into deoxyribonucleotides for DNA synthesis
