ter 10 Biosynthesis (anabolism) al: produce monomers of the four biomolecules ino Acids (Proteins) Simple Sugars (Polysaccarides) cleotides (DNA & RNA) Lipids bacteria synthesize almost all the monomers that they need f ll growth directly, whereas we are more used to thinking of a at get many of their monomers from food. - The simplest building blocks for biosynthesis are the one carbon, oxidized molecules such as CO 2 (carbon fixation)
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Chapter 10 Biosynthesis (anabolism) Goal: produce monomers of the four biomolecules
Chapter 10 Biosynthesis (anabolism) Goal: produce monomers of the four biomolecules Amino Acids (Proteins) Simple Sugars (Polysaccarides) Nucleotides (DNA & RNA) Lipids Most bacteria synthesize almost all the monomers that they need for - PowerPoint PPT Presentation
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Calvin-Benson Cycle (“Dark Reactions” of Photosynthesis)
--- while many autotrophic prokaryotes use the Calvin cycle it isnot the only option as is the case among the eukaryotes
--- the point of the Calvin cycle is to “fix” carbon, create reducedcarbon compounds that can be used for biosynthesis or stored for laterconversion into cellular energy
CO2 CH2OH
--- this process requires tremendous amounts of energy, 3 ATP
and 2 NADPH per CH2OH unit (18 ATP and 12 NADPH per 6 carbon
sugar) however, the energy input is essentially free (sunlight) and most prokaryotic autotrophs inhabit niches where they can afford to sitaround and wait
Glycolysis (Embden-Meyerhof pathway)
Glucose + 2 ATP + 2 NAD+ 2 Pyruvate + 4 ATP + 2 NADH
Produces:--- net 2 ATP--- 2 NADH (for electron transport or NAD+ must be
regenerated by fermentation or biosynthesis)--- several intermediates can be used for biosynthetic
precusors
--- Does NOT produce CO2
Hexose Monophosphate Shunt (HMS)
--- produces NADPH from Glucose--- end product useful for nucleotide biosynthesis and the Calvin cycle
Entner-Doudoroff pathway (ED) --- variation of gylcolysis produces only 1 net ATP but also 1 NADPH
TCA cycle
--- 3 CO2 produced
--- 3 NADH
--- 1 FADH2
--- 1 ATP--- multiple precusors for biosynthesis
Nitrogen Assimilation and Fixation
--- most organisms obtain N from NH4+ (prokaryotic & eukaryotic)
NH4+ + a-ketogluterate Glutamate + NH4
+ Glutamine
(NADPH) (ATP)
--- some prokaryotes can reduce NO3- or NO2
- to NH4+
Biosynthesis
Purine ring
Nitrogen Fixation
--- the ability to reduce atmospheric N2 to NH3
--- requires considerable energy and specialized enzymes--- a few bacteria possess this ability and are required by Earth’s
more complex life forms as a source of useable nitrogen
Nitrogenase, the central enzyme in nitrogen fixation, is oxidized and
inactivated by O2
Sulfur and Phosphorous Uptake
--- both sulfate (SO4-) and phosphate (PO4-) are easily taken upand utilized from the environment if they are available
With sources of the basic chemical building blocks: C, N, O, S, & P mostbacteria can synthesize all 20 commonly appearing amino acidsthe 5 nucleic acid bases as well as the lipids and simple sugars
--- this broad spectrum synthetic ability is what has freed the morecomplex life forms from much of the biosynthetic loadof maintaining ready sources of monomers of the 4 basicbiomolecule types