Chapter 10 Biosynthesis (anabolism) Goal: produce monomers of the four biomolecules

1. 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 cell growth directly, whereas we are more used to thinking of animals that get many of their monomers from food. --- The simplest building blocks for biosynthesis are the one carbon, oxidized molecules such as CO2 (carbon fixation)

2. Use of Reduced Carbon Compounds: Reduced Carbon Compounds Energy & Reducing Equivalents (ATP & NADH) Monomer Biosynthesis Biomolecules

3. Core Biochemical Pathways: One Carbon Fixation Pathways Calvin Cycle Glycolysis (Embden-Meyerhof pathway) Hexose monophosphate shunt Entner-Doudoroff pathway TCA (Kreb’s) cycle Glyoxylate cycle anabolism catabolism

4. Other Ways to “Fix” Carbon Green Sulfur Bacteria --- run TCA cycle in reverse Chloroflexis --- Hydroxypropionate pathway, transfer malate to other pathways Acetogenic bacteria --- CO dehydrogenase pathway (chemoautotrophs) transfers acetate to other pathways Methane OR Methanol --- serine/ formaldehyde pathway modified, reversed TCA cycle --- ribulose monophosphate/ formaldehyde pathway, modified Calvin cycle,

5. Calvin-Benson Cycle (“Dark Reactions” of Photosynthesis) --- while many autotrophic prokaryotes use the Calvin cycle it is not the only option as is the case among the eukaryotes --- the point of the Calvin cycle is to “fix” carbon, create reduced carbon compounds that can be used for biosynthesis or stored for later conversion 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 sit around and wait

6. 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

7. Hexose Monophosphate Shunt (HMS) --- produces NADPH from Glucose --- end product useful for nucleotide biosynthesis and the Calvin cycle

8. Entner-Doudoroff pathway (ED) --- variation of gylcolysis produces only 1 net ATP but also 1 NADPH

9. TCA cycle --- 3 CO2 produced --- 3 NADH --- 1 FADH2 --- 1 ATP --- multiple precusors for biosynthesis

10. 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

11. 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

12. Sulfur and Phosphorous Uptake --- both sulfate (SO4-) and phosphate (PO4-) are easily taken up and utilized from the environment if they are available With sources of the basic chemical building blocks: C, N, O, S, & P most bacteria can synthesize all 20 commonly appearing amino acids the 5 nucleic acid bases as well as the lipids and simple sugars --- this broad spectrum synthetic ability is what has freed the more complex life forms from much of the biosynthetic load of maintaining ready sources of monomers of the 4 basic biomolecule types

13. Biosynthesis Summary