Cell  metabolism  

•  Metabolism:  –  is  the  set  of  life  sustaining  chemical  transforma4ons  within  cells.    

–  is  usually  divided  into  two  categories:  •  Catabolism:  Breaks  down  organic  maFer  and  harvests  energy  by  way  of  cellular  respira4ons  

•  Anabolism:  Uses  energy  to  construct  components  of  cells  such  as  proteins  and  nucleic  acids.  

pensum  

Van  Holde,  Biochemistry  

pensum  

Metabolic  Diversity  (1)    

•  The diversity in microbial cells is the product of almost 4 billion years of evolution

•  Microorganisms differ in size, shape, motility, physiology, pathogenicity, etc.

•  Microorganisms have exploited every conceivable means of obtaining energy from the environment

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pensum  

Figure  2.18  

Organic chemicals

Inorganic chemicals

Chemotrophy Phototrophy

Chemicals Light

Energy Sources

(glucose, acetate, etc.) (H2, H2S, Fe2+, NH4+, etc.)

(glucose + O2 CO2 + H2O) (H2 + O2 H2O) (light)

Chemoorganotrophs Chemolithotrophs Phototrophs

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pensum  

Metabolic  Diversity    (2)    •  Chemoorganotrophs

–  Obtain their energy from the oxidation of organic molecules (Figure 2.18)

–  Aerobes use oxygen to obtain energy –  Anaerobes obtain energy in the absence of oxygen

•  Chemolithotrophs –  Obtain their energy from the oxidation of inorganic

molecules (Figure 2.18) –  Process found only in prokaryotes

•  Phototrophs –  Contain pigments that allow them to use light as an

energy source (Figure 2.18) –  Oxygenic photosynthesis produces oxygen –  Anoxygenic photosynthesis does not produce oxygen

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pensum  

Metabolic  Diversity  (3)  •  All cells require carbon as a major nutrient

–  Autotrophs •  Use carbon dioxide as their carbon source •  Sometimes referred to as primary producers

–  Heterotrophs •  Require one or more organic molecules for their carbon

source •  Feed directly on autotrophs or live off products produced

by autotrophs •  Organisms that inhabit extreme environments are

called extremophiles. Habitats include boiling hot springs, glaciers, extremely salty bodies of water, and high-pH environments

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pensum  

Lehninger,  Biochemistry  

pensum  

Van  Holde,  Biochemistry  

Pensum  unntaF  kjemisk  struktur  for  adenosin  

Energy  /  Energy  storage  •  Prime energy currency in all cells: ATP: Adenosin Triphosphate:

–  ATP -> ADP + Pi ; energy released: 32 kJ/mol

•  Energy (electron) carrier: –  NAD:  Nico4namide  adenine  dinucleo4de  –  FAD:  Flavin  adenine  dinucleo4de

•  Energy produced from catabolism and from ion channels (crossing of membranes)

•  Long-term energy storage involves insoluble polymers that can be oxidized to

generate ATP –  Examples in prokaryotes

•  Glycogen •  Poly-β-hydroxybutyrate and other

polyhydroxyalkanoates •  Elemental sulfur

–  Examples in eukaryotes •  Starch •  Lipids (simple fats)

pensum  

The  molecular  building  blocks  of  the  cells  

Macromolecules/polymers:  •  Carbohydrates  

–  Monosaccharides  (glucose)  major  building  block  –  Func4on:  Cell  wall  component  and  storage  of  energy  

•  Nucleic  acids  –  Nucleo4des  building  blocks  –  Func4on:  Informa4on  storage,  transmission  and  expression  

•  Proteins  –  Amino  acids  building  blocks  –  Func4on:  Enzymes,  Structure,  transport  

•  Lipids  (phospholipids)  –  Gycerol  and  faFy  acids  (and  phosphate)  structural  components  –  Func4on:  Membranes  (plasma  membrane  and  intracellular  compartments)  

 

 

pensum  

Glucose  metabolism  -­‐  overview  

Starch  Glycogen  

Glucose  (6C)  

Pyruvat  (3C)  

Acetyl-­‐CoA  (2C)  

CO2  

Ethanol  (2C)  +  CO2  Lac4c  acid  (3C)  Ace4c  acid  (C2)  Formic  acid  (C1)  

2  CO2  

e  -­‐  

ATP  

e  -­‐  

NAD+  +  H+  +  2e-­‐   NADH  

ATP  ADP  O2   H2O  

Fermenta4on  (without  O2)  

Respira4on  (with  O2)  

TCA  =  sitronsyresyklusen  

pensum  

pensum  

Yeast  w/wo  oxygen    (Renneberg  fig  1.20  and  text)  

•  Respira4on  (w  O2)  –  wanted  for  the  yeast  –  C6H12O6  +  6O2  -­‐>  energy  +  6CO2  +  6H2O  –  produc4on  of  cell  mass  (cell  growth/prolifera4on)  –  Energy  produced:  Up  to  38  ATP  per  glucose  molecule  –  Produc4on  of  energy  via  glycolysis  and  TCA  

•  Fermenta4on  (wo  O2)  –  not  ideal  for  the  yeast  –  C6H12O6  -­‐>  2C2H5O2  +  2CO2  –  Far  less  produc4on  of  cell  mass  than  under  respira4on  (5%)  –  Energy  produced:  1-­‐4  ATP  per  glucose  molecule  –  Because  of  need  of  energy,  produced  by  glycolysis  of  glucose  to  pyruvate,  a  higher  throughput  of  mass  is  needed  and  hence  a  larger  consump4on  of  glucose  and  produc4on  of  by-­‐products  (e.g.  ethanol)(Pasteur  effect)  

pensum  

Gjær  m/u  oksygen  •  M/u  oksygen  bestemmer  genuFrykk  

– Når  O2  blir  lav  endres  genuFrykk  slik  at  andre  enzymer  uFrykkes  i  anaerob  metabolisme  versus  aerob  metabolisme  

•  Anaerob  fermentering,  andre  mikroorganismer  – Melkesyre  (Lactobacillus)  (pluss  flere  eksempler):  Biprodukt  under  produksjon  av  ATP  ved  anaerobe  be4ngelser  

 

pensum  

pensum  

Cell  metabolism  -­‐  overview  •  Metabolism  defini4on  

–  What  is  cell  metabolism?  •  Metabolic  diversity  

–  How  do  different  microorganism  obtain  energy?  Carbon?  •  Energy  carriers  

–  What  are  important  long  term  and  short  term  energy  carriers  in  the  cells?  •  Cellular  macromolecules  

–  What  are  the  major  cellular  macromolecules  and  what  are  their  building  blocks  •  Transforma4on  of  glucose  to  relevant  products  

–  Give  three  relevant  biotechnological  products  from  glucose  metabolism  (names  and  relevance)  

•  No  oxygen  present:  Produc4on  of  ethanol  or  lac4c  acid  –  What  are  the  products  of  respira4on  and  fermenta4on  in  yeast  

•  Major  metabolic  pathways  –  Glucose  can  eventually  be  metabolized  to  polysaccharides,  DNA/RNA,  proteins,  

and  phospholipids.  What  are  the  star4ng  metabolite(s)  seen  from  the  glycolysis  for  the  various  macromolecules?  (this  is  beyond  “pensum”)  

•  Ethics?  –  Are  there  any  ethical  concerns  related  to  what  we  have  learned  in  Chapter  1  and  

about  cells  and  cell  metabolism?