1. 5-a
Microbial Metabolism
pp ;

2. Chapter 5 Overview Metabolism Enzymes
Common energy pathways used by microbes
Fermentation
Aerobic respiration
Anaerobic respiration
Metabolic diversity among organisms

3. Metabolism Energy-Balancing Process Release energy Requires energy
Catabolism
Breakdown of molecules
Sugar  CO2 + H20
Provides ‘building blocks’ for anabolism
Provides energy for anabolism
ATP  ADP + energy
Requires energy
Anabolism
Synthesis of molecules
Amino acids  protein
Provides molecules for catabolism
Provides ATP for catabolism
ADP + energy  ATP
Molecule breakdown coupled with molecules synthesized

4. Enzymes …Enable Energy-Balancing Process
Are a catalyst = speed up reaction
Increase the reaction rate
Lower the energy of activation
Are not altered in the reaction
Are highly specific
Each acts on a specific substance, the substrate
Each catalyzes only one reaction

5. Enzymes AB  A + B Provide a structure, a framework
To allow collisions to occur
And the chemical reaction to occur
AB  A + B
Substrate
Products

6. Energy Requirements - Chemical Reaction
The reaction is: AB  A + B
Fig. 5.2

7. Mechanism of Enzymatic Action:
Fig. 5.4a
When an enzyme and substrate combine:
The substrate is transformed, to products
And the enzyme is recovered, unaltered
Turnover number ~ 1-10,000 molecules per second

8. Naming enzymes: Enzyme classification: Names usually end in –ase
Based on the type of chemical reaction they catalyze
Example: oxidoreductases (ox-redox rxns)
Within each class, named for the specific reaction
If remove hydrogen, called dehydrogenases

9. Enzyme classification (6 classes):

10. Enzyme Components Some enzymes consist only of protein
Most consist of both a protein and a non-protein component
The protein called an apoenzyme
The non-protein part called a cofactor
Cofactors are
Ions of iron, zinc, magnesium, calcium etc*
If a cofactor is an organic molecule, it is called a:
Coenzyme
* p. 119

11. Apoenzymes are inactive by themselves Apoenzymes + cofactors form a
They must be activated by cofactors
Apoenzymes + cofactors form a
Holoenzyme +
Fig. 5.3

12. Enzyme & Cofactors NAD+ NADP+ FMN, FAD Coenzyme A
Nicotinamide adenine dinucleotide
Nicotinamide adenine dinucleotide phosphate
Flavin mononucleotide, Flavin adenine dinucleotide
Important in the Krebs cycle

13. Enzymes are characterized by specificity
Fig. 5.4b
Enzymes are characterized by specificity
Specificity is a function of their active sites (see ‘groove’)
Enzyme + substrate = slight shape change
* Animation: Enzyme–Substrate Interactions. The Microbiology Place.

14. Organisms - Metabolic Diversity
Chemotrophs
Oxidation-reduction reactions of organic or inorganic compounds for energy
Phototrophs
Use light as primary source of energy
Autotrophs
Use CO2 for principal carbon source
Heterotrophs
Use organic carbon source

15. Combine Energy & Carbon
Photoautotrophs
Energy = light; carbon = CO2
Photoheterotrophs
Energy = light; carbon = organic source
Chemoautotrophs
Energy = organic or inorganic compounds; carbon = CO2
Chemoheterotrophs*
Energy = organic or inorganic compounds; carbon = organic source

16. Nutritional Classification of Organisms
Fig. 5.27

17. Q’s All of the following are enzymes except:
Threonine deamainase
Acetyl
Peroxidase
Urease
Enzymes work most effectively at their optimal temperature and pH.
True b. False

18. Q’s
Beggiatoa bacteria use carbon dioxide for their carbon source and hydrogen sulfide as an energy source. This organism is a:
Photoheterotroph
Chemoheterotroph
Photoautotroph
Chemoautotroph
Hint: Fig. 5.27

19. Q’s
In the figure shown, what is the small organic molecule called that is needed to activate the apoenzyme?
A. Holoenzyme B. Enzyme C. Coenzyme D. Substrate E. Reactant

20. Q’s A dehydrogenase is an example of a/an _____________?
Nitrobacter bacteria use CO2 for their carbon source and nitrate ions as an energy source. This organism is a:
Chemoautotroph
Chemoheterotroph
Photoheterotroph
Photoautotroph
Hint: Fig. 5.27

21. Q’s
A coenzyme assists an enzyme by accepting or donating matter. What does NAD+ transfer?
CoA
Electrons
Acetyl groups
ATP
Hint: Table 5.2

22. Q’s
Organisms that use carbon dioxide as a carbon source and energy sources such as ammonia or hydrogen sulfide are called:
Photoautotrophs
Photoheterotrophs
Chemoheterotrophs
Chemoautotrophs
Hint: Fig. 5.27

23. Q’s Organism Carbon Source Energy Source Photoautotroph
Fill in the blanks:
Organism
Carbon Source
Energy Source
Photoautotroph
Photoheterotroph
Chemoautotroph
Chemoheterotroph