1. Microbial Metabolism
Metabolism: Energy and Enzymes

2. METABOLISM
From the Greek term, metaballein,
meaning change.
Pertains to all chemical reactions and
physical workings of the cell.

3. Energy
Defined as the capacity to do work or to
cause particular changes.
Cellular metabolism – the totality of all
chemical reactions that a cell carries
out.
Metabolism- obtain energy and
materials for growth.

4. ATP
Is the central chemical in the energy
transformations of cellular metabolism
ATP cannot be stored for long periods
of time so it must be continually made.

5. Role of Enzymes
Cellular metabolism is based on
chemical reactions catalyzed by
enzymes.
Enzymes are biological catalysts –
accelerate the rates of chemical
reactions.
Most are proteins but a very few are
RNA.

6. ENZYMES
How do they work???

7. Enzymes
Increase rates of a cell’s chemical
reactions by more than a million times.
Energy is required for a chemical
reaction to occur. Enzymes lower
activation energy.

8. Energy of Activation
Increasing thermal energy (heating),
which increases molecular velocity
Increasing the concentration of
reactants, or
Adding a catalyst

11. Enzymes
Exhibit high degree of substrate
specificity.
The enzymes a particular cell
synthesizes will determine which
chemical reactions occur in cellular
metabolism of that cell.
Substrate + E  E-S complex  E +
Product

14. Enzyme Structure
Enzymes can be classified as simple or
conjugated.
Simple – consist of protein alone
Conjugated – protein + nonprotein

15. Enzyme Anatomy
Active Site
Allosteric Site
Co enzyme
Cofactor
Apoenzyme
Holoenzyme

16. Prosthetic Groups

17. Active Site

19. Competitive Inhibition

21. Apoenzyme: Specificity and the Active
Site
Range in size
Exhibit levels of molecular complexity

22. Enzyme Specificity
The apoenzyme of each enzyme differs
from others in its primary structure
Nuances in polypeptide folding
Surface features of the tertiary
structure provide a unique and specific
site

23. Coenzymes
Activities many and varied
Vitamins

24. Classification of Enzyme Function
Site of action
Type of action
Type of substrate

25. Location & Regularity of Enzyme
Action
Exoenzymes – ex.
Penicillinase, lipase,
proteases
Endoenzymes – ex.
Metabolic pathway
enzymes

26. Enzymes
Constitutive
Induced

27. Synthesis & Hydrolysis Reactions
Bacterial cells are constantly in a frenzy
of activity, constantly synthesizing
proteins, DNA, and RNA.
Anabolic Reactions – Condensation
Reactions
Require ATP
Catabolic Reactions – Hydrolysis
Reactions

28. Transfer Reactions by Enzymes
Addition or removal of a functional
group are important to the overall
economy of the cell.
Oxidation – Reduction reactions
Important in metabolic pathways
Role in molecular conversions

29. The Role of Microbial Enzymes in
Disease
Exoenzymes which help bacteria avoid
host defenses or promote their
multiplication in tissues.
Virulence factors or toxins:
Streptococcus pyogenes (streptokinase,
protease); Staphylococcus aureus
(lipases); Pseudomonas aeruginosa
(elastase, collangenase)

30. The Role of Microbial Enzymes in
Disease
Clostridium perfringens (lecithinase C,
lipase)

33. The Sensitivity of Enzymes to their
Environment
Activity of an enzyme is influenced by
the cell’s environment.
Temperature, pH, osmotic pressure
Denaturation – disruption causes
distortion of the enzyme

34. Checklist
Act as organic catalysts to speed up the
rate of cellular reactions
Are composed of protein and may
require cofactors
Have unique characteristics such as
shape, specificity, and function
Enable metabolic reactions to proceed
at a speed compatible with life

35. Checklist
Provide a reactive site for target
molecules called substrates
Associate closely with substrates but do
not become integrated into the reaction
products
Are not used up or permanently
changed by the reaction

36. Checklist
Lower the activation energy required for
a chemical reaction to proceed
Can be recycled, thus function in
extremely low concentrations
Are limited by particular conditions of
temperature and pH

37. Metabolic Pathways and Carbon Flow
The enzymatically mediated metabolic
reactions of a cell proceed via a series
of small discrete steps that establish a
metabolic pathway.
Catabolic
Anabolic

38. Metabolic Pathways
Rarely consist of a single action or step.
Each step catalyzed by an enzyme.
Pathways are interconnected and merge
at different sites.
Pacemakers – sets the rate of a
pathway’s progression.
Respond to various control signals

39. Direct Controls
Competitive Inhibition
Feedback Control
Negative Feedback

40. Controls on Enzyme Synthesis
Enzyme Repression
Enzyme Induction

41. The Pursuit and Utilization of Energy
Biosynthesis, movement, transport, or
growth could proceed without ENERGY

42. Nutritional Patterns Among Bacteria
Two criteria: Energy (E) source & Carbon
(C ) Source
Prototrophs – light as primary E source
Chemotrophs – redox reactions for E
Autotrophs – use CO2
Heterotrophs – require an organic C
source

43. Classification
Photoautotrophs
Photoheterotrophs
Chemoautotrophs
Chemoheterotrophs