bacterial physiology part1, Lecture notes of Chemistry

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Chapter 8: Microbial Metabolism-

the Chemical Crossroads of Life

The Metabolism of Microbes

• (^) Metabolism : All chemical reactions and physical workings

of the cell

• (^) Anabolism : also called biosynthesis- any process that

results in synthesis of cell molecules and structures (usually

requires energy input)

• (^) Catabolism : the breakdown of bonds of larger molecules

into smaller molecules (often release energy)

• (^) Functions of metabolism
  • (^) Assembles smaller molecules into larger macromolecules needed for the cell
  • (^) Degrades macromolecules into smaller molecules and yields energy
  • (^) Energy is conserved in the form of ATP or heat

How do Enzymes Work?

• (^) Energy of activation: the amount of energy which must be overcome for a reaction to proceed. Can be achieved by: - (^) Increasing thermal energy to increase molecular velocity - (^) Increasing the concentration of reactants to increase the rate of molecular collisions - (^) Adding a catalyst
• (^) An enzyme promotes a reaction by serving as a physical site upon which the reactant molecules ( substrates ) can be positioned for various interactions

Enzyme-Substrate Interactions

• (^) For a reaction to take place, a temporary enzyme- substrate union must occur at the active site
• (^) “Lock-and-key” fit
• (^) The bonds are weak and easily reversible

Cofactors: Supporting the Work of Enzymes

• (^) Metallic cofactors
  • (^) Include Fe, Cu, Mg, Mn, Zn, Co, Se
  • (^) Metals activate enzymes, help bring the active site and substrate close together, and participate directly in chemical reactions with the enzyme-substrate complex
• (^) Coenzymes
  • (^) Organic compounds that work in conjunction with an apoenzyme to perform a necessary alteration of a substrate
  • (^) Removes a chemical group from one substrate molecule and adds it to another substrate
  • (^) Vitamins : one of the most important components of coenzymes

Classification of Enzyme

Functions

• Site of action

• Type of action

• Substrate

Rate of Enzyme Production

• Enzymes are not all produced in the cell in

equal amounts or at equal rates

• (^) Constitutive enzymes : always present and in relatively constant amounts
• (^) Regulated enzymes : production is either induced or repressed in response to a change in concentration of the substrate

Synthesis and Hydrolysis Reactions

Figure 8.

Transfer Reactions by Enzymes

• (^) Oxidation-reduction reactions
  • (^) A compound loses electrons ( oxidized )
  • (^) A compound receives electrons ( reduced )
  • (^) Common in the cell
  • (^) Important components- oxidoreductases
• (^) Other enzymes that play a role in necessary molecular conversions by directing the transfer of functional groups: - (^) Aminotransferases - (^) Phosphotransferases - (^) Methyltranferases - (^) Decarboxylases