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Chapter 5. Microbial Metabolism. Catabolic and Anabolic Reactions. Metabolism : The sum of the chemical reactions in an organism. Catabolic and Anabolic Reactions. Catabolism : Provides energy and building blocks for anabolism.

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Chapter 5

Chapter 5

Microbial Metabolism

Catabolic and anabolic reactions
Catabolic and Anabolic Reactions

  • Metabolism:

  • The sum of the chemical reactions in an organism

Catabolic and anabolic reactions1
Catabolic and Anabolic Reactions

  • Catabolism: Provides energy and building blocks for anabolism.

  • Anabolism: Uses energy and building blocks to build large molecules

Catabolic and anabolic reactions2
Catabolic and Anabolic Reactions

  • A metabolic pathway is a sequence of enzymatically catalyzed chemical reactions in a cell

  • Metabolic pathways are determined by enzymes

  • Enzymes are encoded by genes

Collision theory
Collision Theory

  • The collision theory states that chemical reactions can occur when atoms, ions, and molecules collide

  • Activation energy is needed to disrupt electronic configurations

  • Reaction rate is the frequency of collisions with enough energy to bring about a reaction.

  • Reaction rate can be increased by enzymes or by increasing temperature or pressure

Enzyme specificity and efficiency
Enzyme Specificity and Efficiency

  • The turnover number is generally 1 to 10,000 molecules per second

Factors influencing enzyme activity
Factors Influencing Enzyme Activity

  • Temperature

  • pH

  • Substrate concentration

  • Inhibitors

Factors influencing enzyme activity1
Factors Influencing Enzyme Activity

  • Temperature and pH denature proteins

Figure 5.6

Sulfa drugs sulfonamides discovered in the 1930s enzyme inhibitors competitive inhibition
Sulfa drugs (sulfonamides) (Discovered in the 1930s) Enzyme Inhibitors: Competitive Inhibition

Sulfa drugs
Sulfa drugs  

  • a) Structure: Chemically similar (chemical analogues) to the chemical PABA (para-aminobenzoic acid) which is required by microbes. It normally functions as a cofactor in the synthesis of nucleotide nitrogen bases. b) Mode of action: ‘Competitive Inhibition’Normal functioning when no sulfa drugs are present: PABA is used by bacteria to produce folic acid. Folic acid is a bacterial vitamin that is necessary for the production of nucleotides. What molecules are nucleotides made of?

When sulfa drugs are present competitive inhibition
When sulfa drugs are present: Competitive Inhibition

  • Since sulfa drugs are chemically similar to (analogues of) PABA, they may “trick” the enzyme into using the sulfa drug to produce folic acid instead of PABA. In effect, the sulfa drug competes with the PABA. When the enzyme is ‘tricked’, the folic acid in the bacterial cell is defective and will not produce nitrogen bases. It there is a shortage of nitrogen bases, DNA cannot be replicated, and therefore, growth stops (no binary fission). The bacterial cell has been inhibited from reproducing.

Energy production the cell s currency atp and i mean all cells
Energy Production The cell’s ‘currency’ = ATP. And I mean ALL cells.

The generation of atp
The Generation of ATP

  • ATP is generated by the phosphorylation of ADP

3 ways atp is produced in living cells
3 Ways ATP is Produced in Living Cells

  • Substrate-Level Phosphorylation.

    • Occurs during glycolysis (or alternate pathway) during

      • Fermentation (in Microbes and our

  • own skeletal muscle cells and brain

  • Cells)

  • b. Respiration: Glycolysis and Krebs Cycle

  • 2. Oxidative Phosphorylation

  • Occurs during respiratory e- transport chains

  • (aerobic or anaerobic)

  • 3. Photophosphorylation.

  • Occurs during photosynthesis

  • Substrate level phosphorylation
    Substrate-Level Phosphorylation

    • A chemical reaction where a phosphate group is transferred from one molecule to ADP. This requires a specific enzyme that can transfer the phosphate from this specific molecule to ADP.

    • This is how the process of FERMENTATION produces ATP.

    Oxidation reduction reactions
    Oxidation-Reduction Reactions

    • Oxidation: Removal of electrons. The general process of electron donation to an electron acceptor is also referred to as oxidation even though the electron acceptor may not be oxygen.

    • Reduction: Gain of electrons

    • Redox reaction: An oxidation reaction paired with a reduction reaction


    • Light causes chlorophyll to give up electrons. The electrons go through a process similar to what happens during respiration (an electron transport chain and chemiosmosis). This process releases energy used to bond a phosphate to ADP producing ATP.

    • The ATP produced is used to produce food molecules (sugars-glucose).

    Oxidation reduction reactions1
    Oxidation-Reduction Reactions

    • In biological systems, the electrons are often associated with hydrogen atoms. Biological oxidations are often dehydrogenations.

    Oxidative phosphorylation
    Oxidative Phosphorylation

    • Energy released from transfer of electrons (oxidation) of one compound to another (reduction) is used to generate ATP in the electron transport chain

    • An electron transport chain(ETC) couples a chemical reaction between an electron donor (such as NADH) and an electron acceptor (such as O2) to the transfer of H+ ions across a membrane, through a set of mediating biochemical reactions.

    Carbohydrate catabolism
    Carbohydrate Catabolism

    • The breakdown of carbohydrates to release energy

      • Glycolysis (or alternative)

      • Preparatory Step

      • Krebs cycle

      • Electron transport chain

        • Chemiosmosis

        • ADP Phosphorylation


    • The oxidation of glucose to pyruvic acid produces ATP and NADH

    Figure 5.11

    Preparatory stage of glycolysis
    Preparatory Stage of Glycolysis

    • 2 ATP are used

    • Glucose is split to form 2 glucose-3-phosphate

    Figure 5.12, steps 1–5

    Energy conserving stage of glycolysis
    Energy-Conserving Stage of Glycolysis

    • 2 glucose-3-phosphate oxidized to 2 pyruvic acid

    • 4 ATP produced

    • 2 NADH produced

    Figure 5.12, steps 6–10


    • Glucose + 2 ATP + 2 ADP + 2 PO4– + 2 NAD+ 2 pyruvic acid + 4 ATP + 2 NADH + 2H+

    Alternatives to glycolysis
    Alternatives to Glycolysis

    • Pentose phosphate pathway

      • Produces pentoses (Any of a class of monosaccharides having five carbon atoms per molecule and including ribose and several other sugars) and NADPH (used by photosynthetic organisms) and certain amino acids

      • Only net 1 ATP

      • Bacillus subtilis, E. coli

    • Entner-Doudoroff pathway

      • Produces NADPH (photosynthesis) and net 1ATP

      • Pseudomonas, Agrobacterium

    Preparatory step intermediate between glycolysis and krebs cycle
    Preparatory Step Intermediate between Glycolysis and Krebs Cycle

    • Pyruvic acid (from glycolysis) is oxidized and decarboyxlated

    Figure 5.13

    The krebs cycle
    The Krebs Cycle Cycle

    • Series of biochemical reactions in which the large amount of chemical energy now in actyl CoA is released step by step in a series of redox reactions

    • Oxidation of acetyl CoA produces NADH and FADH2

    The krebs cycle1
    The Krebs Cycle Cycle

    Figure 5.13

    The electron transport chain
    The Electron Transport Chain Cycle

    • A series of carrier molecules that are, in turn, oxidized and reduced as electrons are passed down the chain

    • Energy released can be used to produce ATP by chemiosmosis

    An overview of chemiosmosis
    An Overview of Chemiosmosis Cycle

    Figure 5.15

    Respiration Cycle

    Figure 5.16

    Carbohydrate catabolism2
    Carbohydrate Catabolism Cycle

    • Energy produced from Substrate-level phosphorylation only

    Carbohydrate catabolism3
    Carbohydrate Catabolism Cycle

    • ATP produced from complete oxidation of one glucose using aerobic respiration

    • # ATPs Eukaryote vs. Prokaryote?

    A summary of respiration
    A Summary of Respiration Cycle

    • Aerobic respiration: The final electron acceptor in the electron transport chain is molecular oxygen (O2).

    • Anaerobic respiration: The final electron acceptor in the electron transport chain is not O2. Yields less energy than aerobic respiration because only part of the Krebs cycles operates under anaerobic conditions.

    Fermentation Cycle

    • FERMENTATION Scientific definition:

      • Releases energy from oxidation of organic molecules

      • Does not require oxygen

      • Does not use the Krebs cycle or ETC

      • Uses an organic molecule as the final electron acceptor

    An overview of fermentation
    An Overview of Fermentation Cycle

    Figure 5.18a

    End products of fermentation
    End-Products of Fermentation Cycle

    Figure 5.18b

    Types of fermentation
    Types of Fermentation Cycle

    Figure 5.19

    Types of fermentation1
    Types of Fermentation Cycle

    Table 5.4

    Types of fermentation2
    Types of Fermentation Cycle

    Table 5.4

    Photosynthesis Cycle

    Figure 4.15

    Photosynthesis Cycle

    • Conversion of light energy into chemical energy (ATP) and nutrients (glucose)

    • Overall Summary Reaction?

    Photosynthesis Cycle

    • Compare and Contrast

    • Oxidative Phosphorylation and Photophosphorylation.

    Photosynthesis Cycle

    • Oxygenic:

    • Anoxygenic:

    Metabolic diversity among organisms see fig 5 28 p 143
    Metabolic Diversity among Organisms CycleSee Fig. 5.28 p. 143

    Amphibolic pathways
    Amphibolic Pathways Cycle

    Figure 5.33

    Amphibolic pathways1
    Amphibolic Pathways Cycle

    Figure 5.33