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Microbiology. Chapter 8. Part I. Enzymes. Enzymes Catalyze Chemical Reactions of Life. Increase reaction rates without being consumed by the reaction Lower the activation energy Active site is where the substrate binds Active site is where chemistry happens

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Chapter 8

Part i

Part I


Enzymes catalyze chemical reactions of life

Enzymes Catalyze Chemical Reactions of Life

  • Increase reaction rates without being consumed by the reaction

  • Lower the activation energy

  • Active site is where the substrate binds

  • Active site is where chemistry happens

    • Chemistry is performed by side chains of amino acids

    • Cofactors or coenzymes

  • Active site has specificity

Reaction coordinate

Reaction Coordinate

  • Description of energy changes during the reaction

  • Horizontal axis is charts the progessive chemical changes (bond breakage/bond formation) as S is converted into P

  • Vertical axis represents Energy

  • Transition state – not a reaction intermediate

    • Fleeting molecular moment in which bond breakage, bond formation are happening

Reaction coordinate1

Reaction Coordinate

∆G’º = -RTlnK’eq

Just because delta G is favorable

does not mean that the reaction is


Enzyme terminology

Enzyme Terminology

  • Holoenzyme

    • Is a combination of protein (apoenzyme) and one or more cofactors

  • Cofactors

    • Coenzyme – complex organic molecules

    • Metal ions

Enzyme structure

Enzyme Structure

  • Holoenzyme

    • Apoenzyme – protein

    • Cofactors – complex organic molecules

    • Coenzyme – metal ions

  • Active site usually contains the cofactors and coenzymes because they are crucial for the chemistry



Enzyme substrate interactions

Enzyme Substrate Interactions

  • Specificity of active site – induced fit

  • Bonds between substrate and enzyme are weak and reversible

  • Once the enzyme substrate complex has formed chemical reactions occur on the substrate and the product is released

  • Most enzyme reactions are reversible with the exception of enzymes which regulate metabolic pathways

Lysozyme reaction

Lysozyme Reaction

Lysozyme reaction1

Lysozyme Reaction

Types of enzyme inhibition

Types of Enzyme Inhibition

Enzyme location

Enzyme Location

Synthesis and hydrolysis reactions

Synthesis and Hydrolysis Reactions

Enzymes in disease

Enzymes in Disease

  • Virulence Factors

  • Enzymes that are excreted from microorganisms that contribute to the pathogenicity of diseases

Virulence factors

Virulence Factors

  • Streptococcus pyogenes – throat and skin infections

    • Streptokinase – digests blood clots and assists in wound invasion

  • Pseudomonas aeruginose – respiratory and skin pathogen

    • Elastase and collagenase digestive enzymes

  • Clostridium perfringens – gas gangrene

    • Lecithinase C lipase damages cell membranes; therefore massive tissue death

Virulence factors1

Virulence Factors

  • Not all virulence factors secrete enzymes which digest tissues

  • Can protect microbes from effects of drug therapy

  • Penicillinase

    • Inactivates penicillin

Enzymes and their environment

Enzymes and Their Environment

  • Why do you think enzymes only function properly under established conditions of pH, temperature

  • Why do you think agents such as heavy metals and alcohol also have the ability to denature enzymes

  • Take a look at enzyme structure

Part ii

Part II


Metabolism in microbes

Metabolism In Microbes

  • All chemical reactions of a cell

  • Two general classes

    • Anabolism or biosynthesis

    • Catabolism or degradative reactions

Simplified model of metabolism

Simplified Model of Metabolism

Metabolic pathways

Metabolic Pathways

  • The product of one reaction is often the substrate for the next

  • Every pathway has one or more regulatory enzymes

  • All other enzymes in the pathway usually are not regulated

    • They operate whenever the substrate is available

Cell energetics

Cell Energetics

  • Not all cellular reactions are equal with respect to energy

  • Exergonic – Energy Released

  • Endergonic – Energy Requiring

Energy conversions

Energy Conversions

Three stages of metabolism

Three Stages of Metabolism

Glycolysis part i

Glycolysis – Part I

Glycolysis part ii

Glycolysis – Part II

Gap to 1 3 bpg

GAP to 1,3 BPG

Pyruvate dehydrogenase complex

Pyruvate Dehydrogenase Complex

Tca cycle

TCA Cycle

Structure of fad and nad

Structure of FAD and NAD+

  • Both are electron carriers in the ETC

What is the purpose of nadh

What is the purpose of NADH

  • The electron transport chain transfers electrons from NADH to other electron carriers

  • The electrons end up on various molecules

  • However, electron movement is associated with making a proton gradient

  • Proton gradient is responsible for ATP production



Electron transport chain

Electron Transport Chain

Electron transport chain1

Electron Transport Chain

Electron transport chain2

Electron Transport Chain

Etc in humans

ETC in Humans

Atp synthase

ATP Synthase

Is respiration coupled to atp synthase

Is Respiration Coupled to ATP Synthase?



  • How could you uncouple the ETC from the production of ATP

  • What if you treated a cell with a weak hydophobic acid such as FCCP or DNP

Dnp caused uncoupling

DNP Caused Uncoupling

Aerobic respiration

Aerobic Respiration

  • Characteristic of many bacteria, fungi, protozoa, and animals

  • Electrons and hydrogen are taken from highly reduced, high energy compounds

  • Electrons and hydrogen end up on O2 to form H20

  • Much ATP is made

Nutrient processing

Nutrient Processing

  • Extremely varied in bacteria

  • Remember Microbes are classified according to their O2 requirements

    • Aerobic respiration

    • Anaerobic respiration

    • Fermentation

Anaerobic respiration

Anaerobic Respiration

  • System involves the same three pathways as aerobic respiration

  • Final electron acceptor is not 02 but instead NO3-, SO4-, CO3-

Final electron acceptors

Final Electron Acceptors

Electron transport in plants

Electron Transport In Plants

Comparison of etc and atp synthesis

Comparison of ETC and ATP Synthesis

Other fates of pyruvate

Other Fates of Pyruvate

  • Fermentation products can be grouped into two general categories

  • Alcoholic fermentation

  • Acidic fermentation

Other fates of pyruvate1

Other Fates of Pyruvate

Anaerobic metabolism

Anaerobic Metabolism



Alcoholic fermentation

Homolactic acid fermentation

Many fermentation pathways

Many Fermentation Pathways

Other energy sources

Other Energy Sources

  • Glucose is a major source of energy

  • However, for any other organic substance usually there exists a microorganism that can degrade that substance for energy

  • Fats

  • Proteins

  • Any other organic molecule

Fat metabolism

Fat Metabolism

Protein metabolism

Protein Metabolism

Metabolism of the major classes of biomolecules

Metabolism of the Major Classes of Biomolecules

Final electron acceptors1

Final Electron Acceptors

Energy accounting

Energy Accounting

A comparison of metabolic processes

A Comparison of Metabolic Processes

Metabolism crossroads

Metabolism Crossroads

Interconnecting pathways

Interconnecting Pathways

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