3.2 - Environmental Impacts on Enzyme Function

3.2 - Environmental Impacts on Enzyme Function 

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1. Enzyme Structure & Denaturation 

• Enzymes have a unique 3D shape (tertiary structure)  

• Change in 3D shape of the enzyme = denaturation 

  • Caused by changes in temperature or pH 

  • Denaturation is typically irreversible 

    • The catalytic ability of the enzyme is lost or severely decreased 

  • Denaturation is sometimes reversible  

    • This allows the enzyme to regain its catalytic activity 

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2. Temperature Effects 

• Optimal Temperature 

  • Range where enzyme activity is the fastest 

• Increased Temperature 

  • Initial increase in temperature -> faster molecular movement + more enzyme-substrate collisions 

  • Once the temperature increases outside of its optimal range, the enzyme denatures 

• Decreased Temperature 

  • Slow molecular movement -> fewer enzyme-substrate collisions 

  • No denaturation or disruption of enzyme structure, just reduced reaction rate 

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3. pH Effects 

• pH = hydrogen ion concentration in a solution (measured on a log scale) 

  • (-log{H⁺} 

• Small changes in pH values = large shifts in hydrogen ion concentration (10x difference in H⁺ concentration) 

• Optimal pH 

  • Fastest enzyme reaction rate  

• Enzyme denaturation can occur as a result of increases or decreases outside of optimal pH 

• Changes in hydrogen ion concentration can disrupt hydrogen bonds maintaining enzyme structure 

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4. Substrate and Product Concentration 

• Substrate Concentration 

  • Initial increase in substrate concentration -> increased reaction rate 

  • More substrates = more opportunities to collide with enzymes 

  • Substrate saturation -> no further increase in reaction rate + will remain constant if saturation levels are maintained 

• Product Concentration 

  • More products -> fewer chances for enzyme-substrate collisions -> slower reaction rate 

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5. Enzyme Concentration 

• More enzymes = faster reaction rate (more active sites available) 

• Less enzymes = slower reaction rate (less active sties available) 

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6. Inhibitors 

• Competitive Inhibitors 

  • Bind to active site (reversible or irreversible) 

  • Compete with substrate for binding 

  • If inhibitor concentrations > substrate concentration  -> reactions are slowed 

  • If inhibitor concentration < substrate concentration -> reactions can proceed normally 

  •  If inhibitor binding is irreversible -> enzyme function will be prevented  

  • If inhibitor binding is reversibly -> enzyme can regain its function once inhibitor detaches 

• Noncompetitive Inhibitors 

  • Bind to allosteric site (not active site) 

  • Binding causes changes to the 3D structure of the enzyme 

  • Binding prevents enzyme function -> active site is not available anymore  

  • Cannot be overcome by increasing substrate