ENZYMES VIDEO

• Rate of enzyme-controlled reactions

  Depends on the frequency of successful collisions between the substrate and the active site of the enzyme
• Frequency

  • Number of collisions per second
• Calculating the rate of an enzyme-controlled reaction

  Plot the amount of product formed against time, draw a tangent at the point of interest
• Effect of temperature on the rate of an enzyme-controlled reaction

  Select an enzyme, measure the amount of product formed with time at different temperatures, draw tangents to measure the rate of reaction at each temperature
• Optimum temperature


  • For human enzymes, around 40 degrees Celsius
• Optimum temperature for bacteria living in hot springs

  • Around 70 to 80 degrees Celsius
• As temperature increases past the optimum

  The rate of reaction decreases
• Denaturation of enzymes

  • Occurs at higher temperatures when enzyme molecules vibrate more rapidly, causing bonds within the enzyme to break and the tertiary structure to change, leading to the active site no longer being complementary to the substrate
• Enzymes cannot renature after denaturation due to high temperatures
• Temperature coefficient (Q10)

  • Measure the rate of reaction at a certain temperature and at a temperature 10 degrees Celsius higher, then calculate the rate ratio, usually around two
• Q10 does not apply above the optimum temperature as enzymes denature
• End product inhibition in regulating metabolic pathways

  Final product in the pathway inhibits an early stage enzyme, reducing the rate of the metabolic pathway
• Competitive inhibitors

  • Have a structure similar to the substrate, binding to the active site to prevent substrate binding and inhibit enzyme activity
• Non-competitive inhibitors

  • Do not bind to the active site, instead bind to the allosteric site causing a change in enzyme structure, reducing enzyme activity
• Metabolic pathway

  • Series of reactions catalyzed by enzymes where products of one reaction become substrates for the next
• Metabolic pathways

  • Respiration breaks down glucose to release energy, production of amino acids from smaller molecules
• End product inhibition

  Final product inhibits an early stage enzyme, reducing the rate of the metabolic pathway
• End product inhibition is used to regulate metabolic pathways by reducing the rate of the pathway when the final product is not needed in large amounts
• End product inhibition is an example of negative feedback, keeping key molecule levels within a set range
• End product inhibition is an example of non-competitive inhibition as it takes place through the allosteric site of the enzyme