enzyme mark scheme perfect

• What happens to the rate of reaction when enzyme concentration increases with excess substrate?

  The rate of reaction is directly proportional to enzyme concentration.
• Why does the rate of reaction increase when enzyme concentration increases with excess substrate?

  More active sites become available for substrate molecules to bind, forming more enzyme-substrate complexes.
• What is the effect of increasing enzyme concentration when substrate is in excess?

  It leads to an increase in the number of products formed, thus increasing the rate of reaction.
• What occurs when substrate is the limiting factor and enzyme concentration is increased?

  Increasing enzyme concentration has no further effect on the rate of reaction after a certain point.
• What happens to the active sites when substrate is limiting and enzyme concentration is increased?

  There are more active sites than available substrates to bind, leading to a maximum rate being reached.
• What is the relationship between enzyme concentration and rate of reaction when substrate is in excess?

  • Rate of reaction is directly proportional to enzyme concentration.
  • More active sites become available.
  • More enzyme-substrate complexes are formed.
  • Increased product formation leads to a higher reaction rate.
• What occurs when substrate is the limiting factor in relation to enzyme concentration?

  • Increasing enzyme concentration has no further effect on the rate after a certain point.
  • Maximum rate is reached when there are more active sites than substrates.
• What happens to the rate of reaction as substrate concentration increases?

  The rate of reaction increases
• Why does the rate of reaction increase with substrate concentration?

  More collisions between substrates and active sites occur
• What is formed when enzyme and substrate molecules collide?

  Enzyme-substrate complexes
• What is the result of more enzyme-substrate complexes being formed?

  More products are formed
• What happens to the rate of reaction after a certain point of increasing substrate concentration?

  The rate of reaction will not increase any further
• What is the point called when all active sites are occupied with substrates?

  Vmax
• What does Vmax represent in enzyme kinetics?

  It represents the fastest rate at which enzymes are working
• How does increasing substrate concentration affect enzyme activity until Vmax is reached?

  It increases enzyme activity until all active sites are occupied
• If the substrate concentration continues to increase after reaching Vmax, what will happen to the rate of reaction?

  The rate of reaction will remain constant
• explain the importance of the tertiary structure to the functioning of an enzyme


  tertiary structure determines the 3D shape of enzyme

  it forms the active site

  active site has specific tertiary structure

  shape of active site is complementary to substrate

  substrate can fit and bend to the active site

  if tertiary structure inccorect or damaged the enzyme cannot function

  active site is denatured
• described and explain the graph when the ph is too high or too low

  reducing or increasing the ph away from the optimum decreases the rate of reaction

  change in hydrogen concentration can

  disrupt or brak h or ionic bonds

  change order of amino acids in the active site

  change tertiary structure meaning chnage in active site

  enzyme can denature

  active site is no longer complementary to substrate

  less enzyme substrate complexes, so rate decreases
• describe and explain the graph when the ph is at its optimum


  the ph where the rate of reaction is fastesr is called optimum ph

  at optimum ph tertiary structure is complementary to substarte

  enzyme substrate complexes form, so rate is at its highest or fastes
• non competative inhibitors


  non competative bind to enzyme away from the active site at the allosteric site

  binding disrupts the tertiary structure of active site

  this chnages shape of active site bso substrate can no longer bind as not complementary, esc cannot form

  addition of a non competative inhibitor decreases rate of reaction
• competative inhibitors


  they compete with substrates for the active site

  when binding no substrates can then bind

  meaning less or no esc formed so less product is made

  meaning a decrease in rate of reaction

  to get rid of this issue increase concentration of enzymes
• describe and explain how temperature affects enzyme activity


  Rate of reaction rapidly decreases as temperature increases, as enzymes have denatured due to high temperature

  Above optimum, enzyme vibrates more until hydrogen bonds maintaining the tertiary structure break, so shape of active site changes enzymes denatured. Less esc formed as active sites no longer complementary, so rate decreases rapidly
• describe and explain how temperature affects enzyme activity


  as temperature increases the rate increases too, then increases rapidly

  At low temperature less kinetic energy meaning less collisions between enzyme active site and substrate, meaning rate is low

  As temperature increases more kinetic energy so more frequent collisions between active site and substrate so more esc and more products meaning rate is increased

  Graph peaks as temperature increasesrate of reaction has reached optimum for enzyme activity.

  Optimum temerature where collisions between substrate rate of reaction is fastest
• enzymes are


  -catalysts that speed up rate of reaction but remain unchanged and can be reused

  -globular proteins with specific primary structure

  -coiled to a precised 3d shape determined by tertiry structure

  -soulable in water as have hydrophilic r groups outside and hydrophobic r groups on the inside

  -active site that forms from tertiary structure

  -active site is a depression on surface of enzyme that a specific substrate binds

  -active sites have a complementary to shape to the susbtrate
• activation energy


  -minimum amount of energy required to start, known as activation energy

  • enzymes lower activation energy, speeding up rate of reaction by bending bonds between molecules so less energys required for bonds to be broken
• induced fit model


  -active site ot complementary to substrate

  -shape of actve site changes as substarte bibds forming an enzyme substrate complex

  -this bends the bonds in the substrate

  -lowers activation energy leading to reaction