Enzymes

• What is an intracellular enzyme?

  An enzyme that functions inside the cell

  e.g Catalase
• What is an extracellular enzyme?

  An enzyme that functions outside the cell

  e.g Amylase
• How does the temperature affect enzyme activity?

  As temp rises there is more kinetic energy making the molecules move more,increasing the chance of successful collisons.The rate increases to its optinum temp. Hydrogen bonds are broken and enzyme dentaures.
• What is the temperature coefficient?

  The Q10 value for a reaction shows how much the rate of reaction changes when the temperature is raised by 10 degrees.Q10 value of 2 means the rate doubles every 10 degrees
• Whats the Q10 equation?

  rate at higher temp

  -------------------

  rate at lower temp
• Whats the affect on pH on enzyme activity?

  Hydrogen ions interact with polar and charged R-groups.Changing the conc of hydrogen ions therefore changed the degree of the interaction.The more H+ ions present the less R-groups are able to interact with one another breaking the shape of the enzyme
• How does the enzyme concentration effect the enzyme activity?

  • The rate of reaction is proportional to the enzymes concentration
  • Increasing concentration doesn't affect the reaction rate is substrate is limiting
  • More ES complexes formed- increased chances of collisions
• How does substrate concentration affect the enzyme activity?

  • The rate of reaction increases with the increasing substrate concentration up to a point
  • The ES complex has to dissolve before the active sites are free to accomodate more substrate
• Whats the definition of a cofactor?

  • They are non-protein chemical compounds that are required for an enzymes biological activity to occur
• Examples of a cofactor:

  • Inorganic cofactors are usually metal ions
  • Cofactors arent directly involved in the reaction
  • Role of cofactors is to bind the substrae and the enzyme
• What is the definition of coenzymes?

  • Usually organic molecules
  • Participate in enzyme reaction and the role is up help transfer chemical groups between different enzyme
  • They get changed during the reaction but they dont get used up
• What is competitive inhibitors?

  • They bind to the active site as they have a similar shape to the substrate so they bind to the active site but no reaction takes place instead the active site is blocked
  • This reduces the formation of enzyme-substrate complexes
  • Doesn't lead to the formation of the product as the inhibitor isnt identical to the substrate
  • Decreases in the rate of the enzyme-catalysed reaction
• What is non-competitive inhibitor?

  • Dont compete with the substrate for the enzymes active site
  • They attatch to the enzyme in another region which isnt the active site (allosteric site)
  • The binding changes the tertiary structure of the enzyme causing the active site to change shape
  • Results in active site no longer being complementary to the substrate
  • Less enzyme -substrate complexes are formed and the rate of the enzyme-catalysed reaction decreases
• What is reversible inhibition?

  • Inhibition that can be overcome or reversed.
  • Weaker hydrogen bonds or weak ionic bonds
• What is a non-reversible inhibitor?

  • The inhibitor cant be removed easily
  • Strong covalent bonds
• Whats end product inhibition?

  • Important in regulating metabolic pathways
  • The final end product often acts as a regulator of the pathway
  • When end product is high it binds non-competitively to an enzyme in the pathway blocking further production of itself
• What are enzymes?

  • Globular proteins with a complex and unique tertiary structures
  • Theyre known as biological catalysts because they increase the rate of a chemical reaction without being used up in the reaction itself
• What are the stages of an enzyme binding to a substrate?

  • The active site is a unique shape due to the unique tertiary shape of the enzyme- this is complementary to the substrate
  • The substrate binds to the active-site to form an enzyme-substare complex
  • Temporary bonds form between the R groups within the active site of the substrate
  • These bonds lower the activation energy to help break down the substrate into products
  • The products are released from the active site leaving the enzyme free to be used again
• How does the induced fit model differ from the lock and key model?

  • The substrate doesnt fit into the active site so the active site changes shape slightly to make it complementary
• What happens when you increase the substrate concentration with competitive inhibitors?

  • Competitive inhibitors can overcome by increasing the substrate concentration
  • The higher the substrate concentration the more likely it is that that substrates will bind to the active sites than the inhibitor molecules
  • This will reduce the effect of the competitive inhibitor
• Why does increasing the substrate concentration have no effect on the rate of reaction with non-competitive inhibitors?

  • Non-competitive inhibtors cannot be overcome by increasing the substrate concentration
  • Non-competitive inhibitors compete with the substrate to bind to the active site so increasing the amount of substrate has no effect on the rate of reaction