1.2.1 Many proteins are enzymes ( biological molecules)

Question 1

How do enzyme act as biological catalysts

Answer 1

• each enzyme lowers activation energy of reaction it catalyses
• to speed up rate of reaction

Question 2

describe the induced fit model of enzyme action

Answer 2

1) substrate binds to active site of enzyme
2) causing active site to change shape so its complementary to its substrate
3) so enzyme substrate complex forms
4) causing bonds in substrate to bend / distort , lowering activation energy

Question 3

describe how models of enzyme action have changed over time

Answer 3

• initially lock and key model
• active site a fixed shape , complementary to one substrate
• now induced fit model

Question 4

explain the specificity of enzymes

Answer 4

• specific tertiary structure determines shape of active site
  • dependent on sequence of amino acids
  • active site is complementary to a specific substrate
  • only this substrate can bind to active site , inducing fit and forming an enzyme substrate complex

Question 5

describe and explain the effect of enzyme conc on the rate of enzyme controlled reactions

Answer 5

• as enzyme conc increases , rate of reaction increases
  • enzyme conc = limiting factor
  • more enzymes so more available active sites
  • so more enzyme substrate complexes form
• at a certain point , rate of reaction stops increasing
  • substrate conc = limiting factor

Question 6

describe and explain the effect of substrate conc on the rate of enzyme controlled reactions

Answer 6

• as substrate conc increases , rate of rreaction increases
  • substrate conc = limiting factor
  • more enzyme substrate complexes form
• at a certain point , rate of reaction stops increasing
  • enzyme conc = limiting factor
  • as all active sites saturated / occupied

Question 7

describe and explain the effect of temperature on the rate of enzyme controlled reactions

Answer 7

• as temp increases to optimum , rate of reaction infreaeee
  • more kinetic energy
  • more enzyme substrate complexes form
• As temp exceeds optimum , rate of reaction decreases
  • enzymes denature => tertiary structure and active site change shape
  • as hydrogen / ionic bonds break
  • active site no longer complementary
  • so fewer enzyme substrate complexes form

Question 8

describe and explain the effect of pH on the rate of enzyme controlled reactions

Answer 8

• As pH increased / decrease above / below optimum , rate of reaction decreases
  • enzymes denature => tertiary structure and active site change shape
  • as hydrogen / ionic bonds break
  • active site no longer complementary
  • so fewer enzyme substrate complexes form

Question 9

describe and explain the effect of conc of competitive inhibitors on the rate of enzyme controlled reactions

Answer 9

• as conc of competitive inhibitor increases , rate of reaction decreases
  • similar shape to substrate
  • competes for / binds to / blocks active site
  • so substrate cant bind
  • so fewer enzyme substrate complexes form
• increasing substrate conc reduces the fact of inhibitors

Question 10

describe and explain the effect of conc of non competitive inhibitors on the rate of enzyme controlled reactions

Answer 10

• as conc of non competitive inhibitors increases , rate of reaction decreases
  • binds to site other than active site
  • changes enzyme tertiary structure
  • so active site no longer complementary to substrate
  • substrate cant bind
  • so fewer enzyme substrate complexes form
• increasing substrate conc has no effect on rate of reaction as change to active site is permanent