Enzymes

Question 1

what is the active site

Answer 1

a small part of the enzyme that attaches to a substrate to catalyse a reaction

Question 2

features of the active site

Answer 2

-specific and unique in shape due to specific folding and bonding in the tertiary structure of the protein
-so can only attach to substrates that are complementary in shape

Question 3

what is activation energy

Answer 3

a certain amount of energy needed for a reaction to occur

Question 4

what happens to activation energy when enzymes attach to the substrate

Answer 4

-lowers activation energy needed for the reaction
-so speed up the reaction

Question 5

what are the two models of enzyme action

Answer 5

-lock and key
-induced fit

Question 6

explain the lock and key model

Answer 6

-the enzyme active site is a fixed shape
-due to random collisions the substrate can collide and attach to the enzyme forming an enzyme substrate complex
-the charged groups within the active site distort the substrate so lower the activation energy
-the products are then released and the empty active site can be reused

Question 7

what does the lock and key model suggest

Answer 7

-the enzyme is like a lock
-the substrate is like a key
-that fits into it due to its complementary shape

Question 8

explain the induced fit model

Answer 8

-the enzyme active site is induced or slightly changes shape to mould around the substrate
-the formation of an enzyme substrate complex involves the enzyme moulding around the substrate
-this puts a strain on the bonds and lowers the activation energy
-the products are removed and the active site returns to its original shape

Question 9

what does the induced fit model suggest

Answer 9

-the enzyme is like a glove and the substrate is like your hand
-the empty glove is not exactly complementary in shape to your hand but when the hand enters the glove moulds to fit

Question 10

which is the accepted model of enzyme action

Answer 10

the induced fit model

Question 11

which factors affect the rate of enzyme controlled reactions

Answer 11

-temperature
-pH
-substrate concentration
-enzyme concentration
-inhibitors

Question 12

how does temperature being too low affect enzyme action

Answer 12

-not enough kinetic energy for successful collisions between the enzyme and substrate

Question 13

how does temperature being too high affect enzyme action

Answer 13

-enzymes denature
-the active site changes shape and enzyme substrate complexes cannot form

Question 14

how does pH affect enzyme action

Answer 14

-too high or low interferes with the charges in the amino acids in the active site
-this can break ionic and hydrogen bonds which hold the tertiary structure
-this changes shape of active site so enzyme denatures and less enzyme substrate complexes formed

Question 15

how does optimal pH for enzymes vary

Answer 15

different enzymes have a different optimal pH

Question 16

how does insufficient substrate concentration affect enzyme action

Answer 16

-reaction is slower
-fewer collisions between the enzyme and substrate

Question 17

how does insufficient enzyme concentration affect enzyme action

Answer 17

-enzyme active sites will become saturated with substrate
-unable to work any faster

Question 18

what are the kinds of enzyme inhibitors

Answer 18

-competitive inhibitors
-non competitive inhibitors

Question 19

features of competitive inhibitors

Answer 19

-same shape as substrate
-can bind to the active site
-so prevent substrate from binding and the reaction occurring

Question 20

how does increased substrate concentration affect competitive inhibitors

Answer 20

-it will out compete the inhibitor
-knocking them out of the active site

Question 21

features of non competitive inhibitors

Answer 21

-bind to the enzyme away from the active site (the allosteric site)
-causes active site to permanently change shape
-substrate can no longer bind

Question 22

describe the rate of reaction with increasing substrate concentration for competitive inhibitors

Answer 22

-rate of reaction returns to the same as with no inhibitor

Question 23

how does increased substrate concentration affect non competitive inhibitors

Answer 23

the substrate can no longer bind regardless of how much substrate is added

Question 24

describe the rate of reaction with increasing substrate concentration for non competitive inhibitors

Answer 24

-lower at all substrate concentrations