enzymes

Question 1

what is an enzyme

Answer 1

a protein which acts as a biological catalyst

Question 2

explain the induced fit model of an enzyme

Answer 2

the enzyme is a certain shape but alters in the presence of a substrate so that they fit together. this explains how the activation energy is lowered because the change in shape adds energy to the reaction

Question 3

explain the denaturing of an enzyme

Answer 3

hydrogen bonds break in the tertiary structure so the active site changes shape . this means that the enzyme and substrate are no longer complementary so dont form an enzyme substrate complex

Question 4

what is wrong with the lock and key model

Answer 4

suggests enzymes are rigid
suggests enzymes bind somewhere other than the active site

Question 5

give an example of an enzyme catalysed reaction

Answer 5

sucrose + water -> glucose + fructose

Question 6

explain why changing one amino acid in the primary structure of a protein could prevent an enzyme from functioning

Answer 6

the folding of the primary structure will be different which means the folding of the secondary structure will be different. this will effect the hydrogen bonds in the structure so the tertiary bonds will be in a different place which means the active site of the enzyme wont be complementary so less enzyme substrate complexes will be formed

Question 7

what does a graph show when the rate of formation of product is being measured

Answer 7

a line going up at 45 degrees before curving and leveling off
this happens because the limiting reactant has run out

Question 8

what does the graph show when the rate of disappearance of substrate is being measured

Answer 8

the line begins high and steeply falls in a curved shape before leveling off at zero

this is because the substrate has been used up so no more enzyme substrate complexes can form

Question 9

how does temperature effect enzyme action

Answer 9

1.as temp increases rate of reaction increases
2. because molecules have more kinetic energy
3. so more collisions between enzyme and substrate
4.so they are more likeley to become complementary
5. so more enzyme substrate complexes are formed

Question 10

describe what is happening when a graph shows rate of reaction and temperature

Answer 10

rate of reaction increases at a 45 degree angle
the optimum temperature is around 40 oc
at this point the graph is at the top of a curve
it them goes down rapidly because the enzymes have denatured with the increased temp

Question 11

why does temperature cause enzymes to denature

Answer 11

molecules have too much kinetic energy so they are vibrating a lot

Question 12

describe what is happening when a graph shows rate of reaction and Ph

Answer 12

the optimum pH has the greatest rate of reaction and so is at the top of the curve
moving away from the optimum pH the rate of reaction decreases and so does the line on the graph

Question 13

how does a change in pH affect rate of reaction

Answer 13

hydrogen and ionic bonds break in the tertiary structure
this changes the shape of the active site
which deceases the number of enzyme substrate complexes made which decreases rate of reaction

Question 14

how does enzyme concentration effect rate of reaction

Answer 14

graph begins at zero and inclines at 45 degrees - surplus substrate molecules means more enzyme substrate complexes are formed
top of the line - maximum number of complexes formed
leveling off - because substrate is limiting reactant and some active sites are left empty

Question 15

how does substrate concentration effect rate of reaction

Answer 15

graph begins at zero and is a straight line going up - as substrate increases the number of complexes formed increases but some active sites are still empty
top of the line - all active sites are filled
leveling off - substrates are in excess all active sites are filled and no more complexes can be made

Question 16

why are enzymes so specific

Answer 16

because enzymes have an active site which is a certain shape. only substrates that are complementary and bind to the enzyme forming an enzyme substrate complex

Question 17

what is the difference between competitive inhibitor and a non competitive inhibitor

Answer 17

competitive inhibitors bind to the active site because they are a similar shape to the substrate which prevents enzyme substrate complexes forming
where as
non competitive inhibitors bind else where on the enzyme and changes the bonds in the tertiary protein structure so the active site is no longer complementary to the substrate

Question 18

what would happen to rate of reaction if there was a fixed number of substrates and an increasing concentration of competitive inhibitors

Answer 18

less enzyme substrate complexes
competitive inhibitors would bind to active site preventing substrates binding
so decreases rate of reaction

Question 19

what would happen to rate of reaction if there was a fixed number of competitive inhibitors and an increasing concentration of substrate

Answer 19

rate of reaction would increases
more substrates means more enzyme substrate complexes forming

Question 20

what would happen to rate of reaction if there was an increase in non competitive inhibitors

Answer 20

decrease in rate of reaction
because inhibitors would bind to enzyme and change the tertiary structure which changes the shape of an active site so less enzyme substrate complexes form

Question 21

what would happen to rate of reaction if there was an increase in substrate

Answer 21

increase rate of reaction because more substrates will bind to enzymes forming more enzyme substrate complexes