enzymes Flashcards

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1
Q

what is an enzyme

A

a protein which acts as a biological catalyst

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2
Q

explain the induced fit model of an enzyme

A

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

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3
Q

explain the denaturing of an enzyme

A

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

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4
Q

what is wrong with the lock and key model

A

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

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5
Q

give an example of an enzyme catalysed reaction

A

sucrose + water -> glucose + fructose

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6
Q

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

A

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

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7
Q

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

A

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

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8
Q

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

A

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

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9
Q

how does temperature effect enzyme action

A

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

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10
Q

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

A

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

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11
Q

why does temperature cause enzymes to denature

A

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

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12
Q

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

A

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

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13
Q

how does a change in pH affect rate of reaction

A

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

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14
Q

how does enzyme concentration effect rate of reaction

A

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

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15
Q

how does substrate concentration effect rate of reaction

A

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

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16
Q

why are enzymes so specific

A

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

17
Q

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

A

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

18
Q

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

A

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

19
Q

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

A

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

20
Q

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

A

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

21
Q

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

A

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