3.1.4.2 Enzymes Flashcards
Why enzymes only catalyse 1 specific reaction
The active site of the enzyme has a specific tertiary structure that is complementary to the substrate
Only 1 substrate can bind to the active site to form an enzyme substrate complex
Enzymes are biological catalysts that lower the…of the reaction
Activation energy
Enzymes are proteins that have a specific…structure
Tertiary
The lock and key model (GCSE) is upgraded to the…model at A level
Induced fit
Describe the induced fit model (4)
Before the reaction the enzyme isn’t complementary to the substrate
Substrate binds to active site of enzyme forming enzyme substrate complex
The active site of the enzyme changes shape slightly to become complementary to the substrate as it binds
This causes bond strain in the substrate
This lowers the activation energy
4 factors that effect rate of enzyme activity
Temperature
PH
Enzyme concentration
Substrate concentration
How temperature effects rate of enzyme activity
As temperature increases, so does rate of reaction up to the optimum temperature.
This is because the enzymes and substrates have more kinetic energy so are moving faster so there are more successful frequent collisions between the enzymes and substrates so more enzymes substrate complexes are formed
Above optimum temperature, rate of enzyme activity decreases because the enzyme denatures due to the increased kinetic energy breaking the hydrogen/ ionic bonds between the R groups of the amino acids. This changes the tertiary structure of the enzyme’s active site so that it’s no longer complementary to the substrate
So fewer enzyme substrate complexes are formed as the substrate doesn’t fit
Above and below the optimum pH, the rate of enzyme activity is lower because
Changes in pH change the charges on the R groups in the active site of the enzyme which affects the binding of the substrate to the active site.
The change in charges of the R groups also affect the hydrogen and ionic bonds that stabilise the tertiary structure leading to denaturation
Changes in pH changes the charges of the…in the active site of the enzyme
R groups
Initially, increasing temperature increases the rate of enzyme activity because the substrates and enzymes have more…so move faster
Kinetic energy
When the enzymes and substrates have more kinetic energy, they move faster so there are more….collisions
Successful frequent
More successful frequent collisions between enzymes and substrates means more…formed
Enzyme substrate complexes
Above the optimum temperature, increased kinetic energy breaks the…/…bonds between amino acid R groups. This changes the tertiary structure of the active site so it’s no longer…to the substrate and so fewer…are formed (the enzyme becomes denatured)
Hydrogen, ionic
Complementary
Enzyme substrate complexes
When kinetic energy is too high (temperature is above the optimum) the hydrogen and ionic bonds between amino acid R groups are broken so the enzyme denatures and the tertiary structure of the active site changes so the active site is no longer…to the substrate
Complementary
If the active site of the enzyme is no longer complementary to the substrate then fewer …can be formed as the substrate doesn’t fit
Enzyme substrate complexes
How enzyme concentration effects rate of enzyme activity
High enzyme concentration means more successful frequent collisions between enzymes and substrates so more enzyme- substrate complexes formed so there is an increased rate of reaction.
At very high enzyme concentrations, the rate of reaction starts to slow and plateau because the number of enzyme molecules starts to exceed the number of substrate molecules
At very high enzyme concentrations the rate of reaction starts to slow (plateau) because the number of…exceeds the number of…
Enzyme molecules
Substrate molecules
How substrate concentration affects rate of enzyme activity
As substrate concentration increases, rate of reaction increases because there are more successful frequent collisions between the enzymes and substrates so more enzyme- substrate complexes are formed
However when the substrate concentration becomes very high the enzymes becomes saturated with substrate as all active sites are occupied. This means a further increase in substrate concentration won’t result in any more enzyme substrate complexes being formed and so the reaction proceeds at a maximum rate that cannot be increased unless more enzyme is added
Enzymes only catalyse 1 specific reaction because the active site has a specific …structure that’s complementary to the substrate. This means that only 1 substrate can…to the active site to form an…
Tertiary bind
Enzyme- substrate complex
When the substrate binds to the active site, the active site changes shape slightly to become complementary to the substrate which causes bond strain in the substrate and lowers the..
Activation energy
A buffer solution should be close to the…pH of the enzyme
Optimum
For a product time graph, when the graph reaches a plateau the rate of reaction is …
0
(No more product is being formed so no reaction is occurring)
For a substrate- rate graph when the graph plateaus it means that the rate of reaction is…
(Where substrate is substrate concentration and rate is rate of reaction)
At its maximum rate
For all enzyme experiments, the control set up (this is different to the control variable) is the…enzyme solution
Boiled
(The enzyme is denatured)
At a very high substrate concentration, a further increase in concentration won’t result in any more…being formed
Enzyme- substrate complexes
As part of the induced fit model, when the active site of the enzyme changes shape it causes…in the substrate which lowers the…
Bond strain
Activation energy
As part of the induced fit model, before…the active site of the enzyme isn’t complementary to the substrate
The reaction
Inhibitors are substances that…or…interfere with the functioning of the active site of a specific enzyme so decrease rate of reaction
Directly (competitive inhibitors as they bind to the active site)
Indirectly (non competitive inhibitors as they bind to the Allosteric site which then changes the shape of the active site)
…are substances that directly or indirectly interfere with the active site of a specific enzyme so decrease rate of reaction
Inhibitors
Inhibitors are substances that directly or indirectly interfere with the….so decrease rate of reaction
Functioning of the active site of a specific enzyme
Inhibitors… rate of reaction
Decrease
2 types of inhibition are … and…
Competitive
Non competitive
…inhibitors are a similar shape to the substrate
Competitive
Competitive inhibitors are a similar shape to the…
Substrate
…inhibitors aren’t a similar shape to the substrate so don’t look like the substrate
Non competitive
…inhibitors bind to the enzyme at the Allosteric site
Non competitive
Non competitive inhibitors bind to the enzyme at the…site
Allestoric
…inhibitors bind to the enzyme at the active site
Competitive
As they are complementary to the active site (have a similar shape to the substrate)
Competitive inhibitors bind to the enzyme at the…site
Active
Competitive inhibitors have a similar shape to the substrate and are complementary to the active site so bind to the enzyme at the …site
Meanwhile non competitive inhibitors aren’t a similar shape to the substrate or complementary to the active site so bind to the enzyme at the…site
Active
Allosteric
Inhibitors can either bind to the enzyme at the…site or the…site depending on whether they are competitive or non competitive
Active (competitive inhibitors)
Allosteric (non competitive inhibitors)
True or false, competitive inhibitors are the same shape as the substrate
False
They’re similar shape
Competitive inhibitors reduce the number of enzymes substrate complexes that can form by binding to the…
Active site
competitive inhibitors binds to the active site of the enzyme to form a …complex
Enzyme- inhibitor
True or false, in competitive inhibition the rate of reaction can still reach its maximum rate
True
(If substrate concentration is high enough/ higher than the inhibitor concentration as it means there’s a lower chance of the inhibitor binding to the active site and a higher chance of the substrate binding to the active site so a higher chance of enzyme- substrate complexes being formed)
However the maximum rate will be reached more slowly than it would without the inhibitor
For..inhibition the reaction can still reach its maximum rate
Competitive
(If substrate concentration is higher enough)
For..inhibition the reaction can still reach its maximum rate
Competitive
(If substrate concentration is higher enough)
Non competitive inhibitors bind to the Allosteric site of the enzyme to form a …complex
Enzyme- inhibitor
Both competitive and non competitive inhibitors bind to the enzyme to form a…complex
Enzyme- inhibitor
(It’s just the site that they bind to that’s different as competitive inhibitors bind to the active site but non competitive inhibitors bind to the Allosteric site)
When the non competitive inhibitor binds to the Allosteric site of the enzyme it changes the …/ …of the enzyme
Shape of active site
Tertiary structure
(This means that the substrate is no longer complementary so can no longer bind to the active site and fewer enzyme substrate complexes are formed so the rate of reaction decreases)
…make the active site of the enzyme more complementary to the substrate so increase rate if reaction (they work in the opposite way to inhibitors)
Activators
Inhibitors are substances that directly/ indirectly interfere with the…of the active site of a specific enzyme so decrease rate of reaction
Functioning
Both types of inhibition lead to fewer…being formed
Enzyme substrate complexes
Term used to describe enzymes that function outside of cells
Extracellular
Term used to describe an enzyme that functions inside of cells
Intracellular
Intracellular vs extra cellular enzymes
Intracellular enzymes act/ function inside the cell
Extracellular enzymes act/ function outside of the cell
True or false, the source of activation energy for the reaction is normally heat
True
Explain why, in terms of activation energy, an enzyme enables reactions to occur at lower temperatures than without the enzyme
Activation energy is needed to start a chemical reaction and often comes in the form of heat. An enzyme lowers the activation energy of the reaction so less heat is needed so the reaction can take place at a lower temperature than it would without the enzyme
