2.1.4 Enzymes Flashcards
what is an enzyme
A biological catalyst used to speed up the rate of biochemical reactions without
being used up or permanently altered
what are the properties of enzymes
- tertiary structure
- enzymes are specific
- enzyme structure can be disrupted by high temps and extremes of pH
what is the roles of enzymes in catalysing reactions
- enzymes lower the activation energy so the rate of reaction increases
what are intracellular enzymes
enzymes that act within the cells that produce them
what is an example of an intracellular enzyme
-catalase
-this enzyme catalyses the breakdown of hydrogen peroxide into oxygen and water
-this prevents the accusation of toxic hydrogen peroxide inside cells
what are extracellular enzymes
enzymes that act out the cells that produce and secrete them
what is an enzyme of an extracellular enzyme
amylase
- this is secreted by the salivary glands, pancreas, and small intestine to break down starch into maltose
Trypsin
- this is secreted by the pancreas into the small intestine to break down proteins into smaller polypeptides
describe the mechanism of enzyme action
( how the enzyme binds with the substrate)
- enzymes have unique tertiary structure which determines the shape of the active site
- the active site is complementary to the substrate
-the substrate binds to the active site to form an enzyme-substrate complex - temporary bonds form between the R groups within the active site and the substrate
- these bonds lower the activations energy to help break down the substrate into product
- the products are released from the active site, leaving the enzyme free to be used again
describe the lock and key model hypothesis
this model suggest that the substrate fits perfectly into the enzymes ative site in the same way that a key irs into a lock
describe the induced-fit hypothesis
-in this model, the substrate does not perfectly into the enzymes active site.
- the active site slightly changes shape slightly as the substrate enters the enzyme.
- this puts a strain on the substrates bonds which lowers the activation energy
what factors effect enzymes activity
Temperature
pH
Substrate concentration
Enzyme concentration
explain the effect of pH on enzyme activity
- in acidic conditions, H+ ions break the ionic/hydrogen bonds and denature enzymes
- the optimum pH is the pH the enzymes work the fastest at
- in alkaline conditions, OH- ions break ionic bonds or hydrogen bonds and denatures enzymes
explain the effect of temperature on enzyme activity
-The molecules have more kinetic energy, causing more collisions and enzyme-substrate complexes.
-The optimum temperature is the temperature this enzyme works fastest at.
- there are more collisions between the enzyme and the substrate so there are more successful collisions between the enzymes active site and the substrate
-Too much kinetic energy causes the active site to change shape and the enzyme denatures.
what is the temperature coefficent
The temperature coefficient (Q10) is a value that shows how much the rate of reaction changes when the temperature is increased by 10°C.
Q10 = R2/R1
Where:
R2 = The rate of reaction at the higher temperature (+10°C).
R1 = The rate of reaction at the lower temperature.
explain the effect of enzyme concentration on enzyme activity
- at the beginning there are more enzyme molecules which allows for more collisions, so more successful collisions between the substrate and active site
- this forms more enzyme substrate complexes
- until all the substrate molecules available are being acted upon and substrate concentration becomes the limiting factor
explain the effect of substrate concentration on enzyme activity
- there are more substrate molecules, so more collisions, so more successful collisions between the active site of the enzyme and the substrate.
- so forms more enzyme-substrate complexes
- all the enzymes are taken up by substrates, so the enzyme concentration becomes the limiting factor and the rate of reaction stays constant
what is a cofactor
non-protein substances that bind to enzymes to increase their activity
what are the two types of cofactors
- coenzymes
- prosthetic group
what is an example of a cofactor
Cl- is a cofactor for amylase
what is a coenzyme
These are organic cofactors and are usually derived from vitamins
what is a prosthetic group
These are cofactors that are tightly bound to enzymes
what is an example of a prosthetic group
Zn2+ is a prosthetic group for the enzyme carbonic anhydrase
what is an inhibitor
molecules that bind to enzymes to reduce their activity
what is a reversible inhibitor
These form weak bonds (e.g. hydrogen or ionic) with the enzyme.
what is an irreversible inhibitor
an molecule thay forms strong bonds (eg covalen) with the enzyme
what is a competitive inhibitor
it is an inhibitor which binds to the active site of an enzyme to prevent enzyme-substrate complexes
how does a competitor inhibitor work
- competitive inhibitors have a similar shape to the active site
- and so will being to the active site of the enzyme.
- means the substrate wont be able to bind which reduces the formation of enzyme-substrate complexes.
- this reduces the rate of enzyme catalysed reactions
-most competitive inhibitors are reversible as they only bind temporarily to the enzyme
how does the substrate concentration effect competitive inhibitors
- the higher the substrate concentrations, the more likely it is for the substrates to bind to the active sites, rather than the inhibitor molecule.
- this reduces the effect of the competitive inhibitor
what is a non-competitive inhibitor
- Non-competitive inhibitors bind to enzymes away from the active site (allosteric site) to prevent enzyme-substrate complexes.
How does a non-competitive inhibitor work
- the inhibitor will bins to the allosteric site
- this changes the tertiary structure of the enzyme causing the enzymes active site to change shape
- this means the substrate and the enzymes active site is no longer complementary so the substrate and enzyme can no longer bind
- this causes less enzyme-substrate complex’s formed so the rate of the enzyme-catalysed reaction decreases
How does the substrate concentration effect non-competitive inhibitors
- non-competitive inhibitors does compete with the substrate to bond to the active site.
- this means that increasing the amount of substrate will have no effect on the rate of reaction
