properties of enzymes:
- biological catalysts
- are precisely shaped 3D proteins made by protein synthesis (includes active site which is precisely shaped to bind with/be complementary to enzymes target molecule or substrate)
what can enzymes be specific to?
- a single substrate molecule
- or a group of similar reactions or substrates
example of how enzymes can be specific to a single molecule:
they can tell the difference between two isomers and only fit and have an effect on 1 of them
so glucose oxidase can recognise a-glucose but not b-glucose since they are different SHAPED molecules
example of how enzymes can be specific to a group of similar reactions or substrates:
'’group specificity’’ e.g. an enzyme may recognise and break any peptide bond
why are enzymes produced in small concentrations
because they are reusable
what is enzyme action effected by
extreme temperature and extreme pH - if their active site is changed, they will denature; will no longer fit with target substrate so no enzyme-substrate complex is formed - they won’t form a product
Are enzymes fast working?
Yes;1 enzyme molecule may catalyse 1000s reactions/second
are enzymes intracellular or extracellular
can be both
What is anabolism?
The sequences of reactions building larger molecules
(Enzymes catalyse reactions which turns smaller molecules into larger ones in condensation reactions)
What is catabolism?
Sequence of reactions producing smaller molecules - large molecules into smaller ones in hydrolysis reactions which turns
What is metabolism
Sequence of reactions that includes building up and breaking down steps
Enzyme substrate complex
- binding of substrate to enzyme
What is activation energy?
Level of energy required for a reaction to occur- is the energy barrier that has to be overcome for the reaction to occur
What do enzymes do to activation energy?
Reduce the activation energy required
Frequency of reactions will increase as less energy is required
Sequence of events in an enzyme controlled reaction:
- substrate binds to enzyme at active site to produce enzyme (substrate complex)
- whilst attached change occurred to the the substrate to produce the product
- enzyme and product will separate
- active site is now empty and available again (enzymes are reusable)
Why might the enzyme and product separate?
The changed product isn’t strongly attached to the enzyme as the substrate was
Why may the substrate change?
- fitting active site - slightly change shape of substrate (breaks bonds) produces small molecules from larger ones
- AS may contain charged areas - changes in charge distribution
- when 2 molecules enter active site - pressed together - forms bonds between molecules - producing larger molecules from smaller ones
Lock and key hypothesis
Substrate and active site are complementary and they fit or bind to make the enzyme - substrate complex
Induced fit hypothesis
Substrate and active site aren’t complementary but when they come together the active site changes shape to become complementary and fit or bind
What are the two types of enzyme inhibition
non competitive and competitive inhibitors
what are competitive inhibitors
molecules that are structurally similar to normal substrate of the enzyme, so they can enter the active site
what happens if the active site is occupied by a competitive inhibitor?
normal substrate cannot enter the active site
what happens if the competitive inhibitor binds permanently?
enzyme activity is lost since the substrate cannot bind to the active site
if it binds temporarily, the enzyme activity is reduced
what do non-competitive inhibitors do, and what happens?
do not bind to active site so they do not compete with the substrate
instead they bind to the allosteric site, causing the active site to change shape
substrate cannot fit active site, so the enzyme will not work
