Enzymes Flashcards
what are enzymes
are biological catalysts that increase the rate of reaction by lowering the activation energy. they are not used up in the process
normally what type of protein are enzymes
globular
what is a intracellular enzyme
enzymes that work inside the cell
eg catalase, breaks down hydrogen peroxide
what are extracellular enzymes
enzymes that work outside the cell
eg amylase, catalyses hydrolysis of starch
explain the lock and key hypothesis
- like a lock and key, only a specific substrate will fit the active site of an enzyme.
- when the substrate is bound, an enzyme-substrate complex is formed.
- the substrates then react and the products are formed in an enzyme-product complex
what is an active site
an area within the tertiary structure of the enzyme that has a shape that is complementary to the shape of a specific substrate molecule.
explain the induced fit hypothesis
- some evidence suggests that the active site changes shape slightly as the substrate enters
- when the enzyme-substrate complex occurs, due to the enzyme moulding around the substrate, it puts strain on the bonds and lowers the activation energy needed to break them
- when the products are removed the active site returns to its original shape
what are the factors the affect enzyme activity
1- temperature
2- pH
3- enzyme concentration
4- substrate concentration
explain denaturation of enzymes at high temp
- at higher temps, the bonds holding the protein’s tertiary structure, vibrate more
- as temp increases further the bonds vibrations increase until the bonds strain and break
- breaking these bonds results changes in the enzymes tertiary structure, thereofre the active site is no longer complementary
what is an enzymes optimum temp
this is a temperature at which the enzyme has the highest rate of activity.
many enzymes in the human body have an optimum around 37*C
how does pH affect enzyme activity
the active site will only be in the right shape at a certain hydrogen ion concentration, this is the optimum pH
when it changes from the optimum, more acidic or alkaline, the structure of the enzyme is altered, changing the shape of the active site
explain how changing the concentration of substrate increase enzyme activity
when concentration of substrate is increased, the number of substrate molecules in a particular area/volume increases.
the increased number of substrate particles leads to a high collision rate with active site of enzymes and the formation of more enzyme-substrate complexes
what is Vmax
it is the maximum rate of reaction, at this point all the active sites are occupied by substrate particles and no more enzyme-substrate complexes can be formed until products are released from active sites. the only way to increase the rate of reaction would be to add more enzyme or increase the temperature
explain how increasing enzyme concentration increases enzyme activity
increasing concentration of enzymes, increases the number of available active sites in a particular area/volume, leading to the formation of enzyme-substrate complexes at a faster rate.
what types of enzyme inhibitors are there
competitive and non-competitive
how do competitive inhibitors work
- they have similar shape to substrate molecules
- they compete with the substrate molecules to bind the active site, but no reaction takes place
- this blocks the active site so the enzyme cant carry out its function
competitive inhibitors affect on rate of reaction?
- reduces rate of reaction for a given concentration of substrate, does not change Vmax
- substrate concentration is increased enough there will be chance of substrate reaching the active site before the inhibitor, so rate of reaction will increase
how do non-competitive inhibitors work
- bind to the enzyme allosteric site (location other than the active site)
- binding alters the enzymes tertiary structure, meaning active site changes shape
non-competitive inhibitors affect on rate of reaction
increasing the concentration of enzyme or substrate will not overcome the effect of a non-competitive inhibitor.
increasing the concentration of the inhibitor will decrease the rate of reaction further as more active sites are changed.
why would an inhibitor binding be reversible
if the bonds between the enzyme and inhibitor are weaker hydrogen bonds or weak ionic bonds, they can easily be overcome. so the inhibitor can be removed
what is a cofactor?
is a inorganic non-protein compound required to carry out enzyme’s function as a biological catalysts
why would an inhibitor binding be irreversible
the bonds between the enzyme and inhibitor are strong covalent bonds, the bonds cant be easily overcome so the inhibitor cannot be easily removed
what is end-product inhibition
it is when the end product in a metabolic pathway inhibits the enzyme that produces it
it regulates the pathway and controls the amount of end-product that gets made.
what is a coenzyme?
are organic cofactors which do not bind permanently, they facilitate the binding of substrate to enzyme.
many are derived from vitamins
