topic 1 - factors affecting enzyme activity Flashcards
cgp (topic 1A) 12 -13
what are four factors that affect enzyme activity
temperature, pH, enzyme concentration, substrate concentration
why does the rate of an enzyme controlled reaction increase when the temperature increases
when heat is increased, kinetic energy is also increased so molecules move faster - making enzymes more likely to collide with the substrate molecules - the energy of these collisions also increases meaning each collision is more likely to result in a reaction
what happens to the enzyme’s molecules when the temperature rises
they vibrate more
what happens when the temperature goes above a certain level
the vibration of the enzyme’s molecules breaks some of the bonds that hold the enzyme in shape - therefore the active site changes and the enzymes and substrate no longer fit together
what does denatured mean
a protein that has lost its tertiary structure /its tertiary structure has been modified - it no longer functions as a catalyst
what is the normal shape of a protein called
native conformation
what is the reversal of denaturation called
renaturation
what are human enzymes optimum temperature
around 37 C
what are human enzymes optimum pH value
pH 7
what is pepsins optimum pH value
pH 2
what happens if the pH value is above or below the optimum
the H+ and OH- ions found in acids and alkalis can mess up the ionic bonds and hydrogen bonds that hold the enzyme’s tertiary structure in place - making the active site change shape so the enzyme is denatured
why does an increased enzyme concentration increase the rate of reaction
the more enzyme molecules there are in a solution, the more likely a substrate molecule is to collide with one and form an enzyme substrate complex - therefore increased concentration of enzyme increases the rate of reaction
when does adding more enzymes have no further effect
when there’s more than enough enzyme molecules to deal with all the available substrate - if the amount of substrate is limited
why does an increased saturation concentration increase the rate of reaction
the higher the substrate concentration, the faster the reaction - more substrate molecules means a collision between substrate and enzyme is more likely and so more active sites will be used
why does substrate concentration only affect the rate of reaction up to a point
eventually there are so many substrate molecules that all the active sites are full - so adding more makes no difference
what is the saturation point in enzymes
when all enzymes are occupied and are not searching for substrates
why is the initial rate of reaction the highest rate of reaction
because substrate concentration decreases with time during a reaction so if no other variables are changed the rate of reaction will decrease over time too
what can enzyme activity be prevented by
enzyme inhibitors
what are enzyme inhibitors
molecules that bind to the enzyme that they inhibit
what are the two types of inhibition
competitive inhibition and non competitive inhibition
what do competitive inhibitor molecules have a similar shape to
substrate molecules
what do competitive inhibitors compete with and what for
the substrate molecules to bind to the active site but no reaction takes place as they block the active site so no substrate molecules can fit in it
what does how much the enzyme is inhibited depends on
the relative concentrations of the inhibitor and the substrate
what happens if there’s a high concentration of the inhibitor
it will take up nearly all the active sites and hardly any of the substrate will get to the enzyme
what happens if there’s a high concentration of the substrate
the substrate’s chances of getting to an active site before the inhibitor increase - so increasing the concentration of substrate will increase the rate of reaction
what do non competitive inhibitor molecules bond to
the allosteric site
what does the non competitive inhibitor do
it causes the active site to change shape so the substrate molecules can no longer bind to it
why don’t non competitive inhibitors compete with the substrate molecules
because they are a different shape
