factors affecting enzymes Flashcards
define rate of reaction
speed at which reactants are being turned into products
state 4 factors that affect the rate of an enzyme controlled reaction
- temperature
- pH
- substrate concentration
- enzyme concentration
define initial rate of reaction
instantaneous rate at the start of the reaction
describe the significance of initial rate of reaction in investigations into factors affecting rate of enzyme-controlled reactions.
- gradient of tangent to curve at t=0
- concentration of substrate always changes as experiment proceeds - rate constantly changes
- only true rate of reaction is the initial (only moment where the two variables investigated are the only ones influencing rate)
explain why increasing temp from below the optimum towards the optimum increases the rate of reaction.
- increasing temp increases kinetic energy of particles
- particles move faster
- so more frequent successful collisions between substrate and enzyme –> increase in rate
define temperature coefficient (Q10)
measure of how much the rate of a reaction increases with a 10ºC rise in temperature
state the usual value for enzyme controlled reactions
2 (rate doubles with 10˚C increase)
explain why increasing the temperature from the optimum decreases the rate of reaction abruptly
- higher temp = bonds holding enzyme structure tgt vibrate more
- breaking bonds = change in the tertiary structure of the protein = denatured
- active site is no longer complementary to substrate - substrate cant fit - enzyme is no longer a functional catalyst
explain why a pH change away from optimum decreases the rate of reaction.
- hydrogen + ionic bonds between amino R-groups hold protein in precise 3D shape
- change in pH changes H+ concentration (more H+ - acidic - low pH VV)
- active site is only in right shape at optimum pH so changes alter active site
explain how the significance of the pH change can affect enzyme action
- if change is not too significant, enzyme can renature (if pH is back to optimum)
- if change is too significant, enzyme is irreversibly altered, active site no longer complementary - denatured
- because H+ interact with polar + charged R-groups
- if more H+ less R-groups can interact with each other leading to ionic and hydrogen bonds breaking
define Vmax
maximum initial rate of an enzyme-catalysed reaction
explain how increasing the substrate concentration affects the initial rate of an enzyme-controlled reaction.
- as substrate concentration increases, rate of successful collisions between substrate and enzyme increases
- so increases rate of formation of ES complexes
- rate stops increasing when all active sites are occupied
- substrate is no longer limiting, increasing conc will not affect rate (Vmax)
explain how increasing enzyme conc. affects the initial rate of an enzyme-controlled reaction.
- as enzyme concentration increases, more active sites are available + reaction rate increases
- leads to more successful collisions
- increases the rate of formation of ES complexes
- rate stops increasing when substrate runs out
- enzyme is no longer limiting, increasing conc will not affect rate (Vmax) bc there will be nothing for enzymes to bind to
describe how to investigate any of the factors that affect the rate of enzyme-controlled reactions.
use catalase from any living tissue + add it to hydrogen peroxide, measure gas produced (oxygen)
explain how to calculate the rate of change from a graph showing a linear relationship
- pick two points on the line, calculate ∆y/∆x (gradient)
