1.2.1 many proteins are enzymes Flashcards
how do enzymes act as biological catalysts
- each enzyme lowers activation energy of the reaction it catalyses
- to speed up the rate of reaction
what do enzymes catalyse
a wide range if intracellular and extracellular reactions that determine structures and functions from cellular to whole organism level
describe the induced fit model of enzyme action
- substrate binds to ( not completely complementary ) active site of
- causing the active site to change shape ( slightly ) so it is complementary to substrate
- so enzyme-substrate complex forms
- causing bonds in substrate to bend lowering the activation energy
describe how models of enzyme action have changed over time
- initially was lock and key model were active site was a fixed shape, complementary to one substrate
- now induced fit model
describe the specificity of enzymes
- specific tertiary structure determines the shape of the active site ( this is dependent on the sequence of amino acids ( primary structure ) )
- active site is complementary to a specific substrate
- only this substrate can bind to the active site, inducing fit and forming an enzyme-substrate complex
describe and explain the effect of enzyme concentration on the rate of enzyme controlled reactions
- as enzyme concentration increases, rate of reaction increases. due to enzyme concentration being a limiting factor there are more enzymes so more available active sites so more enzyme substrate complexes form
- at a certain point the rate of reaction stops increasing/levels off. substrate concentration is a limiting factor so all substrates are in use
describe and explain the effect of substrate concentration on the rate of enzyme controlled reactions
- as substrate concentration increases, rate of reaction increases. substrate concentration is a limiting factor meaning more E-S complexes form
- at a certain point, rate of reaction stops increasing/levels off as enzyme concentration is a limiting factor as all active sites are occupies
describe and explain the effect of temperature on the rate of enzyme controlled reactions
- as temp increases up to optimum, rate of reaction increases as more kinetic energy so more E-S complexes form
- as temp increases above optimum, rate of reaction decreases as enzymes denature meaning tertiary structure and active site change shape as the hydrogen/ionic bonds break so active site is no longer complementary so fewer E-S complexes form
describe and explain the effect of pH on the rate of enzyme controlled reactions
- as pH increases/decreases above/below an optimum, rate of reaction decreases due to enzymes denaturing as tertiary structure and active site change shape as hydrogen ionic bonds break so active site is no longer complementary and fewer E-S complexes form
describe and explain the effect of concentration of competitive inhibitors on the rate of enzyme controlled reactions
- as concentration of competitive inhibitors increases, rate of reaction decreases due to them being a similar shape to the substrate so they bind to the active site so substrates cant bind and fewer E-S complexes are formed
- increasing substrate concentration reduces this effect of inhibitors however is dependent on relative concentrations of substrate and inhibitor )
describe and explain the effect of concentration of non competitive inhibitors on the rate of enzyme controlled reactions
- as concentration of non competitive inhibitor increases, rate of reaction decreases due to them binding to site other than the active site ( allosteric site ). this changes the enzymes tertiary structure/active site shape so the active site is no longer complementary to substrate so substrates cant bind so fewer E-S complexes form
- increasing substrate concentration has no effect on rate of reaction as the change to the active site is permanent
