3.1.4 Enzymes Flashcards
What are enzymes
Biological catalysts for intra and extracellular reactions
Specific tertiary structure determines shape of active site, complementary to a specific substrate
Formation of ES complexes lowers activation energy of metabolic reactions
Explain the induced fit model of enzyme action
Shape of active site is not directly complimentary to substrate and its flexible
Conformational change in active site makes it complementary to substrate enables ES complexes to form
This puts strain on substrate bonds, lowering Ea
How have models of enzyme action changed
Initially lock and key model - rigid shape of active site complimentary to 1 substrate
Currently induced fit model - explains why binding at allosteric sites can change shape of active site
How could a student identify the activation energy of a metabolic reaction from an energy level diagram
Difference between free energy of substrate and peak of curve
Name 5 factors that affect the rate of enzyme controlled reactions
Enzyme conc
Substrate conc
Conc of inhibitors
pH
Temperature
How does substrate conc affect rate
Given that enzyme conc is fixed, rate increases proportionally to substrate conc
Rate levels off when maximum number of ES complexes form at any given time
How does enzyme conc affect rate
Given that substrate is in excesss, rate increases proportionally to enzyme conc
How does temp affect rate
Rate increases as kinetic increases meaning collisions between active site and enzymes more likely, so more ES complexes form and peaks at optimum temp
Above optimum ionic and H bonds in tertiary structure break = active site no longer complementary to substrate
How does pH affect rate of reaction
maybe rewrite def from notes
Enzymes have a narrow optimum pH range
Outside range, H+/OH- ions interact with H bonds and ionic bonds in tertiary structure causing them to denature
Contrast competitive and non competitive inhibitors
Competitive
Similar shape to substrate = bind to active site
Do not stop reaction, ES complex forms when inhibitor is released
Increasing substrate conc decreases their effect
Non competitive
Bind at allosteric binding site
May permanently stop reaction - triggers active site to change shape
Increasing substrate conc has no impact on their effect
Why is it advantageous to calculate initial rate
Represents maximum rate of reaction before concentration of reactants decreases and end product inhibition
