enzymes Flashcards
what are enzymes
biological catalysts for intra and extracellular reactions
- protein
- substance / molecule that speeds up a chemical reaction without being used up
specific tertiary structure determines shape of amino acid, complementary to a specific substrate
formation of enzyme-substrate complexes lowers activation energy of metabolic reactions
activation energy
energy needed to break existing bonds and form new bonds
induced-fit model
The active site of an enzyme has a specific shape due to its tertiary structure.
The substrate has a complementary shape to the active site, but is not perfectly / fully complementary and is flexible
When the substrate binds to the active site to form an Enzyme-Substrate Complex, it causes the active site to change its shape to become fully complementary.
This strains / bends the bonds in the substrate (EA lowered), causing them to break.
The products are formed and released from the active site.
The active site returns to its original shape.
rates of reaction
check one-note
factors affecting enzyme activity
- concentration of substrate
- concentration of enzyme
- temperature
- pH
- inhibitors
how does substrate concentration affect rate of reaction
given that enzyme concentration is fixed, rate increases proportionally to substrate concentration
rate levels off when maximum number of enzyme-substrate complexes form at any given time
how does enzyme concentration affect rate of reaction
given that substrate is in excess, rate increases proportionally to enzyme concentration
rate levels off when maximum number of enzyme-substrate complexes form at any given time
how does temperature affect rate of reaction
rate increases as kinetic energy increases and peaks at optimum temperature
above optimum - ionic and hydrogen bonds in tertiary structure break so active site no longer complementary to substrate - denaturation
how does pH affect rate of reaction
enzymes have a narrow optimum pH range
outside range - H+ / OH- ions interact with hydrogen bonds and ionic bonds in tertiary structure leading to denaturation
competitive inhibitors
similar shape to substrate = bind to active site
do not stop reaction - enzyme-substrate complex forms when inhibitor is released
increasing substrate concentration decreases their effect
non-competitive inhibitors
bind at allosteric binding site
may permanently stop reaction; triggers active site to change shape
increasing substrate concentration has no impact on their effect
outline how to calculate rate of reaction from a graph
calculate gradient of line or gradient of tangent to a point
initial rate = draw tangent at t=0
online how to calculate rate of reaction from raw data
change in concentration of product or reactant / time
why is it advantageous to calculate initial rate
represents maximum rate of reaction before concentration of reactants decreases and end product inhibition
state formula for pH
pH = -log10 [H+]
