Chapter 1- Enzymes Flashcards
Catalysts
increase reaction rates by lowering the activation energy of a reaction.
Also reduce the energy of the transition state.
However, do not shift a chemical reaction or affect spontaneity
Transition State
the unstable conformation between reactant and product
Enzymes
act as biological catalysts binding to substrates (reactants) and converting them into products.
Bind to substrates at the active site.
Most enzymes are proteins.
Specificity constant
measures how efficient an enzyme is at binding to the substrate and converting it to a product.
When Specificity constant is high the enzymes site will have a high substrate affinity.
Induced fit theory
Enzyme active sites change their shape slightly when substrate binding occurs to fit
Lock and key model
outdated theory of how substrate binds
Ribozyme
non-protein enzyme
is a RNA molecule that is capable of acting as an enzyme by changing speed of reactions.
Cofactor
non-protein molecule that helps enzymes perform reactions by donating or accepting electrons.
Coenzymes
are organic cofactors
ex:vitamins
Metal ions
are inorganic cofactors
ex: Iron (Fe2+), Magnesium (Mg2+)
Holoenzymes
enzymes bound to their cofactor
Apoenzyme
enzyme lacking its cofactor
Prosthetic groups
are cofactors that tightly/covalently bind to their enzyme in a holoenzyme
Protein enzymes
have optimal temperature &pH ranges. If not optimal, temp. and pH can denature protein enzymes resulting in loss of functionality.
DAT Tip: if temperature is around higher optimal range (not too high), this can increase enzymes function for faster reaction
Competitive inhibition
form of enzyme regulation; inhibitors compete with substrates for active sites.
increasing substrate will result in better chance of substrate binding to active site - outcompete a competitive inhibitor by adding more substrate
Enzyme saturation
as saturation of substrate reaches a high level, increased catalysis speed will plateau.
Noncompetitive inhibition
when an inhibitor binds to the allosteric site (different site than the active site) of an enzyme. The inhibitor binding to the allosteric site modifies the active site reducing/blocking binding of substrate.
Allosteric inhibitors cannot be outcompeted by adding more substrate concentration. rate of enzyme catalysis unaffected by increasing substrate conc.
Enzyme kinetics plot
used to visualize how inhibitors affect enzymes
Velocity (V) of reaction
the rate at which a reaction occurs
Vmax
the maximum reaction velocity
Substrate Concentration (X)
increasing the (X) tends to increase the rate of reaction until enzyme becomes saturated with substrate, reaction rate plateauing
Michaelis Constant (KM)
the substrate concentration in which the velocity (V) is 50% of the maximum reaction velocity (Vmax)
Small KM = need a little bit of substrate because enzyme ability/function is still high
Large KM = need many substrates for reaction progression bc enzyme availability/function is low.
Enzyme inhibition Vmax and Km : competitive inhibitor vs noncompetitive inhibitor
Competitive inhibitor: Vmax is not changed; Km is increased as it takes a higher substrate conc. to reach Vmax
Non-competitive inhibitor: Vmax is decreased and Km remains the same because increasing conc. of substrate does not reduce this inhibition bc active sites are unavailable
