Enzymes Flashcards
midterm 1
enzyme general properties
catalysts that direct the pathways of cellular metabolism, remains unchanged themselves
components of an enzyme
apoenzyme: protein component of an enzyme
cofactor: required by some enzymes, could be a metal ion, co-enzyme, or prosthetic group
holoenzyme: comple enzyme
enzyme classifications
- oxidoreductases: transfer of e-
- transferases: group transfer rxns
- hydrolases: hydrolysis rxns
- lyases: formation of double bond
- isomerases: transfer of groups w/in molecules
- ligases: formation of bonds through condensation rxns
rate or velocity definition
the speed of a chemical rxn, whether catalyzed or uncatalyzed
catalyst
increases the rate of a chemical rxn but is not itself changed in the process
substrate
reactants involved in enzymatic rxns
important enzyme characteristics
- enzyme is not changed
- enzyme does not change the equilibrium constant of the rxn, just increases the rate it reaches it
- decrease the free energy of activation
enzyme specificity
highly specific, either for one type or rxn or one substrate (broad and narrow specificity)
factors that effect enzymes
optimal temp: increase in temp before too hot
optimal pH: for proper ionization
conc. of enzyme and substrate
michaelis-menten equation
Vo= Vmax[S]/Km+[S]
michaelis constant
Km (michaelis constant)= [S] at 1/2 Vmax
lower Km means high affinity
lineweaver-burk plot/equation
1/Vo= (Km/Vmax[S]) + (1/Vmax)
plot: y-axis (1/Vo) x-axis (1/[S])
- slope= Km/Vmax
- x-intercept= -1/Km
- y-intercept= 1/Vmax
enzyme inhibition
reversible enzyme inhibitors: bind noncovalently
irreversible enzyme inhibitors: bond covalently and chemically change them
competitive inhibition
a substance that directly competes with enzyme
- Vmax remains the same
- Km increase (lower affinity)
noncompetitive inhibition
inhibitor binds to a different site on the enzyme, leading to no rxn
- Vmax decreases
- Km is unchanged
regulatory enzyme
catalyze the first/early rxn in a metabolic sequence
rate-limiting (rate-determining) step
regulatory enzymes catalyze this step, to control overall pathway
committed step
a chemical rxn that is unique to a specific pathway
feedback inhibition
occurs by end products
allosteric enzyme
activity is regulated by noncovalent interactions at sites other than the catalytic sites
allosteric site
unique region of an enzyme that affects catalysis
allosteric enzyme regulation
positive and negative allosteric effectors can affect affinity of enzyme for its substrate, maximal catalytic activity, or both
