Enzymes Flashcards
What is enzyme specificity?
enzymes will only catalyze a single reaction or class or reactions with certain substrates
What are oxidoreductases?
catalyze oxidation-reduction reactions; transfer of electrons between biological molecules
What is the reductant?
electron donor
What is the oxidant?
electron acceptor
What are transferases?
catalyze the movement of a functional group from one molecule to another
What are kinases?
catalyze the transfer of a phosphate group, generally from ATP, to another molecule
What are hydrolases?
catalyze the breaking of a compound into two molecules using the addition of water
What are lyases?
catalyze the cleavage of a single molecule into two products
What are isomerases?
catalyze the rearrangement of bonds within a molecule
What are ligases?
catalyze the addition or synthesis reactions, generally between large similar molecules, and often require ATP
What is a substrate?
molecule upon which an enzyme acts
What is the enzyme-substrate complex?
physical interaction between enzyme and substrate
What is the active site?
location within the enzyme when the substrate is held during the chemical reaction
What is the lock and key theory?
suggests that the enzyme’s active site (lock) is already in the appropriate conformation for the substrate (key) to bind
What is the induced fit model?
the substrate induces a change in the shape of the enzyme
What are cofactors/coenzymes?
nonprotein molecules that are small in size and can bind to the active site of the enzyme and participate in the catalysis of the reaction, usually by carrying charge through ionization, protonation, or deprotonation
What are apoenzymes?
enzymes without cofactors
What are holoenzymes?
enzymes with cofactors
What are prosthetic groups?
cofactors or coenzymes that are necessary for enzyme function
Ideal pH for most enzymes in the body
7.4
Ideal pH for gastric enzymes in the body
2
Ideal pH for pancreatic enzymes in the body
8.5
What is feedback regulation?
enzymes are subject to regulation by products further down a give metabolic pathway
What is feedforward regulation?
enzymes may be regulated by intermediates that precede the enzyme in the pathway
Zymogens
contain a catalytic (active) domain and regulatory domain
What is competitive inhibition?
when the inhibitor binds at the active site of the enzyme
What is noncompetitive inhibition?
bind to an allosteric site instead of the active site, which induces a conformational change
What is mixed inhibition?
results when an inhibitor can bind to either the enzyme or the enzyme-substrate complex, but has different affinity for each
What is uncompetitive inhibition?
only bind to the enzyme-substrate complex
What is the effect of competitive inhibition on Km and Vmax?
Km - increases
vmax = unchanged
What is the effect of noncompetitive inhibition on Km and Vmax?
Km = unchanged Vmax = decreases
What is the effect of mixed inhibition on Km and Vmax?
Km = increases or decreases Vmax = decreases
What is the effect of uncompetitive inhibition on Km and Vmax?
Km = decreases Vmax = decreases
