Chapter 6: Section 6.3 Flashcards
determines the rate of reaction & how it changes in response to changes in experimental parameters
enzyme kinetics
what affects the rate of enzyme-catalyzed reactions?
substrate concentration [S]
concentration of substrate changes during _____ reaction as substrate converts to ______
in vitro; product
what is V0?
initial rate/ initial velocity
when can substrate be regarded as constant?
when only the beginning of the reaction is monitored and over a small period where a small % of the substrate is converted to product
initial velocity can be seen as a function of ______
substrate concentration [S]
low concentrations of V0 ______ with increase in _____
increases; [S]
what happens when there is a high [S]?
V0 increases by smaller and smaller amounts in response to increase in [S]
point reached beyond increases in V0 are small as [S] ____
increases
V0 region is close to ______
Vmax
enzyme that catalyzes the reaction S<>P is present at a concentration ______ to catalyze the reaction at ____ of 1 micrometer per minute
sufficient; Vmax
what is Km?
Michaelis constant
0.5 micrometer
rate ____ as substrate converts to _____
declines; substrate
tangent to each curve taken at time equals _____ defines the initial velocity of each reaction
zero
What is the ES complex?
ES complex is the state in, which the active site of the enzyme is non-covalently bound to the substrate molecule(s)
What does the 1st enzyme do?
enzyme combines reversibly with its substrate complex in fast reversible step E+S k><k-1ES
What does the 2nd enzyme do?
ES complex breaks down in a slower second step to yield free enzyme and reaction product P: ES k2><k-2 E+P
initial velocity ignores _____ reaction
reverse
slope = ?
delta initial velocity/ delta [S]
what does a slower second reaction limit?
It limits the rate of overall reaction
what is the overall rate proportional to?
proportional to the concentration of species that reacts in the 2nd step > ES
Model mechanism
E+S > ES > E+P
Step 1 of the mechanism
enzyme-substrate complex (ES) - rapid bimolecular step
Step 2 of the mechanism
-ES forms product
-rate-limiting step
-net rate: combines rate constants from all steps [E] & [S]
Characteristics of the enzyme inside of the cell
the enzyme concentration is low and limiting
enzyme kinetics experiments hold ____ constant
[enzyme]
equation of [substrate]
[substrate]tot = [S] + [ES] = [S]
equation of rate
V = k = [ES]
what happens when there is high [S]?
-the enzyme is saturated with substrate
-the reaction is zero order w/ respect [S]: ES _ E + P
what is pseudo?
first-order reaction overall since the rate depends on # of active sites
-only more enzymes increase the reaction rate
what forms of enzyme exist when there a reaction where the enzyme is catalyzed?
2 forms
-free/ uncombined form E
-combined form ES
