Enzymic Kinetics Flashcards
What are Michaelis-Menten kinetics and Lineweaver-Burk plots used for?
To determine the Km and Vmax of an enzyme
To distinguish different types of enzyme inhibition
_____________reaction is a type of chemical reaction in which the rate of reaction is directly proportional to the concentration of one reactant
First order
What is happening in a zero order reaction?
the rate of the reaction is independent of the concentration of the reactant(s)
How does hexokinase contrast glucokinase?
It has a lower Vmax, lower Km, and turns off by high concentrations of glucose-6-P
What same reaction do both hexokinase and glucokinase catalyze?
Glucose —- glucose - 6 - phosphate
The phosphorylation of glucose.
Where is glucokinase found?
In the liver. Nutrients are absorbed from the intestine and go to the liver first, which allows glucokinase to convert excess glucose from a meal to glycogen.
High ________ = high capacity to convert substrate to product.
Vmax
What is significant about adding a P to glucose?
When glucose is phosphorylated, it becomes glucose-6-phosphate, which is an intermediate in both glycolysis (the breakdown of glucose for energy) and glycogenesis (the synthesis of glycogen for energy storage). The addition of a phosphate group makes it less likely for glucose-6-phosphate to leave the cell, effectively trapping the glucose molecule inside the cell for further metabolic processing.
______ also helps determine enzyme efficiency.
Km
Which is a more efficient enzyme, one with a larger or smaller value for Kcat/Km?
smaller
What does Kcat measure?
speed of P formation once ES has been made
What does Km measure?
binding affinity of E and S to make ES
Enzymes with very important physiological function tend to be very ____________.
efficient
What is the general purpose of carbonic anhydrase?
catalyze the interconversion between carbon dioxide (CO2) and bicarbonate ion (HCO3-)
aids in acid/base balance
What is the general purpose of triose phosphate isomerase?
catalyze the interconversion between two three-carbon sugar molecules: dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (G3P). (GLYCOLYSIS)
What is the general purpose of fumarase?
fumarase catalyzes the reversible hydration reactions (CAC)
What is the general purpose of acetylcholinesterase?
regulate the neurotransmitter acetylcholine (ACh) in chemical synapses
_________ kinetics also aids in the study of enzyme inhibition.
M & M
What are 3 types of reversible inhibition?
1.) competitive
2.) uncompetitive
3.) noncompetitive
The inhibition of an enzyme can be ________ or ________
Reversible or irreversible
In (reversible/irreversible) inhibition, the inhibitor can leave, restoring the enzyme to its uninhibited level of activity
reversible
In (reversible/irreversible) inhibition, the inhibitor remains permanently bound to the enzyme.
irreversible
In (competitive/ noncompetitive) inhibition, the inhibitor competes with substrate for binding at the active site.
competitive
In (competitive/uncompetitive) inhibition, the inhibitor does not compete with the substrate for the active site and cannot bind to enzyme alone.
uncompetitive
a (competitive/uncompetitive) inhibitor exerts control by binding to the enzyme-substrate complex.
uncompetitive
In _____________ control, the binding of a regulator at one site on a protein affects the protein’s ability to bind another molecule at a different site.
allosteric
In allosteric control, binding of a regulator changes the shape of an enzyme, which type of bonding is usually implemented?
noncovalent intermolecular forces
allosteric control (always/never) involves shape change of the enzyme.
always
Which is more common, competitive or uncompetitive inhibition?
competitive
G-6-P inhibition of hexokinase is an example of what type of inhibition?
reversible, noncompetitive
What kind of bond is formed in irreversible inhibition?
covalent
(zero/first/second) order reactions are often observed when the reaction is limited by factors other than reactant concentration, such as surface area or enzyme activity.
zero
V = Vmax [S] / (Km + [S])
What is this equation and what does it tell us?
Michaelis-Menten kinetics
Determines how much affinity an enzyme has for a substrate
(M&M)
V= ______
Speed your at
(M&M)
Vmax= ________
max speed conversion
(M&M)
S = _______
substrate concentration
(M&M)
Km = __________
substrate at 1/2 Vmax
how much substrate it takes for enzyme to function at 50% of its capability
In competitive inhibition, the Km is (increased/reduced/unaffected) and the vmax is (increased/reduced/unaffected). What would the LB plot look like?
increased/unaffected/crossed (like 2 lightsabers in a fight=competition)
In uncompetitive inhibition, the Km is (increased/decreased/unaffected) and the vmax is (increased/decreased/unaffected). What would the LB plot look like
reduced/reduced/parallel-shifted up (looks like the 2 parallel lines, Un- = Up!)
In non competitive (mixed) inhibition, the Km is (increased/decreased/unaffected) and the vmax is (increased/decreased/unaffected). What would the LB plot look like
unaffected/reduced/ ((non-Km-petitive) Km does not move so the x-intercept stays the same)
