FOM 2.2.3 Flashcards
In an reaction why doesn’t the concentration of ES go to zero at long time points?
When the system reaches equilibrium, product is going to be turned into reactant and this will create a ES complex
Draw a graph of time vs concentration for the reaction:
E+S <—> ES
ES <—> EP
EP <—> E+P
Draw the lines for S, E, ES and P Also note where the transient state, equilibrium state and steady state are on the graph.
Slide 8 on Quantification of Enzyme reactions Just remember it and dont be a pussy
In a graph for time vs concentration for product formation, what does the slope of it equal?
Slope equals the rate of the reaction Vo
What is the equation for Vo?
Vo = (Vmax)/2 or Vo= k[E][S]
Why does substrate concentration dependence for determining Vo disappear at a high concentration?
The enzyme becomes saturated with substrate and it cannot work any faster
In a graph of substrate concentration vs Vo, how can you determine the amount of substrate present?
By knowing how fast the reaction is occurring you can derive the substrate concentration
What is Vmax?
The maximum rate by which a reaction can occur
What does the Vmax depend on? How can it be altered?
Vmax depends on the concentration of Enzyme present. Increasing the amount of enzyme present can increase the Vmax and decreasing the amount of enzyme can decrease the Vmax
What is Kcat?
The turnover number, the amount of reactions in time. It is independent of [E]
What is the formula for the formation of [ES]?
[ES] = k1[E][S]
What is the formula for the breakdown of [ES]?
[ES] = (k2+k3)[ES]
What is the formula for Km?
(K2+K3)/K1
What is the formula for Vmax?
(k3)([Etotal])
What is the michaelis-menten equation for Vo?
Vo = (Vmax[S])/(Km + [S])
What is Km?
Km is the substrate concentration when the reaction is going at 1/2 Vmax
What happens to Km when the concentration of enzyme in a system is increased or decreased?
The Km is unchanged the only thing that is changed is the Vmax
What it the effect of changing the [Total Enzyme] on Km, Kcat, Vo, and Vmax?
Km - No change Kcat - No change it is independent of the enzyme concentration (Turnover Number) Vo - No change Vmax - Increases or decreases depending on whether enzyme is added or lost
What is the effect of changing the substrate concentration on the Vmax, Kcat, Vo, and Km?
Vmax - no change Kcat - no change Vo - is the observed rate this will change with substrate concentration Km - no change
What will happen to enzyme activity is the concentration of co-enzyme changes?
Concentration of co-enzyme will alter the Vmax of a reaction similar to how the concentration of total enzyme will
What factors influence the kinetic constants?
Temp, pH, salt conc, and mutation in enzyme
What is a basic strategy for detecting reactions when signals are not available from substrate or product?
This happens in many lab tests. The reaction is coupled with another reaction that produces a color change that can be observed. The color will change at a rate that can determine things like rate of reaction or substrate concentration
Explain this picture and why the test might not be able to function at very high levels of glucose
The chromagen is the limiting factor, because eventually at a high enough level of glucose, it will run out.
Aspergillus niger glucose oxidase
Normal adult blood glucose: 65-120 mg/dL = 3.6 – 6.7 mM
Diabetic adults (uncontrolled): ≥ 200 mg/dL = 11.1 mM
550 mg/dL or more = 30 mM
Published Km range: 1.9 to 11.9 mM,
depending on expt’l conditions
pH, temperature, strip matrix
What other parameter could you adjust in order to choose conditions that would allow results to quickly be read by the patient?
A. [Glucose oxidase] B. [H2O2] C. [Glucose] D. [O2]
To make the test quicker it would be easiest to add more glucose oxidase to the reaction.
Aspergillus niger glucose oxidase
Normal adult blood glucose: 65-120 mg/dL = 3.6 – 6.7 mM
Diabetic adults (uncontrolled): ≥ 200 mg/dL = 11.1 mM
550 mg/dL or more = 30 mM
Published Km range: 1.9 to 11.9 mM,
depending on expt’l conditions
pH, temperature, strip matrix
Changed reaction conditions can alter Km. Which of the following would be the most appropriate value?
A. 1.9 mM B. 6.7 mM C. 11.9 mM D. 30 mM
It would be most appropriate to have it at 11.9mM because that would allow for the detection of normal concentrations as well as acutely high conditions
Do this
When [S] equals Km what can be said about the velocity of the reaction?
It is operating at 1/2 Vmax
An enzyme is suddenly introduced to a much higher amount of glucose than normally expected. What would happen to the Km of the reaction?
It would be unchanged
In the stomach a bunch of new enzyme is created to handle the meal that was just eaten. What could is happening to the Km and Vmax?
The Km is still unchanged you dipshit. The new enzyme will increase the Vmax of the reaction though.
What is going on in this picture?
The loss of NADH in reaction 2 is going to be associated with a loss of absorbance at 340 nm. This is going to give a clear picture of how much pyruvate is forming.
