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# Reaction rate and michaelis-menton kinetics

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A) What is the initial velocity v0 called when the substrate concentration [S] >>>KM ([S]&#61664; )?
Label on graph.
B) Simplify the above MM equation using the assumption that [S] >>>KM. From this simplified equation, what is the rate constant that describes the MM kinetics in the region [S] >>>KM?
Indicate on graph.
1. Would this rate be useful in determining the catalytic efficiency of a biological enzyme under physiological conditions?
C) Simplify the above MM equation using assumption the [S] <<KM. From this simplified equation, what is the rate constant that describes the MM kinetics for [S] <<KM?
1. Would this rate be useful in determining the catalytic efficiency of a biological enzyme under physiological conditions?
D) Using the MM equation, what is true about the initial velocity v0 when KM = [S]?
Indicate on the graph.
This is the concentration at which one half of the enzyme's active sites are occupied by substrates.

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#### Solution Preview

A) This represents the Vmax, which would be the top dotted line on the graph

B) If [S] is much bigger than Km, we can essentially pretend Km is zero, so we can simplify

kcat*[E][S]/([S]+0)
=kcat*[E]

Again, this would put us in a concentration range that approaches the Vmax, since it is TOTALLY dependent on enzyme concentration!

This quantity would not be very ...

#### Solution Summary

In this solution a typical michaelis-menten question is posed with a graph, and the various aspects are to be labelled. Also, the equation is derived using different approximations (assuming substrate is much lower than Km, for example). Vmax and Km are identified on the graph, and several conceptual questions regarding enzyme kinetics are answered.

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