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Enzymes and Enzyme Kinetics: Enzyme Classification

by Kevin Ahern, PhD
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    The rates of enzymatic reaction and the affinity enzymes have for their substrates are important concepts to understand. I will deal with these topics in the first part of this presentation covering data analysis. I will also talk about allosterism and the affect it has on enzymes and their catalysis. Next I will talk about substrate binding and how that can happen in different mechanisms within enzymes. And last I will talk about the way that we classify enzymes and understand reactions in a very much broad sense. Okay under Michaelis-Menten Kinetics, we learned that it's important for us to study enzymatic reactions or the conditions where our study states. That is we have relatively constant amounts of ES complex. Under Michaelis-Menten Kinetics, the equation on the top applies and this equation tells us some important things that we are going to learn in this lecture. Now Vo that is the velocity of a reaction is equal to Vmax and that's something that we will discuss in a moment, times the concentration of substrate divided by another quantity called Km, that we will discuss, plus the concentration of substrate. So we have learned two terms here that are gonna become important for us to understand and that's Vmax, the maximum velocity of a reaction and Km which is a quantity that allows us to measure the affinity that an enzyme has for its substrate. Well, first let's start with Vmax. With Vmax, it's important to understand what it is, and why it is and how that happens. We saw when we plotted Vo versus the concentration of sustrate below, that, we saw that the curve grew and then it leveled off. And the reason it levels off is due to the way that enzyme work and the way that they...

    About the Lecture

    The lecture Enzymes and Enzyme Kinetics: Enzyme Classification by Kevin Ahern, PhD is from the course Enzymes and Enzyme Kinetics. It contains the following chapters:

    • Michaelis-Menten Kinetics: Considerations
    • Michaelis-Menten Kinetcs: Parameters
    • Perfect Enzyme & Lineweaver Burk Plot
    • Catalysis Considerations
    • Binding of Multiple Substrates
    • Classification of Enzymes

    Included Quiz Questions

    1. ...is not the same as Vmax/2.
    2. ...is proportional to the affinity of the enzyme for substrate.
    3. ...varies with substrate concentration.
    4. ...increases as the amount of enzyme decreases.
    1. ...give hyperbolic plots of V0 vs [S].
    2. ...are ones where the substrate changes the enzyme’s binding affinity when it is bound.
    3. ...have varying Km values.
    4. ...have constant Vmax values.
    1. ...an enzyme’s affinity for its substrate.
    2. ...the amount of enzyme required to get to Vmax/2.
    3. ..substrate necessary for Vmax
    4. ...amount of enzyme necessary to get to Kcat.
    1. ...Kcat is independent of the amount of enzyme used in a reaction.
    2. ...Vmax requires calculation of Km/2.
    3. ...Kcat is directly related to the amount of enzyme used.
    4. ...Kcat/2 gives a more accurate measure of Km.
    1. ...has a high Kcat and a low Km.
    2. ...has a high Vmax and Km.
    3. ...has a low Kcat and a high Km.
    4. ...is limited only by the diffusion of the enzyme in the solution.
    1. ...Km is the negative reciprocal of the value of the X-intercept.
    2. ...Vmax is equal to the value where the line crosses the Y-axis.
    3. ...the slope of the line is equal to Kcat/Km.
    4. ...Kcat is equal to the value of the X-intercept.
    1. ...R/T flipping occurs independently of binding of substrate.
    2. ...binding of substrate causes the enzyme to flip T/R state.
    3. ...the R-state is favored.
    4. ...binding of allosteric effector(s) cause the enzyme to flip states.
    1. ...binding of molecules causes the enzyme to flip T/R states.
    2. ...flipping occurs independently of binding of substrate.
    3. ...the R-state is favored.
    4. ...binding of product(s) cause the enzyme to flip states.
    1. ...ordered binding requires one substrate to bind first.
    2. ...the ping-pong mechanism refers to the enzyme flipping between T and R states.
    3. ...random binding allows the enzyme to rapidly switch between two different states.
    4. ...random binding is best explained by the Induced fit model.
    1. ...lyases catalyze breaking of bonds.
    2. ...transferases transfer energy to create high energy molecules.
    3. ...ligases break bonds.
    4. ...hydrolases use water to put together molecules.

    Author of lecture Enzymes and Enzyme Kinetics: Enzyme Classification

     Kevin Ahern, PhD

    Kevin Ahern, PhD


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