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Enzymes and substrate concentration

Create a saturation curve by directly recording the initial velocity for each substrate concentration.

    B05 · Enzymes and substrate concentrationReady
    Create a saturation curve by directly recording the initial velocity for each substrate concentration. You can also experiment with the numbers and controls below.

    Life Sciences, Metabolism, Plant Physiology / Principles and Exploration

    Enzymes and substrate concentration — principles and investigation

    The speed of an enzyme reaction does not increase endlessly at the same rate even if the substrate is continuously increased. Compare saturation curves by changing substrate concentration, enzyme amount, and competitive inhibitor conditions. Distinguishing between the maximum reaction rate and the substrate concentration at which half that rate is reached allows interpretation of changes in enzyme quantity and competitive inhibition.

    How does it work?

    The amount of enzyme is proportional to Vmax. Competitive inhibition increases the apparent Km while maintaining the Vmax for the same amount of enzyme.

    Key relationship

    v = Vmax[S] / (Km(1+[I]/Ki)+[S])

    Try this investigation

    1. The orange substrate occupies the active site of the green enzyme. Compare market share and initial speed. The combined picture is an explanatory rendering of the statistical share.
    2. Create a saturation curve by directly running and recording the initial velocities at substrate concentrations of 0, 1, 2, 4, 8, and 16. All numbers are virtual relative values.
    3. Fix the substrate concentration and compare by doubling the enzyme amount or adding competitive inhibition of [I]=Ki.

    Interpreting your results

    With no inhibitor and [S] = Km, what is the initial reaction rate?

    If you put [S]=Km in v=Vmax[S]/(Km+[S]), v=Vmax/2. Competitive inhibition where [I]=Ki doubles the apparent Km and does not change Vmax.

    Assumptions and limitations

    It is a Michaelis-Menten initial velocity model that uses virtual relative values. Vmax=10×relative amount of enzyme, actual enzyme parameters have not been confirmed. It does not address substrate depletion, adverse reactions, rate reduction over time, temperature, denaturation, or non-competitive inhibition. 4 s is the combined observation production period and not the product accumulation rate measurement time.