When the velocity of enzyme activity is plotted against substrate

concentration, which of the following is obtained?

Hyperbolic curve

Parabola

Straight line with positive slope

Straight line with negative slope

When the velocity of enzyme activity is plotted against substrate concentration, the correct answer is hyperbolic curve. This relationship follows Michaelis-Menten kinetics, where reaction rate increases with substrate levels until enzyme saturation at Vmax.

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Why Hyperbolic Curve?

Enzymes bind substrates at active sites, forming enzyme-substrate complexes that drive catalysis. At low substrate concentrations, velocity rises nearly linearly as more complexes form. As concentration increases, sites saturate, causing the curve to plateau asymptotically toward maximum velocity (Vmax), creating the hyperbolic shape.

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The Michaelis constant (Km) marks the substrate concentration at half Vmax, quantifying enzyme-substrate affinity. This plot is fundamental in enzyme kinetics studies.

Parabola Option

A parabola implies symmetric upward or downward bending, like y=x2y=x2, which does not fit enzyme saturation. Enzyme rates do not continue accelerating indefinitely; they level off, ruling out this quadratic form.

Straight Line with Positive Slope

This suggests direct proportionality (first-order kinetics), valid only at very low substrate levels where enzyme is unsaturated. Overall, the plot deviates as saturation occurs, forming a curve instead.

Straight Line with Negative Slope

Negative slopes indicate inhibition or decreasing rates, irrelevant here without inhibitors. Enzyme velocity always increases or plateaus with substrate, never decreases.