MCQs

Additional enzyme molecules remain unused if substrate molecules are limiting.

Changes in pH alter the ionization of amino acid side chains, affecting substrate binding and catalytic function.

Up to the optimum temperature, increased molecular motion enhances effective collisions. Above the optimum, denaturation becomes the dominant effect.

Low temperatures slow molecular motion without permanently altering enzyme structure. Normal activity usually returns when the temperature is restored to the optimum value.

As substrate becomes depleted, enzyme-substrate complex formation decreases, reducing the overall reaction rate.

Temperature and pH strongly influence enzyme activity. Keeping them constant allows the effect of the experimental variable to be measured accurately.

More enzyme molecules provide more active sites, allowing more substrate molecules to be converted into product per unit time.

The ionization state of amino acid residues determines substrate binding and catalytic efficiency. Changes in pH alter these charges.

Thermophilic enzymes are structurally adapted to function efficiently at temperatures that would denature most ordinary enzymes.

Enzymes from different organisms and tissues have different amino acid compositions and structures, resulting in different optimum temperatures.

At low substrate concentrations, many active sites remain free. Therefore, increasing substrate concentration proportionally increases enzyme-substrate complex formation.

At saturation, all enzyme molecules are engaged in enzyme-substrate complexes, so increasing substrate concentration no longer increases the reaction rate.

High temperatures disrupt hydrogen bonds and other weak interactions, causing loss of the enzyme's three-dimensional structure and decreasing catalytic activity.

If substrate is insufficient, additional enzyme molecules remain unused because there are not enough substrate molecules to occupy their active sites.

Constant pH allows accurate measurement of other variables by preventing changes in the enzyme's active site charge.

Trypsin is adapted to the alkaline environment of the small intestine, where its catalytic residues remain correctly ionized.

Pepsin functions optimally around pH 2 due to the highly acidic conditions of the stomach.

Correct protonation of amino acid side chains is essential for substrate binding and catalysis. Extreme pH alters these charges.

Heat primarily disrupts weak interactions such as hydrogen bonds, altering the shape of the active site and reducing enzyme activity.