MCQs

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.

Low temperature slows the movement of enzyme and substrate molecules, reducing effective collisions. The effect is generally reversible.

With substrate in excess, the reaction rate depends mainly on the number of enzyme molecules available to catalyze the reaction.

Maximum velocity (Vmax) is reached when every active site is occupied. Adding more substrate cannot further increase the reaction rate.

At low substrate concentrations, many enzyme active sites are unoccupied. Increasing substrate concentration increases the frequency of enzyme-substrate complex formation and accelerates the reaction.

Increasing both enzyme and substrate together provides more catalytic sites and sufficient substrate, leading to a marked increase in reaction rate until another factor becomes limiting.

Each enzyme has a unique active site with specific amino acid residues that require particular ionization states for maximum catalytic efficiency.

Excessive heat disrupts the three-dimensional conformation required for catalytic activity, resulting in denaturation.

Higher temperature increases kinetic energy, producing more frequent effective collisions until the optimum temperature is reached.

Most human intracellular enzymes function best near neutral pH because this reflects the physiological environment of body cells.

Highly alkaline conditions alter the tertiary structure by disrupting weak bonds, leading to reduced catalytic activity or denaturation.

Fewer enzyme molecules mean fewer active sites are available for catalysis, reducing the reaction rate.

With excess substrate, every added enzyme molecule finds substrate to act upon, causing the reaction rate to increase proportionally.

Changes in pH alter the charge of amino acid side chains, affecting substrate binding and catalytic activity without changing the enzyme's molecular mass.

Once every enzyme molecule has formed an enzyme-substrate complex, the enzyme becomes saturated. The reaction reaches Vmax, and additional substrate cannot further increase the rate.