MCQs

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.

Temperature affects both reaction kinetics and enzyme stability. Even small deviations from the optimum can alter experimental results.

At substrate saturation, all available active sites are occupied, so adding more substrate cannot further increase the reaction rate.

Extreme pH alters the ionization of amino acid side chains and disrupts the interactions maintaining the enzyme's tertiary structure.

Each enzyme functions best within a specific pH range because proper ionization of amino acid residues in the active site is maintained.

With excess substrate available, more enzyme molecules provide additional active sites, increasing the overall reaction rate nearly proportionally.