Enzymology

Which of the following statements is FALSE concerning enzymes?

• Enzymes increase the rate of a reaction

• Enzymes change the reaction equilibrium

• Enzymes are specific for their substrates

• Enzymes are regulated through genetic and/or allosteric processes

The rate (or activity) of an enzyme-catalysed reaction is dependent on which of the following? Choose all those that apply

• pH

• temperature

• presence of cofactors

• incubation time

• type of buffer

Which of the following is the correct definition of Km?

• Km is the enzyme concentration at half-maximal velocity

• Km is the substrate concentration at initial phase velocity

• Km is inversely proportional to Vmax

• Km is the substrate concentration a half-maximal velocity

• Km is the rate limiting constant in enzymatic reactions

A high Km value indicates which of the following?

• weak binding affinity of an enzyme towards its substrate

• a high initial velocity was achieved upon addition of substrate

• the enzyme is saturated with substrate

• strong binding affinity of an enzyme towards its substrate

A low Km value indicates which of the following?

• weak binding affinity of an enzyme towards its substrate

• a high initial velocity was achieved upon addition of substrate

• the enzyme is saturated with substrate

• strong binding affinity of an enzyme towards its substrate

Using the equation above, calculate the rate of velocity when [S] = 5 x Km

• 80.3%

• 83.3%

• 65%

• 38.8%

• 89%

Using the equation above, calculate the rate of velocity when [S] = 10 x Km

• 91%

• 9.1%

• 19%

• 99.1%

• 79.1%

When is zero-order kinetics observed?

• when reaction rate is independent of [S] because the enzyme is saturated with substrate

• when reaction rate is dependent of [S] because the enzyme is saturated with substrate

• when reaction rate is independent of Km because the enzyme is saturated with substrate

• when Vmax is the same as Km because the enzyme is saturated with substrate

• when a non-competitive inhibitor is present thus affecting enzyme-substrate complex formation

When is first-order kinetics observed?

• when a competitive inhibitor is present thus reducing chance of enzyme-substrate complexes forming

• when reaction rate is dependent of [S] because the enzyme is saturated with substrate

• when reaction rate is independent of Km because the enzyme is saturated with substrate

• when the initial velocity of the reaction is directly proportional to the substrate concentration

• when a non-competitive inhibitor is present thus affecting enzyme-substrate complex formation

What phenomenon is observed when V = Vmax?

• non-competitive inhibition

• second-order kinetics

• first-order kinetics

• zero-order kinetics

• competitive inhibition