Exam Two

Calculate Ki for molecule X. Ki = ________ µM

0.5

The Vmax for this reaction is 10 µM s-1. What is the Km of this enzyme-catalyzed reaction? _______ µM

2

An enzyme concentration of 0.005 µM was used in this experiment. What is the value of kcat for this reaction? __________ s-1

2000

The enzyme phosphoglycerate mutase catalyzes the conversion of 3-phosphoglycerate to 2-phosphoglucerate. The ΔG°′ for the reaction is -4.6 kJ mol-1. Determine the equilibrium constant, K′eq, for the reaction at T = 310 K. Use R = 8.315 x 10-3 kJ mol-1 K-1 K′eq = ______________

5.96

The amount of enzyme-substrate complex [ES] at a given substrate concentration is determined by the _____________ of that enzyme-catalyzed reaction.

Km

What is a catalyst?

a substance which increases the speed of a reaction, without being changed or used up in the reaction

The model for enzyme-substrate complementarity that states: an enzyme exists in an ensemble of structures. Substrate binds to enzyme molecules preorganized to be complementary to substrates. Other molecules of the enzyme will change shape to maintain equilibrium between different forms of the enzyme.

conformational selection

The type of enzyme -catalyzed reaction with multiple substrates that requires an enzyme-intermediate formed by a covalent bond between the enzyme active site and a group from the first substrate that binds is a(n)

double displacement (ping-pong) reaction.

The steady state assumption in Michaelis-Menten kinetics states that the concentration of _________ remains constant throughout the experiment measuring product formation as a function of time.

enzyme-substrate complex (ES)

Which of the following statements is true for enzymes that follow Michaelis-Menten kinetics?

if only the initial rate is used to calculate the rate in an experiment, k-2 can be omitted.

Repeating the same experiment with a concentration of 10 µM molecule X would ____________ the value of Kmapp compared to the value determined using 2 µM molecule X.

increase

Does a catalyst speed up the rate of the reaction in the forward or reverse direction?

it increases the rate in BOTH directions

What does a catalyst do to the activation energy?

it lowers the activation energy barrier

What type of biological molecules are most (almost all) enzymes?

proteins

At [substrate] = 3.0 µM, what percentage of total enzyme (ET) is present as part of an ES complex? _______%

60

Repeating the same experiment with a concentration of 10 µM molecule X would ____________ the value of Vmax compared to the value determined using 2 µM molecule X.

not change

Which one of the following statements is true regarding enzymes?

the majority of enzymes are proteins, but the majority of proteins do not function as enzymes

A higher concentration of products relative to substrates will contribute ______________ to the overall ΔG of a reaction.

unfavorably