Exam 7: Enzyme Mechanisms

The Lineweaver-Burk plot shows data obtained for an enzyme in the absence and presence of a reversible inhibitor. Which type of inhibitor was used in the experiment?

Hexokinase catalyzes the phosphorylation of glucose to glucose 6-phosphate. Hexokinase belongs to which enzyme class?

A Lineweaver-Burk plot displays parallel lines for an enzyme in the absence and presence of increasing amounts of an inhibitor. The inhibitor in this experiment

A patient presents with symptoms associated with the disease beriberi. An analysis of pyruvate dehydrogenase complex activity shows significantly reduced levels from normal. Predict how a deficiency in a coenzyme may be the culprit. Specify the coenzyme involved.

Which of the following is true of the induced-fit model of enzyme catalysis but NOT of the lock and key model of enzyme catalysis?

An experiment is performed in which the kinetics of an enzyme-catalyzed reaction at different pHs is monitored. It is found that the K_m does not change but that the k_cat increases as the pH goes above 7. Which of the following is true?

Propose an experiment to determine the presence of a predicted hydrophobic channel in a newly discovered enzyme. At your disposal you have the purified enzyme, the ability to analyze the enzyme by X-ray crystallography, a spectrophotometer, the enzyme substrate, and polyethylene glycol. Be sure to explain how the results will determine if the protein contains a hydrophobic channel.

Using words, define initial velocity (v₀) for an enzyme-catalyzed reaction.

The conversion of 2-phosphoglycerate to phosphoenolpyruvate is an example of which type of reaction?

K_M is equal to

The regulation of a biomolecule through the addition or removal of a molecular tag involves __________ reactions.

A kinase adds a phosphate group to a target enzyme, altering the catalytic efficiency of the enzyme. This is an example of

Justify how an enzyme that catalyzes a hydrolysis reaction does not contradict the concept that enzyme active sites are microenvironments that exclude excess water.

What three amino acids are targeted for phosphorylation by kinases?

Nitrite reductase contains two histidine amino acids that coordinate a Cu²⁺ ion. When the ion is present in the enzyme, the ion is a __________ and the enzyme is a _.

The catalytic triad of chymotrypsin is composed of His57, Ser195, and

Refer to the reaction coordinate diagram below. At what point is there a maximum number of interactions between the enzyme and the compound that it is binding?

An enzyme undergoes a mutation that causes it to lose the ability to be regulated via phosphorylation. Which of the following mutations may lead to this loss of regulation? Assume that the overall structure is not altered by the mutation.

Define the term zymogen.

Phosphorylation of __________ in glycogen phosphorylase shifts the enzyme to the __________.