Exam 8: Energy, Enzymes, and Metabolism

Refer to the graph below. This graph shows the change in the rate of a reaction catalyzed by an enzyme as temperature is increased.At point _______, the low activity is due to denaturation of the enzyme, whereas at point _______, the low activity is due to low kinetic energies of the substrate and enzyme molecules in solution.

A readily reversible reaction, in which reactants and products have almost equal free energies, is indicated by a

You are working with an enzyme and wish to determine its saturation point.You note that the reaction rate increases slowly at first, then increases dramatically over a narrow range of substrate concentrations, and then levels off, creating a sigmoid reaction curve.It is likely that this enzyme is regulated by

A biochemist generates an enzyme activity curve for an unknown enzyme.The curve is shown below. Which statement best explains the shape of this curve?

Refer to the figure below. The graph was constructed from reaction-rate data collected using a constant amount of purified enzyme and increasing concentrations of substrate.Under conditions at point X, the graph indicates that the reaction rate changed dramatically when just a small increase in substrate concentration was made.Under conditions at point Y, the reaction rate changed very little with the same increase in substrate concentration.Explain why.

Some enzymes cause chemical bonds in their substrates to become stretched as the substrate binds to the active site.This change is called

Refer to the figure below. This figure illustrates the _______, which applies to all energy transformations in the universe, including all biological transformations.

The enzyme -amylase increases the rate at which starch is broken down into smaller oligosaccharides by _______ of the reaction.

Which term describes the high-energy state that two substrates must form before the reaction can proceed?

Refer to the figure below. The figure shows the metabolic conversions between metabolite X and metabolite Y in a cell.Each direction of this conversion is catalyzed by a different enzyme.Explain how this arrangement enables shifts in the flux of molecules in different metabolic directions, depending on the needs of the cell.

In the presence of alcohol dehydrogenase, the rate of reduction of acetaldehyde to ethanol increases as the concentration of acetaldehyde increases.Eventually, the rate of the reaction reaches a maximum, at which point further increases in the concentration of acetaldehyde have no effect.Why?

Which type of inhibitor can be overcome completely by the addition of more substrate?

The graph of enzyme activity versus substrate concentration for an enzyme has a sigmoidal (S-shaped) appearance.Such an activity curve indicates which type of enzyme?

An enzyme is found to be inhibited by a molecule that has a very different shape and size than either of the enzyme's two substrates.Moreover, the inhibitory molecule can bind to the enzyme in the absence of the substrates, and when it does bind, the molecule causes the enzyme to dissociate from a four-part quaternary structure to a two-part structure.What type of inhibitor is the molecule?

To be metabolized, glucose must be converted to glucose 6-phosphate.However, the phosphorylation of glucose to form glucose 6-phosphate is endergonic with a positive G.How do cells circumvent this problem?

Refer to the figure below. NAD⁺ functions as a coenzyme in many enzyme-catalyzed reactions.The changes that take place in this coenzyme are the same for all of these reactions and are illustrated in the figure.It is likely that, in these reactions, NAD⁺

You observe an enzymatic reaction that exhibits a standard relationship between reaction rate and substrate concentration as it converts substrate B to product C.When you add compound A, the creation of product C comes to a complete stop.You add large quantities of substrate B but still are unable to create product C in the presence of compound A.Compound A is therefore most likely a

The enzyme glucose oxidase binds the six-carbon sugar glucose and catalyzes its conversion to glucono-1,5-lactone.Mannose is also a six-carbon sugar, but glucose oxidase cannot bind mannose.The specificity of glucose oxidase is based on the

In thermodynamic terms, water held back by a dam represents _______ energy.

The five reactions listed are catalyzed by enzymes in a cell.Which reaction is catalyzed by an oxidoreductase?