Bio Unit 3 quiz

Aminolevulinate dehydratase (ALAD) is an enzyme that relies on zinc as a coenzyme. A zinc ion binds to the ALAD

active site, where it forms favorable interactions with the side chains of three amino acids. Researchers have found that substituting a lead ion for a zinc ion in the ALAD

active site causes inhibition of ALAD.

Which of the following statements best helps explain how the lead ion causes inhibition of ALAD?

• It changes the shape and charge of the substrate so that it becomes more compatible with ALAD’s active site.

• It changes the amino acid sequence of the ALAD protein so that the enzyme catalyzes a different reaction.

• It changes the three-dimensional structure of the active site so that ALAD is no longer compatible with its substrate.

• It changes the enzyme-substrate complex so that the transition state is more stable and the reaction proceeds at a faster rate.

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NGSS.HS-PS1-2

Acetylcholinesterase (AChE) is a protein that catalyzes the conversion of acetylcholine to acetate and choline. When the concentration of AChE in an aqueous solution is held constant, the rate of the reaction catalyzed by AChE increases with increasing concentrations of substrate. At low concentrations of acetylcholine, a small increase in the substrate concentration results in a large increase in the reaction rate. At high concentrations of acetylcholine, however, a large increase in the substrate concentration results in only a small increase in the reaction rate.

Which of the following statements correctly explains the observed effect of the acetylcholine concentration on the rate of the enzyme-catalyzed reaction?

• The active site of AChE is specific for acetylcholine, and only one substrate molecule can occupy the active site at a time.

• AChE begins converting product into substrate as the acetylcholine concentration changes from low to high.

• The AChE protein becomes denatured as the acetylcholine concentration changes from low to high.

• The substrate specificity of AChE changes as the acetylcholine concentration changes from low to high

A researcher proposes a model to explain how enzyme-substrate interactions determine enzyme specificity. The model is based on the idea that substrate molecules form favorable interactions with the amino acid side chains in an enzyme’s active site.

Based on the model, which of the following statements best explains an enzyme’s specificity for a particular substrate molecule?

• A hydrophilic molecule interacts with nonpolar side chains in the enzyme’s active site.

• A hydrophobic molecule interacts with polar side chains in the enzyme’s active site.

• A molecule with positive charges interacts with positively charged side chains in the enzyme’s active site.

• A molecule with negative charges interacts with positively charged side chains in the enzyme’s active site.

• pH4 buffer solution and hydrogen peroxide only

• All five pH buffer solutions combined hydrogen peroxide only

• Water, hydrogen peroxide, and yeast

• Water and yeast only

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• Test tubes 1 and 2 only

• Test tubes 5 and 6 only

• Test tubes 1, 3, 5, and 7

• Test tubes 2, 4, 6, and 8

• It will show whether the changes observed in group 1 depend on the metabolic activity of soil bacteria.

• It will show whether the changes observed in group 1 depend on the type of plants used in the experiment.

• It will show the average growth rate of seedlings that are maintained in a nonsterile environment.

• It will show the changes that occur in the roots of seedlings following an infection by soil bacteria.

• It will act as a control for test tube 4 by showing the effect of the presence or absence of the substrate.

• It will act as a control for test tube 4 by showing the effect of a change in environmental temperature.

• It will act as a control for test tube 6 by showing the effect of the presence or absence of the enzyme.

• It will act as a control for test tube 6 by showing the effect of a change in sodium chloride concentration.

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NGSS.HS-PS1-5

Researchers investigated the effect of urea on the three-dimensional structure of a certain enzyme. The researchers dissolved the enzyme in an aqueous buffer solution and added urea to the solution. The enzyme did not appear to have a secondary or tertiary structure. The researchers carefully removed the urea from the solution and determined that the enzyme had the original secondary and tertiary structure again.

Based on the results of the experiment, which of the following statements best predicts the effect of urea on the enzyme’s function?

• Function will be disrupted by adding the urea and regained by removing the urea.

• Function will be disrupted by adding the urea, but it will not be regained by removing the urea.

• Function will be gained by adding the urea and disrupted by removing the urea.

• Function will be unaffected by the addition and removal of the urea.

• The amount of product will decrease until the reaction rate goes to zero.

• The amount of product will decrease until the reaction reaches its equilibrium point or until the enzyme is been used up by the reaction.

• The amount of product will increase until the reaction reaches its equilibrium point or until the substrate is used up by the reaction.

• The amount of product will increase without stopping because the enzyme will be unchanged by the reaction.

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NGSS.HS-PS1-5

• Young European flycatchers hatch from eggs when caterpillar biomass is available for the young birds to consume and convert into energy for growth.

• European flycatcher hatchlings begin to need energy to leave the nest only after the caterpillars have turned into pupae.

• Female European flycatchers require energy to lay eggs, so they lay their eggs when the caterpillar biomass is maximal.

• The energy requirements for hatching European flycatchers and caterpillars are proportional to each other.

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