quiz. AP. enzyme 1

A researcher proposes a model of an enzyme-catalyzed reaction in which a reactant is converted to a product. The model is based on the idea that the reactant passes through a transition state within the enzyme-substrate complex before the reactant is converted to the product.

Which of the following statements best helps explain how the enzyme speeds up the reaction?

• The enzyme’s active site binds to and stabilizes the reactant, which decreases the free-energy change of the reaction.

• The enzyme’s active site binds to and stabilizes the transition state, which decreases the activation energy of the reaction.

• The enzyme’s active site binds to and stabilizes the product, which increases the amount of energy released by the reaction.

• The enzyme’s active site binds to and stabilizes both the reactant and the product at the same time, which increases the reaction’s equilibrium constant.

Tags

NGSS.HS-PS1-5

Which of the following statements best helps explain the reaction specificity of an enzyme?

• The free energy of the reactants is greater than the free energy of the products.

• The equilibrium constant of the reaction is much greater than 1.

• The shape and charge of the substrates are compatible with the active site of the enzyme.

• The concentration of the enzyme inside living cells is greater than the concentration of substrate.

The enzyme hexokinase catalyzes the conversion of glucose to glucose-6-phosphate, which is an important step in glycolysis. The reaction involves the transfer of a phosphate group from ATP to glucose.Either a glucose molecule or a water molecule can fit in the active site of hexokinase. The presence of a water molecule in hexokinase’s active site would result in the hydrolysis of ATP

to ADP

instead of the conversion of glucose to glucose-6-phosphate.

Which of the following statements best helps explain the reaction specificity of hexokinase?

• Both glucose and water are polar molecules that form favorable interactions with charged and polar amino acid side chains in hexokinase’s active site.

• Both glucose and water have oxygen atoms that can form covalent bonds with the phosphorus atoms of phosphate groups.

• Glucose is an energy-rich organic molecule that can be broken down by glycolysis to produce ATP

  , whereas water is an inorganic molecule.

• Glucose has the right shape and charge to cause hexokinase to undergo a structural change needed for catalysis, whereas water does not.

Amylase is a protein that catalyzes the conversion of starch to simple sugars. Amylase activity in an aqueous solution can be measured by using iodine as a starch indicator. A solution containing iodine and starch will have a dark-blue color, whereas a solution containing iodine but no starch will have a light-brown color. The color change of an iodine solution from dark blue to light brown can be used to measure the rate at which starch is converted to simple sugars. A student designs an experiment to investigate the effect of environmental pH on amylase function. The design of the experiment is presented in Table 1 .

Which of the following statements best justifies the inclusion of test tube V as a control in the experiment?

• It will provide a measurement of amylase activity at an acidic pH

• It will provide a measurement of amylase activity at a basic pH.

• It will show the color change that occurs in the absence of enzyme activity.

• It will show the color change that occurs in the absence of the amylase protein

Tags

NGSS.HS-PS1-2

A researcher claims that some bacteria contain factors that influence the function of a particular enzyme but other bacteria do not. To test the claim experimentally, the researcher will grow two different bacterial strains in separate liquid cultures and isolate the contents of the cells in each culture. The researcher will add different combinations of cellular contents, substrate, and enzyme to test tubes containing a buffer solution adjusted to the optimal pH of the enzyme and then measure the rate of product formation. The design of the researcher’s experiment is presented in Table 1.

Which of the following statements best justifies the inclusion of test tubes 3 and 7 in the experiment?

• They will show whether the isolated cellular contents have enzymatic activity.

• They will show whether environmental pH

  affects the function of the enzyme.

• They will show the rate of product formation in the absence of bacterial factors.

• They will show the rate of product formation in the absence of the substrate.

A researcher designs an experiment to investigate the effect of environmental temperature on the function of an enzyme. For each trial included in the experiment, the researcher will add the enzyme and its substrate to an aqueous buffer solution and then measure the amount of product formed over 20 minutes.

Which of the following must remain the same for all trials of this experiment?

• The initial concentration of the substrate

• The final concentration of the product

• The three-dimensional structure of the enzyme

• The temperature of the aqueous buffer solution

Gelatin is a protein that is derived from collagen which is found in the bones, skin, and connective tissue of animals. To investigate the ability of various enzymes to digest gelatin, a group of students set up an assay involving camera film. Camera film contains gelatin and appears black when exposed to light but turns clear as the gelatin gets broken down. The students incubated pieces of exposed camera film in test tubes, each containing one of three different enzyme solutions (trypsin, lipase, or amylase) as indicated in Figure 1. The students recorded the time it took for the enzymes to digest the gelatin in each test tube, turning the film from black to clear.

Which of the following would be the most appropriate control for this experiment?

• A test tube containing no camera film

• A test tube containing only a piece of exposed camera film

• A test tube containing a piece of exposed camera film submerged in water

• A test tube containing a piece of exposed camera film and all three enzyme solutions

A researcher claims that different enzymes exhibit maximal function over different pH

ranges. To test the claim, the researcher carries out an experiment that includes three different enzymes: pepsin, salivary amylase, and arginase. The results of the experiment are represented in Figure 1.

Which of the following actions will provide the most appropriate negative control for the experiment?

• Repeating the experiment with a fourth enzyme

• Repeating the experiment at several different temperatures

• Repeating the experiment with denatured enzymes

• Repeating the experiment using several different methods for measuring pH

A researcher claims that increasing the environmental temperature by 10°C

will double the rate of an enzyme-catalyzed reaction. To test the claim, the researcher designs an experiment that uses a particular enzyme isolated from plants. The design of the experiment is presented in Table 1. For each test tube in the experiment, the researcher will measure the rate of product formation.

Which of the following statements best helps justify the inclusion of test tube 5 as a control in the experiment?

• It will provide a measurement of product formation in the absence of the substrate.

• It will provide a measurement of product formation in the presence of a denatured enzyme.

• It will show the effect of doubling the amount of substrate on the rate of product formation.

• It will show the effect of increased enzyme activity on the rate of product formation.