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- 1. Multiple Choice
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.
- 2. Multiple Choice
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.
- 3. Multiple Choice
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.
- 4. Multiple Choice
The diagram shows energy changes in a specific chemical reaction with and without the addition of an enzyme to the reaction. Which of the following questions can be answered by the diagram?
Does the addition of an enzyme reduce the activation energy required for a reaction?
Does the addition of an enzyme result in the formation of covalent bonds?
Does the addition of an enzyme produce a greater amount of products?
Does the addition of an enzyme change the pathway for the reaction?
- 5. Multiple Choice
To study the effects of catalase on its substrate, hydrogen peroxide, students made solutions of different hydrogen peroxide concentrations. The activity of the enzyme was measured by the amount it took for disks covered in catalase to convert the hydrogen peroxide to oxygen and water and float to the surface on the bubbles.
Which of the following experimental designs should be used as a control?
Place a catalase-soaked disk in a beaker of water
Drop the disks from different heights into the solution
Poke the floating disks back down to the bottom of the beaker and retime the rise of the disks
Shake the beakers during the time the disks are rising
Dip the disks in the 5% solution before putting them in any other solution
- 6. Multiple Choice
A researcher claims that increasing temperature by 10 degrees will double the rate of an enzyme-catalyzed reaction. To test this, he designed an experiment. For each tube, the researcher will measure the rate of product formation
Which best justifies the inclusion of tube 5 as a control?
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
- 7. Multiple Choice
A researcher claims that different enzymes exhibit maximal function over different pH ranges. To test this, they carry out an experiment that includes 3 different enzymes: pepsin, salivary amylase, and arginase.
Which of the following actions will provide the most appropriate negative control for the experiment?
Repeating the experimenet 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
- 8. Multiple Choice
Gelatin is a protein found in bones and skin of animals. To investigate the ability of enzymes to digest gelatin, students used camera film, which contains gelatin, and appears black but turns clear when gelatin is broken down. They incubated film in tubes of trypsin, lipase, and amylase. and recorded the time it took for enzymes to digest the gelatin, 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
- 9. Multiple Choice
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 in this experiment?
The initial concentration of teh substrate
the final concentration of the product
the three-dimensional structure of the enzyme
the temperature of the aqueous buffer solution
- 10. Multiple Choice
A researcher claims that some bacteria contain things the change the function of a particular enzyme. To test this, they will grow 2 different bacteria in separate cultures and isolate the contents of the cells from each. They will add different combinations of cell contents, substrate, and enzyme to test tubes at the optimal pH for the enzyme and then measure the rate of product formation.
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
- 11. Multiple Choice
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.
Which of the following 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 amylas 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
- 12. Multiple Choice
Which of the following can be used to determine the rate of enzyme-catalyzed reactions?
Rate of disappearance of the enzyme
Rate of disappearance of the substrate
Rate of disappearance of the product
Change in volume of the solution
Increase in activation energy
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