ap bio test 3

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? A The initial concentration of the substrate B The final concentration of the product C The three-dimensional structure of the enzyme D The temperature of the aqueous buffer solution

A

A set of five additional test tubes were prepared and used as controls. Which of the following best describes the contents expected to be contained in one of the five control test tubes? A pH 4 buffer solution and hydrogen peroxide only B All five pH buffer solutions combined and hydrogen peroxide only C Water, hydrogen peroxide, and yeast D Water and yeast only

A

Based on Figure 1, which of the following statements best predicts the effect that a change from a moderately acidic environment (pH near 6) to a basic environment will have on peroxidase activity? A Peroxidase activity will decrease. B Peroxidase activity will increase. C Peroxidase activity will stay the same. D Peroxidase activity will increase at first and then decrease.

A

Based on the data, scientists claim that the reproductive behavior of European flycatchers is influenced by the availability of energy sources. Which of the following statements best justifies this claim? A Young European flycatchers hatch from eggs when caterpillar biomass is available for the young birds to consume and convert into energy for growth. B European flycatcher hatchlings begin to need energy to leave the nest only after the caterpillars have turned into pupae. C Female European flycatchers require energy to lay eggs, so they lay their eggs when the caterpillar biomass is maximal. D The energy requirements for hatching European flycatchers and caterpillars are proportional to each other.

A

Based on the results of the experiment, which of the following statements best predicts the effect of urea on the enzyme's function? A Function will be disrupted by adding the urea and regained by removing the urea. B Function will be disrupted by adding the urea, but it will not be regained by removing the urea. C Function will be gained by adding the urea and disrupted by removing the urea. D Function will be unaffected by the addition and removal of the urea.

A

Muscle contraction depends on A TP hydrolysis. During periods of intense exercise, muscle cells rely on the ATP supplied by three metabolic pathways: glycolysis, mitochondrial respiration, and the phosphagen system Figure 1 shows the rates at which the three metabolic pathways produce A TP following the start of an intense period of exercise. Which of the following correctly uses the data to justify the claim that the phosphagen system is an immediate, short- term source of ATP for muscle cells? A. ATP production by the phosphagen system increases and decreases rapidly following the start of the exercise period. B. ATP production by the phosphagen system increases gradually and continuously throughout the entire exercise period. C. The ATP produced by the phosphagen system contains more energy per molecule than does the ATP produced by the other pathways. D. ATP hydrolysis in muscle cells occurs immediately after the start of the exercise period but stops before the end of the exercise period.

A

Which of the following statements best helps justify the inclusion of group 2 as one of the controls in the experiment? A It will show whether the changes observed in group 1 depend on the metabolic activity of soil bacteria. B It will show whether the changes observed in group 1 depend on the type of plants used in the experiment. C It will show the average growth rate of seedlings that are maintained in a nonsterile environment. D It will show the changes that occur in the roots of seedlings following an infection by soil bacteria.

A

Which of the following statements best justifies the inclusion of test tubes 3 and 7 in the experiment? (A The will show whether the isolated cellular contents have enzymatic activity. (B They will show whether environmental pH affects the function of the enzyme. C They will show the rate of product formation in the absence of bacterial factors. D They will show the rate of product formation in the absence of the substrate

A

Which of the following statements correctly explains the observed effect of the acetylcholine concentration on the rate of the enzyme-catalyzed reaction? A The active site of AChE is specific for acetylcholine, and only one substrate molecule can occupy the active site at a time. B AChE begins converting product into substrate as the acetylcholine concentration changes from low to high. C The AChE protein becomes denatured as the acetylcholine concentration changes from low to high. D The substrate specificity of AChE changes as the acetylcholine concentration changes from low to high.

A

A researcher claims that the synthesis of ATP from ADP and inorganic phosphate (Pi) is essential to cellular function. Which of the following statements best helps justify the researcher's claim? A. ADP is a small molecule that some cells release into their environment as a way of communicating with other cells. B. ATP hydrolysis is an energy-releasing reaction that is often coupled with reactions that require an input of energy. C. Inorganic phosphate (Pi) is a substance that cells typically acquire from their environment. d. ATP synthase is a mitochondrial enzyme that catalyzes the conversion of ADP and P: to ATP.

B

Which of the following statements best clarifies how the data support the researcher's claim? A The thylakoid membrane is more permeable to carbon dioxide than to polar molecules. B ATP synthase activity depends on a proton gradient across the thylakoid membrane. C Some enzymes embedded in the thylakoid membrane catalyze the hydrolysis of ATP. D Carbon fixation in the Calvin-Benson cycle takes place in the stroma of chloroplasts.

B

Which of the following statements best helps explain how the enzyme speeds up the reaction? A The enzyme's active site binds to and stabilizes the reactant, which decreases the free-energy change of the reaction. B The enzyme's active site binds to and stabilizes the transition state, which decreases the activation energy of the reaction. C The enzyme's active site binds to and stabilizes the product, which increases the amount of energy released by the reaction. D 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.

B

Which of the following would be the most appropriate control for this experiment? A A test tube containing no camera film B A test tube containing only a piece of exposed camera film C A test tube containing a piece of exposed camera film submerged in water D A test tube containing a piece of exposed camera film and all three enzyme solutions

C

Which of the following statements best helps justify the inclusion of test tube 5 as a control in the experiment? A It will provide a measurement of product formation in the absence of the substrate. B It will provide a measurement of product formation in the presence of a denatured enzyme. C It will show the effect of doubling the amount of substrate on the rate of product formation. D It will show the effect of increased enzyme activity on the rate of product formation.

B

Which of the following statements provides reasoning that supports the claim that brown fatty tissue keeps an animal warm? A The uncoupling protein in this tissue increases the production of ATP and causes more body heat to be produced to warm the animal. B The uncoupling protein in this tissue reduces the proton gradient across the membrane and thus produces heat to warm the animal without ATP production. C The uncoupling protein in this tissue causes an increase in the proton gradient, which causes more ATP to be produced that helps to warm the animal. D The uncoupling protein in this tissue reduces the production of ATP and creates an increase in the proton gradient that allows more heat energy to be produced to warm the animal.

B

Which test tubes are controls in the experiment? A Test tubes 1 and 2 only B Test tubes 5 and 6 only C Test tubes 1, 3, 5, and 7 D Test tubes 2, 4, 6, and 8

C

A researcher claims that only a portion of the light energy captured by green plants is available for growth and repair. Which of the following observations best helps justify the researcher's claim? A. Light-capturing pigment molecules in green plants absorb red, blue, and violet light but reflect green light. B. The energy of a photon of light is proportional to its frequency and inversely proportional to its wavelength. C. As light energy is converted to chemical energy by metabolic processes, some of the energy is lost as heat. D. Captured energy is stored in the molecular bonds of organic molecules, including simple sugars and starch

C

One of the researchers proposes using oxygen gas production to measure reaction rates. Which of the following statements best justifies the use of the proposed modification as a way of creating an appropriate control for the investigation? A The experiment can be repeated without hydrogen peroxide, which will help eliminate an uncontrolled variable. B The experiment can be repeated without peroxidase, which will introduce a second independent variable. C The experiment can be repeated without guaiacol, which will reveal the effect of guaiacol on the reaction rates. D The experiment can be repeated without water, which will reveal whether the reaction can occur inside a living cell.

C

Protein digestion in humans is primarily carried out by three enzymes. Pepsin is found in the stomach (pH 2), where it aids in the breakdown of large proteins into smaller peptides, while trypsin and chymotrypsin are found in the small intestine (pH 8), where they aid in the further breakdown of the proteins into amino acids and dipeptides that can be absorbed into the bloodstream. Graph 1 shows the effect of pH on the activity levels of the three enzymes. Which of the following best predicts how the structure and function of pepsin will change as it enters the small intestine? A. Pepsin will not change in shape and will continue to break down proteins in the small intestine. B. Pepsin will not change in shape but may not work due to the basic environment of the small intestine. C. Pepsin will change in shape because of the basic environment of the small intestine; therefore, its enzymatic activity will decrease. D. Pepsin will change in shape because of the presence of trypsin and chymotrypsin in the

C

Which of the following actions will provide the most appropriate negative control for the experiment? A Repeating the experiment with a fourth enzyme B Repeating the experiment at several different temperatures C Repeating the experiment with denatured enzymes D Repeating the experiment using several different methods for measuring pH

C

Which of the following best predicts the immediate result of adding more substrate to the reaction mixture at the point indicated by the arrow in Figure 1? A The amount of product will decrease until the reaction rate goes to zero. B The amount of product will decrease until the reaction reaches its equilibrium point or until the enzyme is been used up by the reaction. C The amount of product will increase until the reaction reaches its equilibrium point or until V the substrate is used up by the reaction. D The amount of product will increase without stopping because the enzyme will be unchanged by the reaction.

C

Which of the following statements best helps explain how the lead ion causes inhibition of ALAD? A It changes the shape and charge of the substrate so that it becomes more compatible with ALAD's active site. B It changes the amino acid sequence of the ALAD protein so that the enzyme catalyzes a different reaction. C It changes the three-dimensional structure of the active site so that ALAD is no longer compatible with its substrate. D It changes the enzyme-substrate complex so that the transition state is more stable and the reaction proceeds at a faster rate.

C

Which of the following statements best helps explain the reaction specificity of an enzyme? A The free energy of the reactants is greater than the free energy of the products. B The equilibrium constant of the reaction is much greater than 1. C The shape and charge of the substrates are compatible with the active site of the enzyme. D The concentration of the enzyme inside living cells is greater than the concentration of substrate.

C

Which of the following statements best helps justify the inclusion of test tube 5 in the experiment? A It will act as a control for test tube 4 by showing the effect of the presence or absence of the substrate. B It will act as a control for test tube 4 by showing the effect of a change in environmental temperature. C It will act as a control for test tube 6 by showing the effect of the presence or absence of the enzyme. D It will act as a control for test tube 6 by showing the effect of a change in sodium chloride concentration.

C

Which of the following statements best helps justify the researcher's claim by providing a relevant example? A Yeast cells produce protein kinases, which are enzymes that catalyze the transfer of phosphate groups from ATP to protein substrates. B Yeast cells produce DNA polymerases, which are enzymes that catalyze the conversion of free nucleotides into strands of DNA C Yeast cells produce invertase, which is an enzyme that catalyzes the conversion of the disaccharide sucrose into glucose and fructose. D Yeast cells produce catalase, which is an enzyme that catalyzes the conversion of hydrogen peroxide into water and oxygen gas.

C

Which of the following statements best justifies the inclusion of test tube V as a control in the experiment? A It will provide a measurement of amylase activity at an acidic pH. (B) It will provide a measurement of amylase activity at a basic pH. (C It will show the color change that occurs in the absence of enzyme activity. D It will show the color change that occurs in the absence of the amylase protein.

C

Which of the following statements best establishes a connection between the observation and the researcher's claim? A Some antibiotics inhibit the synthesis of bacterial cell walls. B Some antibiotics inhibit protein synthesis in bacteria cells. C Some plasmids cannot exist in a bacterial cell with certain other plasmids. D Some plasmids contain antibiotic resistance genes.

D

Alcohol dehydrogenase (ADH) is an enzyme that aids in the decomposition of ethyl alcohol (CH, OH) into nontoxic substances. Methyl alcohol acts as a competitive inhibitor of ethyl alcohol by competing for the same active site on ADH. When attached to ADH, methyl alcohol is converted to formaldehyde, which is toxic in the body. Which of the following statements best predicts the effect of increasing the concentration of substrate (ethyl alcohol), while keeping the concentration of the inhibitor (methyl alcohol) constant? A. There will be an increase in formaldehyde because ADH activity increases. B. Competitive inhibition will be terminated because ethyl alcohol will bind to methyl alcohol and decrease ADH activity. C. The peptide bonds in the active site of the enzyme will be denatured, inhibiting the enzyme. D. Competitive inhibition will decrease because the proportion of the active sites occupied by substrate will increase.

D

Based on the model, which of the following statements best explains an enzyme's specificity for a particular substrate molecule? A A hydrophilic molecule interacts with nonpolar side chains in the enzyme's active site. B A hydrophobic molecule interacts with polar side chains in the enzyme's active site. C A molecule with positive charges interacts with positively charged side chains in the enzyme's active site. D A molecule with negative charges interacts with positively charged side chains in the enzyme's active site.

D

Which of the following actions will provide a negative control for the investigation? A Repeating the experiment at 25°C B Repeating the experiment using twice the amount of hydrogen peroxide C Repeating the experiment using twice the amount of peroxidase D Repeating the experiment using heat- denatured peroxidase

D

Which of the following statements best helps explain the reaction specificity of hexokinase? A Both glucose and water are polar molecules that form favorable interactions with charged and polar amino acid side chains in hexokinase's active site. B Both glucose and water have oxygen atoms that can form covalent bonds with the phosphorus atoms of phosphate groups. C Glucose is an energy-rich organic molecule that can be broken down by glycolysis to produce ATP, whereas water is an inorganic molecule. D Glucose has the right shape and charge to cause hexokinase to undergo a structural change needed for catalysis, whereas water does not.

D

Which of the following statements best helps justify the researcher's claim? A Organisms contain enzymes that lower the activation energies of specific chemical reactions. B An ecosystem is formed by the interaction of a community of organisms with their surrounding environment. C Photosynthetic organisms use the organic molecules produced during photosynthesis for growth and repair. D The total system that includes photosynthetic organisms and the Sun becomes less ordered over time.

D

Which of the following statements best justifies the researcher's claim? A The additional pigments allow the cyanobacteria to store light energy so that it can be used at night to continue photosynthesis. B The additional pigments block light and prevent it from reaching photosynthetic organisms at greater depths, so no photosynthetic organisms can live below the surface waters containing cyanobacteria. C The additional pigments require energy and cellular resources to produce, so they can be used as an energy source during times of insufficient light. D The additional pigments absorb light at wavelengths that green algae cannot absorb; this may allow cyanobacteria to capture more light energy for photosynthesis than green algae can in certain areas.

D

Which of the following types of evidence will best support the researcher's claim? A Evidence that some of the earliest eukaryotes used oxygen to produce ATP by cellular respiration B Evidence that the earliest plants produced oxygen as a by-product of photosynthesis C Evidence that some of the earliest organisms carried out photosynthesis without producing oxygen D Evidence that the cyanobacteria produced oxygen as a by-product of photosynthesis

D