UNIT 3 AP QUESTIONS

A researcher designs an experiment to investigate whether soil bacteria trigger the synthesis of defense enzymes in plant roots. The design of the experiment is presented in Table 1. For each group in the experiment, the researcher will determine the average rate of change in the amount of defense enzymes in the roots of the seedlings. Table 1. An experiment to investigate the effect of soil bacteria on plant defenses 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 It will show whether the changes observed in group 1 depend on the metabolic activity of soil bacteria.

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

Muscle contraction depends on ATP 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 ATP 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? * ATP production by the phosphagen system increases and decreases rapidly following the start of the exercise period. ATP production by the phosphagen system increases gradually and continuously throughout the entire exercise period. ATP hydrolysis in muscle cells occurs immediately after the start of the exercise period but stops before the end of the exercise period.

ATP production by the phosphagen system increases and decreases rapidly following the start of the exercise period.

Scientists investigated the effect of oxygen levels on the net rate of carbon fixation in two types of plants. The plants were grown in either well-watered soil (control) or dry soil and then exposed to either 21% or 1% O2 . The net rate of CO2 fixation for both types of plants was measured. Data are shown in Figure 1 and Figure 2 . Which of the following statements about the rate of CO2 fixation in the two types of plants is supported by the data shown in the figures? * At 21% O2 , plant type 2 has a lower rate of CO2 fixation than plant type 1 does in both types of soil. At 1% O2 , plant type 2 has a higher rate of CO2 fixation than plant type 1 does in the dry soil but not in the control soil. The rate of CO2 fixation is the same in both types of plants in the control soil at both oxygen levels. Plant types 1 and 2 have a statistically different rate of CO2 fixation in both soil types at both oxygen levels.

At 21% O2 , plant type 2 has a lower rate of CO2 fixation than plant type 1 does in both types of soil.

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.

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.

Which of the following best explains the connection between energy, growth, and the maintenance of an ordered system in the experiment? * Energy input from light is required for the grass to grow and maintain an ordered structure. The grass obtains the energy for growth and maintenance of order from nutrients from the soil. The grass couples the release of energy from the light reactions with the production of oxygen (O2) used to produce sugars for growth. Energy is required for the growth of the grass but not the maintenance of order.

Energy input from light is required for the grass to grow and maintain an ordered structure.

A researcher claims that the initial rise of oxygen in Earth's early atmosphere, which occurred approximately 2.3 billion years ago, resulted from the metabolic activity of prokaryotic organisms. The claim is based on an interpretation of the geochemical and fossil evidence represented in Figure 1. Figure 1. Selected events in geologic time based on geochemical and fossil evidence 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 ATPATP 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

Evidence that the cyanobacteria produced oxygen as a by-product of photosynthesis

Which of the following questions is most relevant to understanding the Calvin cycle? * How is ATP used in the formation of 3-carbon carbohydrates? How is ATP produced in chemiosmosis? How is NADP+ reduced to NADPH? How does chlorophyll capture light?

How is ATP used in the formation of 3-carbon carbohydrates?

Researchers investigated the influence of environmental pH on the activity of peroxidase, an enzyme that catalyzes the conversion of hydrogen peroxide to water and oxygen gas. In an experiment, the researchers added a hydrogen peroxide solution containing guaiacol to several identical test tubes and adjusted the solution in each test tube to a different pH. The researchers included the guaiacol because it caused the solutions to change color as the reactions proceeded, which the researchers relied on for measuring reaction rates. Finally, the researchers added the same amount of peroxidase to each test tube and measured the rate of each reaction at 23°C. The results of the experiment are represented in Figure 1. Figure 1. The effect of pH on peroxidase activity Which of the following actions will provide a negative control for the investigation? A Repeating the experiment at 25°C25°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

Repeating the experiment using heat-denatured peroxidase

A researcher claims that genetic variation provides organisms with the ability to survive and reproduce in different environments. To support the claim, the researcher makes the following observation: bacteria that contain plasmids (small DNA molecules) are resistant to a wider range of antibiotics than are bacteria that contain no plasmids. 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.

Some plasmids contain antibiotic resistance genes.

A student designs an experiment to investigate the influence of temperature on enzyme function. The student's plan is presented in Table 1. Table 1. An experiment to investigate the influence of temperature on enzyme function Test TubeSubstrate AddedEnzyme AddedTemperature 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

Test tubes 1, 3, 5, and 7

In an experiment, a researcher prepares a reaction mixture by dissolving a substance in a buffered solution. The substance is the substrate of a certain enzyme. The researcher adds a small amount of the enzyme to the reaction mixture and measures the amount of product that is formed over time. The data are represented in Figure 1. Figure 1. The amount of product formed by an enzyme-catalyzed reaction over time 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 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.

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

Brown fat is a type of fat tissue found in hibernating mammals. Inside the mitochondria of these fat tissue cells, these mammals have an uncoupling protein embedded in the inner mitochondrial membrane. This uncoupling protein allows hydrogen ions to leak from the intermembrane space back into the mitochondrial matrix. Figure 1 shows details of the processes in the inner mitochondrial membrane. Figure 1. Processes in the inner mitochondrial membrane 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 ATPATP 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 ATPATP production. C The uncoupling protein in this tissue causes an increase in the proton gradient, which causes more ATPATP to be produced that helps to warm the animal. D The uncoupling protein in this tissue reduces the production of ATPATP and creates an increase in the proton gradient that allows more heat energy to be produced to warm the animal.

The uncoupling protein in this tissue reduces the proton gradient across the membrane and thus produces heat to warm the animal without ATPATP production.

European flycatchers feed caterpillars to their hatchlings. Graph 1 shows the average dates of hatching and fledging (leaving the nest), and the biomass of the caterpillars between early May (when flycatcher young hatch) and June (when fledging of young occurs). Graph 1. Comparison of European flycatcher hatching and fledging dates and caterpillar biomass 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.

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

To test the hypothesis that a particular plant synthesizes storage lipids by using glyceraldehyde 3-phosphate (G3P) from photosynthesis, a researcher plans to use radiolabeled precursors to track the molecules through the biosynthetic pathway. Which of the following radiolabeled precursors is most appropriate for the researcher to use? * A15N-labeled N2, because atmospheric nitrogen is fixed to amino acids by photosynthesis (B)14C-labeled COy, because atmospheric carbon is fixed to carbohydrates by photosynthesis C35g-labeled methionine, because amino acids are incorporated into lipids during photosynthesis D32p-labeled phosphate, because lipids are stored in plants as phospholipids

(B)14C-labeled COy, because atmospheric carbon is fixed to carbohydrates by photosynthesis

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 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.

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

A researcher claims that a certain herbicide suppresses plant growth by inhibiting chloroplast function. To test the claim, the researcher treats isolated chloroplasts with increasing concentrations of the herbicide. The data from the experiment are presented in Table 1. Table 1. The effect of an herbicide on the function of isolated chloroplasts Herbicide Concentration (μg/L)pH Difference across Thylakoid MembraneATP Production03.5Very high22.5Moderate80.5Very low320Very low 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 ATPATP synthase activity depends on a proton gradient across the thylakoid membrane. C Some enzymes embedded in the thylakoid membrane catalyze the hydrolysis of ATPATP. D Carbon fixation in the Calvin-Benson cycle takes place in the stroma of chloroplasts.

ATPATP synthase activity depends on a proton gradient across the thylakoid membrane.

Pectinase is a protein that catalyzes the breakdown of pectic polysaccharides in plant cell walls. A researcher designs an experiment to investigate the effect of salinity on the ability of pectinase to lower the activation energy of the reaction involved. The design of the experiment is presented in Table 1. For each test tube, the researcher will measure the amount of product formed over 20 minutes. 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 It will act as a control for test tube 6 by showing the effect of the presence or absence of the enzyme.

Which of the following best predicts how the structure and function of pepsin will change as it enters the small intestine? Pepsin will not change in shape and will continue to break down proteins in the small intestine. Pepsin will not change in shape but may not work due to the basic environment of the small intestine. Pepsin will change in shape because of the basic environment of the small intestine; therefore, its enzymatic activity will decrease. Pepsin will change in shape because of the presence of trypsin and chymotrypsin in the small intestine, both of which act as competitive inhibitors.

C Pepsin will change in shape because of the basic environment of the small intestine; therefore, its enzymatic activity will decrease

Alcohol dehydrogenase (ADHADH) is an enzyme that aids in the decomposition of ethyl alcohol (C2H5OH)(C2H5OH) into nontoxic substances. Methyl alcohol acts as a competitive inhibitor of ethyl alcohol by competing for the same active site on ADHADH. When attached to ADHADH, 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? There will be an increase in formaldehyde because ADHADH activity increases. Competitive inhibition will be terminated because ethyl alcohol will bind to methyl alcohol and decrease ADHADH activity. The peptide bonds in the active site of the enzyme will be denatured, inhibiting the enzyme. Competitive inhibition will decrease because the proportion of the active sites occupied by substrate will increase.

Competitive inhibition will decrease because the proportion of the active sites occupied by substrate will increase.

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? 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.

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

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.

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

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? 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.

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

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.

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

Which of the following statements best justifies the inclusion of test tube VV as a control in the experiment? It will provide a measurement of amylase activity at an acidic pHpH. It will provide a measurement of amylase activity at a basic pHpH. 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.

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

Which of the following claims is best supported by the experimental results? * Light is required for the electron transport chain to transfer electrons. Water, not carbon dioxide, is the source of electrons used in the light-dependent reaction of photosynthesis. Carbon dioxide is the source of carbon used by green plants to build carbohydrates. DCPIP provides a significant source of electrons to the electron transport chain of the light reaction in the absence of light.

Light is required for the electron transport chain to transfer electrons.

Researchers investigated the influence of environmental pH on the activity of peroxidase, an enzyme that catalyzes the conversion of hydrogen peroxide to water and oxygen gas. In an experiment, the researchers added a hydrogen peroxide solution containing guaiacol to several identical test tubes and adjusted the solution in each test tube to a different pH. The researchers included the guaiacol because it caused the solutions to change color as the reactions proceeded, which the researchers relied on for measuring reaction rates. Finally, the researchers added the same amount of peroxidase to each test tube and measured the rate of each reaction at 23°C. The results of the experiment are represented in Figure 1. Figure 1. The effect of pH on peroxidase activity 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.

Peroxidase activity will decrease.

Based on the data shown, changes in the light intensity resulted in changes in the rate of which of the following processes? * Excretion Photosynthesis Respiration Translation Transcription

Photosynthesis

What most likely causes the trends in oxygen concentration shown in the graph above? * The water becomes colder at night and thus holds more oxygen. Respiration in most organisms increases at night. More organisms are respiring at night than during the day. Photosynthesis produces more oxygen than is consumed by respiration during the day.

Photosynthesis produces more oxygen than is consumed by respiration during the day.

A researcher claims that different enzymes exhibit maximal function over different pHpH 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. Figure 1. The effect of pHpH on three different enzymes 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

Repeating the experiment with denatured enzymes

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? 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.

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

Phycobiliproteins are a complex of accessory pigments and proteins found in cyanobacteria but not in green algae. A researcher claims that the phycobiliprotein pigments in cyanobacteria allow the cyanobacteria to survive in certain aquatic niches better than green algae can. 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.

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.

A researcher is investigating the effects of a chemical that makes thylakoid membranes permeable to hydrogen ions ( H+ ). Which of the following is the most likely direct effect of adding the chemical to plant cells? * The plant cells will split fewer water molecules into hydrogen ions and oxygen. The plant cells will produce less NADPH . Chlorophyll will require less light energy to excite its electrons. The chloroplasts will generate less ATP .

The chloroplasts will generate less ATP .

In most freshwater fish, nitrogenous waste is primarily excreted as ammonia, which is highly soluble in water and is toxic at low concentrations. In terrestrial mammals, ammonia is converted to urea before it is excreted. Urea is also highly soluble in water but is less toxic than ammonia at low concentrations. Which of the following best explains why freshwater fish do not convert ammonia to urea for excretion? * The metabolic pathways of fish do not normally involve nitrogen consumption. The dilution of ammonia by direct excretion into freshwater conserves energy. Ammonia is concentrated in tissues, where it is stored prior to excretion. The nitrogen in ammonia is recycled for use in protein and nucleotide synthesis.

The dilution of ammonia by direct excretion into freshwater conserves energy.

Researchers investigated the influence of environmental pH on the activity of peroxidase, an enzyme that catalyzes the conversion of hydrogen peroxide to water and oxygen gas. In an experiment, the researchers added a hydrogen peroxide solution containing guaiacol to several identical test tubes and adjusted the solution in each test tube to a different pH. The researchers included the guaiacol because it caused the solutions to change color as the reactions proceeded, which the researchers relied on for measuring reaction rates. Finally, the researchers added the same amount of peroxidase to each test tube and measured the rate of each reaction at 23°C. The results of the experiment are represented in Figure 1. Figure 1. The effect of pH on peroxidase activity 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? 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.

The experiment can be repeated without guaiacol, which will reveal the effect of guaiacol on the reaction rates.

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

The initial concentration of the substrate

Which of the following is an important difference between light-dependent and light-independent reactions of photosynthesis? * The light-dependent reactions occur only during the day; the light-independent reactions occur only during the night. The light-dependent reactions occur in the cytoplasm; the light-independent reactions occur in chloroplasts. The light-dependent reactions utilize CO2 and H2O; the light-independent reactions produce CO2 and H2O. The light-dependent reactions depend on the presence of both photosystems I and II; the light-independent reactions require only photosystem I. The light-dependent reactions produce ATP and NADPH; the light-independent reactions use energy stored in ATP and NADPH.

The light-dependent reactions produce ATP and NADPH; the light-independent reactions use energy stored in ATP and NADPH.

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

A researcher claims that the incorporation of carbon dioxide into organic molecules during photosynthesis does not violate the second law of thermodynamics. 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.

The total system that includes photosynthetic organisms and the Sun becomes less ordered over time.

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 pHpH 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.

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

A researcher claims that budding yeast are able to survive in different environments because they produce enzymes that allow them to use different molecules as sources of matter and energy. 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 ATPATP to protein substrates. B Yeast cells produce DNADNA polymerases, which are enzymes that catalyze the conversion of free nucleotides into strands of DNADNA. 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.

Yeast cells produce invertase, which is an enzyme that catalyzes the conversion of the disaccharide sucrose into glucose and fructose.

A student placed 20 tobacco seeds of the same species on moist paper towels in each of two petri dishes. Dish A was wrapped completely in an opaque cover to exclude all light. Dish B was not wrapped. The dishes were placed equidistant from a light source set to a cycle of 14 hours of light and 10 hours of dark. All other conditions were the same for both dishes. The dishes were examined after 7 days, and the opaque cover was permanently removed from dish A. Both dishes were returned to the light and examined again at 14 days. The following data were obtained. According to the results of this experiment, germination of tobacco seeds during the first week is: * increased by exposure to light unaffected by light intensity prevented by paper towels accelerated in green-leaved seedlings

increased by exposure to light

The enzyme peroxidase is found in many organisms. It catalyzes the breakdown of hydrogen peroxide into water and oxygen gas. The rate of peroxidase activity at different pHpH values was assessed by students in the lab. The students' results are shown in graph 1. Graph 1. Effect of pHpH on peroxidase activity If the experiment is repeated at pHpH 11, the observed activity level of the enzyme will most likely be the same as the level at pHpH 7 lower than the level at pHpH 9 greater than the level at pHpH 9 between the levels observed at pHpH 5 and pHpH 7.

lower than the level at pHpH 9

Catalase is an enzyme found in yeast cells that facilitates the chemical breakdown of hydrogen peroxide to water and oxygen gas. An experiment was conducted to determine the effect of pH on catalase function. Five buffer solutions of varying pH (2, 4, 6, 8, and 10) were prepared and added to separate test tubes. Hydrogen peroxide (H2O2) was added to each test tube. Yeast was added, and the reactions were timed. After 1 minute the amount of oxygen gas released was determined by measuring the foam layer produced in each test tube. Figure 1 illustrates the experimental setup. Figure 1. Illustration of experimental procedure 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 pHpH buffer solutions combined and hydrogen peroxide only C Water, hydrogen peroxide, and yeast D Water and yeast only

pH 4 buffer solution and hydrogen peroxide only

Carbohydrate-synthesizing reactions of photosynthesis directly require * light products of the light reactions darkness O2 and H2O chlorophyll and CO2

products of the light reactions