UNIT 3 AP BIO
Process in which CO2, is released as a by-product of oxidation-reduction reactions
(Krebs cycle (citric acid cycle)
Figure 1. Key steps in the metabolic pathway of glucose Based on Figure 1, the net number of ATP molecules produced during glycolysis from the metabolism of a single glucose molecule is closest to which of the following?
2
During aerobic cellular respiration, oxygen gas is consumed at the same rate as carbon dioxide gas is produced. In order to provide accurate volumetric measurements of oxygen gas consumption, the experimental setup should include which of the following?
A substance that removes carbon dioxide gas
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 a piece of exposed camera film submerged in water
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. Which of the following statements best clarifies how the data support the researcher's claim?
ATP synthase activity depends on a proton gradient across the thylakoid membrane.
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?
As light energy is converted to chemical energy by metabolic processes, some of the energy is lost as heat.
Process in which carbon from CO2 is incorporated into organic molecules
Calvin cycle (light-independent reactions of photosynthesis)
Alcohol dehydrogenase (ADH) is an enzyme that aids in the decomposition of ethyl alcohol (C2H5OH) 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?
Competitive inhibition will decrease because the proportion of the active sites occupied by substrate will increase.
A researcher claims that different metabolic pathways allow bacteria 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?
E. coli bacteria reproduce in liquid media containing either glucose or galactose.
A scientist claims that Elysia chlorotica, a species of sea slug, is capable of photosynthesis. Which of the following observations provides the best evidence to support the claim?
Elysia chlorotica grows when exposed to light in the absence of other food sources.
Which of the following types of evidence will best support the researcher's claim?
Evidence that the cyanobacteria produced oxygen as a by-product of photosynthesis
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.
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?
Glucose has the right shape and charge to cause hexokinase to undergo a structural change needed for catalysis, whereas water does not.
Cyanobacteria contain a variety of pigment molecules, as shown in Table 1. As a result, the color of cyanobacteria cultures can vary significantly based on the relative amount of each pigment produced. A researcher placed a culture of cyanobacteria under green lights. Within a few weeks, the appearance of the cyanobacteria changed from green to red. The researcher claimed the color change in the culture was the result of an adaptation allowing greater photosynthesis. Which of the following provides the best reasoning to justify the researcher's claim?
In green light, more phycoerythrin molecules are produced, allowing more green light to be absorbed, thus increasing photosynthesis.
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 ALADactive site causes inhibition of ALAD. Which of the following statements best helps explain how the lead ion causes inhibition of ALAD?
It changes the three-dimensional structure of the active site so that ALAD is no longer compatible with its substrate.
Which of the following statements best helps justify the inclusion of test tube 5 in the experiment?
It will act as a control for test tube 6 by showing the effect of the presence or absence of the enzyme
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 presence of a denatured enzyme.
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?
Young European flycatchers hatch from eggs when caterpillar biomass is available for the young birds to consume and convert into energy for growth.
Which of the following statements best justifies the inclusion of test tube V as a control in the experiment?
It will show the color change that occurs in the absence of enzyme activity.
Which of the following statements best helps justify the inclusion of group 2 as one of the controls in the experiment?
It will show whether the changes observed in group 1 depend on the metabolic activity of soil bacteria.
Process in which O2 is released as a by-product of oxidation-reduction reactions
Light-dependent reactions of photosynthesis
In chloroplasts, ATP is synthesized from ADP plus inorganic phosphate (Pi)(Pi) in a reaction catalyzed by ATP synthase molecules that are embedded in the thylakoid membrane. Which of the following statements provides evidence to support the claim that no ATP will be synthesized in the absence of a proton gradient across the thylakoid membrane?
No ATP is synthesized when channel proteins that allow the free passage of protons are inserted into the thylakoid membrane.
Which of the following statements provides evidence to support the claim that no ATP will be synthesized in the absence of a proton gradient across the thylakoid membrane?
No ATP is synthesized when channel proteins that allow the free passage of protons are inserted into the thylakoid membrane.
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?
Peroxidase activity will decrease.
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 denatured enzymes
Which of the following actions will provide a negative control for the investigation?
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
Some plasmids contain antibiotic resistance genes.
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.
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?
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.
In addition to the pigments commonly associated with photosynthesis, a certain photosynthetic species contains two additional pigment types. Which of the following best supports the claim that this species is better adapted to environmental changes than other photosynthetic species are?
The additional pigments allow the species containing them to harvest energy from wavelengths of light that the other photosynthetic species cannot use.
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?
The amount of product will increase until the reaction reaches its equilibrium point or until the substrate is used up by the reaction.
Which of the following best describes the process by which the bacteria are breaking down the glucose to produce lactic acid?
The bacteria are breaking down sugars in the absence of oxygen.
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 chloroplasts will generate less ATP.
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 transition state, which decreases the activation energy of the reaction.
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 guaiacol, which will reveal the effect of guaiacol on the reaction rates.
3.C 0/1 MC point 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 figure above shows an organelle typically found in eukaryotic cells. Which of the following best describes the function of the double membrane system of this organelle?
The inner membrane has specialized proteins that create a hydrogen ion concentration gradient between the intermembrane space and the matrix.
Figure 1. Accumulation of acetyl-CoACoA under different conditions Which of the following best describes the cellular location where pyruvate dehydrogenase is most likely active?
The mitochondrial matrix
Figure 1. Change in the relative concentration of product over time Figure 1 shows the amount of product produced in an enzyme-catalyzed reaction over five minutes. Which of the following best explains how the rate of the reaction changes over time?
The rate decreases because the ratio of product to substrate increases.
Which of the following statements best helps explain the reaction specificity of an enzyme?
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?
The total system that includes photosynthetic organisms and the Sun becomes less ordered over time.
Which of the following statements provides reasoning that supports the claim that brown fatty tissue keeps an animal warm?
The uncoupling protein in this tissue reduces the proton gradient across the membrane and thus produces heat to warm the animal without ATP production.
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.
Which of the following best describes the role of water in photosynthesis?
Water molecules donate electrons to the electron transport chain.
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?
Yeast cells produce invertase, which is an enzyme that catalyzes the conversion of the disaccharide sucrose into glucose and fructose.
The carbon 'that makes up organic molecules in plants is derived directly from
carbon fixed in photosynthesis
If the experiment is repeated at pH 11, the observed activity level of the enzyme will most likely be
lower than the level at ph 9
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?
pH 4 buffer solution and hydrogen peroxide only
Which of the following best predicts how the structure and function of pepsin will change as it enters the small intestine?
pepsin will change in shape because of the basic environment of the small intestine, therefore its enzymatic activity will decrease
Carbohydrate-synthesizing reactions of photosynthesis directly require
products of the light reactions
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 molecule with negative charges interacts with positively charged side chains in the enzyme's active site.
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?
ATP hydrolysis is an energy releasing reaction that is often coupled with reactions that require an input of energy
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?
ATPATP production by the phosphagen system increases and decreases rapidly following the start of the exercise period.
A researcher claims that increased atmospheric carbon dioxide levels cause increased growth rates in plants. Which of the following statements best supports the researcher's claim?
Atmospheric carbon dioxide is the raw material for photosynthesis, which plants rely on for producing sugars and other organic compounds.
Which of the following questions will best direct an investigation of the mechanism of ATP synthase?
Is the phosphorylation of ADP by ATP synthase dependent on the formation of a proton gradient?
Which test tubes are controls in the experiment?
Test tubes 1, 3, 5, and 7
