AP Biology Unit 1-4 (All questions)

4.7 Glycogen synthetase kinase 3 beta is a protein kinase that has been implicated in many types of cancer. Depending on the cell type, the gene for glycogen synthetase kinase 3 beta (GSK3β) can act either as an oncogene or as a tumor suppressor. Which of the following best predicts how GSK3β mutations can lead to the development of cancer? A Cells with inactive GSK3βGSK3β fail to trigger apoptosis. B Cells with inactive GSK3βGSK3β fail to proceed past the G2/MG2/M checkpoint. C Cells with overactive GSK3βGSK3β are more likely to repair DNADNA damage. D Cells with overactive GSK3βGSK3β have longer cell cycles.

A Cells with inactive GSK3βGSK3β fail to trigger apoptosis.

3.6 During respiration, most ATP is formed as a direct result of the net movement of A potassium against a concentration gradient B protons down a concentration gradient C electrons against a concentration gradient D electrons through a channel E sodium ions into the cell

B protons down a concentration gradient

1.2 Students conducted a controlled experiment to investigate whether sawdust provides enough nutrients to support plant growth. The students separated ten nearly identical sunflower seedlings into two groups. They grew the seedlings in the first group in potting soil and the seedlings in the second group in sawdust composed mostly of cellulose. After twenty days, the students recorded observations about the seedlings in each group. The students' observations are presented in the table. The observed differences between the groups most likely resulted from differences in the ability of the seedlings to produce which of the following monomers? A B C D

c

4.6 A group of researchers cultured yeast cells in a nutrient-rich environment and a nutrient-poor environment and observed the duration of the stages of their cell cycles. The results of their study are summarized in Table 1. The cell cycle of yeast cells grown in the nutrient-poor environment is approximately what percent of the cell cycle of yeast cells grown in the nutrient-rich environment? A 168 B 127 C 179 D 160

A 168

3.4 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? A ATPATP production by the phosphagen system increases and decreases rapidly following the start of the exercise period. B ATPATP production by the phosphagen system increases gradually and continuously throughout the entire exercise period. C The ATPATP produced by the phosphagen system contains more energy per molecule than does the ATPATP produced by the other pathways. D ATPATP hydrolysis in muscle cells occurs immediately after the start of the exercise period but stops before the end of the exercise period.

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

2.4 Which of the following best describes the numbered areas? A Areas 1 and 3 are polar, since the membrane molecules are aligned with water molecules. B Area 2 is polar, since water has been excluded from this area of the membrane. C Areas 1 and 3 are hydrophilic, since membrane molecules formed covalent bonds with water. D Area 2 is nonpolar, since hydrogen bonds between the adjacent lipids hold the membrane together.

A Areas 1 and 3 are polar, since the membrane molecules are aligned with water molecules.

3.6 The figures below illustrate the similarities between ATP synthesis in mitochondria and chloroplasts. The figures can best assist in answering which of the following questions? A Do electron transport chains create a gradient so that ATP synthase can generate ATP molecules? B What are the sources of energy that drive mitochondrial and chloroplast electron transport systems? C What is the optimal temperature at which ATP synthase chemically converts ADP and a phosphate group into one molecule of ATP? D What is the evolutionary relationship between the ATP synthase in mitochondria and the ATP synthase in chloroplasts?

A Do electron transport chains create a gradient so that ATP synthase can generate ATP molecules?

2.1 All eukaryotic cells contain at least one Golgi complex, typically located in the cytoplasm and near the endoplasmic reticulum. Which of the following best describes a process that occurs within the Golgi complex? A Enzymatic modification of newly synthesized integral membrane proteins B Synthesis of cytosolic proteins based on the nucleotide sequences of mRNAsmRNAs C Degradation of proteins by hydrolytic enzymes contained within the complex D Synthesis of various types of lipids

A Enzymatic modification of newly synthesized integral membrane proteins

2.7 The illustration shows the active transport of hydrogen ions through a membrane protein. Which of the following best predicts the effect of not having ATP available to supply energy to this process? A H+H+ ions will stop moving through the protein. B H+H+ ions will move in the other direction through the protein. C H+H+ ions will continue to move through the protein in the original direction but at a slower rate. D H+H+ ions will begin to move through the phospholipid portion of the membrane in the original direction.

A H+H+ ions will stop moving through the protein.

2.4 A model of the plasma membrane showing several biological molecules, including a transmembrane protein, is shown in Figure 1. Which statement best explains why correct protein folding is critical in the transmembrane protein shown above? A Interactions of the hydrophobic and hydrophilic amino acids help to anchor the protein in the membrane. B Interactions of the peptide bonds of the protein with the membrane will affect the rate at which substances can cross the membrane. C Interactions of the protein and phospholipids increase membrane fluidity. D Interactions of the quaternary structure of the protein will increase hydrogen bonding in the membrane and make the membrane less fluid.

A Interactions of the hydrophobic and hydrophilic amino acids help to anchor the protein in the membrane.

4.3 A student claims that the Y chromosome contains the sex-determining region gene, known as the SRY gene, which causes male fetuses to develop testes. Which of the following provides correct information about cell signaling that supports the claim? A The SRYSRY gene produces a protein that binds to specific regions of DNADNA in certain tissues, which affects the development of these tissues. B The SRYSRY gene produces a protein that deletes portions of the XX chromosome in males so that male characteristics can develop. C The SRYSRY gene produces an RNARNA segment that is exported from specific cells and targets the developing gonads. D The SRYSRY gene is found only in tissues of the developing gonads.

A The SRYSRY gene produces a protein that binds to specific regions of DNADNA in certain tissues, which affects the development of these tissues.

2.5 A team of biologists develop a new drug, and one team member hypothesizes that the drug is incapable of freely passing across the plasma membrane and requires the help of membrane proteins to enter cells. Alternatively, another biologist on the team hypothesizes that the drug can diffuse passively across the plasma membrane like O2 and CO2 can. Which of the following, if true about the drug, best supports the alternative hypothesis that the new drug will exhibit simple diffusion across plasma membranes? A The drug is a small nonpolar molecule. B The drug is a small charged molecule. C The drug is a large polar molecule. D The drug is a large charged molecule.

A The drug is a small nonpolar molecule.

3.2 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 The initial concentration of the substrate

2.2 Muscle cells have high ATP demands. Which of the following is a scientific claim about how the structure of the mitochondria in muscle cells should be different than it is in other cells because of the high energy demands of mitochondria? A The inner membrane of the mitochondria in muscle cells should have more folds to increase the surface area, allowing more ATPATP to be synthesized. B The inner membrane of the mitochondria in muscle cells should be more permeable to large enzymes, allowing the same reactions to occur in both compartments of the mitochondria. C The outer membrane of the mitochondria in muscle cells should be thicker, allowing more rapid diffusion of molecules into the mitochondria. D The outer membrane of the mitochondria of muscle cells should have more folds, increasing the surface area for faster diffusion of molecules from the cytoplasm.

A The inner membrane of the mitochondria in muscle cells should have more folds to increase the surface area, allowing more ATPATP to be synthesized.

4.4 The epinephrine signaling pathway plays a role in regulating glucose homeostasis in muscle cells. The signaling pathway is activated by the binding of epinephrine to the beta-2 adrenergic receptor. A simplified model of the epinephrine signaling pathway is represented in Figure 1. Which of the following outcomes will most likely result from the irreversible binding of GDP to the G protein? A The intracellular concentration of glycogen will increase. B The intracellular concentration of activated protein kinase A will increase. C The intracellular concentration of cyclic AMPAMP will increase. D The intracellular concentration of glucose-1-phosphate will increase.

A The intracellular concentration of glycogen will increase.

3.6 Two nutrient solutions are maintained at the same pH. Actively respiring mitochondria are isolated and placed into each of the two solutions. Oxygen gas is bubbled into one solution. The other solution is depleted of available oxygen. Which of the following best explains why ATP production is greater in the tube with oxygen than in the tube without oxygen? A The rate of proton pumping across the inner mitochondrial membrane is lower in the sample without oxygen. B Electron transport is reduced in the absence of a plasma membrane. C In the absence of oxygen, oxidative phosphorylation produces more ATP than does fermentation. D In the presence of oxygen, glycolysis produces more ATP than in the absence of oxygen.

A The rate of proton pumping across the inner mitochondrial membrane is lower in the sample without oxygen.

3.2 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? A They will show whether the isolated cellular contents have enzymatic activity. B They will show whether environmental pHpH 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 They will show whether the isolated cellular contents have enzymatic activity.

3.4 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 ADPADP is a small molecule that some cells release into their environment as a way of communicating with other cells. B ATPATP hydrolysis is an energy-releasing reaction that is often coupled with reactions that require an input of energy. C Inorganic phosphate (Pi)(Pi) is a substance that cells typically acquire from their environment. D ATPATP synthase is a mitochondrial enzyme that catalyzes the conversion of ADPADP and PiPi to ATPATP.

B ATPATP hydrolysis is an energy-releasing reaction that is often coupled with reactions that require an input of energy.

3.7 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? A Rhizobia bacteria form close associations with the roots of bean plants. B E. coli bacteria reproduce in liquid media containing either glucose or galactose. C The antibiotic rifampicin inhibits the growth of some bacterial strains but not of others. D Some viruses that infect bacteria reproduce by either the lysogenic cycle or the lytic cycle.

B E. coli bacteria reproduce in liquid media containing either glucose or galactose.

3.5 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? A Elysia chlorotica will die if not exposed to light. B Elysia chlorotica grows when exposed to light in the absence of other food sources. C Elysia chlorotica grows faster when exposed to light than when placed in the dark. D Elysia chlorotica grows in the dark when food sources are available.

B Elysia chlorotica grows when exposed to light in the absence of other food sources.

2.2 Which of the following claims is scientifically accurate and consistent with an observation that a decrease in lysosome production within a cell leads to a decline in mitochondrial activity? A A lack of lysosomes will cause a decrease in the synthesis of enzymes necessary for cellular respiration. B Fewer lysosomes will be available to break down macromolecules to provide the necessary nutrients for cellular respiration. C Fewer lysosomes will be available to store materials required for the functioning of the mitochondria. D Lysosomes will not be available to modify proteins so that they are targeted to the mitochondria.

B Fewer lysosomes will be available to break down macromolecules to provide the necessary nutrients for cellular respiration.

2.5 Plant cell walls are composed of cellulose, while fungal cell walls are composed of chitin. A group of scientists hypothesize that this difference means the cell wall has largely different functions in plant cells and fungal cells. Alternatively, another group of scientists hypothesize that despite their biochemical differences, plant and fungal cell walls serve similar functions. Which of the following observations would best support the alternative hypothesis described above? A Plant cell walls are found just outside the plasma membrane, while fungal cell walls are found just beneath the plasma membrane. B In both plant cells and fungal cells, the cell wall surrounds the outside of the cell membrane. C Some plant cells have secondary cell walls that confer additional rigidity, while fungal cells do not. D Photosynthesis occurs in plant cells, but it does not occur in fungal cells.

B In both plant cells and fungal cells, the cell wall surrounds the outside of the cell membrane.

3.7 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? A In green light, more chlorophyll a molecules are produced, reflecting more light to other cyanobacteria to be used for photosynthesis. B In green light, more phycoerythrin molecules are produced, allowing more green light to be absorbed, thus increasing photosynthesis. C In green light, cyanobacteria that have more phycocyanin molecules are less likely to survive and reproduce. D In green light, cyanobacteria that have more allophycocyanin molecules are more likely to survive and reproduce.

B In green light, more phycoerythrin molecules are produced, allowing more green light to be absorbed, thus increasing photosynthesis.

4.2 The epinephrine signaling pathway plays a role in regulating glucose homeostasis in muscle cells. The signaling pathway is activated by the binding of epinephrine to the beta-2 adrenergic receptor. A simplified model of the epinephrine signaling pathway is represented in Figure 1. Based on Figure 1, which of the following statements best describes the epinephrine signaling pathway? A It involves the opening and closing of ion channels. B In involves enzymes activating other enzymes. C It involves changes in the expression of target genes. D It involves protons moving down a concentration gradient.

B In involves enzymes activating other enzymes.

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

4.5 Figure 1 is a proposed model of the feedback system controlling erythrocyte (red blood cell) production. Based on the model in Figure 1, if a person travels from sea level to a high elevation location, which of the following correctly predicts the response to the decreased blood oxygen level?

B More erythropoietin will be secreted from the kidneys, increasing production of erythrocytes.

2.9 Which of the following statements best explains the processes of passive and active transport? A Passive transport is the net movement of substances down a concentration gradient that requires metabolic energy. Active transport is the movement of substances up a concentration gradient that does not require energy. B Passive transport is the net movement of substances down a concentration gradient that does not require metabolic energy. Active transport is the movement of substances up a concentration gradient that requires energy. C Passive transport is the net movement of substances up a concentration gradient that requires metabolic energy. Active transport is the movement of substances down a concentration gradient that does not require metabolic energy. D Passive transport is the net movement of substances up a concentration gradient that does not require metabolic energy. Active transport is the movement of substances down a concentration gradient that requires energy.

B Passive transport is the net movement of substances down a concentration gradient that does not require metabolic energy. Active transport is the movement of substances up a concentration gradient that requires energy.

1.2 Which of the following statements best describes how organisms such as rabbits obtain the carbon necessary for building biological molecules? A Rabbits eat plants and use energy absorbed from the plants to make carbon atoms from electrons, protons, and neutrons in the air. B Rabbits eat plants and break down plant molecules to obtain carbon and other atoms that they rearrange into new carbon-containing molecules. C Rabbits eat plants and use water absorbed from the plants to hydrolyze CO2CO2, which the rabbits breathe in from the air and use as a carbon source. D Rabbits eat plants and make carbon-containing molecules by using carbon atoms that the plants absorbed from the soil and stored in the cells of their leaves.

B Rabbits eat plants and break down plant molecules to obtain carbon and other atoms that they rearrange into new carbon-containing molecules.

2.9 Cholesterol is an important component of animal cell membranes. Cholesterol molecules are often delivered to body cells by the blood, which transports the molecules in the form of cholesterol-protein complexes. The complexes must be moved into the body cells before the cholesterol molecules can be incorporated into the phospholipid bilayers of cell membranes. Based on the information presented, which of the following is the most likely explanation for a buildup of cholesterol molecules in the blood of an animal? A The animal's body cells are defective in exocytosis. B The animal's body cells are defective in endocytosis. C The animal's body cells are defective in cholesterol synthesis. D The animal's body cells are defective in phospholipid synthesis.

B The animal's body cells are defective in endocytosis

1.6 DNA and RNA are nucleic acids that can store biological information based on the sequence of their nucleotide monomers. Figure 1 shows a short segment of each of the two types of nucleic acids. Which of the following best describes a structural difference between DNA and RNA? A DNADNA contains four types of nitrogenous bases, whereas RNARNA contains only two types of nitrogenous bases. B The backbone of DNADNA contains deoxyribose, whereas the backbone of RNARNA contains ribose. C A DNADNA molecule is composed of two parallel strands with the same 5′5′ to 3′3′ directionality, whereas an RNARNA molecule is composed of only one 5′5′ to 3′3′ strand. D Phosphate groups provide rigidity to DNADNA, but RNARNA is flexible and contains no phosphate groups.

B The backbone of DNADNA contains deoxyribose, whereas the backbone of RNARNA contains ribose.

1.5 Researchers compared similar proteins from related organisms in different habitats. They found that the proteins from organisms living in harsh environments had a greater number of cysteine amino acids than did proteins from organisms not living in harsh environments. The structure of cysteine is shown. Bonds can form between the sulfur atom of different cysteine amino acids (S-S bonds). Which of the following best describes the effect of a greater number of cysteine amino acids on the stability of the proteins? A The change has no effect on the stability of the protein because only one type of amino acid is involved. B The change leads to increased protein stability because of an increased number of S-SS-S bonds in the tertiary structure of the proteins. C The change leads to decreased protein stability because of an increased number of S-SS-S bonds in the tertiary structure of the proteins. D The change leads to increased protein stability only when the added cysteine amino acids are next to other cysteine amino acids in the primary structure.

B The change leads to increased protein stability because of an increased number of S-SS-S bonds in the tertiary structure of the proteins.

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

4.4 Glucocorticoids are steroid hormones that control cellular responses through several different signaling pathways. One of the signaling pathways involves the glucocorticoid receptor, an intracellular protein that is activated by binding to a glucocorticoid molecule. A simplified model of the glucocorticoid receptor signaling pathway is represented in Figure 1. Which of the following statements best predicts the effect of a mutation that results in a loss of the glucocorticoid receptor's ligand binding function? A The transduction of the glucocorticoid signal across the plasma membrane will be blocked. B The glucocorticoid receptor will remain associated with the accessory proteins. C The rate of diffusion of glucocorticoid molecules into the cell will increase. D The concentration of glucocorticoid receptors inside the nucleus will increase.

B The glucocorticoid receptor will remain associated with the accessory proteins.

2.4 The model below shows the structure of a portion of a plasma membrane in an animal cell. Which statement best explains the orientation of the phospholipid molecules in this model? A The nonpolar portions of the phospholipid molecules are attracted to the internal and external environments. B The hydrophilic phosphate groups of the phospholipid molecules are attracted to the aqueous internal and external environments. C The embedded proteins attract the fatty acid tails of the phospholipids, so the tails point away from the internal and external aqueous environments. D The fatty acid tails of the phospholipid molecules are hydrophilic and are repelled by the internal and external aqueous environments.

B The hydrophilic phosphate groups of the phospholipid molecules are attracted to the aqueous internal and external environments.

1.6 figure 1 represents a nucleic acid fragment that is made up of four nucleotides linked together in a chain. Which of the following characteristics of Figure 1 best shows that the fragment is RNA and not DNA? A The 5′5′ to 3′3′ orientation of the nucleotide chain B The identity of each nitrogenous base C The charges on the phosphate groups D The type of bond linking the nucleotides together

B The identity of each nitrogenous base

2.10 The figure shows a process by which a cell might absorb food from its surrounding environment and break it down for use as a source of energy and matter. The process involves lysosomes, which are membrane-bound organelles that contain hydrolytic enzymes. Activation of the hydrolytic enzymes requires an acidic pH, and lysosomes maintain an internal acidic pH by using ion pumps. Which of the following outcomes will most likely result from a loss of ion pump function in the cell's lysosomes? A The internal pHpH of the lysosomes will decrease, which will prevent the activation of hydrolytic enzymes and interfere with the intracellular digestion of food. B The internal pHpH of the lysosomes will increase, which will prevent the activation of hydrolytic enzymes and interfere with the intracellular digestion of food. C The internal pHpH of the lysosomes will decrease, which will activate hydrolytic enzymes and enhance the intracellular digestion of food. D The internal pHpH of the lysosomes will increase, which will activate hydrolytic enzymes and enhance the intracellular digestion of food.

B The internal pHpH of the lysosomes will increase, which will prevent the activation of hydrolytic enzymes and interfere with the intracellular digestion of food.

2.7 A cell's membrane potential is maintained by the movement of ions into and out of the cell. A model showing the influence of membrane proteins on the movement of sodium (Na+) and potassium (K+) ions across the plasma membrane is presented in Figure 1. Based on the model presented in Figure 1, which of the following outcomes will most likely result from a loss of protein X function? A The membrane potential will be disrupted by an increase in Na+Na+ concentration inside the cell. B The membrane potential will be disrupted by an increase in K+K+ concentration inside the cell. C The membrane potential will be maintained by the Na+−K+Na+⁢−⁢K+ pump moving more K+K+ ions into the cell. D The membrane potential will be maintained by the diffusion of Na+Na+ ions into the cell.

B The membrane potential will be disrupted by an increase in K+K+ concentration inside the cell.

4.4 Figure 1 shows a model of a signal transduction cascade, initiated by the binding of a ligand to the transmembrane receptor protein A. A DNA mutation changes the shape of the extracellular domain of transmembrane receptor protein A produced by the cell. Which of the following predictions is the most likely consequence of the mutation? A Production of activated molecule 1 will stop, but production of activated molecules 2 and 3 will continue. B The molecule that normally binds to protein AA will no longer attach, deactivating the cellular response. C The molecule that normally binds to protein AA will not enter the cell, thus no cellular response will occur. D Since protein AA is embedded in the membrane, the mutation will be silent and not affect the cellular response.

B The molecule that normally binds to protein AA will no longer attach, deactivating the cellular response.

1.1 Which statement best helps explain the formation of the hydrogen bond represented in the figure? A The oxygen has a partial positive charge, and the nitrogen has a partial negative charge. B The nitrogen has a partial negative charge, and the hydrogen attached to the oxygen has a partial positive charge. C The hydrogen attached to the oxygen has a partial negative charge, and the nitrogen also has a partial negative charge. D The nitrogen has a partial positive charge, and the hydrogen attached to the oxygen also has a partial positive charge.

B The nitrogen has a partial negative charge, and the hydrogen attached to the oxygen has a partial positive charge.

4.5 The coagulation cascade controls blood clot formation in response to blood vessel injury. Thrombin is an enzyme that plays a key role in regulating the coagulation cascade. A simplified model of thrombin's role in regulating the coagulation cascade is represented in Figure 1. Argatroban is a competitive inhibitor of thrombin. Which of the following effects on the coagulation cascade is most likely to result from inhibiting thrombin activity with argatroban? A The activation of clotting factors will be blocked. B The rate of fibrin formation will decrease. C Thrombin will be converted to prothrombin. D The rate of blood clot formation will increase.

B The rate of fibrin formation will decrease.

2.1 Organelles such as mitochondria and the endoplasmic reticulum have membranes that compartmentalize reactions and other metabolic processes. To function properly, the organelles must move substances across their membranes. Which of the following statements describes a feature shared by mitochondria and the endoplasmic reticulum that increases the efficiency of their basic functions? A They have rigid, nonfluid membranes. B They have highly folded membranes. C They have membranes composed of many carbohydrates. D They have double membranes, with one membrane enclosed within the other.

B They have highly folded membranes.

2.7 Which statement best describes the effect on water transport across the cell membrane if the aquaporin in the figure ceases to function? A Water molecules will no longer be able to move across the cell membrane. B Water molecules will still be able to move across the cell membrane but at a slower rate. C Water molecules will only be able to enter the cell by active transport. D Water molecules will move across the cell membrane at a faster rate without the aquaporin regulating their flow.

B Water molecules will still be able to move across the cell membrane but at a slower rate.

3.3 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 pH values was assessed by students in the lab. The students' results are shown in graph 1. A the same as the level at pHpH 7 B lower than the level at pHpH 9 C greater than the level at pHpH 9 D between the levels observed at pHpH 5 and pHpH 7.

B lower than the level at pHpH 9

2.8 Directions: Each group of questions below concerns an experimental or laboratory situation or data. In each case, first study the description of the situation or data. Then choose the one best answer to each question following it and fill in the corresponding circle on the answer sheet. Dialysis tubing is permeable to water molecules but not to sucrose. Four dialysis tubes are half filled with 5 percent, 10 percent, 20 percent, and 40 percent sucrose solutions, respectively, and two dialysis tubes are half filled with distilled water. The dialysis tubes are all sealed at both ends, and the initial masses are determined. Five dialysis tubes are placed into beakers containing distilled water, and the sixth dialysis tube, containing distilled water, is placed into a 40 percent sucrose solution. The masses of the dialysis tubes are recorded at 30-minute intervals for 90 minutes, as shown in the table below. To model a plant cell, a permeable, nonflexible case is placed around each piece of dialysis tubing. The greatest pressure potential will develop within dialysis tube number A 2 B 3 C 4 D 5 E 6

C 4

1.3 Which of the following best describes the formation of the bond shown in Figure 1 ? A An ionic bond is formed between a carbon atom of one amino acid and the nitrogen atom of the other amino acid. B An ionic bond is formed when the negative charge of an OHOH group is balanced by the positive charge of a hydrogen ion. C A covalent bond is formed between a carbon atom and a nitrogen atom along with the formation of H2OH2O . D A covalent bond is formed that replaces the hydrogen bond between the OHOH group and the HH atom.

C A covalent bond is formed between a carbon atom and a nitrogen atom along with the formation of H2OH2O .

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

2.10 Which of the following statements best predicts the effect of increasing the permeability of the mitochondrial membranes to large molecules? A ATPATP production will increase because of an increase in the rate at which proteins diffuse out of mitochondria. B ATPATP production will increase because of an increase in the mixing of mitochondrial and cytosolic substances. C ATPATP production will decrease because of an increase in the occurrence of uncontrolled chemical reactions. D ATPATP production will decrease because of an increase in the surface area of the mitochondrial membranes.

C ATPATP production will decrease because of an increase in the occurrence of uncontrolled chemical reactions.

2.6 An investigator wants to understand whether a newly found membrane protein is involved in membrane transport of a certain particle. Which investigation will help determine whether the new membrane protein is a channel protein involved in membrane transport? A Add small nonpolar molecules to the extracellular space and measure the direction of particle movement of the molecules. B Measure the rate of extracellular fluid movement into the intracellular space. C Add more of the proteins to the plasma membrane and measure the rate of the particle movement. D Remove ATPATP from the intracellular space and measure the rate of the particle movement into the intracellular space.

C Add more of the proteins to the plasma membrane and measure the rate of the particle movement.

3.4 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 As light energy is converted to chemical energy by metabolic processes, some of the energy is lost as heat.

4.6 Figure 1 shows the number of chromosomes observed in an actively dividing human cell at each stage of cell division. Figure 1. Number of chromosomes in a human cell at different stages of cell division Which of the following presents a correct interpretation of the changes in chromosome number depicted in Figure 1 ? A DNADNA replication occurs between metaphase and anaphase, doubling the number of chromosomes. Between telophase and cytokinesis, the cell divides in two, with each cell receiving half of the replicated chromosomes. B New chromosomes formed during prophase are doubled during anaphase and are recombined before cytokinesis. C Chromosomes enter metaphase containing two chromatids attached by a centromere. During anaphase, the chromatids are separated, each becoming a chromosome. Cytokinesis distributes the chromosomes into two separate cells. D At anaphase a cell contains two identical copies of each chromosome, but following telophase, one of the copies is broken down into nucleotides.

C Chromosomes enter metaphase containing two chromatids attached by a centromere. During anaphase, the chromatids are separated, each becoming a chromosome. Cytokinesis distributes the chromosomes into two separate cells.

4.1 Notch is a receptor protein displayed on the surface of certain cells in developing fruit fly embryos. Notch's ligand is a membrane-bound protein called Delta that is displayed on the surface of adjacent cells. When Notch is activated by its ligand, the intracellular tail of the Notch protein becomes separated from the rest of the protein. This allows the intracellular tail to move to the cell's nucleus and alter the expression of specific genes. Which of the following statements best explains Delta's role in regulating cell communication through the Notch signaling pathway? A Delta transmits a chemical signal to all the cells of a developing embryo. B Delta allows the cells of a developing embryo to communicate without making direct contact. C Delta restricts cell communication to short distances within a developing embryo. D Delta determines which cells in a developing embryo express the gene that encodes the Notch protein.

C Delta restricts cell communication to short distances within a developing embryo.

4.6 Researchers performed an experiment to determine the effect of certain genetic mutations on mitosis in tropical fruit fly embryos. They determined the percentage of cells in each of four phases of mitosis as shown in Figure 1. Figure 1. Percent of cells in phases of mitosis Which of the following patterns is shown by the data? A Mutant 1 cells are more similar to mutant 3 cells than to wild-type cells. B In wild-type cells, the percent of cells in anaphase is twice the amount of those in telophase C In mutant 3 cells, more time is spent in prophase/prometaphase than in the later stages of mitosis. D The percent of mutant 2 cells in anaphase is higher than that of mutant 1 cells.

C In mutant 3 cells, more time is spent in prophase/prometaphase than in the later stages of mitosis.

2.6 The transport of a substance across a plasma membrane of a specific organelle requires energy. The rate at which the transport takes place also depends on temperature. A scientist isolated the specific organelle and then used the following treatments to determine the conditions that will result in the maximal transport. All treatments contained the extracted organelle and were maintained at 25°C. The data from this experiment indicate that maximal rate of transport of protein X at 25°C occurs at an ATP concentration of 1.0μm/mL. Which procedure should be done next to gather data needed to meet the scientist's objective? A Incubate samples with the same four ATPATP concentrations at 30°C30°C. B Incubate samples containing 5.0μm/mL5.0μm/mL of ATPATP at four temperatures other than 25°C25°C. C Incubate samples containing 1.0μm/mL1.0μm/mL of ATPATP at four temperatures other than 25°C25°C. D Incubate samples containing 1.0μm/mL1.0μm/mL of ATPATP at 25°C25°C and determine the rate of transport for four other proteins.

C Incubate samples containing 1.0μm/mL1.0μm/mL of ATPATP at four temperatures other than 25°C25°C.

4.2 The epinephrine signaling pathway plays a role in regulating glucose homeostasis in muscle cells. The signaling pathway is activated by the binding of epinephrine to the beta-2 adrenergic receptor. A simplified model of the epinephrine signaling pathway is represented in Figure 1. Which of the following statements best describes the role of adenylyl cyclase in the epinephrine signaling pathway? A It converts a polymer to its monomer subunits. B It moves substances across the plasma membrane. C It accelerates the production of a second messenger. D It transfers phosphate groups from ATPATP to protein substrates.

C It accelerates the production of a second messenger.

4.2 In a certain signal transduction pathway, the binding of an extracellular molecule to a cell-surface protein results in a rapid increase in the concentration of cyclic AMP inside the cell. The cyclic AMP binds to and activates cytosolic enzymes that then activate other enzymes in the cell. Which of the following statements best describes the role of cyclic AMP in the signal transduction pathway? A It acts as a signaling molecule that passes the signal from the cell to other cells. B It acts as a receptor that carries the signal from outside the cell to inside the cell. C It acts as a second messenger that helps relay and amplify the signal within the cell. D It acts as a channel protein that transmits the signal across the cell's nuclear membrane.

C It acts as a second messenger that helps relay and amplify the signal within the cell.

3.2 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? A It will provide a measurement of amylase activity at an acidic pHpH. B It will provide a measurement of amylase activity at a basic pHpH. 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 It will show the color change that occurs in the absence of enzyme activity.

2.11 The endosymbiont theory proposes a model for the evolution of mitochondria. According to the model, an ancestral eukaryote engulfed a small, free-living prokaryotic organism. The engulfed prokaryote then formed an endosymbiotic relationship with the eukaryotic host. Which of the following observations best supports the model? A Prokaryotes and eukaryotes acquire nutrients from the surrounding environment. B Organelles such as mitochondria and the endoplasmic reticulum have membranes composed of phospholipids. C Mitochondria and some prokaryotes share similar metabolic reactions that produce ATPATP. D Eukaryotes evolved after prokaryotes and have more complex structures.

C Mitochondria and some prokaryotes share similar metabolic reactions that produce ATPATP.

3.5 In chloroplasts, ATP is synthesized from ADP plus inorganic phosphate (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? A Blocking electron flow from one carrier to the next in the electron transport chains blocks formation of a proton gradient in the thylakoid. B Increasing the proton concentration difference across the thylakoid membrane is not associated with a parallel increase in the rate of ATPATP synthesis. C No ATPATP is synthesized when channel proteins that allow the free passage of protons are inserted into the thylakoid membrane. D No ATPATP is synthesized while the Calvin cycle is synthesizing carbohydrates and using ATPATP and NADPHNADPH at a high rate.

C No ATPATP is synthesized when channel proteins that allow the free passage of protons are inserted into the thylakoid membrane.

3.3 Protein digestion in humans is primarily carried out by three enzymes. Pepsin is found in the stomach (pH2), where it aids in the breakdown of large proteins into smaller peptides, while trypsin and chymotrypsin are found in the small intestine (pH8), 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 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.

4.5 The epinephrine signaling pathway plays a role in regulating glucose homeostasis in muscle cells. The signaling pathway is activated by the binding of epinephrine to the beta-2 adrenergic receptor. A simplified model of the epinephrine signaling pathway is represented in Figure 1. Cyclic AMP phosphodiesterase is an enzyme that catalyzes the conversion of cyclic AMP to a different molecule. Which of the following best predicts the effect of inhibiting cyclic AMP phosphodiesterase in a muscle cell stimulated by epinephrine? A The concentration of cyclic AMPAMP will decrease because adenylyl cyclase will no longer be activated. B The G protein will diffuse out of the cell because it will no longer bind to the plasma membrane. C Phosphorylase kinase will remain active because protein kinase A will no longer be deactivated. D Glycolysis will stop because epinephrine signaling will no longer stimulate glycogen breakdown.

C Phosphorylase kinase will remain active because protein kinase A will no longer be deactivated.

3.2 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? 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 pHpH

C Repeating the experiment with denatured enzymes

2.2 Researchers have proposed a model of the process by which a newly synthesized protein is transported to the plasma membrane and secreted into the extracellular space. The model is represented in Figure 1. Based on the model, the newly synthesized protein is transported directly from the endoplasmic reticulum to which of the following? A The nucleus B The plasma membrane C The Golgi complex D The extracellular space

C The Golgi complex

1.1 The carbohydrates glucose, galactose, and fructose have the same chemical formula (C6H12O6) but different structural formulas, as represented in the figure. Which of the following statements about glucose, galactose, and fructose is most likely true? A The carbohydrates have the same properties because they have the same number of carbon, hydrogen, and oxygen atoms. B The carbohydrates have the same properties because they each have a single carbon-oxygen double bond. C The carbohydrates have different properties because they have different arrangements of carbon, hydrogen, and oxygen atoms. D The carbohydrates have different properties because they have different numbers of carbon-carbon bonds.

C The carbohydrates have different properties because they have different arrangements of carbon, hydrogen, and oxygen atoms.

2.11 Researchers claimed that a particular organelle originated from a free-living prokaryotic cell that was engulfed by a larger cell, as shown in Figure 1. Which of the following provides evidence to best support the researchers' claim? A The organelle has a phospholipid membrane. B The organelle has protein in the membrane. C The organelle has a double membrane. D The organelle has an internal aqueous environment that is similar to the cytosol of the larger cell.

C The organelle has a double membrane.

3.3 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? A There will be an increase in formaldehyde because ADHADH activity increases. B Competitive inhibition will be terminated because ethyl alcohol will bind to methyl alcohol and decrease ADHADH 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.

C The peptide bonds in the active site of the enzyme will be denatured, inhibiting the enzyme.

4.1 Vertebrate immune responses involve communication over short and long distances. Which of the following statements best helps explain how cell surface proteins, such as MHC proteins and T cell receptors, mediate cell communication over short distances? A The proteins receive electrical signals from nerve cells. B The proteins leave the cell and travel in the bloodstream to other cells. C The proteins interact directly with proteins on the surfaces of other cells. D The proteins bind to molecules secreted by cells located in other parts of the body.

C The proteins interact directly with proteins on the surfaces of other cells.

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

4.7 Researchers studying cell cycle regulation in budding yeast have observed that a mutation in the CDC15 gene causes cell cycle arrest in telophase when the yeast cells are incubated at an elevated temperature. Which of the following statements best predicts the effect of the cell cycle arrest on proliferating yeast cells? A The yeast cells will transition out of G0G0 but will fail to complete the G1G1 phase. B The yeast cells will initiate mitosis but will fail to complete the G2G2 phase. C The yeast cells will replicate their chromosomes but will fail to complete cytokinesis. D The yeast cells will replicate their organelles but will fail to complete the S phase.

C The yeast cells will replicate their chromosomes but will fail to complete cytokinesis.

2.9 In an experiment, cells were isolated from an aquatic plant and suspended in pond water, a sucrose sugar solution, or distilled water. All of the cells were then viewed under a microscope. Compared with the cell in the pond water, the cell in the sugar solution appeared shriveled, and the cell in the distilled water appeared inflated. The results of the experiment are represented in Figure 1. Which of the following statements best explains the observations represented in Figure 1 ? A There was a net movement of sucrose out of the cell suspended in the sugar solution and a net movement of sucrose into the cell suspended in the distilled water. B There was a net movement of sucrose into the cell suspended in the sugar solution and a net movement of sucrose out of the cell suspended in the distilled water. C There was a net movement of water out of the cell suspended in the sugar solution and a net movement of water into the cell suspended in the distilled water. D There was a net movement of water into the cell suspended in the sugar solution and a net movement of water out of the cell suspended in the distilled water.

C There was a net movement of water out of the cell suspended in the sugar solution and a net movement of water into the cell suspended in the distilled water.

3.6 ATP serves as a common energy source for organisms because A it is the smallest energy molecule B it stores the least energy of any energy source C its energy can be easily transferred to do cellular work D it is extremely stable and can be stored in the cell for long periods of time E traces of it have been found in fossils of ancient organisms dating back to the beginning of life on Earth

C its energy can be easily transferred to do cellular work

4.6 What is the expected percent change in the DNA content of a typical eukaryotic cell as it progresses through the cell cycle from the start of the G1 phase to the end of the G2 phase? A −100%−100% B −50%−50% C +50%+50% D +100%+100%

D +100%+100%

4.6 Researchers determined the average amount of time that a particular type of eukaryotic cell spends in each phase of the cell cycle. The data collected by the researchers are represented in Figure 1. Figure 1. The average amount of time spent by a particular type of eukaryotic cell in each phase of the cell cycle Based on Figure 1, what percent of the time required to complete a full cycle do the cells typically spend in interphase? A 5%5% B 35%35% C 50%50% D 95%95%

D 95%95%

3.5 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? A Atmospheric carbon dioxide is produced by the burning of fossil fuels, which are formed from the remains of living organisms such as plants. B Atmospheric carbon dioxide is a byproduct of cellular respiration, which is a metabolic process that occurs in plants and other living organisms. C Atmospheric carbon dioxide typically enters plant leaves through stomata, which plants rely on for regulating gas exchange with the atmosphere. D Atmospheric carbon dioxide is the raw material for photosynthesis, which plants rely on for producing sugars and other organic compounds.

D Atmospheric carbon dioxide is the raw material for photosynthesis, which plants rely on for producing sugars and other organic compounds.

2.5 Aquaporins are channel proteins that facilitate the transport of water across the cell membrane. One group of researchers hypothesizes that without functional aquaporins, no water will be able to enter the cell. A different group proposes an alternative hypothesis, stating that even with nonfunctional aquaporins, a small amount of water will still cross the cell membrane. An experiment is set up in which plant cells with mutated (nonfunctional) aquaporins and plant cells with normally functioning aquaporins are both placed in distilled water. Which of the following data would support the alternative hypothesis? A Cells with functional aquaporins exhibit low turgor pressure and are hypertonic. B Cells with functional aquaporins exhibit high turgor pressure and are hypotonic. C Cells with mutated aquaporins exhibit an absence of turgor pressure and are completely plasmolyzed. D Cells with mutated aquaporins exhibit moderate turgor pressure and are hypertonic.

D Cells with mutated aquaporins exhibit moderate turgor pressure and are hypertonic.

3.1 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? 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 Unknown node type: fontUnknown node type: font, 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 Glucose has the right shape and charge to cause hexokinase to undergo a structural change needed for catalysis, whereas water does not.

4.3 The epinephrine signaling pathway plays a role in regulating glucose homeostasis in muscle cells. The signaling pathway is activated by the binding of epinephrine to the beta-2 adrenergic receptor. A simplified model of the epinephrine signaling pathway is represented in Figure 1. A researcher claims that the epinephrine signaling pathway controls a catabolic process in muscle cells. Which of the following statements best helps justify the researcher's claim? A Epinephrine is a signaling molecule that binds to a transmembrane protein. B The G protein in the epinephrine signaling pathway consists of three different subunits. C Phosphorylase kinase catalyzes the hydrolysis of ATPATP. D Glycogen phosphorylase catalyzes the conversion of glycogen to glucose-1-phosphate.

D Glycogen phosphorylase catalyzes the conversion of glycogen to glucose-1-phosphate.

1.1 Based on Figure 1, which of the following best describes how the properties of water at an air-water interface enable an insect to walk on the water's surface? A Covalent bonds between water molecules and the air above provide cohesion, which causes tiny bubbles to form under the feet of the insect. B Ionic bonds between molecules at the surface of the water provide an electric charge, which attracts the feet of the insect, keeping it on the surface. C Polar covalent bonds between molecules at the surface of the water provide adhesion, which supports the weight of the insect. D Hydrogen bonds between molecules at the surface of the water provide surface tension, which allows the water surface to deform but not break under the insect.

D Hydrogen bonds between molecules at the surface of the water provide surface tension, which allows the water surface to deform but not break under the insect.

2.6 Water is constantly diffusing into the cytosol of freshwater single-celled organisms. In order to maintain the proper solute concentrations in the cytosol, contractile vacuoles pump out the excess water. An experimenter placed single-celled organisms into various saline concentrations and recorded the ATP used by the contractile vacuole. The data are shown in the graph. Of the following, which additional investigation can be used to determine when the cells are in an isotonic solution? A Decreasing the salinity of the environment a little at a time until the ATPATP usage reaches a maximum B Decreasing the salinity of the environment a little at a time until ATPATP usage reaches a minimum C Increasing the salinity of the environment a little at a time until ATPATP usage reaches a maximum D Increasing the salinity of the environment a little at a time until the ATPATP usage reaches a minimum

D Increasing the salinity of the environment a little at a time until the ATPATP usage reaches a minimum

1.3 Polypeptides are continuously being formed and degraded. One of these processes is shown. Which statement is the most accurate description of the reaction shown in Figure 1? A It represents monomers linked by dehydration synthesis. B It represents a polypeptide chain that folds to form the tertiary structure. C It represents a polypeptide chain that is denatured into the primary structure. D It represents a polypeptide chain that is broken down through a hydrolysis reaction.

D It represents a polypeptide chain that is broken down through a hydrolysis reaction.

1.5 The CFTR protein is made up of 1,480 amino acids linked together in a chain. Some humans produce a version of the CFTR protein in which phenylalanine (an amino acid) has been deleted from position 508 of the amino acid chain. Which of the following best predicts how the amino acid deletion will affect the structure of the CFTR protein? A It will have no observable effect on the structure of the CFTRCFTR protein. B It will affect the primary structure of the CFTRCFTR protein, but the other levels of protein structure will not be affected. C It will affect the secondary and tertiary structures of the CFTRCFTR protein, but the primary structure will not be affected. D It will affect the primary, secondary, and tertiary structures of the CFTRCFTR protein.

D It will affect the primary, secondary, and tertiary structures of the CFTRCFTR protein.

4.3 Ethylene causes fruits to ripen. In a signaling pathway, receptors activate transcription factors, which ultimately leads to ripening. Which of the following best supports the claim that ethylene initiates the signal transduction pathway that leads to ripening of fruit? A Ethylene is a simple gaseous molecule, which makes it easily detected by receptors. B Fruit will ripen in closed containers without exposure to air. C Ethylene synthesis is under both positive and negative feedback regulation. D Loss-of-function mutations in ethylene receptors result in changes to the ripening process.

D Loss-of-function mutations in ethylene receptors result in changes to the ripening process.

2.10 Changing the shape or morphology of the mitochondrial inner membrane can change the efficiency of mitochondrial function. Which of the following outcomes will most likely result from a change in the shape of the mitochondrial inner membrane from a highly folded surface to a smooth, flat surface? A Mitochondria will become more efficient because the inner mitochondrial membrane will become more permeable to ions. B Mitochondria will become more efficient because the total volume of the mitochondria will increase. C Mitochondria will become less efficient because the inner mitochondrial membrane will become less permeable to large molecules. D Mitochondria will become less efficient because the surface area of the inner mitochondrial membranes will decrease.

D Mitochondria will become less efficient because the surface area of the inner mitochondrial membranes will decrease.

1.6 Which of the following conclusions is most clearly supported by the representations of nucleic acid #1 and nucleic acid #2 ? A Nucleic acid #1#1 contains only purines, whereas nucleic acid #2#2 contains only pyrimidines. B Nucleic acid #1#1 contains the sugar ribose, whereas nucleic acid #2#2 contains the sugar deoxyribose. C Nucleic acid #1#1 contains positively charged phosphate groups, whereas nucleic acid #2#2 does not. D Nucleic acid #1#1 contains adenine-thymine base pairs, whereas nucleic acid #2#2 does not.

D Nucleic acid #1#1 contains adenine-thymine base pairs, whereas nucleic acid #2#2 does not.

2.1 Cells contain smaller components called organelles that are necessary for a cell's survival. Organelle functions have often been compared to components of larger systems. Which of the following functional differences between the rough and smooth endoplasmic reticulum (ER) is explained by the structural differences between them? A Rough ERER breaks down toxic substances, and smooth ERER only transports them out of the cell. B Rough ERER can synthesize and package lipids for export, and smooth ERER cannot. C Rough ERER can produce ATPATP, and smooth ERER cannot. D Rough ERER can synthesize and package proteins for export, and smooth ERER cannot.

D Rough ERER can synthesize and package proteins for export, and smooth ERER cannot.

2.11 Which of the following statements best supports the claim that certain organelles within eukaryotic cells evolved from free-living prokaryotic cells? A The cytoplasm of both eukaryotes and prokaryotes is surrounded by a plasma membrane. B Eukaryotes and prokaryotes both contain ribosomes, but the ribosomes of eukaryotes are more complex in structure than those of prokaryotes. C Eukaryotes exchange segments of internal membranes between the endoplasmic reticulum and Golgi apparatus, but prokaryotes have no such internal membranes. D Some organelles contain their own DNADNA that is more similar to prokaryotic DNADNA in structure and function than to the eukaryotic DNADNA found in the cell's nucleus.

D Some organelles contain their own DNADNA that is more similar to prokaryotic DNADNA in structure and function than to the eukaryotic DNADNA found in the cell's nucleus.

3.7 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? A The increased pigment concentration better facilitates energy production within the cells of the species. B The pigment combination allows the organism to absorb heat as well as light, making better use of available energy. C The additional pigments allow the species to outcompete other species for the wavelengths of light commonly used in photosynthesis. D The additional pigments allow the species containing them to harvest energy from wavelengths of light that the other photosynthetic species cannot use.

D The additional pigments allow the species containing them to harvest energy from wavelengths of light that the other photosynthetic species cannot use.

1.2 The figure shows a model of the exchange of matter between the organisms that live together in an aquarium. The model includes matter exchange between plants, fish, and bacteria. The bacteria are represented as rod-shaped organisms living in the gravel at the bottom of the aquarium. Which of the following statements best describes how molecules released by the fish become nutrients for the plants? A The carbon dioxide molecules released by the fish are converted by the bacteria to oxygen atoms, which are used by the plants to make water molecules. B The oxygen molecules released by the fish are converted by the bacteria to ammonia molecules, which are used by the plants to make lipids and fatty acids. C The nitrites released by the fish are converted by the bacteria to carbon dioxide molecules, which are used by the plants to make carbohydrates. D The ammonia molecules released by the fish are converted by the bacteria to nitrates, which are used by the plants to make proteins and nucleic acids.

D The ammonia molecules released by the fish are converted by the bacteria to nitrates, which are used by the plants to make proteins and nucleic acids.

4.6 The relative amount of DNA in a cell at various stages of the cell cycle is shown in Figure 1 . Figure 1. Amount of DNA per cell during different stages of the cell cycle, relative to the beginning of the G1 stage Which of the following best describes how the amount of DNA in the cell changes during M phase? A The amount of DNADNA doubles as the DNADNA is replicated. B The amount of DNADNA slightly increases as a result of new organelle synthesis. C The amount of DNADNA does not change while the cell grows. D The amount of DNADNA is halved as the cell divides into two daughter cells.

D The amount of DNADNA is halved as the cell divides into two daughter cells.

4.7 Cancer cells behave differently than normal body cells. For example, they ignore signals that tell them to stop dividing. Which of the following conditions will most likely cause a normal body cell to become a cancer cell? A The environment already contains cancer cells. B The environment has an abundance of nutrients. C The environment lacks signals that would otherwise tell the cell to stop dividing. D The environment contains mutagens that induce mutations that affect cell-cycle regulator proteins.

D The environment contains mutagens that induce mutations that affect cell-cycle regulator proteins.

1.3 Figure 1 represents a common process that occurs in organisms. Which of the following is an accurate description of the process shown in Figure 1 ? A The linking of amino acids with an ionic bond as an initial step in the protein synthesis process B The formation of a more complex carbohydrate with the covalent bonding of two simple sugars C The hydrolysis of amino acids with the breaking of covalent bonds with the release of water D The formation of a covalent peptide bond in a dehydration synthesis reaction

D The formation of a covalent peptide bond in a dehydration synthesis reaction

2.8 The rate of transpiration, the flow of water through the stem, and leaf water potential are measured in a tree during a 24-hour period under normal environmental conditions. The results from these measurements are shown in the graphs below. All of the following changes would be likely to decrease the rate of transpiration at 8 A.M. EXCEPT A causing the stomata to close B increasing the humidity of the atmosphere C increasing the water potential of the atmosphere D increasing the water potential of the soil E placing the plant in total darkness

D increasing the water potential of the soil

2.8 Directions: Each group of questions below concerns an experimental or laboratory situation or data. In each case, first study the description of the situation or data. Then choose the one best answer to each question following it and fill in the corresponding circle on the answer sheet. Dialysis tubing is permeable to water molecules but not to sucrose. Four dialysis tubes are half filled with 5 percent, 10 percent, 20 percent, and 40 percent sucrose solutions, respectively, and two dialysis tubes are half filled with distilled water. The dialysis tubes are all sealed at both ends, and the initial masses are determined. Five dialysis tubes are placed into beakers containing distilled water, and the sixth dialysis tube, containing distilled water, is placed into a 40 percent sucrose solution. The masses of the dialysis tubes are recorded at 30-minute intervals for 90 minutes, as shown in the table below. The contents of which dialysis tube are initially isotonic to the distilled water in the beaker? A 1 B 2 C 3 D 4 E 5

E 5

2.8 Directions: Each group of questions below concerns an experimental or laboratory situation or data. In each case, first study the description of the situation or data. Then choose the one best answer to each question following it and fill in the corresponding circle on the answer sheet. Dialysis tubing is permeable to water molecules but not to sucrose. Four dialysis tubes are half filled with 5 percent, 10 percent, 20 percent, and 40 percent sucrose solutions, respectively, and two dialysis tubes are half filled with distilled water. The dialysis tubes are all sealed at both ends, and the initial masses are determined. Five dialysis tubes are placed into beakers containing distilled water, and the sixth dialysis tube, containing distilled water, is placed into a 40 percent sucrose solution. The masses of the dialysis tubes are recorded at 30-minute intervals for 90 minutes, as shown in the table below. A net movement of water into the beaker occurs in which of the following dialysis tubes? A 2 B 3 C 4 D 5 E 6

E 6

1.5 A small protein is composed of 110 amino acids linked together in a chain. As shown in Figure 1, the first and last five amino acids in the chain are hydrophobic (have nonpolar and uncharged R-groups), whereas the remaining 100 amino acids are hydrophilic (have charged or polar R-groups). The nature of the R-group determines if the amino acid is hydrophobic or hydrophilic. A mutation results in the production of a version of the small protein that is only 105 amino acids long, as shown in Figure 2. Five of the hydrophobic amino acids are missing from one end of the chain. Which of the following best depicts the tertiary structures of the two proteins in water? The diagrams in the options are not drawn to the same scale as those in Figure 1 and Figure 2. A B C D

a

3.6 Which of the following statements about mitochondrial chemiosmosis is NOT true? A A proton gradient is established across the inner membrane of the mitochondrion. B The potential energy released from the mitochondrial proton gradient is used to produce ATP. C The mitochondrial proton gradient provides energy for muscle contraction. D Proteins embedded in the inner mitochondrial membrane play an important role in ATP synthesis. E Heat energy is required to establish the electron transport chain.

E Heat energy is required to establish the electron transport chain.