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(bio chem) Which of the following best describes the formation of the bond shown in Figure 1 ? two make one 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 OH 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 H2O . D A covalent bond is formed that replaces the hydrogen bond between the OH group and the H atom.

C A covalent bond is formed between a carbon atom and a nitrogen atom along with the formation of H2O .

(bio chem) The synthesis of protein or carbohydrate polymers always produces which of the following as a byproduct? A ATP B Oxygen C Carbon dioxide D Urea E Water

E Water

(unit 1) Water molecules are polar covalent molecules. There is a partial negative charge near the oxygen atom and partial positive charges near the hydrogen atoms due to the uneven distribution of electrons between the atoms, which results in the formation of hydrogen bonds between water molecules. The polarity of water molecules contributes to many properties of water that are important for biological processes. Which of the following models best demonstrates the arrangement of hydrogen bonds between adjacent water molecules?

3.A researcher proposes a model to explain how enzyme-substrate interactions determine enzyme specificity. The model is based on the idea that substrate molecules form favorable interactions with the amino acid side chains in an enzyme's active site. Based on the model, which of the following statements best explains an enzyme's specificity for a particular substrate molecule? A A hydrophilic molecule interacts with nonpolar side chains in the enzyme's active site. B A hydrophobic molecule interacts with polar side chains in the enzyme's active site. C A molecule with positive charges interacts with positively charged side chains in the enzyme's active site. D A molecule with negative charges interacts with positively charged side chains in the enzyme's active site.

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

(unit 1)Different polysaccharides are used by plants for energy storage and structural support. The molecular structures for two common polysaccharides are shown in Figure 1. Starch is used by plants for energy storage, and cellulose provides structural support for cell walls. The monomer used to construct both molecules is glucose. The figure presents segments of two polysaccharides, and is labeled Comparison of segments of starch and cellulose. The upper segment is labeled Starch, and the bottom segment is labeled Cellulose. Each segment is constructed of four glucose monomers, shown in ring form, and each glucose monomer has a C H 2 O H group attached to a particular carbon atom in the ring. In the segment of starch, each C H 2 O H group is oriented upwards and all the O atoms that join one ring to the next are oriented downwards. In the cellulose molecule, both the C H 2 O H groups and the O atoms that join one ring to the next are oriented in an alternating up and down pattern. A study determined the effect of two different digestive enzymes, A and B, on these two polysaccharides. Table 1 presents the data from the study. Table 1. Effect of Enzymes A and B on Cellulose and Starch Test Tube Polysaccharide Added Enzyme Added Glucose Detected after 5 Minutes at 37°C 1 Cellulose A No 2 Cellulose B Yes 3 Starch A Yes 4 Starch B No Mammals do not produce digestive enzyme B. However, sheep and cattle are two types of mammals that contain microorganisms in their digestive tract that produce enzyme B. Which of the following would most likely occur if cattle lost the ability to maintain a colony of microorganisms in their digestive tract? A Cattle would no longer be able to synthesize cellulose. B Cattle would have to convert cellulose to starch before digesting it. C Cattle would have to start producing enzyme B without the help of the bacteria. D Cattle would no longer be able to use cellulose as a primary source of glucose.

D Cattle would no longer be able to use cellulose as a primary source of glucose.

(unit 2) Researchers have proposed a model of chloroplast evolution. According to the model, chloroplasts evolved from a small prokaryotic organism that was engulfed by an ancestral eukaryote. The engulfed prokaryote then formed an endosymbiotic relationship with the eukaryotic host. Which of the following observations best supports the model? A Chloroplasts are separated from other subcellular compartments by semipermeable membranes. B Prokaryotic and eukaryotic organisms both acquire nutrients from the surrounding environment. C Eukaryotes evolved after prokaryotes and have more complex structures. D Chloroplasts and some prokaryotes share similar photosynthetic reactions.

D Chloroplasts and some prokaryotes share similar photosynthetic reactions.

(unit 1) Different polysaccharides are used by plants for energy storage and structural support. The molecular structures for two common polysaccharides are shown in Figure 1. Starch is used by plants for energy storage, and cellulose provides structural support for cell walls. The monomer used to construct both molecules is glucose. The figure presents segments of two polysaccharides, and is labeled Comparison of segments of starch and cellulose. The upper segment is labeled Starch, and the bottom segment is labeled Cellulose. Each segment is constructed of four glucose monomers, shown in ring form, and each glucose monomer has a C H 2 O H group attached to a particular carbon atom in the ring. In the segment of starch, each C H 2 O H group is oriented upwards and all the O atoms that join one ring to the next are oriented downwards. In the cellulose molecule, both the C H 2 O H groups and the O atoms that join one ring to the next are oriented in an alternating up and down pattern. A study determined the effect of two different digestive enzymes, A and B, on these two polysaccharides. Table 1 presents the data from the study. Table 1. Effect of Enzymes A and B on Cellulose and Starch Test Tube Polysaccharide Added Enzyme Added Glucose Detected after 5 Minutes at 37°C 1 Cellulose A No 2 Cellulose B Yes 3 Starch A Yes 4 Starch B No Mammals do not produce digestive enzyme B. However, sheep and cattle are two types of mammals that contain microorganisms in their digestive tract that produce enzyme B. Which of the following best describes the process that adds a monosaccharide to an existing polysaccharide? A The monosaccharide is completely broken down by a specific enzyme and then the atoms are reorganized and made into a polysaccharide. B Ionic bonds are formed between adjacent carbon atoms of the monosaccharide and the polysaccharide by adding water (H2O) and a specific enzyme. C A specific enzyme removes the hydrogen (H) from the monosaccharide and the hydroxide (OH) from the polysaccharide, creating a bond between the two and creating a water (H2O) molecule. D A specific enzyme removes two hydroxides (OH), one from the monosaccharide, and one from the polysaccharide, creating a bond between the two monosaccharides and creating a hydrogen peroxide (H2O2) molecule.

C A specific enzyme removes the hydrogen (H) from the monosaccharide and the hydroxide (OH) from the polysaccharide, creating a bond between the two and creating a water (H2O) molecule.

(unit 2) The cell membrane is selectively permeable due to its structure. Thus, the internal environment of the cell is distinct from the external environment of the cell. One biologist hypothesizes that small nonpolar molecules readily pass through the membrane. Another biologist alternatively hypothesizes that these types of molecules require channel and transport proteins that are embedded in the membrane in order to move across the membrane. Which of the following data would best refute this alternative hypothesis? A Ethanol is found in the cytosol of cells when they are briefly exposed to a ten percent ethanol solution. B Cells become oxygen deficient when membrane protein activity is blocked. C CO2 and N2 movement in and out of cells is unaffected when membrane protein activity is blocked. D Sodium ions cannot move across the cell membrane when membrane protein activity is blocked.

C CO2 and N2 movement in and out of cells is unaffected when membrane protein activity is blocked.

(Unit 1) Which of the following is common feature of the illustrated reactions showing the linking of monomers to form macromolecules? A Two identical monomers are joined by a covalent bond. B Two different monomers are joined by a covalent bond. C Monomers are joined by a covalent bond, and a water molecule is produced. D Monomers are joined by ionic bonds, and a water molecule is produced.

C Monomers are joined by a covalent bond, and a water molecule is produced.

(unit 2) Figure 1. Testosterone movement across the cellular membrane The figure presents a cellular membrane bilayer. A point between two lipid molecules on the outer surface of the membrane is labeled 1. A protein associated only with the outer surface membrane is labeled 2. A channel protein embedded in the membrane is labeled 3. A solid appearing protein with an extracellular chain of sugars is embedded in the membrane and is labeled 4. Testosterone is a small steroid hormone that is important in cell signaling. Which of the following indicates where testosterone enters a cell and why it is able to cross at that point? A 1, because testosterone is nonpolar and can diffuse through the membrane. B 2, because testosterone covalently binds to a surface protein and transports into the cell. C 3, because testosterone dissolves in water and flows through the channel. D 4, because testosterone is filtered out of the extracellular fluid and taken into the cell by endocytosis.

A 1, because testosterone is nonpolar and can diffuse through the membrane.

(bio chem) Which of the following correctly illustrates a dipeptide and an amino acid in the optimal position to form a tripeptide? A A dipeptide chain situated left to right. The first central carbon has an amino group on the left, an R-group above, hydrogen below and a carbonyl on the right. The carbonyl is bonded to the amine group of the second central carbon which has an R-group above, hydrogen below and a carboxyl group on the right. The amino acid is situated to the right of the dipeptide with the central carbon bonded to an amino group on the left, an R-group above and a carboxyl group on the right. B A dipeptide chain situated left to right. The first central carbon is bonded to a carboxyl group on the left, an R-group above, hydrogen below, and an amino group to the right. The amino group is bonded to the amino group of the second central carbon which has an R-group above, hydrogen below and a carboxyl group to the right. The amino acid is situated to the right of the dipeptide with the central carbon bonded to a carboxyl group on the left, an R-group above, hydrogen below and carboxyl group on the right. C A dipeptide chain situated left to right. The first central carbon is bonded to an amino group on the left, an R-group above, hydrogen below and a carbonyl to the right. The carbonyl is bonded to a second carbonyl group, which is bonded to the second central carbon. The second central carbon has an R-group above, hydrogen below and amino group to the right. The amino acid is situated to the right of the dipeptide with the central carbon bonded to an amino group on the left, an R-group above, hydrogen below and a methyl group to the right. D A dipeptide chain situated left to right. The first central carbon is bonded to a carboxyl group on the left, an R-group above, hydrogen below, and an amino group to the right. The amino group is bonded to the carbonyl of the second central carbon. The second central carbon has an R-group above, hydrogen below and an amino group to the right. The amino acid is situated to the right of the dipeptide with the central carbon bonded to a methyl group on the left, an R side chain above, hydrogen below and carboxyl group on the right.

A A dipeptide chain situated left to right. The first central carbon has an amino group on the left, an R-group above, hydrogen below and a carbonyl on the right. The carbonyl is bonded to the amine group of the second central carbon which has an R-group above, hydrogen below and a carboxyl group on the right. The amino acid is situated to the right of the dipeptide with the central carbon bonded to an amino group on the left, an R-group above and a carboxyl group on the right.

(unit 1) In vascular plants, water flows from root to leaf via specialized cells called xylem. Xylem cells are hollow cells stacked together like a straw. A student explains that evaporation of water from the leaf pulls water up from the roots through the xylem, as shown in Figure 1. Figure 1. Model of water movement through the xylem, with magnified models of water movement in the stem and leaf. Which statement describes how water is pulled up through the xylem to the leaves of the plant? A As water exits the leaf, hydrogen bonding between water molecules pulls more water up from below. B As water exits the leaf, signals are sent to the roots to pump more water up to the leaves through the xylem by adhesion. C Evaporation from the leaf decreases the hydrogen bonds that form between the water molecules in the xylem, which helps the water molecules to be pulled up the xylem. D Evaporation of water from the leaf increases the hydrogen bonds that form between water molecules in the air, providing the energy for transport.

A As water exits the leaf, hydrogen bonding between water molecules pulls more water up from below.

(unit 2) A magnesium sulfate solution taken orally can cause a net movement of water into the large intestine, which results from water molecules diffusing through aquaporins embedded in the cells of the intestinal lining. By which of the following mechanisms do the water molecules most likely move into the large intestine? A By passive transport from an area of low osmolarity to an area of high osmolarity B By passive transport from an area of high osmolarity to an area of low osmolarity C By active transport from an area of low osmolarity to an area of high osmolarity D By active transport from an area of high osmolarity to an area of low osmolarity

A By passive transport from an area of low osmolarity to an area of high osmolarity

(unit 2) Aldosterone (a steroid hormone) is a small, nonpolar, hydrophobic molecule that enters a target cell by moving across the plasma membrane, down a concentration gradient. Based on the information presented, how does aldosterone most likely enter target cells? A By simple diffusion B By facilitated diffusion C By active transport D By endocytosis

A By simple diffusion

3.Researchers investigated the effect of urea on the three-dimensional structure of a certain enzyme. The researchers dissolved the enzyme in an aqueous buffer solution and added urea to the solution. The enzyme did not appear to have a secondary or tertiary structure. The researchers carefully removed the urea from the solution and determined that the enzyme had the original secondary and tertiary structure again. Based on the results of the experiment, which of the following statements best predicts the effect of urea on the enzyme's function? A Function will be disrupted by adding the urea and regained by removing the urea. B Function will be disrupted by adding the urea, but it will not be regained by removing the urea. C Function will be gained by adding the urea and disrupted by removing the urea. D Function will be unaffected by the addition and removal of the urea.

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

3.A researcher designs an experiment to investigate whether soil bacteria trigger the synthesis of defense enzymes in plant roots. The design of the experiment is presented in Table 1. For each group in the experiment, the researcher will determine the average rate of change in the amount of defense enzymes in the roots of the seedlings. Table 1. An experiment to investigate the effect of soil bacteria on plant defenses Group Number of Seedlings,Type of Soil Treatment Solution 1 10 Sterile potting soil Contains actively reproducing soil bacteria 2 10 Sterile potting soil Contains heat-killed soil bacteria 3 10 Sterile potting soil Contains no soil bacteria Which of the following statements best helps justify the inclusion of group 2 as one of the controls in the experiment? A It will show whether the changes observed in group 1 depend on the metabolic activity of soil bacteria. B It will show whether the changes observed in group 1 depend on the type of plants used in the experiment. C It will show the average growth rate of seedlings that are maintained in a nonsterile environment. D It will show the changes that occur in the roots of seedlings following an infection by soil bacteria.

A It will show whether the changes observed in group 1 depend on the metabolic activity of soil bacteria.

3.Researchers investigated the influence of environmental pH on the activity of peroxidase, an enzyme that catalyzes the conversion of hydrogen peroxide to water and oxygen gas. In an experiment, the researchers added a hydrogen peroxide solution containing guaiacol to several identical test tubes and adjusted the solution in each test tube to a different pH. The researchers included the guaiacol because it caused the solutions to change color as the reactions proceeded, which the researchers relied on for measuring reaction rates. Finally, the researchers added the same amount of peroxidase to each test tube and measured the rate of each reaction at 23°C. The results of the experiment are represented in Figure 1. Figure 1. The effect of pH on peroxidase activity Based on Figure 1, which of the following statements best predicts the effect that a change from a moderately acidic environment (pH near 6) to a basic environment will have on peroxidase activity? A Peroxidase activity will decrease. B Peroxidase activity will increase. C Peroxidase activity will stay the same. D Peroxidase activity will increase at first and then decrease.

A Peroxidase activity will decrease.

(unit 2) Intravenous (IV) therapy is used for fluid replacement in instances of dehydration in humans and other animals. One type of IV fluid is essentially a saltwater solution. To determine the best concentration for therapy in people, a team of students is researching the effects of solutions of different salt concentrations on red blood cells. The following observations were made from three different red blood cell samples viewed under a microscope. The figure presents three blood cells. The left cell is swollen, the middle cell is of normal disc shape, and the right cell is shrunken and irregular. 0.3% Saline (Cells swell) 0.9% Saline (Cells unchanged) 1.5% Saline (Cells shrink) The team wants to extend the research project. What should the team of students do next to obtain data that are more conclusive? A Repeat the process with other salt concentrations. B Develop a model to explain why the cells react differently to different salt concentrations. C Repeat the process using red blood cells from other animals. D Develop an experimental procedure that uses a stain that makes the organelles of red blood cells more visible.

A Repeat the process with other salt concentrations.

(unit 1) Figure 1 shows three amino acids that are part of a polypeptide chain. Figure 2 shows the same section of the chain after a mutation has occurred. Two figures are presented. Figure 1 presents the Original Amino Acid Chain, with an aspartic acid on the left, followed by a cysteine, followed by a lysine. Aspartic acid has a negative 1 charge on its R group, cysteine has an uncharged R group composed of a carbon atom bonded to two hydrogen atoms and an S H group, and lysine has a positive 1 charge on its R group. Figure 2 presents the Mutated Amino Acid Chain, with an aspartic acid on the left, followed by a valine, followed by a lysine. Aspartic acid has a negative 1 charge on its R group, valine has an uncharged R group composed of a carbon atom bonded to one hydrogen atom and two C H 3 groups, and lysine has a positive 1 charge on its R group. How might this change affect the structure and function of the protein? A The R-group of the new amino acid, valine, has different chemical properties than the R-group of cysteine. This will cause the protein to misfold and not function properly in the cell. B The new amino acid, valine, has replaced cysteine in the new protein. Since the number of amino acids has remained the same, there will be no change in the three-dimensional folding, or function, of the protein. C Since this is a linear section, it does not influence protein folding. Thus, there will be no change in protein structure or function. D Since the new amino acid is bounded on one side by an amino acid with a negatively charged R-group and by an amino acid on the other side with a positively charged R-group, the charges will balance and the protein will fold as usual.

A The R-group of the new amino acid, valine, has different chemical properties than the R-group of cysteine. This will cause the protein to misfold and not function properly in the cell.

3.Acetylcholinesterase (AChE) is a protein that catalyzes the conversion of acetylcholine to acetate and choline. When the concentration of AChE in an aqueous solution is held constant, the rate of the reaction catalyzed by AChE increases with increasing concentrations of substrate. At low concentrations of acetylcholine, a small increase in the substrate concentration results in a large increase in the reaction rate. At high concentrations of acetylcholine, however, a large increase in the substrate concentration results in only a small increase in the reaction rate. Which of the following statements correctly explains the observed effect of the acetylcholine concentration on the rate of the enzyme-catalyzed reaction? A The active site of AChE is specific for acetylcholine, and only one substrate molecule can occupy the active site at a time. B AChE begins converting product into substrate as the acetylcholine concentration changes from low to high. C The AChE protein becomes denatured as the acetylcholine concentration changes from low to high. D The substrate specificity of AChE changes as the acetylcholine concentration changes from low to high.

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

(unit 1) Different polysaccharides are used by plants for energy storage and structural support. The molecular structures for two common polysaccharides are shown in Figure 1. Starch is used by plants for energy storage, and cellulose provides structural support for cell walls. The monomer used to construct both molecules is glucose. The figure presents segments of two polysaccharides, and is labeled Comparison of segments of starch and cellulose. The upper segment is labeled Starch, and the bottom segment is labeled Cellulose. Each segment is constructed of four glucose monomers, shown in ring form, and each glucose monomer has a C H 2 O H group attached to a particular carbon atom in the ring. In the segment of starch, each C H 2 O H group is oriented upwards and all the O atoms that join one ring to the next are oriented downwards. In the cellulose molecule, both the C H 2 O H groups and the O atoms that join one ring to the next are oriented in an alternating up and down pattern. A study determined the effect of two different digestive enzymes, A and B, on these two polysaccharides. Table 1 presents the data from the study. Table 1. Effect of Enzymes A and B on Cellulose and Starch Test Tube Polysaccharide Added Enzyme Added Glucose Detected after 5 Minutes at 37°C 1 Cellulose A No 2 Cellulose B Yes 3 Starch A Yes 4 Starch B No Mammals do not produce digestive enzyme B. However, sheep and cattle are two types of mammals that contain microorganisms in their digestive tract that produce enzyme B. Based the information provided, which of the following statements best describes why starch and cellulose provide different functions in plants? A The differences in the assembly and organization of the monomers of these two polymers result in different chemical properties. B Since starch and cellulose are composed of identical monomers, the cellular environment where they are located controls their function. C The monomers of cellulose are connected by covalent bonds, making it idea for structural support. D The monomers of starch are connected by ionic bonds, making it ideal for energy storage for plants.

A The differences in the assembly and organization of the monomers of these two polymers result in different chemical properties.

(bio chem) 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. The figure presents the primary structure of the original protein. The 110 amino acids of the protein are represented as 110 circles. A key indicates that black circles represent hydrophobic amino acids, and gray circles represent hydrophilic amino acids. The first 5 amino acids and the last five amino acids are hydrophobic, as represented by black circles. The intervening 100 amino acids are hydrophilic, as represented by gray circles. The figure presents the primary structure of the mutated protein. The 105 amino acids of the protein are represented as 105 circles. A key indicates that black circles represent hydrophobic amino acids, and gray circles represent hydrophilic amino acids. The last five amino acids are hydrophobic, as represented by black circles. The 100 remaining amino acids are hydrophilic, as represented by gray circles. 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 The figure presents two tertiary structures of proteins. The first, labeled Original Protein, appears to be a cluster of hydrophilic amino acids, with the hydrophobic amino acids buried in the middle. The second, labeled Mutated Protein, appears to be almost identical to the Original, with one hydrophilic amino acid sticking out of the cluster. B The figure presents two tertiary structures of proteins. The first, labeled Original Protein, appears to be a cluster of hydrophilic amino acids, with 2 segments of 5 hydrophobic amino acids sticking out to either side. The second, labeled Mutated Protein, appears to be a cluster of hydrophilic amino acids, with one segment of 5 hydrophobic amino acids sticking straight upward. C The figure presents two tertiary structures of proteins. The first, labeled Original Protein, is a long unfolded chain of hydrophilic amino acids, with 5 hydrophobic amino acids at each end. The second, labeled Mutated Protein, is a long unfolded chain of hydrophilic amino acids that is missing 5 hydrophobic amino acids from one end. D The figure presents two tertiary structures of proteins. The first, labeled Original Protein, is a circular, unfolded chain of amino acids. The second, labeled Mutated Protein, is a circular, unfolded chain of hydrophilic amino acids, with the 5 hydrophobic amino sticking out from the top of the circle.

A The figure presents two tertiary structures of proteins. The first, labeled Original Protein, appears to be a cluster of hydrophilic amino acids, with the hydrophobic amino acids buried in the middle. The second, labeled Mutated Protein, appears to be almost identical to the Original, with one hydrophilic amino acid sticking out of the cluster.

(unit 2) Lysosomes digest food particles brought into a cell by endocytosis. After a vesicle containing food particles fuses with a lysosome, H+ ions are transported into the lysosome from the cytosol. This significantly lowers the pH of the lysosome relative to the cytosol and activates the enzymes that digest the particles. Which of the following best predicts what will happen to the lysosomal enzymes if the proteins that transport H+ ions from the cytosol into the lysosome are damaged? A The lysosomal enzymes will not become active, since there will be no active transport of H+ ions. B The lysosomal enzymes will not become active, since H+ ions will diffuse out of the lysosome. C The lysosomal enzymes will become active, since facilitated diffusion will move H+ ions into the lysosome. D The lysosomal enzymes will become active, since passive diffusion will move H+ ions into the lysosome.

A The lysosomal enzymes will not become active, since there will be no active transport of H+ ions.

(unit 2) Stomata are pores on the surfaces of the leaves and stems of plants that regulate gas exchange between the plants and the atmosphere. Researchers found that the stomata density on the leaves of a species of plant change as the concentration of CO2 in the atmosphere changes. When grown at 350 ppm CO2 the plant has an average density of 300 stomata per mm2, but when grown at 400 ppm CO2 the plant has an average density of 250 stomata per mm2. Which of the following best describes how the ratio of the density of stomata (stomata per mm2) per CO2 concentration (ppm CO2) changes as the CO2 concentration increases? A The ratio decreases from 0.86 to 0.63, because fewer stomata are needed at higher CO2 concentrations. B The ratio decreases from 1.6 to 1.2, because fewer stomata are needed at higher CO2 concentrations. C The ratio increases from 0.63 to 0.86, because more stomata are needed at higher CO2 concentrations. D The ratio increases from 1.2 to 1.6, because more stomata are needed at higher CO2 concentrations.

A The ratio decreases from 0.86 to 0.63, because fewer stomata are needed at higher CO2 concentrations.

3.European flycatchers feed caterpillars to their hatchlings. Graph 1 shows the average dates of hatching and fledging (leaving the nest), and the biomass of the caterpillars between early May (when flycatcher young hatch) and June (when fledging of young occurs). Graph 1. Comparison of European flycatcher hatching and fledging dates and caterpillar biomass Based on the data, scientists claim that the reproductive behavior of European flycatchers is influenced by the availability of energy sources. Which of the following statements best justifies this claim? A Young European flycatchers hatch from eggs when caterpillar biomass is available for the young birds to consume and convert into energy for growth. B European flycatcher hatchlings begin to need energy to leave the nest only after the caterpillars have turned into pupae. C Female European flycatchers require energy to lay eggs, so they lay their eggs when the caterpillar biomass is maximal. D The energy requirements for hatching European flycatchers and caterpillars are proportional to each other.

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

3.Catalase is an enzyme found in yeast cells that facilitates the chemical breakdown of hydrogen peroxide to water and oxygen gas. An experiment was conducted to determine the effect of pH on catalase function. Five buffer solutions of varying pH (2, 4, 6, 8, and 10) were prepared and added to separate test tubes. Hydrogen peroxide (H2O2) was added to each test tube. Yeast was added, and the reactions were timed. After 1 minute the amount of oxygen gas released was determined by measuring the foam layer produced in each test tube. Figure 1 illustrates the experimental setup. The figure illustrates the experimental procedure by showing 3 test tubes to indicate the sequence of steps. The first test tube contains a solution of a certain p H. H 2 O 2 is added to this tube. The second test tube contains the solution of a certain p H plus H 2 O 2. A yeast solution is added to this tube. After one minute, the third test tube shows a bracketed area above the surface of the solution, and the area is labeled Measure Foam Layer. Figure 1. Illustration of experimental procedure A set of five additional test tubes were prepared and used as controls. Which of the following best describes the contents expected to be contained in one of the five control test tubes? A pH 4 buffer solution and hydrogen peroxide only B All five pH buffer solutions combined and hydrogen peroxide only C Water, hydrogen peroxide, and yeast D Water and yeast only

A pH 4 buffer solution and hydrogen peroxide only

3.A researcher claims that a certain herbicide suppresses plant growth by inhibiting chloroplast function. To test the claim, the researcher treats isolated chloroplasts with increasing concentrations of the herbicide. The data from the experiment are presented in Table 1. Table 1. The effect of an herbicide on the function of isolated chloroplasts Herbicide Concentration (μg/L) pH Difference across Thylakoid Membrane ATP Production 0-3.5 Very high 2-2.5 Moderate 8-0.5 Very low 32-0 Very low Which of the following statements best clarifies how the data support the researcher's claim? A The thylakoid membrane is more permeable to carbon dioxide than to polar molecules. B ATP synthase activity depends on a proton gradient across the thylakoid membrane. C Some enzymes embedded in the thylakoid membrane catalyze the hydrolysis of ATP. D Carbon fixation in the Calvin-Benson cycle takes place in the stroma of chloroplasts

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

(unit 2) A study was conducted to understand the factors controlling the rate at which molecules or ions travel across cell membranes. An artificial membrane was created that was composed of a phospholipid bilayer only. The speed at which various substances crossed this membrane was measured. Some substances can pass through an actual cell membrane much faster than they passed through the artificial membrane in this study. Which of the following statements best explains this finding? A Actual cell membranes have a much thicker phospholipid bilayer than the artificial membrane does. B Actual cell membranes have a variety of proteins embedded in the membrane that are absent in the artificial membrane. C Hydrophobic substances spend more time between the two layers of phospholipid in the artificial membrane than they do between the layers in an actual membrane. D Hydrophilic substances spend more time attached to the polar region of the phospholipids in the artificial membrane than they do attached to the polar region of the phospholipids in an actual membrane.

B Actual cell membranes have a variety of proteins embedded in the membrane that are absent in the artificial membrane.

(unit 2) Some cells, such as intestinal cells, exchange a lot of material with their surroundings. The surface-to-volume ratio of these cells affects the efficiency of material exchange. The table provides measurements of four different eukaryotic cells. Cell 1 2 3 4 Total surface area (μm2) 40 60 80 100 Total volume (μm3) 20 10 30 20 Based on the data, which cell is likely to be most effective in the exchange of materials? A Cell 1 B Cell 2 C Cell 3 D Cell 4

B Cell 2

B Changing the deoxyriboses to riboses by adding −OH groups

(unit 2) In an experiment, researchers compared the growth of two different plants, plant X and plant Y. The researchers maintained the plants under nearly identical conditions and observed that plant X grew faster than plant Y. The researchers also observed that the inner mitochondrial membranes of plant X had more folds than did those of plant Y. Which of the following conclusions about increasing the number of folds in the inner mitochondrial membrane is best supported by the results of the experiment? A It increases the efficiency of photosynthesis, which results in faster cell growth. B It increases the surface area available for ATP production, which results in faster cell growth. C It increases the amount of space available for storing cellular wastes, which results in faster cell growth. D It increases the rate of protein transport to the plasma membrane, which results in faster cell growth.

B It increases the surface area available for ATP production, which results in faster cell growth.

(unit 2) In an experiment, researchers provided a radiolabeled amino acid to living plant cells. After one hour, the researchers determined the amount of the radiolabeled amino acid that was in each of several subcellular compartments. The results of the experiment are represented in the table. RELATIVE AMOUNTS OF RADIOLABELED AMINO ACID Nucleus Mitochondria Endoplasmic Reticulum Cytosol 2.1 2.7 1.9 1 Which of the following conclusions about the radiolabeled amino acid is best supported by the results of the experiment? A It was mostly incorporated into nucleic acids that store the biological information. B It was mostly incorporated into proteins that regulate and manage metabolic reactions. C It was mostly incorporated into lipids that help separate cells from their surrounding environment. D It was mostly incorporated into carbohydrates that form protective structures outside the cells.

B It was mostly incorporated into proteins that regulate and manage metabolic reactions.

(bio chem) The figure shows a grass plant at the top. An arrow points from the plant to a molecule composed of three hexagonal rings joined sequentially by O atoms. Another arrow points from this molecule to a rabbit. A final arrow points from the rabbit to another molecule. The molecule has a backbone of 16 sequential C atoms. 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 CO2, 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.

(unit 2) The figure shows a representation of a protein embedded in a cell membrane. The numbers indicate different structural regions of the protein. The figure presents a cell membrane lipid bilayer. A protein is embedded in one half of the bilayer. The exposed surface of the protein that protrudes from the membrane is labeled 1, and the part of the protein that associates with the fatty acid tails in the interior of the membrane is labeled 2. Based on the figure, which of the following statements best describes the relationship between regions 1 and 2 of the protein? A Region 1 is hydrophilic because it interacts with the interior of the membrane, whereas region 2 is hydrophobic because it interacts with an aqueous environment. B Region 1 is hydrophilic because it interacts with an aqueous environment, whereas region 2 is hydrophobic because it interacts with the interior of the membrane. C Region 1 is hydrophobic because it interacts with the interior of the membrane, whereas region 2 is hydrophilic because it interacts with an aqueous environment. D Region 1 is hydrophobic because it interacts with an aqueous environment, whereas region 2 is hydrophilic because it interacts with the interior of the membrane. Answer B

B Region 1 is hydrophilic because it interacts with an aqueous environment, whereas region 2 is hydrophobic because it interacts with the interior of the membrane.

(unit 1) Different polysaccharides are used by plants for energy storage and structural support. The molecular structures for two common polysaccharides are shown in Figure 1. Starch is used by plants for energy storage, and cellulose provides structural support for cell walls. The monomer used to construct both molecules is glucose. The figure presents segments of two polysaccharides, and is labeled Comparison of segments of starch and cellulose. The upper segment is labeled Starch, and the bottom segment is labeled Cellulose. Each segment is constructed of four glucose monomers, shown in ring form, and each glucose monomer has a C H 2 O H group attached to a particular carbon atom in the ring. In the segment of starch, each C H 2 O H group is oriented upwards and all the O atoms that join one ring to the next are oriented downwards. In the cellulose molecule, both the C H 2 O H groups and the O atoms that join one ring to the next are oriented in an alternating up and down pattern. A study determined the effect of two different digestive enzymes, A and B, on these two polysaccharides. Table 1 presents the data from the study. Table 1. Effect of Enzymes A and B on Cellulose and Starch Test Tube Polysaccharide Added Enzyme Added Glucose Detected after 5 Minutes at 37°C 1 Cellulose A No 2 Cellulose B Yes 3 Starch A Yes 4 Starch B No Mammals do not produce digestive enzyme B. However, sheep and cattle are two types of mammals that contain microorganisms in their digestive tract that produce enzyme B. Based on Figure 1, which of the following best compares the atomic structures of starch and cellulose? A Starch is composed of carbon, hydrogen, and oxygen, while cellulose also contains nitrogen. B Starch and cellulose are composed of repeating glucose monomers; however, in cellulose every other glucose monomer is rotated 180 degrees. C Starch is composed of monomers that each have a CH2OH group, while cellulose only has a CH2OH group on every other monomer. D Starch and cellulose are composed of identical monomers and therefore have identical structures.

B Starch and cellulose are composed of repeating glucose monomers; however, in cellulose every other glucose monomer is rotated 180 degrees.

(unit 2) Some membrane proteins help maintain the concentrations of ions inside a cell by transporting the ions across the cell's plasma membrane. Other membrane proteins form pores in the plasma membrane through which the ions can diffuse. A model showing the influence of membrane proteins on the movement of sodium (Na+) and potassium (K+) ions across a plasma membrane is presented in Figure 1. The figure presents a bilayer plasma membrane, which separates the cytosol from the extracellular region. In the cytosol, the concentration of N a plus is low, and the concentration of K plus is high. In the extracellular region, the concentration of N a plus is high, and the concentration of K plus is low. Three membrane proteins are embedded in the plasma membrane. One protein has a channel, through which N a plus leaks into the cytolsol from the extracellular region. Another protein has a channel, through which K plus leaks out from the cytosol into the extracellular region. A third protein is a pump protein, through which Na plus is pumped out from the cytosol to the extracellular region and K plus is pumped into the cytosol from the extracellular region. Figure 1. Section of a cell's plasma membrane, showing ion concentrations and membrane proteins Based on the model presented in Figure 1, which of the following changes will most likely result from a depletion of available ATP stores inside the cell? A The Na+ concentration outside the cell will increase. B The Na+concentration inside the cell will increase. C The K+ concentration inside the cell will increase. D The K+ concentration outside the cell will decrease.

B The Na+concentration inside the cell will increase.

(bio chem) 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 DNA contains four types of nitrogenous bases, whereas RNA contains only two types of nitrogenous bases. B The backbone of DNA contains deoxyribose, whereas the backbone of RNA contains ribose. C A DNA molecule is composed of two parallel strands with the same 5′ to 3′ directionality, whereas an RNA molecule is composed of only one 5′ to 3′ strand. D Phosphate groups provide rigidity to DNA, but RNA is flexible and contains no phosphate

B The backbone of DNA contains deoxyribose, whereas the backbone of RNA contains ribose.

(bio chem) 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-S bonds in the tertiary structure of the proteins. C The change leads to decreased protein stability because of an increased number of S-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-S bonds in the tertiary structure of the proteins.

3.A researcher claims that spinach leaves capture the most energy from light waves in the range of 500 nm to 600 nm. To test the claim, the researcher will place spinach leaves in separate chambers and expose the leaves to different wavelengths of light. For each chamber, the researcher will measure the amount of oxygen gas (O2) that is produced in one hour. Which of the following graphs best represents data from the experiment that will support the researcher's claim? A The curve begins close to the top of the vertical axis at 400 nanometers, and slants downwards and to the right at a constant rate until it reaches 500 nanometers. The curve then moves horizontally to the right until 600 nanometers. The curve then slants upwards and to the right at a constant rate until it returns to its original height above the horizontal axis at 700 nanometers. B The curve begins close to the bottom of the vertical axis at 400 nanometers, and slants upwards and to the right at a constant rate until it reaches 500 nanometers. The curve then moves horizontally to the right until 600 nanometers. The curve then slants downwards and to the right at a constant rate until it returns to its original height above the horizontal axis at 700 nanometers. C The curve begins close to the top of the vertical axis at 400 nanometers, and moves downwards and to the right at a decreasing rate until just past 500 nanometers, where it levels out. The curve then moves approximately horizontally to the right until almost 600 nanometers, where it begins to curve downwards and to the right at an increasing rate until 700 nanometers, where it ends slightly above the horizontal axis. D The curve begins close to the bottom of the vertical axis at 400 nanometers, and moves upwards and to the right at a decreasing rate until just past 500 nanometers, where it levels out. The curve then moves approximately horizontally to the right until almost 600 nanometers, where it begins to curve upwards and to the right at an increasing rate until 700 nanometers, where it ends close to the top of the vertical axis.

B The curve begins close to the bottom of the vertical axis at 400 nanometers, and slants upwards and to the right at a constant rate until it reaches 500 nanometers. The curve then moves horizontally to the right until 600 nanometers. The curve then slants downwards and to the right at a constant rate until it returns to its original height above the horizontal axis at 700 nanometers.

(unit 2) A student is using dialysis bags to model the effects of changing solute concentrations on cells. The student places one dialysis bag that contains 25 mL of distilled water into each of two beakers that are filled with 200 mL of distilled water. (Figure 1). The membrane of each dialysis bag membrane contains pores that allow small solutes such as monoatomic ions to pass through but are too small for anything larger to pass. After 30 minutes, 5 mL of a concentrated solution of albumin (a medium-sized, water-soluble protein) is added to one of the two beakers. Nothing is added to the other beaker. After two more hours at room temperature, the mass of each bag is determined. There is no change in the mass of the dialysis bag in the beaker to which no albumin was added. Which of the graphs below best represents the predicted change in mass over time of the dialysis bag in the beaker to which albumin was added? A The figure presents a graph in the coordinate plane. The horizontal axis is labeled Time, in minutes, and the numbers 0 through 150, in increments of 30, are indicated. The vertical axis is labeled Relative Mass of Dialysis Bag. The axis has an arrowhead at the top end, and no numbers are indicated along it. The graphed line begins at 0 minutes, about halfway up the vertical axis, and extends horizontally to the right until it ends at 150 minutes. A label indicates Albumin Added at 30 minutes. B The figure presents a graph in the coordinate plane. The horizontal axis is labeled Time, in minutes, and the numbers 0 through 150, in increments of 30, are indicated. The vertical axis is labeled Relative Mass of Dialysis Bag. The axis has an arrowhead at the top end, and no numbers are indicated along it. The graphed line begins at 0 minutes, about halfway up the vertical axis, and extends horizontally to the right until 30 minutes. A label indicates Albumin Added at 30 minutes. The graphed line starts to move downward and to the right at 30 minutes until it ends at 150 minutes, just above the horizontal axis. C The figure presents a graph in the coordinate plane. The horizontal axis is labeled Time, in minutes, and the numbers 0 through 150, in increments of 30, are indicated. The vertical axis is labeled Relative Mass of Dialysis Bag. The axis has an arrowhead at the top end, and no numbers are indicated along it. The graphed line begins at 0 minutes, about one third of the way up the vertical axis, and moves upward and to the right until it is about halfway up the vertical axis at 30 minutes. A label indicates Albumin Added at 30 minutes. The graphed line then moves downward and to the right until it ends at 150 minutes, about one third of the way up the vertical axis. D The figure presents a graph in the coordinate plane. The horizontal axis is labeled Time, in minutes, and the numbers 0 through 150, in increments of 30, are indicated. The vertical axis is labeled Relative Mass of Dialysis Bag. The axis has an arrowhead at the top end, and no numbers are indicated along it. The graphed line begins at 0 minutes, about halfway up the vertical axis, and extends horizontally to the right until 30 minutes. A label indicates Albumin Added at 30 minutes. The graphed line then moves upward and to the right until it ends at 150 minutes, near the top of the vertical axis.

B The figure presents a graph in the coordinate plane. The horizontal axis is labeled Time, in minutes, and the numbers 0 through 150, in increments of 30, are indicated. The vertical axis is labeled Relative Mass of Dialysis Bag. The axis has an arrowhead at the top end, and no numbers are indicated along it. The graphed line begins at 0 minutes, about halfway up the vertical axis, and extends horizontally to the right until 30 minutes. A label indicates Albumin Added at 30 minutes. The graphed line starts to move downward and to the right at 30 minutes until it ends at 150 minutes, just above the horizontal axis.

(bio chem) Which of the following characteristics of Figure 1 best shows that the fragment is RNA and not DNA? A The 5′ to 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

(bio chem) Which of the following best describes how amino acids affect the tertiary structure of a protein? A The number of amino acids determines the tertiary structure of the protein. B The interactions of the different R-groups with other R-groups and with their environment determine the tertiary structure of the protein. C The R-group of the last amino acid that is added to a growing polypeptide chain determines the next amino acid that is added to the chain. D The sequence of the amino acids in the polypeptide chain determines the protein's primary structure but has no effect on its tertiary structure.

B The interactions of the different R-groups with other R-groups and with their environment determine the tertiary structure of the protein.

(bio chem) Water and ammonia interact to form hydrogen bonds, as represented in the figure. The figure presents the molecular structure of water and ammonia as well as the interactions of these two molecules. 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.

(unit 2) A scientist is studying the various prokaryotic and eukaryotic species found floating in a sample of water taken from a marine ecosystem. Which cellular component will be found in the widest range of organisms in the sample? A The chloroplast, since all organisms need a source of energy. B The ribosome, since all organisms need to synthesize proteins. C The mitochondrion, since all organisms need to break down glucose. D The cell wall, since all marine organisms need them for support.

B The ribosome, since all organisms need to synthesize proteins.

3.Brown fat is a type of fat tissue found in hibernating mammals. Inside the mitochondria of these fat tissue cells, these mammals have an uncoupling protein embedded in the inner mitochondrial membrane. This uncoupling protein allows hydrogen ions to leak from the intermembrane space back into the mitochondrial matrix. Figure 1 shows details of the processes in the inner mitochondrial membrane. Figure 1. Processes in the inner mitochondrial membrane Which of the following statements provides reasoning that supports the claim that brown fatty tissue keeps an animal warm? A The uncoupling protein in this tissue increases the production of ATP and causes more body heat to be produced to warm the animal. B The uncoupling protein in this tissue reduces the proton gradient across the membrane and thus produces heat to warm the animal without ATP production. C The uncoupling protein in this tissue causes an increase in the proton gradient, which causes more ATP to be produced that helps to warm the animal. D The uncoupling protein in this tissue reduces the production of ATP and creates an increase in the proton gradient that allows more heat energy to be produced to warm the animal.

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

(bio chem) Which of the following best describes the structures of carbohydrates? A They only occur as disaccharides. B They occur as monomers, chains of monomers, and branched structures. C They only occur as long and branched structures. D They occur as chains of monomers that hydrogen bond with complementary chains of monomers.

B They occur as monomers, chains of monomers, and branched structures.

(unit 2) Beetroot cells contain a family of dark red pigments called betalains. The selectively permeable nature of the beetroot cells keeps the internal environment of the cell separate from the external environment of the cell. Researchers are interested in determining whether the selective permeability of beetroot cells is due to the cell membrane or if it is due to the cell wall. Exposure to cellulase is known to damage the structure of the cell wall. An experiment is set up in which beetroot cells are placed in an aqueous solution with cellulase and in one without cellulase. Which of the following results best refutes the alternative hypothesis that selective permeability is a consequence of the cell wall? A When beetroot cells are placed in a solution with cellulase, the solution turns dark red. B When beetroot cells are placed in a solution with cellulase, the solution remains clear. C When beetroot cells are placed in a solution, it turns dark red with or without cellulase present. D Since plant cells contain cell membranes, not cell walls, the alternate hypothesis cannot be tested.

B When beetroot cells are placed in a solution with cellulase, the solution remains clear.

(unit 1) The figure presents three different models of a double-stranded segment of a D N A molecule. A key indicates the shading that corresponds to each nitrogenous base in the models, adenine, guanine, either thymine or uracil, and cytosine. Model 1 presents a relatively detailed but flat model of D N A, with alternating pentagons and circles representing the D N A backbone. A nitrogenous base is attached to each pentagon. A dotted outline around one circle, one pentagon, and one nitrogenous base is labeled Nucleotide. Hydrogen bonds between nitrogenous bases on the separate strands connect the two strands of nucleotides. The bottom left and top right ends of the strands are labeled 3 prime ends, and the bottom right and top left ends are labeled 5 prime ends. Model 2 presents a more simplified and also flat model of D N A, with the D N A backbones represented as long narrow rectangles. Pairs of nucleotides attached to the backbones hold the two strands together. Model 3 presents a yet more simplified model of D N A, showing a coiled D N A helix. The D N A backbone is shown as a ribbon, and narrow rectangular poles, shaded to represent the different nitrogenous bases, represent pairs of nucleotides connecting the two strands. The figure presents the flat structure of a three-nucleotide D N A molecule, with pentagons representing the pentose sugar and circles representing the phosphate group. Nitrogenous bases are attached to the sugar-phosphate backbones, and hydrogen bonds between the pairs of nitrogenous bases connect the two strands. The bottom of the left strand of the molecule is labeled 3 prime, and the bottom of the right strand is labeled 5 prime. From top to bottom, adenine on the left strand is bonded to thymine on the right, guanine on the left is bonded to cytosine on the right, and thymine on the left is bonded to adenine on the right, through a bond labeled X. On the left strand, the bond between the sugar and the phosphate that connect the second and third nucleotides is labeled W. On the right strand, the bond connecting the sugar of the middle nucleotide with cytosine to the phosphate of the top nucleotide with thymine is labeled Y. Also on the right side, the bond connecting the phosphate of the middle nucleotide with cytosine to the sugar of the bottom nucleotide with adenine is labeled Z. Figure 1. Four different bonds (W, X, Y, and Z) in a DNA molecule Figure 1 represents a segment of DNA. Radiation can damage the nucleotides in a DNA molecule. To repair some types of damage, a single nucleotide can be removed from a DNA molecule and replaced with an undamaged nucleotide. Which of the four labeled bonds in Figure 1 could be broken to remove and replace the cytosine nucleotide without affecting the biological information coded in the DNA molecule? A Bond X only B Bond W only C Bonds Y and Z at the same time D Bonds W and Z at the same time

C Bonds Y and Z at the same time

(unit 1) The figure presents two molecules. Molecule 1 represents R N A, which is a single stranded helix. Nitrogenous bases are attached to a backbone. Molecule 2 represents D N A, which is a double stranded helix. Nitrogenous bases join the two strands together. Figure 1. Molecule 1 represents RNA, and molecule 2 represents DNA. Which of the following best describes a structural similarity between the two molecules shown in Figure 1 that is relevant to their function? A Both molecules are composed of the same four nucleotides, which allows each molecule to be produced from the same pool of available nucleotides. B Both molecules are composed of the same type of five-carbon sugar, which allows each molecule to act as a building block for the production of polysaccharides. C Both molecules contain nucleotides that form base pairs with other nucleotides, which allows each molecule to act as a template in the synthesis of other nucleic acid molecules. D Both molecules contain nitrogenous bases and phosphate groups, which allows each molecule to be used as a monomer in the synthesis of proteins and lipids.

C Both molecules contain nucleotides that form base pairs with other nucleotides, which allows each molecule to act as a template in the synthesis of other nucleic acid molecules.

(bio chem) Which of the following is responsible for the cohesive property of water? A Hydrogen bonds between the oxygen atoms of two adjacent water molecules B Covalent bonds between the hydrogen atoms of two adjacent water molecules C Hydrogen bonds between the oxygen atom of one water molecule and a hydrogen atom of another water molecule D Covalent bonds between the oxygen atom of one water molecule and a hydrogen atom of another water molecule E Hydrogen bonds between water molecules and other types of molecules

C Hydrogen bonds between the oxygen atom of one water molecule and a hydrogen atom of another water molecule

(unit 2) Some viral infections can lead to the rupture of the lysosome membrane. Which prediction of the effect of this disruption of cellular compartmentalization is most likely correct? A Enzymes will be released that will specifically target the virus. B Cellular osmotic concentrations will change, preventing viral entry into the cell. C Hydrolytic enzymes will be released, which will cause cell death. D Intracellular digestion of organic materials will increase, which will increase the energy available to the cell for fighting the virus.

C Hydrolytic enzymes will be released, which will cause cell death.

(unit 2) Researchers investigate the transport of a certain protein into cells by endocytosis. In an experiment, the researchers incubate the cells in the presence of the protein and measure the amount of the protein that is absorbed into the cells over a five-minute period. Based on their observations, what should the researchers do to further clarify how the availability of the protein outside the cells affects the rate of endocytosis of the protein? A Incubate the cells in the absence of the protein. B Incubate the cells in the presence of several different proteins. C Incubate the cells in the presence of several different concentrations of the protein. D Incubate the cells in the presence of the protein for several different lengths of time.

C Incubate the cells in the presence of several different concentrations of the protein.

3.Aminolevulinate dehydratase (ALAD) is an enzyme that relies on zinc as a coenzyme. A zinc ion binds to the ALAD active site, where it forms favorable interactions with the side chains of three amino acids. Researchers have found that substituting a lead ion for a zinc ion in the ALAD active site causes inhibition of ALAD. Which of the following statements best helps explain how the lead ion causes inhibition of ALAD? A It changes the shape and charge of the substrate so that it becomes more compatible with ALAD's active site. B It changes the amino acid sequence of the ALAD protein so that the enzyme catalyzes a different reaction. C It changes the three-dimensional structure of the active site so that ALAD is no longer compatible with its substrate. D It changes the enzyme-substrate complex so that the transition state is more stable and the reaction proceeds at a faster rate.

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

3.Pectinase is a protein that catalyzes the breakdown of pectic polysaccharides in plant cell walls. A researcher designs an experiment to investigate the effect of salinity on the ability of pectinase to lower the activation energy of the reaction involved. The design of the experiment is presented in Table 1. For each test tube, the researcher will measure the amount of product formed over 20 minutes. Table 1. An experiment to investigate the effect of salinity on pectinase function Test Tube, Sodium Chloride Concentration, Temperature, Substrate Added, Pectinase Added 1 0 23 Yes No 2 0 23 Yes Yes 3 0.5 23 Yes No 4 0.5 23 Yes Yes 5 1.0 23 Yes No 6 1.0 23 Yes Yes 7 1.5 23 Yes No 8 1.5 23 Yes Yes Which of the following statements best helps justify the inclusion of test tube 5 in the experiment? A It will act as a control for test tube 4 by showing the effect of the presence or absence of the substrate. B It will act as a control for test tube 4 by showing the effect of a change in environmental temperature. C It will act as a control for test tube 6 by showing the effect of the presence or absence of the enzyme. D It will act as a control for test tube 6 by showing the effect of a change in sodium chloride concentration.

C It will act as a control for test tube 6 by showing the effect of the presence or absence of the enzyme.

(bio chem) This group of questions refers to the following groups of biological compounds used to carry the genetic code (A) Proteins (B) Carbohydrates (C) Nucleic acids (D) Lipids (E) Steroids A Proteins B Carbohydrates C Nucleic acids D Lipids E Steroids

C Nucleic acids

(bio chem) The molecular structures of linoleic acid and palmitic acid, two naturally occurring substances, are shown in the figure. The figure presents the molecular structures of linoleic acid and palmitic acid. Each molecule has a long carbon backbone that is represented by zig zag lines. The carbon atom at one end of each molecule is bonded with an O H group and double-bonded with an O atom. Linoleic acid has an 18-carbon backbone with double bonds between two pairs of carbon atoms. Palmitic acid has a 16-carbon backbone with no double-bonds between carbon atoms. Based on the molecular structures shown in the figure, which molecule is likely to be solid at room temperature? A Linoleic acid, because the absence of carbon-carbon double bonds allows the molecules to pack closely together. B Linoleic acid, because the presence of carbon-carbon double bonds prevents the molecules from packing closely together. C Palmitic acid, because the absence of carbon-carbon double bonds allows the molecules to pack closely together. D Palmitic acid, because the presence of carbon-carbon double bonds prevents the molecules from packing closely together.

C Palmitic acid, because the absence of carbon-carbon double bonds allows the molecules to pack closely together.

(unit 1) Which of the following describes a key difference among the 20 amino acids that are used to make proteins? A Only some amino acids have an R-group. B Only some amino acids have a carboxyl group (COOH). C Some amino acids are hydrophobic. D Some amino acids contain the element phosphorus.

C Some amino acids are hydrophobic.

3.A student designs an experiment to investigate the influence of temperature on enzyme function. The student's plan is presented in Table 1. Table 1. An experiment to investigate the influence of temperature on enzyme function Test Tube, Substrate Added, Enzyme Added, Temperature 1 Yes No 10 2 Yes Yes 10 3 Yes No 20 4 Yes Yes 20 5 Yes No 30 6 Yes Yes 30 7 Yes No 40 8 Yes Yes 40 Which test tubes are controls in the experiment? A Test tubes 1 and 2 only B Test tubes 5 and 6 only C Test tubes 1, 3, 5, and 7 D Test tubes 2, 4, 6, and 8

C Test tubes 1, 3, 5, and 7

3.In an experiment, a researcher prepares a reaction mixture by dissolving a substance in a buffered solution. The substance is the substrate of a certain enzyme. The researcher adds a small amount of the enzyme to the reaction mixture and measures the amount of product that is formed over time. The data are represented in Figure 1. The curve begins at the intersection of the 2 axes, then moves upwards and to the right at about a 45 degree angle. The curve then levels off, becoming approximately horizontal as it moves to the right. A point indicated about two thirds of the way along the horizontal region of the curve is labeled Add More Substrate. Figure 1. The amount of product formed by an enzyme-catalyzed reaction over time Which of the following best predicts the immediate result of adding more substrate to the reaction mixture at the point indicated by the arrow in Figure 1? A The amount of product will decrease until the reaction rate goes to zero. B The amount of product will decrease until the reaction reaches its equilibrium point or until the enzyme is been used up by the reaction. C The amount of product will increase until the reaction reaches its equilibrium point or until the substrate is used up by the reaction. D The amount of product will increase without stopping because the enzyme will be unchanged by the reaction.

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

(bio chem) 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.

3.Researchers investigated the influence of environmental pH on the activity of peroxidase, an enzyme that catalyzes the conversion of hydrogen peroxide to water and oxygen gas. In an experiment, the researchers added a hydrogen peroxide solution containing guaiacol to several identical test tubes and adjusted the solution in each test tube to a different pH. The researchers included the guaiacol because it caused the solutions to change color as the reactions proceeded, which the researchers relied on for measuring reaction rates. Finally, the researchers added the same amount of peroxidase to each test tube and measured the rate of each reaction at 23°C. The results of the experiment are represented in Figure 1. Figure 1. The effect of pH on peroxidase activity One of the researchers proposes using oxygen gas production to measure reaction rates. Which of the following statements best justifies the use of the proposed modification as a way of creating an appropriate control for the investigation? A The experiment can be repeated without hydrogen peroxide, which will help eliminate an uncontrolled variable. B The experiment can be repeated without peroxidase, which will introduce a second independent variable. C The experiment can be repeated without guaiacol, which will reveal the effect of guaiacol on the reaction rates. D The experiment can be repeated without water, which will reveal whether the reaction can occur inside a living cell.

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

(unit 1) The figure shows the results of an experiment to investigate the effects of an enriched CO2 environment on plant growth. Identical plants were separated into different groups and grown either in a standard CO2 environment (400 ppm CO2) or in an enriched CO2 environment (700 ppm CO2). Of the plants in each environment, half were grown under ideal conditions and half were grown under stressed conditions. The figure presents a bar graph. Two categories are given on the horizontal axis, labeled Ideal Conditions and Stressed Conditions. Each category has two bars. A key indicates that one bar corresponds to 400 parts per million of C O 2, and that the other bar corresponds to 700 parts per million of C O 2. The vertical axis is labeled Total Dry Weight, in grams per plant, and the numbers 0 through 2.5, in increments of 0.5, are indicated. The data for each bar, by category, are as follows. Note that all values are approximate. Ideal Conditions. 400 parts per million of C O 2, 1.9 grams per plant. 700 parts per million of C O 2, 2.1 grams per plant. Stressed Conditions. 400 parts per million of C O 2, 1.1 grams per plant. 700 parts per million of C O 2, 1.5 grams per plant. Based on the figure, which statement best describes the observed relationship between atmospheric CO2 enrichment and plant growth under ideal and stressed conditions? A The increase in atmospheric CO2 had no observable effect on plant growth under either ideal or stressed conditions. B The increase in atmospheric CO2 resulted in a greater increase in plant growth under ideal conditions than under stressed conditions. C The increase in atmospheric CO2 resulted in a greater increase in plant growth under stressed conditions than under ideal conditions. D The increase in atmospheric CO2 resulted in an inhibition of plant growth under both ideal and stressed conditions.

C The increase in atmospheric CO2 resulted in a greater increase in plant growth under stressed conditions than under ideal conditions.

(unit 2) Gaucher disease is an inherited disorder in which cells of the body are unable to break down a particular type of lipid, resulting in a buildup of the lipid in some tissues and organs. Based on the information provided, Gaucher disease results most directly from a defect in the function of which of the following organelles? A The smooth endoplasmic reticulum B The nucleus C The lysosome D The mitochondrion

C The lysosome

(unit 1) Phosphorous (P) is an important nutrient for plant growth. Figure 1 shows Arabidopsis thaliana plants grown under phosphorus‐sufficient (left) and phosphorus‐starved (right) conditions for six weeks. The figure presents two potted plants. The plant on the left is labeled Phosphorus Sufficient, and is large. The plant on the right is labeled Phosphorus Starved, and is small. Figure 1. Arabidopsis thaliana plants grown for six weeks. Which of the following is the most likely reason for the difference in leaf growth? A The phosphorus-starved plant was unable to synthesize both the required proteins and lipids, limiting growth. B The phosphorus-starved plant was unable to synthesize both the required proteins and carbohydrates, limiting growth. C The phosphorus-starved plant was unable to synthesize both the required nucleic acids and lipids, limiting growth. D The phosphorus-starved plant was unable to synthesize both the required carbohydrates and nucleic acids, limiting growth.

C The phosphorus-starved plant was unable to synthesize both the required nucleic acids and lipids, limiting growth.

(unit 2) Hereditary spherocytosis (HS) is a disorder of red blood cells that causes the cells to be smaller and spherical instead of having the usual flattened, biconcave shape. The average diameter of normal red blood cells is 7.2μm, and the average diameter of red blood cells in a person with HS was found to be 6.7μm. The normal red blood cell has an average surface area of 136μm2 and an average volume of 91μm3. Which of the following provides an accurate calculation of the surface area to volume ratio of an HS red blood cell, as well as a prediction of its effect on the efficient transferring of oxygen compared to a normal red blood cell? A The ratio is 0.45, and the cells are more efficient at transferring oxygen. B The ratio is 1.12, and the cells are less efficient at transferring oxygen. C The ratio is 0.89, and the cells are less efficient at transferring oxygen. D The ratio is 141, and the cells are more efficient at transferring oxygen.

C The ratio is 0.89, and the cells are less efficient at transferring oxygen.

(unit 2) Which of the following transport mechanisms will be affected most directly by a temporary shortage of ATP molecules inside the cell? A The movement of water molecules through aquaporins B The diffusion of oxygen molecules across the plasma membrane C The transport of glucose molecules against a concentration gradient D The facilitated diffusion of Ca2+ ions into the cell

C The transport of glucose molecules against a concentration gradient

3.A researcher claims that budding yeast are able to survive in different environments because they produce enzymes that allow them to use different molecules as sources of matter and energy. Which of the following statements best helps justify the researcher's claim by providing a relevant example? A Yeast cells produce protein kinases, which are enzymes that catalyze the transfer of phosphate groups from ATP to protein substrates. B Yeast cells produce DNA polymerases, which are enzymes that catalyze the conversion of free nucleotides into strands of DNA. C Yeast cells produce invertase, which is an enzyme that catalyzes the conversion of the disaccharide sucrose into glucose and fructose. D Yeast cells produce catalase, which is an enzyme that catalyzes the conversion of hydrogen peroxide into water and oxygen gas.

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

(bio chem) A feature of organic compounds NOT found in inorganic compounds is the presence of... A ionizing chemical groups B electrons C carbon atoms covalently bonded to each other D oxygen E hydrogen bonds

C carbon atoms covalently bonded to each other

3.A researcher claims that the initial rise of oxygen in Earth's early atmosphere, which occurred approximately 2.3 billion years ago, resulted from the metabolic activity of prokaryotic organisms. The claim is based on an interpretation of the geochemical and fossil evidence represented in Figure 1. Evidence of Earliest Organisms, 3.9 billion years ago. Earliest Oxygen, 3.5 billion years ago. Evidence of Cyanobacteria, 2.8 billion years ago. Atmospheric Oxygen, 2.4 billion years ago. Earliest Eukaryotes, 2.0 billion years ago. Earliest Plants, 0.85 billion years ago. Figure 1. Selected events in geologic time based on geochemical and fossil evidence Which of the following types of evidence will best support the researcher's claim? A Evidence that some of the earliest eukaryotes used oxygen to produce ATP by cellular respiration B Evidence that the earliest plants produced oxygen as a by-product of photosynthesis C Evidence that some of the earliest organisms carried out photosynthesis without producing oxygen D Evidence that the cyanobacteria produced oxygen as a by-product of photosynthesis

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

(bio chem)Figure 1 is a diagram of water molecules at the air-water interface at the surface of a pond. The figure presents a diagram of the alignment of water molecules at an air-water interface. e. The water molecules are identically aligned at the surface of the water. For each water molecule, one of the smaller atoms with the partial positive change is situated at the bottom of the larger atom, toward the water below. Vertical dotted lines extend downward from these smaller atoms. Horizontal dotted lines are drawn between the upper portions of neighboring water molecules. Figure 1. Alignment of water molecules at air-water interface 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.

(bio chem) Which of the following is most directly responsible for water's unique properties? A It contains oxygen atoms. B It contains hydrogen atoms. C It is an ionic compound. D It forms hydrogen bonds. E It is nonpolar.

D It forms hydrogen bonds.

(unit 1) Figure 1 shows a short segment of a double-stranded nucleic acid molecule. The figure presents a double-stranded nucleic acid molecule. Bonds between alternating sugars and phosphate groups connect three nucleotides on each strand. The end of each strand at the bottom of the figure is labeled, with one strand labeled 3 prime end and the other strand labeled 5 prime end. The order of nitrogenous bases on one strand is guanine, adenine, and cytosine. The corresponding order of nitrogenous bases on the other strand is cytosine, thymine, and guanine. Bonds shown between the nitrogenous bases of the two strands hold the two strands together. Specifically, the guanine is bonded to the cytosine by three bonds, the adenine is bonded to the thymine by two bonds, and the cytosine is bonded to the guanine by three bonds. Figure 1. A short segment of a double-stranded nucleic acid molecule Which of the following statements is correct about the molecule shown in Figure 1 ? A It is RNA because of the relative direction of the two strands. B It is RNA because of the number of different nucleotides found in the molecule. C It is DNA because of the nature of the hydrogen bonds between guanine and cytosine. D It is DNA because of the nucleotides present.

D It is DNA because of the nucleotides present.

(unit 2) Euglenids are single-cell eukaryotes that live in aquatic environments. The chloroplasts found inside euglenids are enveloped by three membranes, as represented in Figure 1. The inner membrane of euglenid chloroplasts resembles the thylakoid membrane. The figure presents a Euglenid. A chloroplast is labeled inside the euglenid. There is also an enlarged zoomed-in figure of a portion of the chloroplast. The three membranes of the envelope that surrounds the chloroplast are labeled Chloroplast Envelope, and the innermost membrane of the three is labeled Inner Membrane. The zoom-in also shows a portion of a thylakoid inside the chloroplast itself, and a label points to the thylakoid membrane. Figure 1. Simplified diagram of a euglenid, showing the structure of the chloroplast envelope Which of the following claims about the origin of the euglenid chloroplast is best supported by the three-membrane structure of the envelope? A It originated from the spontaneous assembly of organic molecules into a lipid bilayer inside a free-living prokaryote. B It originated from the fusion of the plasma membranes of two different free-living photosynthetic prokaryotes. C It originated from the incorporation of a photosynthetic prokaryote into a eukaryotic cell by a single endosymbiotic event. D It originated from the incorporation of a photosynthetic prokaryote into a eukaryotic cell by two endosymbiotic events.

D It originated from the incorporation of a photosynthetic prokaryote into a eukaryotic cell by two endosymbiotic events.

(bio chem) Polypeptides are continuously being formed and degraded. One of these processes is shown. The figure presents the molecular structures of polypeptides. An arrow that is joined by another arrow labeled H 2 O points to two shorter molecules. Figure 1. Polypeptide reaction 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.

(unit 2) Which of the following observations best supports the claim that mitochondria evolved from once-free-living prokaryotic cells by the process of endocytosis? A Mitochondria produce ATP. B Mitochondria contain proteins. C Mitochondria exchange substances with the cytosol. D Mitochondria are surrounded by a double membrane.

D Mitochondria are surrounded by a double membrane.

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

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

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

D Repeating the experiment using heat-denatured peroxidase

3.A researcher claims that genetic variation provides organisms with the ability to survive and reproduce in different environments. To support the claim, the researcher makes the following observation: bacteria that contain plasmids (small DNA molecules) are resistant to a wider range of antibiotics than are bacteria that contain no plasmids. Which of the following statements best establishes a connection between the observation and the researcher's claim? A Some antibiotics inhibit the synthesis of bacterial cell walls. B Some antibiotics inhibit protein synthesis in bacteria cells. C Some plasmids cannot exist in a bacterial cell with certain other plasmids. D Some plasmids contain antibiotic resistance genes.

D Some plasmids contain antibiotic resistance genes.

(unit 1) A polypeptide is polymer of amino acids held together by peptide bonds. The process of dehydration synthesis creates these peptide bonds, as shown in Figure 1. The figure presents the chemical reaction that links two amino acids. The two amino acids are identical except for their R groups. The central atom in each amino acid is a carbon atom. The left side of each amino acid is an N H 2 group in which a nitrogen atom is bonded to two hydrogen atoms, and the right side of each amino acid is a C O O H group in which a carbon atom is double bonded to an oxygen atom and single bonded to the oxygen atom of an O H group. The R group of the first amino acid is labelled R prime, and the R group of the second amino acid is labelled R double prime. The two amino acids are joined by a peptide bond, and a molecule of water is produced. The peptide bond consists of a bond between a carbon and a nitrogen atom. The carbon atom in the peptide bond is also bonded to the carbon atom that bears the R prime group and double bonded to an oxygen atom. The nitrogen atom in the peptide bond is also bonded to the carbon atom that bears the R double prime group and to a hydrogen atom. Figure 1. Amino acids are linked through the formation of peptide bonds. As shown in Figure 1, an amino acid must have which of the following properties in order to be incorporated into a polypeptide? A The ability to remain stable in the presence of water molecules B An R-group that is compatible with the R-group of the last amino acid incorporated C A central carbon atom that reacts with a nitrogen atom to form the peptide bond D The ability to form a covalent bond with both its NH2 group and its COOH group

D The ability to form a covalent bond with both its NH2 group and its COOH group

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

D The additional pigments absorb light at wavelengths that green algae cannot absorb; this may allow cyanobacteria to capture more light energy for photosynthesis than green algae can in certain areas.

(bio chem) 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. The figure shows a diagram of the exchange of matter between organisms that live in an aquarium. An arrow indicates that a plant provides O 2 for a fish, and the fish provides C O 2 for the plant. The fish also provides ammonia, N H 3, for bacteria living in the gravel. The bacteria convert the ammonia to nitrites, N O 2, and to nitrates, N O 3, that are taken up by the plant. 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.

(unit 2) A group of mutations, known as MT-ND1, have been identified in mitochondrial DNA. These mutations are associated with a number of debilitating diseases stemming from the production of nonfunctional proteins in the mitochondria. Which of the following cellular deficiencies would most likely be related to these MT-ND1 mutations? A The cell is unable to synthesize most proteins required for normal cell functions. B The cell is unable to break down toxic materials and would accumulate large volumes of these materials. C The cell is able to synthesize proteins, but the proteins would not fold properly and would not contain the correct molecular tags for export from the cell. D The cell is unable to complete reactions related to electron transport and ATP production.

D The cell is unable to complete reactions related to electron transport and ATP production.

(unit 2) Two competing hypotheses exist regarding the cell membrane structure. One hypothesis states that membrane structure is static and membrane components throughout the bilayer are rigidly bound. Alternatively, the other hypothesis states that cell membranes are a fluid mosaic in which membrane components may drift within the bilayer around the surface of the cell. An experiment is set up in which membrane proteins of two different cells are fluorescently labeled with two different colors and then fused as shown in Figure 1. The figure presents a model of a cell fusion experiment. There are two cells, and the membranes of each cell have proteins embedded in them. The membrane proteins in one cell are colored grey, and the membrane proteins in the other cell are colored black. The figure shows the grey cell and the black cell beginning to merge. Figure 1. Model of initiation of cell fusion experiment Which of the following results, one hour after membrane fusion, best supports the alternative hypothesis that the cell membrane is a fluid mosaic? A The figure presents a model of a cell. The membrane of the cell has only grey proteins embedded in it. B The figure presents a model of a cell. The membrane of the cell has only black proteins embedded in it. C The figure presents a model of a cell. The membrane of the cell has both grey proteins and black proteins embedded in it. The black proteins are concentrated in one area of the cell membrane, and the grey proteins are concentrated in a separate area of the cell membrane. D The figure presents a model of a cell. The membrane of the cell has both grey proteins and black proteins embedded in it. The grey proteins and black proteins are distributed throughout the cell membrane, and are not concentrated in particular areas.

D The figure presents a model of a cell. The membrane of the cell has both grey proteins and black proteins embedded in it. The grey proteins and black proteins are distributed throughout the cell membrane, and are not concentrated in particular areas.

(unit 2) Cholesterol is a naturally occurring substance that helps regulate the fluidity of a cell's plasma membrane. A cholesterol molecule can be represented as having a polar head and a nonpolar region, as shown in the figure. The figure presents a cholesterol molecule. A black dot indicates the polar head, which is attached to a nonpolar region that is represented by a sequence of four hexagons or a pentagon, each of which shares one side with the previous and/or next component of the region. Which of the following models shows how cholesterol molecules most likely interact with the phospholipid bilayer of a cell's plasma membrane? A The figure presents a phospholipid bilayer and cholesterol molecules. The polar head of each cholesterol molecule is situated between the heads of the phospholipids, and the nonpolar region extends out and away from the membrane. B The figure presents a phospholipid bilayer and cholesterol molecules. Each cholesterol molecule lies flat against the outer surface of the membrane so that the polar head and nonpolar region of each molecule are both in contact with the phospholipid heads. C The figure presents a phospholipid bilayer and cholesterol molecules. The cholesterol molecules are located in the interior of the membrane and separate the two layers of the bilayer from each other. D The figure presents a phospholipid bilayer and cholesterol molecules. The polar head of each cholesterol molecule is situated between the heads of the phospholipids, and the nonpolar region extends into the interior of the membrane between the phospholipid tails.

D The figure presents a phospholipid bilayer and cholesterol molecules. The polar head of each cholesterol molecule is situated between the heads of the phospholipids, and the nonpolar region extends into the interior of the membrane between the phospholipid tails.

(bio chem)Figure 1 represents a common process that occurs in organisms. The figure shows a reaction between two molecules. one+another=a big one with h20 at the end 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

D The linear sequence of the base pairs

(unit 2) A certain type of specialized cell contains an unusually large amount of rough endoplasmic reticulum (ER). Which of the following functions is this cell type most likely specialized to perform? A The production and secretion of steroids B The destruction of toxic materials produced in other cells of the organism C The synthesis of polysaccharides for energy storage D The production and secretion of proteins

D The production and secretion of proteins

3.A researcher claims that the incorporation of carbon dioxide into organic molecules during photosynthesis does not violate the second law of thermodynamics. Which of the following statements best helps justify the researcher's claim? A Organisms contain enzymes that lower the activation energies of specific chemical reactions. B An ecosystem is formed by the interaction of a community of organisms with their surrounding environment. C Photosynthetic organisms use the organic molecules produced during photosynthesis for growth and repair. D The total system that includes photosynthetic organisms and the Sun becomes less ordered over time.

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

(unit 2) Researchers conducted an experiment to investigate the effects of a valinomycin treatment on skeletal muscle cells. Valinomycin is a naturally occurring substance that can be used as a drug. The results of the experiment are presented in the table. Relative Rates of ATP Production Time after Treatment Untreated Cells Valinomycin-Treated Cells 5 minutes 1.0 0.3 10 minutes 7.7 2.7 Which of the following claims about the effects of the valinomycin treatment is best supported by the data presented in the table? A The valinomycin treatment caused an increase in the activity of the rough endoplasmic reticulum. B The valinomycin treatment caused an increase in the activity of the Golgi complex. C The valinomycin treatment caused a decrease in the activity of the lysosome. D The valinomycin treatment caused a decrease in the activity of the mitochondria.

D The valinomycin treatment caused a decrease in the activity of the mitochondria.

(unit 1) As shown in the diagram, when environmental temperatures drop below freezing, a layer of ice typically forms on the surface of bodies of freshwater such as lakes and rivers. Which of the following best describes how the structure of ice benefits the organisms that live in the water below? A The water molecules in ice are closer together than those in liquid water, so the ice prevents the passage of air to the water, maintaining a constant gas mixture in the water. B The water molecules in ice are closer together than those in liquid water, so the ice forms a barrier that protects the organisms in the water from the freezing air temperatures. C The water molecules in ice are farther apart than those in liquid water, so the ice floats, maintaining the warmer, denser water at the lake bottom. D The water molecules in ice are farther apart than those in liquid water, so the ice floats, preventing the escape of gases from the liquid water.

D The water molecules in ice are farther apart than those in liquid water, so the ice floats, preventing the escape of gases from the liquid water.

(unit 2) Certain bacteria can use both ethyl alcohol and acetate as sources of nutrients. In an experiment where both nutrients are available to a bacterial population, the following results were obtained and graphed. The figure presents two curves in the first quadrant of a coordinate plane, titled "Movement of Nutrients into Bacterial Cells." The horizontal axis is labeled Concentration Outside Cells, in milimolarity, and the numbers 0.1, 1.0, 10.0, and 100.0 are indicated at equal intervals. The vertical axis is labeled Rate of Entry of Substance, in micromoles per minute, and the numbers 10, 100, and 1,000 are indicated at equal intervals. The first curve, labeled Acetate, is a straight line that begins at the point 0.1 milimolar, 1.5 micromoles per minute, and moves upward and to the right, passing through the point 1.0 milimolar, 10.4 micromoles per minute. The curve then passes through the point 10.0 milimolars, 107 micromoles per minute, and ends at the point 100.0 milimolars, 1,020 micromoles per minute. The second curve, labeled Ethyl Alcohol, begins at the point 0.1 millimolar, 7 micromoles per minute, and moves gradually upward and to the right, passing through the point 1.0 millimolar, 20 micromoles per minute. It then passes through the point 10.0 millimolar, 35 micromoles per minute, and ends at the point 100.0 milimolar, 50 micromoles per minute. What additional procedure would best help determine whether these movements are due to active transport or to passive transport? A Repeat the original experiment, but at three different temperatures. Compare the transport rates among the three temperatures. B Repeat the original experiment, but add a substance known to block movement of molecules across aquaporins. Compare the rates on the two graphs. C Use two additional treatments, one containing only ethyl alcohol and one containing only acetate. Compare the graphs of these two treatments with the original graph. D Use two additional treatments, one containing only ethyl alcohol and one containing only acetate. Include a substance known to block ATP use by the plasma membrane. Compare the graphs of these two treatments to the original graph.

D Use two additional treatments, one containing only ethyl alcohol and one containing only acetate. Include a substance known to block ATP use by the plasma membrane. Compare the graphs of these two treatments to the original graph.

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