AP Biology MCQ's PDF

## The carbohydrates glucose, galactose, and fructose have the same chemical formula (C6H12O6) but different structural formulas, as represented in the figure - H-C=O C H=0 CH2OH H-C-OH H-C-OH C=0 HO-C-H HO-C-H HO-C-H H-C-OH HO-C-H H-C-OH H-C-OH H-C-OH...

## The carbohydrates glucose, galactose, and fructose have the same chemical formula (C6H12O6) but different structural formulas, as represented in the figure - H-C=O C H=0 CH2OH H-C-OH H-C-OH C=0 HO-C-H HO-C-H HO-C-H H-C-OH HO-C-H H-C-OH H-C-OH H-C-OH H-C-OH CH2OH CH2OH CH2OH - Glucose - Galactose - Fructose ### Which of the following statements about glucose, galactose, and fructose is most likely true? - The carbohydrates have the same properties because they have the same number of carbon, hydrogen, and oxygen atoms. - The carbohydrates have the same properties because they each have a single carbon-oxygen double bond. - **The carbohydrates have different properties because they have different arrangements of carbon, hydrogen, and oxygen atoms.** - The carbohydrates have different properties because they have different numbers of carbon-carbon bonds. ### Water and ammonia interact to form hydrogen bonds, as represented in the figure - H H-N:---H-0: H H - Hydrogen Bond ### Which statement best helps explain the formation of the hydrogen bond represented in the figure - The oxygen has a partial positive charge, and the nitrogen has a partial negative charge. - **The nitrogen has a partial negative charge, and the hydrogen attached to the oxygen has a partial positive charge.** - The hydrogen attached to the oxygen has a partial negative charge, and the nitrogen also has a partial negative charge. - The nitrogen has a partial positive charge, and the hydrogen attached to the oxygen also has a partial positive charge. - Figure 1 is a diagram of water molecules at the air-water interface at the surface of a pond - Air - Water - * Partial positive charge - * Partial negative charge - 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? - Covalent bonds between water molecules and the air above provide cohesion, which causes tiny bubbles to form under the feet of the insect. - lonic 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. - Polar covalent bonds between molecules at the surface of the water provide adhesion, which supports the weight of the insect. - **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.** ### The CFTR protein is made up of 1,480 amino acids linked together in a chain. Some humans produce a version of the CFTR protein in which phenylalanine (an amino acid) has been deleted from position 508 of the amino acid chain. ### Which of the following best predicts how the amino acid deletion will affect the structure of the CFTR protein? - It will have no observable effect on the structure of the CFTR protein. - It will affect the primary structure of the CFTR protein, but the other levels of protein structure will not be affected. - It will affect the secondary and tertiary structures of the CFTR protein, but the primary structure will not be affected. - **It will affect the primary, secondary, and tertiary structures of the CFTR protein.** - 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). - H H HO CH2 SH H - Figure 1. Chemical structure of cysteine ### Which of the following best describes the effect of a greater number of cysteine amino acids on the stability of the proteins? - The change has no effect on the stability of the protein because only one type of amino acid is involved. - **The change leads to increased protein stability because of an increased number of S-S bonds in the tertiary structure of the proteins.** - The change leads to decreased protein stability because of an increased number of S-S bonds in the tertiary structure of the proteins. - 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. - 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. - HO -Figure 1. Primary structure of original protein Hydrophilic Amino Acid Hydrophobic Amino Acid - HO - Figure 2. Primary structure of mutated protein Hydrophilic Amino Acid Hydrophobic Amino Acid ### 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. - Original Protein - Mutated Protein - Glycogen synthetase kinase 3 beta is a protein kinase that has been implicated in many types of cancer. Depending on the cell type, the gene for glycogen synthetase kinase 3 beta (*GSK3B*) can act either as an oncogene or as a tumor suppressor. ### Which of the following best predicts how *GSK3B* mutations can lead to the development of cancer? - **Cells with inactive *GSK3B* fail to trigger apoptosis.** - Cells with inactive *GSK3B* fail to proceed past the G2/M checkpoint. - Cells with overactive *GSK3B* are more likely to repair DNA damage. - Cells with overactive *GSK3B* have longer cell cycles. ### Cancer cells behave differently than normal body cells. For example, they ignore signals that tell them to stop dividing. ### Which of the following conditions will most likely cause a normal body cell to become a cancer cell? - The environment already contains cancer cells. - The environment has an abundance of nutrients. - The environment lacks signals that would otherwise tell the cell to stop dividing. - **The environment contains mutagens that induce mutations that affect cell-cycle regulator proteins.** - Researchers studying cell cycle regulation in budding yeast have observed that a mutation in the *CDC15* gene causes cell cycle arrest in telophase when the yeast cells are incubated at an elevated temperature. Which of the following statements best predicts the effect of the cell cycle arrest on proliferating yeast cells? - The yeast cells will transition out of G0 but will fail to complete the G1 phase. - The yeast cells will initiate mitosis but will fail to complete the G2 phase. - **The yeast cells will replicate their chromosomes but will fail to complete cytokinesis.** - The yeast cells will replicate their organelles but will fail to complete the S phase. - The molecular structures of linoleic acid and palmitic acid, two naturally occurring substances, are shown in the figure. - H H H H H - Linoleic Acid - Palmitic Acid ### Based on the molecular structures shown in the figure, which molecule is likely to be solid at room temperature? - Linoleic acid, because the absence of carbon-carbon double bonds allows the molecules to pack closely together. - Linoleic acid, because the presence of carbon-carbon double bonds prevents the molecules from packing closely together. - **Palmitic acid, because the absence of carbon-carbon double bonds allows the molecules to pack closely together.** - Palmitic acid, because the presence of carbon-carbon double bonds prevents the molecules from packing closely together. ### Which of the following best describes the structures of carbohydrates? - They only occur as disaccharides. - **They occur as monomers, chains of monomers, and branched structures.** - They only occur as long and branched structures. - They occur as chains of monomers that hydrogen bond with complementary chains of monomers. ### Which of the following best describes how amino acids affect the tertiary structure of a protein? - The number of amino acids determines the tertiary structure of the protein. - **The interactions of the different R-groups with other R-groups and with their environment determine the tertiary structure of the protein.** - 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. - The sequence of the amino acids in the polypeptide chain determines the protein's primary structure but has no effect on its tertiary structure. - A model of the plasma membrane showing several biological molecules, including a transmembrane protein, is shown in Figure 1. - Polar Areas of Protein - Nonpolar Area of Protein - Figure 1. Phospholipid bilayer with transmembrane protein ### Which statement best explains why correct protein folding is critical in the transmembrane protein shown above? - **Interactions of the hydrophobic and hydrophilic amino acids help to anchor the protein in the membrane.** - Interactions of the peptide bonds of the protein with the membrane will affect the rate at which substances can cross the membrane. - Interactions of the protein and phospholipids increase membrane fluidity. - Interactions of the quaternary structure of the protein will increase hydrogen bonding in the membrane and make the membrane less fluid. - The model below shows the structure of a portion of a plasma membrane in an animal cell ### Which statement best explains the orientation of the phospholipid molecules in this model? - The nonpolar portions of the phospholipid molecules are attracted to the internal and external environments. - **The hydrophilic phosphate groups of the phospholipid molecules are attracted to the aqueous internal and external environments.** - The embedded proteins attract the fatty acid tails of the phospholipids, so the tails point away from the internal and external aqueous environments. - The fatty acid tails of the phospholipid molecules are hydrophilic and are repelled by the internal and external aqueous environments. - Areas 1 and 3 are polar, since the membrane molecules are aligned with water molecules. - Area 2 is polar, since water has been excluded from this area of the membrane. - Areas 1 and 3 are hydrophilic, since membrane molecules formed covalent bonds with water. - **Area 2 is nonpolar, since hydrogen bonds between the adjacent lipids hold the membrane together.** - A researcher claims that increased atmospheric carbon dioxide levels cause increased growth rates in plants. ### Which of the following statements best supports the researcher's claim? - Atmospheric carbon dioxide is produced by the burning of fossil fuels, which are formed from the remains of living organisms such as plants. - Atmospheric carbon dioxide is a byproduct of cellular respiration, which is a metabolic process that occurs in plants and other living organisms. - Atmospheric carbon dioxide typically enters plant leaves through stomata, which plants rely on for regulating gas exchange with the atmosphere. - **Atmospheric carbon dioxide is the raw material for photosynthesis, which plants rely on for producing sugars and other organic compounds.** - In chloroplasts, ATP is synthesized from ADP plus inorganic phosphate (Pi) in a reaction catalyzed by ATP synthase molecules that are embedded in the thylakoid membrane. ### Which of the following statements provides evidence to support the claim that no ATP will be synthesized in the absence of a proton gradient across the thylakoid membrane? - Blocking electron flow from one carrier to the next in the electron transport chains blocks formation of a proton gradient in the thylakoid. - Increasing the proton concentration difference across the thylakoid membrane is not associated with a parallel increase in the rate of ATP synthesis. - **No ATP is synthesized when channel proteins that allow the free passage of protons are inserted into the thylakoid membrane.** - No ATP is synthesized while the Calvin cycle is synthesizing carbohydrates and using ATP and NADPH at a high rate. - A scientist claims that *Elysia chlorotica*, a species of sea slug, is capable of photosynthesis. ### Which of the following observations provides the best evidence to support the claim? - *Elysia chlorotica* will die if not exposed to light. - ***Elysia chlorotica* grows when exposed to light in the absence of other food sources.** - *Elysia chlorotica* grows faster when exposed to light than when placed in the dark. - *Elysia chlorotica* grows in the dark when food sources are available. - Figure 1 shows a model of how a channel protein influences the movement of a particle across a cell's plasma membrane. - Extracellular Space - Channel Protein - Plasma Membrane - Intracellular Space (cytosol) - Figure 1. A section of a cell's plasma membrane, showing a channel protein and a concentration gradient across the membrane ### An investigator wants to understand whether a newly found membrane protein is involved in membrane transport of a certain particle. Which investigation will help determine whether the new membrane protein is a channel protein involved in membrane transport - Add small nonpolar molecules to the extracellular space and measure the direction of particle movement of the molecules. - Measure the rate of extracellular fluid movement into the intracellular space. - **Add more of the proteins to the plasma membrane and measure the rate of the particle movement.** - Remove ATP from the intracellular space and measure the rate of the particle movement into the intracellular space. - Water is constantly diffusing into the cytosol of freshwater single-celled organisms. In order to maintain the proper solute concentrations in the cytosol, contractile vacuoles pump out the excess water. An experimenter placed single-celled organisms into various saline concentrations and recorded the ATP used by the contractile vacuole. The data are shown in the graph. - Relative Use of ATP by the Contractile Vacuole Relative Salinity of Environment ### Of the following, which additional investigation can be used to determine when the cells are in an isotonic solution? - Decreasing the salinity of the environment a little at a time until the ATP usage reaches a maximum - Decreasing the salinity of the environment a little at a time until ATP usage reaches a minimum - Increasing the salinity of the environment a little at a time until ATP usage reaches a maximum - **Increasing the salinity of the environment a little at a time until the ATP usage reaches a minimum** - The transport of a substance across a plasma membrane of a specific organelle requires energy. The rate at which the transport takes place also depends on temperature. A scientist isolated the specific organelle and then used the following treatments to determine the conditions that will result in the maximal transport. All treatments contained the extracted organelle and were maintained at 25°C. - The data from this experiment indicate that maximal rate of transport of protein X at 25°C occurs at an ATP concentration of 1.0 µm/mL. - 0.2 µm/mL ATP - 1.0 µm/mL ATP - 2.0 μm/mL ATP - 5.0 μm/mL ATP - Figure 1. The four ATP concentrations used in the experiment ### Which procedure should be done next to gather data needed to meet the scientist's objective? - Incubate samples with the same four ATP concentrations at 30°C. - Incubate samples containing 5.0 µm/mL of ATP at four temperatures other than 25°C. - **Incubate samples containing 1.0 µm/mL of ATP at four temperatures other than 25°C.** - Incubate samples containing 1.0 µm/mL of ATP at 25°C and determine the rate of transport for four other proteins. - Aquaporins are channel proteins that facilitate the transport of water across the cell membrane. One group of researchers hypothesizes that without functional aquaporins, no water will be able to enter the cell. A different group proposes an alternative hypothesis, stating that even with nonfunctional aquaporins, a small amount of water will still cross the cell membrane. An experiment is set up in which plant cells with mutated (nonfunctional) aquaporins and plant cells with normally functioning aquaporins are both placed in distilled water. ### Which of the following data would support the alternative hypothesis? - Cells with functional aquaporins exhibit low turgor pressure and are hypertonic. - Cells with functional aquaporins exhibit high turgor pressure and are hypotonic. - Cells with mutated aquaporins exhibit an absence of turgor pressure and are completely plasmolyzed. - **Cells with mutated aquaporins exhibit moderate turgor pressure and are hypertonic.** - Plant cell walls are composed of cellulose, while fungal cell walls are composed of chitin. A group of scientists hypothesize that this difference means the cell wall has largely different functions in plant cells and fungal cells. Alternatively, another group of scientists hypothesize that despite their biochemical differences, plant and fungal cell walls serve similar functions. ### Which of the following observations would best support the alternative hypothesis described above? - Plant cell walls are found just outside the plasma membrane, while fungal cell walls are found just beneath the plasma membrane. - **In both plant cells and fungal cells, the cell wall surrounds the outside of the cell membrane.** - Some plant cells have secondary cell walls that confer additional rigidity, while fungal cells do not. - Photosynthesis occurs in plant cells, but it does not occur in fungal cells. - A team of biologists develop a new drug, and one team member hypothesizes that the drug is incapable of freely passing across the plasma membrane and requires the help of membrane proteins to enter cells. Alternatively, another biologist on the team hypothesizes that the drug can diffuse passively across the plasma membrane like O2 and CO2 can. ### Which of the following, if true about the drug, best supports the alternative hypothesis that the new drug will exhibit simple diffusion across plasma membranes? - **The drug is a small nonpolar molecule.** - The drug is a small charged molecule. - The drug is a large polar molecule. - The drug is a large charged molecule. - Cholesterol is an important component of animal cell membranes. Cholesterol molecules are often delivered to body cells by the blood, which transports the molecules in the form of cholesterol-protein complexes. The complexes must be moved into the body cells before the cholesterol molecules can be incorporated into the phospholipid bilayers of cell membranes. ### Based on the information presented, which of the following is the most likely explanation for a buildup of cholesterol molecules in the blood of an animal? - The animal's body cells are defective in exocytosis. - **The animal's body cells are defective in endocytosis.** - The animal's body cells are defective in cholesterol synthesis. - The animal's body cells are defective in phospholipid synthesis. ### Which of the following statements best explains the processes of passive and active transport? - Passive transport is the net movement of substances down a concentration gradient that requires metabolic energy. - Active transport is the movement of substances up a concentration gradient that does not require energy. - **Passive transport is the net movement of substances down a concentration gradient that does not require metabolic energy. Active transport is the movement of substances up a concentration gradient that requires energy.** - Passive transport is the net movement of substances up a concentration gradient that requires metabolic energy. Active transport is the movement of substances down a concentration gradient that does not require metabolic energy. - Passive transport is the net movement of substances up a concentration gradient that does not require metabolic energy. Active transport is the movement of substances down a concentration gradient that requires energy. - In an experiment, cells were isolated from an aquatic plant and suspended in pond water, a sucrose sugar solution, or distilled water. All of the cells were then viewed under a microscope. Compared with the cell in the pond water, the cell in the sugar solution appeared shriveled, and the cell in the distilled water appeared inflated. The results of the experiment are represented in Figure 1. - 000 - Cell in Pond Water - Cell in Sugar Solution - Cell in Distilled Water #- Figure 1. The results of an experiment using aquatic plant cells ### Which of the following statements best explains the observations represented in Figure 1? - There was a net movement of sucrose out of the cell suspended in the sugar solution and a net movement of sucrose into the cell suspended in the distilled water. - There was a net movement of sucrose into the cell suspended in the sugar solution and a net movement of sucrose out of the cell suspended in the distilled water. - **There was a net movement of water out of the cell suspended in the sugar solution and a net movement of water into the cell suspended in the distilled water.** - There was a net movement of water into the cell suspended in the sugar solution and a net movement of water out of the cell suspended in the distilled water. - H H H H + H H OH H CH3 OH H HO H N-C-C-N-C + H2O H H HCH3OH - Figure 1. Formation of a peptide bond ### Which of the following best describes the formation of the bond shown in Figure 1. - An ionic bond is formed between a carbon atom of one amino acid and the nitrogen atom of the other amino acid. - An ionic bond is formed when the negative charge of an OH group is balanced by the positive charge of a hydrogen ion. - A covalent bond is formed between a carbon atom and a nitrogen atom along with the formation of H2O. - **A covalent bond is formed that replaces the hydrogen bond between the OH group and the H atom.** - Figure 1 represents a common process that occurs in organisms. - H H H H N + N- H H OH H CH3 OH H HO H N-C-C-N-C + H2O H H HCH3OH - Figure 1. Structural formula for a common biological reaction ### Which of the following is an accurate description of the process shown in Figure 1? - The linking of amino acids with an ionic bond as an initial step in the protein synthesis process - The formation of a more complex carbohydrate with the covalent bonding of two simple sugars - The hydrolysis of amino acids with the breaking of covalent bonds with the release of water - **The formation of a covalent peptide bond in a dehydration synthesis reaction** - Polypeptides are continuously being formed and degraded. One of these processes is shown. - H R2 H R4 H R6 H N C C N C N C H N C-OH H H || H R₁ H Ο R3 H R5 H H2O H R2 H H H R4 H R6 N C C N H C N C C OH H C N C C N C-OH R₁ H Ο R3 H H H R5 H - Figure 1. Polypeptide reaction ### Which statement is the most accurate description of the reaction shown in Figure 1 - It represents monomers linked by dehydration synthesis. - It represents a polypeptide chain that folds to form the tertiary structure. - It represents a polypeptide chain that is denatured into the primary structure. - **It represents a polypeptide chain that is broken down through a hydrolysis reaction.** - A researcher claims that different metabolic pathways allow bacteria to use different molecules as sources of matter and energy. ### Which of the following statements best helps justify the researcher's claim by providing a relevant example? - Rhizobia bacteria form close associations with the roots of bean plants. - **E. coli bacteria reproduce in liquid media containing either glucose or galactose.** - The antibiotic rifampicin inhibits the growth of some bacterial strains but not of others. - Some viruses that infect bacteria reproduce by either the lysogenic cycle or the lytic cycle. - Cyanobacteria contain a variety of pigment molecules, as shown in Table 1. As a result, the color of cyanobacteria cultures can vary significantly based on the relative amount of each pigment produced. - TABLE 1. PHOTOPIGMENTS IN CYANOBACTERIA - Pigment - Color of Reflected Light - Chlorophyll a - Green - Phycocyanin - Blue - Allophycocyanin - Blue - Phycoerythrin - Red - A researcher placed a culture of cyanobacteria under green lights. Within a few weeks, the appearance of the cyanobacteria changed from green to red. The researcher claimed the color change in the culture was the result of an adaptation allowing greater photosynthesis. ### Which of the following provides the best reasoning to justify the researcher's claim? - In green light, more chlorophyll a molecules are produced, reflecting more light to other cyanobacteria to be used for photosynthesis. - **In green light, more phycoerythrin molecules are produced, allowing more green light to be absorbed, thus increasing photosynthesis.** - In green light, cyanobacteria that have more phycocyanin molecules are less likely to survive and reproduce. - In green light, cyanobacteria that have more allophycocyanin molecules are more likely to survive and reproduce. - In addition to the pigments commonly associated with photosynthesis, a certain photosynthetic species contains two additional pigment types ### Which of the following best supports the claim that this species is better adapted to environmental changes than other photosynthetic species are? - The increased pigment concentration better facilitates energy production within the cells of the species. - The pigment combination allows the organism to absorb heat as well as light, making better use of available energy. - The additional pigments allow the species to outcompete other species for the wavelengths of light commonly used in photosynthesis. - **The additional pigments allow the species containing them to harvest energy from wavelengths of light that the other photosynthetic species cannot use.** - The illustration shows the active transport of hydrogen ions through a membrane protein. - H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ ATP H+ ### Which of the following best predicts the effect of not having ATP available to supply energy to this process? - **H+ ions will stop moving through the protein.** - H+ ions will move in the other direction through the protein. - H+ ions will continue to move through the protein in the original direction but at a slower rate. - H+ ions will begin to move through the phospholipid portion of the membrane in the original direction. - Aquaporin - Cell Membrane ### Which statement best describes the effect on water transport across the cell membrane if the aquaporin in the figure ceases to function? - Water molecules will no longer be able to move across the cell membrane. - **Water molecules will still be able to move across the cell membrane but at a slower rate.** - Water molecules will only be able to enter the cell by active transport. - Water molecules will move across the cell membrane at a faster rate without the aquaporin regulating their flow. - A cell's membrane potential is maintained by the movement of ions into and out of the cell. A model showing the influence of membrane proteins on the movement of sodium (Na+) and potassium (K+) ions across the plasma membrane is presented in Figure 1. - Extracellular Concentrations: - [Na+] High - [K+] Low - Na+ - Pumped Out - K+ - Leaks Out - Cytosol - Protein X - Na+ - Leaks In - K+ - Pumped In - Cytosol Concentrations: - [Na+] Low - [K+] High - 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 outcomes will most likely result from a loss of protein X function? - The membrane potential will be disrupted by an increase in Na+ concentration inside the cell. - **The membrane potential will be disrupted by an increase in K+ concentration inside the cell.** - The membrane potential will be maintained by the Na+ - K+ pump moving more K+ ions into the cell. - The membrane potential will be maintained by the diffusion of Na+ ions into the cell. - Grass with Plant Starch - CH₂OH - CH₂OH - CH₂OH - OH - OH - OH - OH - Rabbit - H H H HO H H H H H H H H H H ### Which of the following statements best describes how organisms such as rabbits obtain the carbon necessary for building biological molecules? - Rabbits eat plants and use energy absorbed from the plants to make carbon atoms from electrons, protons, and neutrons in the air. - **Rabbits eat plants and break down plant molecules to obtain carbon and other atoms that they rearrange into new carbon-containing molecules.** - 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. - 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. - 02 - Water - 0 - CO2 - Ammonia - (NH3) - Nitrates - (NO3) - Nitrites - (NO2) - Gravel ### Which of the following statements best describes how molecules released by the fish become nutrients for the plants? - 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. - 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. - The nitrites released by the fish are converted by the bacteria to carbon dioxide molecules, which are used by the plants to make carbohydrates. - **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.** - Students conducted a controlled experiment to investigate whether sawdust provides enough nutrients to support plant growth. The students separated ten nearly identical sunflower seedlings into two groups. They grew the seedlings in the first group in potting soil and the seedlings in the second group in sawdust composed mostly of cellulose. After twenty days, the students recorded observations about the seedlings in each group. The students' observations are presented in the table. - Treatment Group - Mean Seedling Height - Observations - Seedlings in potting soil - 18.5 cm - The leaves have a dark green color and are normal in size. - Seedlings in sawdust - 4.8 cm - The leaves have a grayish color and are small in size. ### The observed differences between the groups most likely resulted from differences in the ability of the seedlings to produce which of the following monomers? - CH2OH - H - H - H/H - H-C-C-C - H - and - HO OH - H - HOH - OH OH OH - H HO - H - R - = - N-C-C - only - H - H - OH - H2N - N - H R - G N-C-C - H - H OH - H₂N - HO - OP - fo -OH - and - HO-P-O - -0 - OH - HHH - and - H-C-C-C - HHH - O-H - A researcher claims that the synthesis of ATP from ADP and inorganic phosphate (Pi) is essential to cellular function. ### Which of the following statements best helps justify the researcher's claim? - ADP is a small molecule that some cells release into their environment as a way of communicating with other cells. - **ATP hydrolysis is an energy-releasing reaction that is often coupled with reactions that require an input of energy.** - Inorganic phosphate (Pi) is a substance that cells typically acquire from their environment. - ATP synthase is a mitochondrial enzyme that catalyzes the conversion of ADP and P₁ to ATP. - A researcher claims that only a portion of the light energy captured by green plants is available for growth and repair. ### Which of the following observations best helps justify the researcher's claim? - Light-capturing pigment molecules in green plants absorb red, blue, and violet light but reflect green light. - The energy of a photon of light is proportional to its frequency and inversely proportional to its wavelength. - **As light energy is converted to chemical energy by metabolic processes, some of the energy is lost as heat.** - Captured energy is stored in the molecular bonds of organic molecules, including simple sugars and starch. - Muscle contraction depends on ATP hydrolysis. During periods of intense exercise, muscle cells rely on the ATP supplied by three metabolic pathways: glycolysis, mitochondrial respiration, and the phosphagen system. Figure 1 shows the rates at which the three metabolic pathways produce ATP following the start of an intense period of exercise. - ATP Production (kcal/kg/min) - 45 - 40 - 35 - 30 - 25 - 20 - 15 - 10 - 5 - 0 - Phosphagen - Glycolysis - Mitochondrial respiration - 0 10 20 30 40 50 60 70 80 90 100 - Time (seconds) - Figure 1. ATP production by three metabolic pathways following the start of an intense period of exercise ### Which of the following correctly uses the data to justify the claim that the phosphagen system is an immediate, short-term source of ATP for muscle cells? - ATP production by the phosphagen system increases and decreases rapidly following the start of the exercise period. - ATP production by the phosphagen system increases gradually and continuously throughout the entire exercise period. - The ATP produced by the phosphagen system contains more energy per molecule than does the ATP produced by the other pathways. - **ATP hydrolysis in muscle cells occurs immediately after the start of the exercise period but stops before the end of the exercise period.** - Which of the following claims is scientifically accurate and consistent with an observation that a decrease in lysosome production within a cell leads to a decline in mitochondrial activity? - A lack of lysosomes will cause a decrease in the synthesis of enzymes necessary for cellular respiration. - **Fewer lysosomes will be available to break down macromolecules to provide the necessary nutrients for cellular respiration.** - Fewer lysosomes will be available to store materials required for the functioning of the mitochondria. - Lysosomes will not be available to modify proteins so that they are targeted to the mitochondria. - Muscle cells have high ATP demands. Which of the following is a scientific claim about how the structure of the mitochondria in muscle cells should be different than it is in other cells because of the high energy demands of mitochondria? - The inner membrane of the mitochondria in muscle cells should have more folds to increase the surface area, allowing more ATP to be synthesized. - **The inner membrane of the mitochondria in muscle cells should be more permeable to large enzymes, allowing the same reactions to occur in both compartments of the mitochondria.** - The outer membrane of the mitochondria in muscle cells should be thicker, allowing more rapid diffusion of molecules into the mitochondria. - The outer membrane of the mitochondria of muscle cells should have more folds, increasing the surface area for faster diffusion of molecules from the cytoplasm. - Researchers have proposed a model of