AP Bio MASTER QUESTION CHAPTERD
Which feature of model 1 best illustrates how biological information is coded in a DNA molecule? A The 5′5′ and 3′3′ labels at the ends of each strand B The labeling of the hydrogen bonds between base pairs C The lines connecting sugars and phosphate groups that represent covalent bonds D The linear sequence of the base pairs
Answer D Correct. The sequence of base pairs in a DNADNA molecule plays a central role in the coding of biological information.
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.
Answer A Correct. As water exits the leaf, hydrogen bonding pulls more water molecules up through the leaf and xylem by cohesion.
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. 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 TubePolysaccharide AddedEnzyme AddedGlucose Detected after 5 Minutes at 37°C1CelluloseANo2CelluloseBYes3StarchAYes4StarchBNo 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.
Answer A Correct. The identical orientations of the glucose monomers in starch create a polysaccharide with alpha bonds that is easy to break down into glucose for energy use. The alternating orientations of the glucose monomers in cellulose create beta bonds that produce a rigid polymer that is difficult to digest for energy use.
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. How might this change affect the structure and function of the protein? A The R-groupR-group of the new amino acid, valine, has different chemical properties than the R-groupR-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-groupR-group and by an amino acid on the other side with a positively charged R-groupR-group, the charges will balance and the protein will fold as usual.
Answer A Correct. Three-dimensional folding of a protein is due to interactions among the R groups of the amino acids. Cysteine has a sulfhydryl group, which may form a disulfide bridge with another part of the polypeptide chain. Valine has no sulfhydryl group and is nonpolar, which will affect how the polypeptide will fold.
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. 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 TubePolysaccharide AddedEnzyme AddedGlucose Detected after 5 Minutes at 37°C1CelluloseANo2CelluloseBYes3StarchAYes4StarchBNo 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 CH2OHCH2OH group, while cellulose only has a CH2OHCH2OH group on every other monomer. D Starch and cellulose are composed of identical monomers and therefore have identical structures.
Answer B Correct. Both starch and cellulose are both composed of repeating glucose molecules; however, the orientation of every other glucose in cellulose is upside down compared with the ones on either side.
A student wants to modify model 1 so that it represents an RNA double helix instead of a DNA double helix. Of the following possible changes, which would be most effective in making model 1 look more like RNA than DNA? A Changing the sequence of the base pairs B Changing the deoxyriboses to riboses by adding −OH−OH groups C Changing the shapes of the nitrogenous bases to match those shown in model 2 D Changing the sugar-phosphate backbone to a ribbon, as shown in model 3
Answer B Correct. RNARNA contains ribose, whereas DNADNA contains deoxyribose. A ribose sugar has an −OH−OH group linked to the 2′2′ carbon that a deoxyribose sugar does not have.
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. 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 CO2CO2 had no observable effect on plant growth under either ideal or stressed conditions. B The increase in atmospheric CO2CO2 resulted in a greater increase in plant growth under ideal conditions than under stressed conditions. C The increase in atmospheric CO2CO2 resulted in a greater increase in plant growth under stressed conditions than under ideal conditions. D The increase in atmospheric CO2CO2 resulted in an inhibition of plant growth under both ideal and stressed conditions.
Answer C Correct. Based on the figure, the increase in atmospheric CO2CO2 resulted in a greater increase in plant growth under stressed conditions than under ideal conditions.
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 XX only B Bond WW only C Bonds YY and ZZ at the same time D Bonds WW and ZZ at the same time
Answer C Correct. By breaking bonds YY and ZZ at the same time, the cytosine nucleotide could be removed from the DNADNA molecule and replaced with an undamaged cytosine without changing the biological information stored in the DNADNA.
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-groupR-group. B Only some amino acids have a carboxyl group (COOH)(COOH). C Some amino acids are hydrophobic. D Some amino acids contain the element phosphorus.
Answer C Correct. Due to having nonpolar R-groupsR-groups, 10 of the 20 amino acids are hydrophobic. Interactions between hydrophobic amino acids play an important role in determining protein structure and function.
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.
Answer C Correct. Nucleotides form base pairs with other nucleotides. The base pairing allows a strand of RNARNA or DNADNA to act as a template in the synthesis of other nucleic acid molecules. Examples include the cellular processes of DNADNA replication (DNADNA is used as a template to make DNADNA), transcription (DNADNA is used as a template to make RNARNA), and reverse transcription (RNARNA is used as a template to make DNADNA).
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. 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.
Answer C Correct. Phosphorus is used to make nucleic acids and certain lipids. Without phosphorus atoms, nucleic acids and lipids cannot be made for the plant to use for growth.
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.
Answer C Correct. The monomers of the two reactions illustrated are joined by covalent bonds with the production of a water molecule.
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.
Answer C Correct. The water molecules in ice are farther from each other than are water molecules in liquid water, so ice is less dense than liquid water and floats on its surface, while the denser water at 4 degrees Celsius sinks to the bottom, maintaining a steady temperature all winter.
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. 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 TubePolysaccharide AddedEnzyme AddedGlucose Detected after 5 Minutes at 37°C1CelluloseANo2CelluloseBYes3StarchAYes4StarchBNo 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)(H2O) and a specific enzyme. C A specific enzyme removes the hydrogen (HH) from the monosaccharide and the hydroxide (OHOH) from the polysaccharide, creating a bond between the two and creating a water (H2OH2O) molecule. D A specific enzyme removes two hydroxides (OH)(OH), one from the monosaccharide, and one from the polysaccharide, creating a bond between the two monosaccharides and creating a hydrogen peroxide (H2O2H2O2) molecule.
Answer C Correct. This is a description of dehydration synthesis, which joins multiple monosaccharides to create a polysaccharide and produces water (H2OH2O) molecules.
Figure 1 shows a short segment of a double-stranded nucleic acid molecule. 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 RNARNA because of the relative direction of the two strands. B It is RNARNA because of the number of different nucleotides found in the molecule. C It is DNADNA because of the nature of the hydrogen bonds between guanine and cytosine. D It is DNADNA because of the nucleotides present.
Answer D Correct. The figure indicates that one of the nucleotides is thymine. Thymine is found in DNADNA and not in RNARNA.
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? A B C D
Answer D Correct. The hydrogen bonds between these water molecules correctly show the attractive force between the hydrogen atom of one water molecule and the oxygen atom of the adjacent water molecule.
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. 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 TubePolysaccharide AddedEnzyme AddedGlucose Detected after 5 Minutes at 37°C1CelluloseANo2CelluloseBYes3StarchAYes4StarchBNo 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 BB without the help of the bacteria. D Cattle would no longer be able to use cellulose as a primary source of glucose.
Answer D Correct. Without the enzyme BB produced by microorganisms in their digestive tract, cellulose would pass through the digestive tract without being digested.