AP BIO Unit 1 Exam

AP Bio unit 1 Exam Q1 Surfaces of bodies of water Which of the following best explains why surface tension is created on the surface of bodies of water? Water molecules are attracted to each other because the hydrogen atoms donate electrons to oxygen atoms. Water molecules are attracted to each other because the sharing of electrons between hydrogen and oxygen is unequal. Water molecules are attracted to substances dissolved in the water because most dissolved substances are positively charged. Water molecules are attracted to substances dissolved in the water because most dissolved substances are negatively charged. Q2 Amino acid R groups and protein structure Scientists examined the folded structure of a purified protein resuspended in water and found that amino acids with nonpolar R groups were primarily buried in the middle of the protein, whereas amino acids with polar R groups were primarily on the surface of the protein. Which of the following best explains the location of the amino acids in the folded protein? Polar R groups on the surface of the protein can form ionic bonds with the charged ends of the water molecules. Polar R groups are too bulky to fit in the middle of the protein and are pushed toward the protein's surface. Nonpolar R groups that cannot form hydrogen bonds with water are pushed into the middle of the protein. Nonpolar R groups from different parts of the protein form covalent bonds with each other to maintain the protein's structure. Q3 Amino acid substitution - polar to nonpolar A mutation in the gene coding for a single-polypeptide enzyme results in the substitution of the amino acid serine, which has a polar R group, by the amino acid phenylalanine, which has a nonpolar R group. When researchers test the catalysis of the normal enzyme and the mutated enzyme, they find that the mutated enzyme has much lower activity than the normal enzyme does. Which of the following most likely explains how the amino acid substitution has resulted in decreased catalytic activity by the mutated enzyme? The substitution decreased the mass of the enzyme so that the mutated enzyme binds more weakly to the substrate than the normal enzyme does. The substitution altered the secondary and tertiary structure of the enzyme so that the mutated enzyme folds into a different shape than the normal enzyme does. The substitution caused many copies of the mutated enzyme to cluster together and compete for substrate to bind. The substitution caused the directionality of the enzyme to change such that the amino terminus of the normal enzyme has become the carboxy terminus of the mutated enzyme. Q4 Amino acid bonding with 5 answer options tRNA molecules deliver amino acids to ribosomes where the amino acid next forms an ionic bond with another amino acid is deaminated and catabolized becomes an anticodon is covalently bonded to a growing polypeptide forms hydrogen bonds with esters Q5 Protein or carbohydrate polymers, 5 options The synthesis of protein or carbohydrate polymers always produces which of the following as a byproduct? ATP Oxygen Carbon dioxide Urea Water Q6 Tertiary Structure 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. Q7 Water's unique properties with 5 answer options Which of the following is most directly responsible for water's unique properties? It contains oxygen atoms. It contains hydrogen atoms. It is an ionic compound. It forms hydrogen bonds. It is nonpolar. Q8 Proteins 1 chemical composition: General Directions: Answers must be in essay form. Outline form is not acceptable. Labeled diagrams may be used to supplement discussion, but in no case will a diagram alone suffice. It is important that you read each question completely before you begin. Proteins-large complex molecules are major building blocks of all living organisms. Discuss the following in relation to proteins. The chemical composition and levels of structure of proteins Q9 Digestion of Starch by Amylase Amylase is an enzyme that converts carbohydrate polymers into monomers. Glycogen synthase is one of the enzymes involved in converting carbohydrate monomers into polymers. Which of the following best explains the reactions of these enzymes? Amylase aids in the removal of a water molecule to break covalent bonds whereas glycogen synthase aids in the addition of a water molecule to form covalent bonds. Amylase aids in the addition of a water molecule to break covalent bonds whereas glycogen synthase aids in the removal of a water molecule to form covalent bonds. Amylase aids in the addition of a water molecule to form covalent bonds whereas glycogen synthase aids in the removal of a water molecule to break covalent bonds. Amylase aids in the removal of a water molecule to form covalent bonds whereas glycogen synthase aids in the addition of a water molecule to break covalent bonds. Q10 Hydrolysis of Carbohydrates ? Which of the following best describes the hydrolysis of carbohydrates? The removal of a water molecule breaks a covalent bond between sugar monomers. The removal of a water molecule forms a covalent bond between sugar monomers. The addition of a water molecule breaks a covalent bond between sugar monomers. The addition of a water molecule forms a covalent bond between sugar monomers. Q11 Polarity of Water The diagram shows how water can adhere to the xylem in the stems of plants, which contributes to water movement in the plant. Water Molecule Xylem Cell Which of the following best explains how water is able to move upward from the roots of a plant, through its xylem in the stem, and out to the leaves? Xylem Cell Wall Water is polar, and the walls of the xylem are nonpolar. Water molecules have the ability to form hydrogen bonds with one another but not with the xylem walls. Water is nonpolar, and the walls of the xylem are polar. Water molecules are able to form hydrogen bonds with the xylem walls, and they are pulled up the xylem. Water and the xylem are both nonpolar. Water molecules have the ability to form hydrogen bonds with one another but not with the xylem walls. Water and the xylem are both polar, Water molecules have the ability to form hydrogen bonds with each other and with the walls of the xylem. Q12 Liver function test surface tension A common test for liver function involves sprinkling sulfur powder onto a sample of urine (mostly water with dissolved bodily waste). Sulfur powder sprinkled on a sample from an individual with impaired liver function will sink because the urine contains a high level of bile salts, while the sulfur powder sprinkled on normal urine samples will float. Which of the following best explains why bile salts cause the sulfur powder to sink? Bile salts decrease the surface tension of the urine sample. Bile salts increase the water potential of the urine. Bile salts increase the density of the urine sample. Bile salts decrease the strength of the covalent bonds within a water molecule. Q13 Lipid hydrogenation The process of hydrogenation is used in the food industry to convert lipids that are liquids at room temperature into solids at room temperature. The process involves the chemical addition of hydrogen atoms to the fatty acid tails of lipids, breaking some or all of the carbon-carbon double bonds in the fatty acid tails Which of the following best explains why hydrogenation converts liquid lipids to solid lipids? Hydrogenation makes the fatty acids more saturated, enabling them to be more densely packed together. Hydrogenation makes the fatty acids less saturated, enabling them to be more densely packed together. Hydrogenation makes the fatty acids more saturated, resulting in fewer lipid molecules fitting within a given space. Hydrogenation makes the fatty acids less saturated, resulting in fewer lipid molecules fitting within a given space. Q14 Parts of an amino acid H H Which part of the amino acid most likely contributes to the hydrophobic behavior of this region of the polypeptide? N-C-C H CH3 OH Figure 1. An amino acid The amino acid in Figure 1 is found in a region of a polypeptide that folds away from water. Amine (NH2) group Carboxyl (COOH) group Methyl (CH3) group Hydrogen (H) atom Q15 Effect of chemical on a protein A chemical binds to a protein composed of a single polypeptide chain and prevents the formation of an alpha helix that is typically formed in the absence of the chemical. Which of the following best describes the effect the chemical has on the structure of the protein? The primary structure held together by covalent bonds is affected. The secondary structure held together by hydrogen bonds is affected. The secondary, tertiary, and quaternary structures are affected. All levels of protein structure are affected.