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IGERS UNIVERSITY NEWARE Federatet Department of Biological Sciences 120:960 Biochemistry Summer 2023 Prof. Cervantes Exam 1 Student's name (Last, First): Multiple choice (2 pt. per question) Choose the one alternative that best completes the statement or answers the question. Mark on the Akindi answer sheet, you may use pen to change your answer, but make sure to use a good eraser. You must properly fill in your RU ID on the Akindi sheet: otherwise, the system will not grade you. If you do not know your RU ID, you can find it next to your name on the signing in sheet. 1. Which of the following is a physical property of water that results from hydrogen bonding? a solid state that is less dense than the liquid state high surface tension the ability to solubilize polar molecules a high boiling point relative to molecular weight all of the above In a water molecule, hydrogens are partially oxygen is partially, negative; negative positive; positive positive; negative negative; positive none of the above 3. Molecules such as methanol and ethanol are very soluble in water because they do not form intermolecular H-bonds they contain C H groups that donate H-bonds to water they contain O-H groups that can form multiple H-bonds with water They contain C-H groups that accept H-bonds from water they tend to avoid contact with each other 1. In a hydrogen bond between a water molecule and another biomolecule, the partial charge on a hydrogen of the water interacts with the partial charge on a hydrogen of the other molecule the hydrogen bond will typically form between a hydrogen atom and either a nitrogen, sulfur, or oxygen allom a hydrogen iori on the water molecule forms an ionic bond with a hydride ion on the other molecule the hydrogen atom is located between an oxygen atom of the water and a carbon atom of the other molecule a hydrogen on the water molecule forms a covalent bond to an oxygen or nitrogen atom on the other molecule 5. Which of the following statements about water is not true? In the liquid state it is only 15% less hydrogen bonded than in the solid state at 0°C. It dissolves salts and polar substances. It can form two hydrogen bonds per water molecule. It has a high dielectric constant. It packs in a hexagonal- (honeycomb-) shaped lattice when the temperature falls below 0°C. 6. When considering O, N, and F, the shortest hydrogen bond with an-OH gl since this atom is O, the most electronegative of the three the one with the largest number of unpaired electrons the Heaviest F the most electronegathe None of the above . As per Pauling's scale, fluor (F) is the most electronegative element, this makes it... 7 avery weak hydrogen bond donne a very strong hydrogen bond acceptor a very strong hydrogen bond donor. an important hydrogen bond donor in biological systems. a strong Arrhenius acid. Hydrophobic interactions between nonpolar molecules depend on strong permanant dipoles in the nonpolar molecules requine the presence of surrounding water molecules are the result of strong repulsion between water and nonpolar molecules are the result of strong attractions between nonpolar molecules result from the tendency of water to maximize contact with nonpolar molecules Blood pH is approximately 7.35 and the total concentration of H₂CO₂ + HCOs ions is approximately 20 mM. What is the ratio of bicarbonate ions to carbonic acid in blood under thes conditions (Ka for H₂CO₂ = 4.3×10)7]. 0.983:1 4.3:1 7.35:1 9.6:1 None of the above D. What is the pH of a solution that contains three parts acetic acid and one part sodium acetate? The pKa for acetic acid is 4,76. 5.24 5.06 4.46 4.28 cannot be determined from the given information 1. Which of the following shows the buffer that is found in the bloodstream? HPO H₃PO₄ +H HPO HPO+H HPO POH H.CO, HCO₂ +H 400, COH 12. A strong acid is completely ionized in water, whereas a weak acid is totally ionized impossible to dissociate only partially lonized another name for a strong base only dissociable in organic solvents 13. The pH of coffee is 5.6. The pH of grapefruit juice is 2.6. This means that the proton concentration in coffee is A. 1,000 times higher than in grapefruit juice