Visual Anatomy Physiology Chemical Level of Organization

Visual Anatomy & Physiology Chemical Level of Organization Multiple-Choice Questions 1) Atoms are electrically neutral A) because the number of protons and neutrons are equal. B) because the number of protons and electrons are equal. C) because the number of neutrons and electrons are equal. D) only when the atomic numbers are even. E) when electron shells are full. Answer: B 2) An element is defined as a pure substance consisting only of A) atoms of the same atomic number. B) atoms of the same atomic mass. C) unbonded atoms. D) atoms that are created in research laboratories. E) atoms that occur naturally on earth. Answer: A 3) One reason that electrons remain in their electron shells is that they A) are repelled by one another's negative charges. B) naturally resist change. C) are immobile. D) are attracted to the positive protons in the nucleus. E) associate with neutrons. Answer: D 4) Elements found within the body at amounts lower than 0.0002 percent are called A) minerals. B) vitamins. C) metabolites. D) trace elements. E) metals. Answer: D 5) The atomic number of an element describes the A) number of protons in the nucleus. B) number of neutrons in the nucleus. C) weight of a single atom in amu. D) number of electrons needed to fill the shells. E) number of atoms needed to create a 1 gram quantity. Answer: A 6) The element that is important both to living things in its gaseous form and as a component of water is A) hydrogen. B) oxygen. C) carbon. D) hydroxide. E) helium. Answer: B 7) The number of protons present in an element is revealed by A) the atomic mass. B) the molecular formula. C) the atomic number. D) the electron shells available. E) determining the difference between the atomic number and the atomic mass. Answer: C 8) The most abundant element, by weight, found in the human body is A) hydrogen. B) helium. C) carbon. D) oxygen. E) nitrogen. Answer: D 9) Isotopes have the same number of ________ but different numbers of ________. A) protons; neutrons B) protons; electrons C) neutrons; protons D) neutrons; electrons E) electrons; protons Answer: A 10) The atomic mass of an atom describes the A) number of protons in the nucleus. B) number of neutrons in the nucleus. C) number of electrons in the nucleus. D) total weight of both protons and neutrons in the nucleus. E) number of atoms needed to bond. Answer: D 11) The atomic number of an element is 7. How many electrons does it have? A) one B) two C) seven D) fourteen E) Not enough information is given. Answer: C 12) The atomic number of an atom is 2. The mass number is 4. Which of the following statements is accurate? A) There are 6 protons, 6 neutrons, and 6 electrons. B) There are 12 protons, 12 neutrons, and 12 electrons. C) There are 2 protons, 4 neutrons, and 2 electrons. D) There are 2 protons, 2 neutrons, and 2 electrons. E) There are 2 protons, 2 neutrons, and 4 electrons. Answer: D 13) The atomic number of an atom is 6 and its atomic mass is 12. Which of the following statements is accurate? A) There are 6 protons, 6 neutrons, and 6 electrons. B) There are 12 protons, 12 neutrons, and 12 electrons. C) There are 6 protons, 12 neutrons, and 6 electrons. D) There are 2 protons, 2 neutrons, and 2 electrons. E) There are 2 protons, 2 neutrons, and 4 electrons. Answer: A 14) The mass number of an element is 7. How many neutron(s) does it have? A) one B) two C) seven D) fourteen E) Not enough information is given Answer: E Figure 2.1 Use Figure 2.1 to answer the following questions: 15) The particle labeled "A" is a(n) A) proton. B) neutron. C) electron. D) molecule. E) cell. Answer: C 16) The area labeled "B" holds A) electrons only. B) protons only. C) neutrons only. D) protons and neutrons. E) protons and electrons. Answer: D 17) The first energy level of atoms holds ________ electron(s). A) one B) two C) three D) four E) eight Answer: B 18) The second energy level of atoms holds ________ electron(s). A) one B) two C) three D) four E) eight Answer: E 19) Adding electrons to an atom A) turns it into an anion. B) changes its atomic number. C) changes its atomic mass. D) turns it into a cation. E) turns it into either an anion or a cation. Answer: A 20) Atoms with filled outer shells A) form both anions and cations. B) form anions. C) form cations. D) do not bond. E) form only covalent bonds. Answer: D 21) Lithium has an atomic number of 3. How many electrons are in the second energy level? A) one B) two C) three D) four E) zero Answer: A 22) Nitrogen has an atomic number of 7. How many electrons are normally in the third energy level? A) one B) two C) three D) four E) zero Answer: E 23) Which of the following statements about helium (atomic number 2) and neon (atomic number 10) is FALSE? A) Both are inert. B) Both have full outer energy shells. C) Both are highly reactive. D) Both are will not form chemical bonds with other atoms. E) Both are inert gases. Answer: C 24) A chemical entity that contains at least two different elements bonded together is a(n) A) molecule. B) atom. C) element. D) ion. E) compound. Answer: E 25) NaCl is a(n) A) anion. B) cation. C) compound. D) molecule. E) atom. Answer: C 26) In solutions of polar molecules, partial positive charges of one polar molecule will be attracted to partial negative charge on a neighboring polar molecule. This results in ________ bonds. A) hydrogen B) ionic C) partial D) covalent E) carbon Answer: A 27) Water is a(n) A) ionic compound. B) diatomic molecule. C) nonpolar covalent molecule. D) inert gas. E) polar covalent molecule. Answer: E 28) Which of the following statements about pure water is FALSE? A) Pure water contains ionic bonds. B) Pure water demonstrates polarity. C) Pure water has hydrogen bonds. D) Pure water carries partial charges. E) Pure water is a polar covalent compound. Answer: A 29) Chloride (Cl-) is a(n) A) ion. B) compound. C) molecule. D) atom. E) bond. Answer: A 30) Assume that K+, H+, Na+, Br-, and Cl- are all available for bonding. Which combination is NOT a possible ionic interaction? A) KCl B) KNa C) HCl D) NaCl E) KBr Answer: B 31) Assume that K+, H+, Na+, Br-, and Cl- are all available for bonding. Which combination is a possible ionic interaction? A) HH B) HCl C) KNa D) HNa E) HK Answer: B 32) Which of the following statements is TRUE? A) Compounds always are ionic. B) Compounds always are covalent. C) Compounds always contain at least two different elements. D) Molecules always contain at least two different elements. E) Compound and molecule are synonyms. Answer: C Figure 2.2 Use Figure 2.2 to answer the following questions: 33) The bonds labeled "A" are a representation of ________ bonds. A) covalent B) metal C) hydrogen D) nonpolar E) ionic Answer: C 34) The substance labeled "B" is A) a salt. B) a solute. C) a carbohydrate. D) water. E) a protein. Answer: D 35) The substance labeled "B" is held together by ________ bonds. A) covalent B) metal C) hydrogen D) nonpolar E) ionic Answer: A 36) Which of the following is NOT a requirement of all chemical reactions? A) heat B) energy transfer C) rearrangement of atoms D) bonding E) reactants Answer: A 37) Enzymes are substances that can promote chemical reactions because they can A) increase activation energy. B) lower activation energy. C) destabilize reactants. D) break chemical bonds. E) promote new chemical bond formation. Answer: B 38) Chemical reactions that release energy are A) endergonic. B) exergonic. C) catalyzed. D) enzymatic. E) equilibrated. Answer: B 39) The starting substances in a chemical reaction are called A) reactants. B) products. C) enzymes. D) exergonic. E) catalysts. Answer: A 40) Which correctly represents the chemical notation of an atom that has lost two electrons? A) Cl- B) Na+ C) Ca2+ D) S2- E) O?- Answer: C 41) Which is a likely strategy in a living system to overcome activation energy barriers for chemical reactions? A) Heat the reactants. B) Provide a catalyst. C) Increase cellular pressure. D) Decrease the temperature. E) Add energy from carbohydrates. Answer: B 42) Which of the following represents the chemical notation of three carbon dioxide molecules? A) 3CO2 B) C3O6 C) 3CO D) 3C2O E) C3O3 Answer: A 43) Which of the following does NOT represent a correctly balanced chemical reaction? A) C + 2O = CO2 B) 2H + 2O = 2H2O C) 2H +O = H2O D) 2H2 + 2O = 2H2O E) 2C +2O2 = 2CO2 Answer: B 44) Chemical reactions in your digestive tract break down large food fragments into smaller, absorbable fragments. What type of chemical reaction is this? A) decomposition B) synthesis C) exchange D) dehydration E) peptide Answer: A 45) Decomposition reactions A) result in products smaller than reactants. B) assemble larger molecules. C) are energetically uphill reactions. D) are synthetic. E) never require water. Answer: A 46) What is the commonality shared by hydrolysis and dehydration reactions? A) Both are anabolic. B) Both are catabolic. C) Both are exchange reactions. D) Both are decomposition reactions. E) Both involve water. Answer: E 47) Which of the following is NOT true of hydrolysis? A) Hydrolysis is a type of decomposition. B) Hydrolysis contributes to catabolism. C) Water molecules are split during hydrolysis. D) Biological hydrolysis reactions require a catalyst. E) Hydrolysis produces larger products from smaller reactants. Answer: E 48) Synthesis of new, large biological molecules in the body A) is endergonic. B) is exergonic. C) creates energy. D) requires hydrolysis. E) results in no net energy balance. Answer: A 49) The energy that is required to carry out biological synthesis is provided by A) endergonic reactions carried out on food molecules. B) exergonic reactions carried out on food molecules. C) anabolic chemical reactions. D) exchange reactions. E) dehydration synthesis. Answer: B 50) Water composes ________ percent of the human body, by weight. A) 50 B) 75 C) 25 D) 66 E) 1 Answer: D 51) Which of the following types of substances are NOT likely to associate with water? A) proteins B) sugars C) fats and oils D) electrolytes E) salts Answer: C 52) The term electrolyte refers to the group of chemicals that A) are compounds. B) are soluble. C) are not soluble in water, but are soluble in oil. D) are molecules. E) dissolve and dissociate in water. Answer: E 53) The high heat capacity of water A) is responsible for thermal inertia. B) is important in dehydration reactions. C) aids lubrication of joints. D) makes water an excellent solvent. E) causes water temperature to change rapidly. Answer: A 54) Ion excretion is primarily controlled by the ________ system. A) urinary B) cardiovascular C) skeletal D) digestive E) integumentary Answer: A 55) Which of the following would NOT be considered hydrophilic? A) electrolytes B) polar covalent molecules C) ionic molecules D) nonpolar molecules E) water Answer: D 56) Whole blood is considered a(n) A) colloid. B) suspension. C) electrolyte. D) organ system. E) amalgam. Answer: B 57) The distinction between a colloid and a suspension is that A) a suspension's particles settle out of solution but a colloid's particles do not. B) colloids contain larger particles. C) suspensions are not solutions but colloids are. D) suspensions are more Jello-like. E) colloids are always temporary. Answer: A 58) Which of the following is NOT an important property of water for the function of the human body? A) lubrication B) reactivity C) high heat capacity D) solubility E) hydrophobicity Answer: E 59) The behavior expected of a polar covalent molecule in water is to A) be nonsoluble. B) ionize. C) conduct electricity. D) create the formation of hydration spheres. E) dissociate. Answer: D 60) Which of the following statements is TRUE? A) All electrolytes are insoluble. B) All soluble compounds are electrolytes. C) All electrolytes are molecules. D) All compounds are electrolytes. E) All electrolytes are compounds. Answer: E 61) Salts are substances that can be described as A) electrolytes containing hydrogen ions. B) electrolytes containing hydroxide ions. C) electrolytes containing both hydrogen ions and hydroxide ions. D) electrolytes containing neither hydrogen ions nor hydroxide ions. E) not electrolytes. Answer: D 62) Sodium hydroxide (NaOH) is considered a base because it A) dissociates and releases Na+, which resembles H+. B) dissolves and releases OH-, which absorbs H+. C) is part of normal buffering systems. D) is not normally found within biological systems. E) dissociates and releases H+. Answer: B 63) Which of the following is NOT a direct potential negative effect of abnormal pH? A) broken chemical bonds B) cellular and tissue damage C) changes in protein shape D) disruption of water balance E) alteration of cellular function Answer: D 64) A substance that dissociates completely and releases hydrogen ions is called a A) strong acid. B) strong base. C) weak acid. D) weak base. E) salt. Answer: A 65) Which statement about alkalosis is FALSE? A) It represents abnormally high blood pH. B) It is caused by abnormally high hydrogen ion levels. C) It can be life threatening. D) It can cause sustained muscle contractions. E) It can damage protein structure. Answer: B 66) A solution with a pH of 3.7 would best be described as A) acidic. B) alkaline. C) buffered. D) physiological. E) neutral. Answer: A 67) A solution of pH 8 has ________ alkalinity than a solution of pH 4. A) greater B) lesser C) no more Answer: A 68) A cook adds vinegar (acetic acid) to a marinade. As a result, A) hydrogen ion concentration increases and pH increases. B) hydrogen ion concentration increases and pH decreases. C) hydrogen ion concentration decreases and pH increases. D) hydrogen ion concentration decreases and pH decreases. E) hydrogen ion concentration and pH are unaffected. Answer: B 69) An aspiring actress hyperventilates on opening night at the high school musical. As her carbon dioxide levels fall due to non-productive respiration, so does her blood hydrogen ion concentration. How is this condition described? A) pH is increasing; this is acidosis. B) pH is decreasing; this is acidosis. C) pH is increasing; this is alkalosis. D) pH is decreasing; this is alkalosis. E) Not enough information is given. Answer: C 70) Organic compounds A) always contain both C and H. B) always contain only C. C) cannot contain C. D) always include acids and bases. E) can be either ionic or covalent. Answer: A 71) Which of the following statements about inorganic compounds is FALSE? A) They can be either covalent or ionic. B) They can be important metabolites. C) They can never contain carbon. D) They may be electrolytes. E) They can contain partial charges. Answer: C 72) The basic unit of carbohydrates is the A) monosaccharide. B) disaccharide. C) starch. D) amino acid. E) fatty acid. Answer: A 73) Roughly half, by weight, of the typical U.S. diet consists of A) carbohydrates. B) fats and oils. C) protein. D) simple sugars. E) nutrients. Answer: A 74) Which of the following is a monosaccharide? A) fructose B) sucrose C) lactose D) maltose E) glycogen Answer: A 75) Which of the following is NOT a disaccharide? A) glucose B) sucrose C) lactose D) maltose Answer: A 76) Carbohydrates account for approximately ________ percent of total body weight. A) 66 B) 100 C) 50 D) 10 E) 1 Answer: E 77) Where does disaccharide dehydration synthesis of lactose typically occur? A) digestive tract B) lungs C) only in plants D) mammary glands of a nursing mother E) kidneys Answer: D Learning Outcome: 2. 8 78) Hydrolysis reactions are responsible for A) breakdown of maltose in the digestive tract. B) formation of glycogen in the liver. C) formation of sucrose in sugar beets. D) conversion of fructose into glucose. E) formation of water. Answer: A 79) Fatty acids consist of A) a carbonyl and a long hydrocarbon tail. B) many alcohols and a long hydrocarbon tail. C) a carbon and multiple alcohols. D) a phosphate on a long hydrocarbon entail. E) four fused carbon rings. Answer: A Learning Outcome: 2.9 80) Lipids typically contain a carbon-to-hydrogen ratio of A) 1 : 1. B) 1 : 2. C) 2 : 1. D) 2 : 3. E) 1 : 3. Answer: B Learning Outcome: 2.9 81) Lipids contain A) fewer oxygens than carbohydrates. B) more oxygens than carbohydrates. C) roughly the same number of oxygens as carbohydrates. D) no oxygens at all, but more hydrogens than carbohydrates. Answer: A Learning Outcome: 2.9 82) The lipid typically used for energy storage is a A) steroid. B) fatty acid. C) triglyceride. D) cholesterol. E) phospholipid. Answer: C Learning Outcome: 2.9 83) Fatty acids with all single C-C bonds are A) saturated. B) unsaturated. C) polyunsaturated. D) hydrophilic. E) soluble. Answer: A Learning Outcome: 2.9 84) Fatty acids with at least one double C-C bond are A) saturated. B) unsaturated. C) polyunsaturated. D) hydrophilic. E) soluble. Answer: B Learning Outcome: 2.9 85) Fatty acids with multiple double C-C bonds are A) saturated. B) unsaturated. C) polyunsaturated. D) hydrophilic. E) soluble. Answer: C Learning Outcome: 2.9 86) A shared chemical property of lipids is that most are A) electrolytes. B) insoluble. C) steroids. D) hydrophilic. E) inorganic. Answer: B Learning Outcome: 2.9 87) The reaction used to create triglycerides is A) hydrolysis. B) dehydration. C) glyceride. D) exchange reaction. E) catabolism. Answer: B Learning Outcome: 2.9 88) A structural component of cell membranes is a(n) A) fatty acid. B) fat. C) oil. D) steroid. E) triglyceride. Answer: D Learning Outcome: 2.9 89) When metabolized for energy, lipids provide A) twice as much energy as a similarly sized carbohydrate. B) half as much energy as a similarly sized carbohydrate. C) roughly the same amount of energy as a similarly sized carbohydrate. D) no energy, but provide building blocks. E) no energy, but reduce cholesterol. Answer: A Learning Outcome: 2.9 90) A triglyceride consists of A) steroid molecules. B) phosphate, glycerol, and a fatty acid. C) three fatty acids and a glycerol. D) three glycerols and a fatty acid. E) three fatty acids in a fused ring. Answer: C Learning Outcome: 2.9 91) The structure that acts as an effective barrier between two aqueous solutions is a A) cholesterol. B) membrane. C) steroid. D) micelle. E) triglyceride. Answer: B 0 92) A major component of the cell membrane is A) triglycerides. B) monoglycerides. C) cortisol. D) phospholipids. E) fats. Answer: D 0 93) Phospholipids are composed of A) steroid molecules. B) a phosphate group, glycerol, and two fatty acids. C) three fatty acids and a glycerol. D) three glycerols and a fatty acid. E) three fatty acids in a fused ring. Answer: B 0 94) When large numbers of phospholipids aggregate into a droplet this structure is called a(n) A) micelle. B) membrane. C) fat. D) oil. E) phosphate bridge. Answer: A 0 95) Which of the following is NOT a steroid? A) cholesterol B) lauric acid C) cortisol D) estrogen E) testosterone Answer: B 0 96) Steroids all share A) the same attached functional groups. B) the function as a biological sex hormone. C) hydrophilicity. D) a distinctive four-carbon ring framework. E) fatty acid derivatives. Answer: D 0 97) Which of the following is NOT a structural lipid? A) cholesterol B) phospholipids C) estrogen D) triglycerides Answer: C 0 98) Phospholipids and glycolipids can be distinguished because glycolipids contain a A) steroid. B) carbohydrate. C) fatty acid. D) phosphate. E) glycerol. Answer: B 0 Figure 2.3 Use Figure 2.3 to answer the following questions: 99) The substance labeled "A" is named A) cholesterol. B) phospholipid. C) triglyceride. D) lycolipid. E) channel protein. Answer: B 0 100) The substance labeled "B" is named A) cholesterol. B) phospholipid. C) triglyceride. D) lycolipid. E) channel protein. Answer: A 0 101) The most abundant organic compounds in the human body are A) proteins. B) carbohydrates. C) lipids. D) steroids. E) nucleic acids. Answer: A 1 102) The subunit of proteins is called a(n) A) monosaccharide. B) disaccharide. C) amino acid. D) fatty acid. E) nucleic acid. Answer: C 1 103) Which of the following is NOT a constituent of all amino acids? A) amino group B) central carbon C) carboxyl group D) side chain E) alcohol group Answer: E 1 104) How many different amino acids are found in proteins? A) two B) three C) ten D) twenty E) twenty-two Answer: D 1 105) The bond that links two amino acids together in a protein chain is called a(n) ________ bond. A) dipeptide B) ionic C) hydrogen D) peptide E) protein Answer: D 1 106) The reaction used to create protein linkages is A) hydrolysis. B) dehydration. C) glyceride. D) exchange. E) catabolism. Answer: B 1 107) Primary protein structure refers to A) the sequence of amino acids in a protein. B) regular three-dimensional structures like spirals or sheets. C) interactions between polypeptide chains and water. D) two or more interacting polypeptides. E) any interaction involving hydrogen bonds. Answer: A 1 108) Quaternary protein structure refers to A) the sequence of amino acids in a protein. B) regular three-dimensional structures like spirals or sheets. C) interactions between polypeptide chains and water. D) two or more interacting polypeptides. E) any interaction involving hydrogen bonds. Answer: D 1 109) High body temperatures deleteriously affect proteins by A) disrupting tertiary and quaternary structures. B) disrupting primary protein structure. C) removing side chains. D) destroying amino acids. E) causing side chains to exchange places. Answer: A 1 Figure 2.4 Use Figure 2.4 to answer the following questions: 110) The substances in this figure are undergoing a reversible pair of chemical reactions. What type of large macromolecule is being depicted? A) starch B) glycogen C) cholesterol D) dipeptide E) nucleic acid Answer: D 1 111) The type of reaction being carried out by the arrow labeled "A" is A) dehydration. B) hydrolysis. C) exchange. D) ionic. E) catabolic. Answer: A 1 112) The type of reaction being carried out by the arrow labeled "B" is A) dehydration. B) hydrolysis. C) exchange. D) ionic. E) catabolic. Answer: B 1 113) The bond labeled "C" is a ________ bond. A) hydrogen B) substrate-enzyme C) dehydration D) peptide E) protein Answer: D 1 114) The reactants in biological chemical reactions are called A) catalysts. B) products. C) enzymes. D) substrates. E) inhibitors. Answer: D 2 115) The location of substrate binding in an enzyme is called the A) active site. B) inhibitor. C) catalyst. D) substrates. E) reactant. Answer: A 2 116) A researcher is studying enzyme activity. Unfortunately, during a power outage, the enzyme overheats. Which statement is NOT likely to be true of the enzyme? A) Its active site is disrupted. B) It has alterations to tertiary structure. C) It has alterations to primary structure. D) It will no longer catalyze the reaction. E) Its secondary structure has been disrupted. Answer: C 2 117) Choose the answer that places the following steps involved in enzymatic catalysis of biological reactions into the logical sequence of events. 1. Enzyme free to repeat process 2. Enzyme-substrate complex forms 3. Chemical reaction 4. Product detachment 5. Substrate binding at the active site 6. Temporary reversible change in enzyme shape A) 5; 2; 6; 3; 4; 1 B) 5; 2; 3; 6; 4; 1 C) 5; 2; 1; 3; 6; 4 D) 1; 3; 5; 2; 6; 4 E) 1; 4; 5; 2; 6; 3 Answer: A 2 118) The most common energy donor(s) in enzymatic reactions is/are A) ATP. B) glucose. C) sucrose. D) catalysts. E) vitamins. Answer: A 119) The structure that consists of one phosphate bonded to an adenosine is called A) ATP. B) ADP. C) AMP. D) creatine. E) the nitrogenous base. Answer: C 120) ATP and related molecules are high-energy because they carry A) high-energy phosphate groups. B) high-energy bonds. C) ionic bonds. D) ribose sugars. E) high-energy nitrogenous bases. Answer: B 121) The individual subunits of a nucleic acid are A) monosaccharides. B) disaccharides. C) fatty acids. D) amino acids. E) nucleotides. Answer: E 122) The primary role of nucleic acids is A) biosynthesis. B) information storage and transfer. C) energy storage. D) metabolism. E) structural. Answer: B 123) Which of the following is NOT a component of a nucleotide? A) ribose B) phosphate C) nitrogenous base D) alcohol group Answer: D 124) The reaction used to create nucleic acid linkages is A) hydrolysis. B) dehydration. C) glyceride. D) exchange. E) catabolism. Answer: B 125) Guanine has the ability to form complementary base pairing with A) guanine. B) thymine. C) uracil. D) cytosine. E) adenine. Answer: D 126) What type of bond forms between complementary nitrogenous bases? A) polar covalent B) nonpolar covalent C) ionic D) hydrogen E) peptide Answer: D 127) Which of the following is an appropriate complementary pair of nucleotides? A) A-T B) A-G C) T-G D) T-C E) A-C Answer: A 128) The backbone of a nucleic acid molecule consists of A) sugars covalently bonded to one another. B) alternating sugars and phosphates covalently bonded together. C) alternating sugars and nitrogenous bases covalently bonded together. D) hydrogen bonded nitrogenous bases. E) hydrogen bonded sugars and phosphates. Answer: B 129) Which of the following is NOT a difference between DNA and RNA? A) Only DNA has a sugar component. B) RNA is single stranded. C) DNA is usually much longer. D) RNA contains U instead of T. E) RNA has direct contact with protein synthesis. Answer: A Figure 2.5 Use Figure 2.5 to answer the following questions: 130) The ribbon-like structure labeled "A" represents A) phosphate groups. B) nitrogenous bases. C) amino acid side chains. D) a sugar-phosphate backbone. E) complementary base pairing. Answer: D 131) The box labeled "B" represents a(n) A) guanine nitrogenous base. B) adenine nitrogenous base. C) guanine amino acid side chain. D) sugar-phosphate backbone. E) ribose sugar. Answer: A 132) The dotted lines labeled "C" represent A) covalent bonds. B) sugar-phosphate backbone. C) complementary hydrogen bonds. D) ionic bonds. E) peptide bonds. Answer: C Essay Questions 1) Atoms contain discrete numbers of protons, neutrons, and electrons. Explain why they do not have discrete atomic mass values. Answer: All elements contain various isotopes, which are different forms of the same atom having the same atomic number, but differing numbers of neutrons in their atomic core. Each isotope has a characteristic mass. Researchers who are aware of how abundant each isotope is are able to determine the average mass value. The mass number reported for each element is that average value. 2) Explain why it is necessary to study chemistry in an anatomy class. Answer: Living organisms are assemblies of chemicals that are arranged into naturally occurring hierarchical orders. Since the human body is composed of chemicals, such as water, electrolytes, and macromolecules, for a complete understanding of the higher level of organization, such as organ systems, you must understand the intricacies of the lower levels, such as atoms. 3) Explain why the visual representation of atoms with electrons in shells is not truly accurate. Answer: Electrons in energy levels are actually known to travel in very complex patterns around the nucleus. It is, however, useful in anatomy and physiology to simplify the representation of electrons in order to make simple predications about bonding patterns. 4) Explain, in terms of chemical energy, how and why consuming more food than is required for daily activity usually results in weight gain. Answer: Living organisms such as humans eat food as fuel sources. That fuel is then used to provide the energy needed for activation of the set of metabolic chemical reactions that occur in the body. Nature has devised the strategy of allowing the organism to store the excess fuel for the future when more fuel is "purchased" through ingestion than is needed at that time. In our evolutionary history this was a valuable survival characteristic, allowing humans and other animals to live on stored energy when food sources where not readily available (drought, winter, etc.). In advanced cultures, with food often readily available at all times, metabolic imbalance and weight gain often occur. 5) Name at least three body systems that are involved in the maintenance of electrolyte balance, explaining what the system's specific contribution is. Answer: The skeletal system is involved in storage of electrolytes, particularly calcium and phosphate, within bone tissue. Limited amounts of electrolytes may be excreted through sweat pores in the integumentary system. We ingest and absorb our electrolytes with our digestive system. Both the nervous and endocrine systems are communication systems that have receptors able to monitor electrolytes, and the ability to send chemical or electrical messages that promote homeostatic response to electrolyte imbalances. Finally, the urinary system contains the kidneys, the major organs responsible for monitoring and maintaining electrolyte levels. 6) Fructose and glucose both share the same molecular formula, C6H12O6. Explain how the body is capable of treating them differently. Answer: Organic compounds contain inherent three-dimensional structure. This means that molecules that appear similar on paper might actually have very different appearances in solution when the orientations of their chemical bonds are apparent. Enzymes do not see atoms; they actually are capable of distinguishing patterns and shapes of charges. 7) Carbohydrates are typically 50 percent by weight of healthy diet, yet represent less than 2 percent of body composition by weight. Explain, with respect to the function of carbohydrates, why this is true. Answer: The major function of carbohydrates is to provide energy to drive anabolic chemical reactions, such as synthesis, in cells. The majority of carbohydrate that is absorbed by the digestive system is sent to catabolic pathways that break the chemical bonds of the monosaccharides and transfer that bond energy to ATP, the most common high-energy compound in the body. ATP is then used to drive anabolic chemical reactions. A limited amount of carbohydrate is used for structural purposes in animals. 8) Compare and contrast DNA and RNA. Answer: Both DNA and RNA consist of polymers of nucleotides, and each building block nucleotide consists of a ribose sugar, a nitrogenous base, and a phosphate group. DNA consists of very long (usually in excess of 45 million base pairs) double-stranded segments. RNA is almost always single-stranded, and typically will have strands varying from 100 to 50,000 bases in length. In RNA molecules the nitrogenous base thymine (T) is replaced with uracil (U). DNA stands for deoxyribonucleic acid, and RNA stands for ribonucleic acid, the names representing that the ribose sugar of DNA is lacking one oxygen. DNA is normally constrained to the nucleus of the cell and functions as a blueprint storage of that organism's genetic material. RNA is produced in the nucleus but then travels into the cytoplasm to direct protein synthesis. In other words, RNA is a copy of the genetic material.