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MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) The simplest chemical units of matter are 1) _______ A) molecules. B) atoms. C) electrons. D) protons. E) neutrons. 2) Which of the following is the largest in size? A) a proton B) an electron C) a neutron D) a molecule E) an atom 2) _______ 3) Isotopes of an element differ in the number of A) electron clouds. B) electrons in the nucleus. C) protons in the nucleus. D) electrons in energy shells. E) neutrons in the nucleus. 3) _______ 4) The atomic number represents the number of A) electrons in an ion. B) protons and neutrons. C) neutrons in an atom. D) protons in an atom. E) neutrons and electrons. 4) _______ 5) All atoms with the same atomic number are grouped into A) compounds. B) elements. C) cells. D) isotopes. E) molecules. 5) _______ 6) The mass number of an atom indicates the number of A) protons and neutrons in the nucleus. B) protons in the nucleus. C) electrons in the outer shells. D) protons and electrons in an atom. E) neutrons in the nucleus. 6) _______ 7) Radioisotopes have unstable A) electron clouds. B) isotopes. C) nuclei. D) ions. E) protons. 7) _______ 8) The chemical behavior of an atom is determined by A) the number of neutrons. B) the mass of the atom. C) the size of the atom. D) the number of protons. E) the number and arrangement of electrons. 8) _______ 9) Ions with a positive charge are called A) isotopes. B) cations. C) anions. D) polyatomic ions. E) radicals. 9) _______ 10) In living cells, the weakest bond between two or more atoms is the ________ bond. A) nonpolar B) covalent C) hydrogen D) ionic E) polar 10) ______ 11) Ionic bonds are formed when A) electrons are completely transferred from one atom to another. B) two or more atoms lose electrons at the same time. C) a pair of electrons is shared unequally by two atoms. D) hydrogen forms bonds with negatively charged atoms in the same or different molecule. E) atoms share electrons. 11) ______ 12) In a molecule of nitrogen, three pairs of electrons are shared by two nitrogen atoms. The type of bond that is formed would be an example of a(n) A) double covalent bond. B) triple covalent bond. C) single covalent bond. D) hydrogen bond. E) polar covalent bond. 12) ______ 13) If a pair of electrons is unequally shared between two atoms, a(n) ________ occurs. A) double covalent bond B) hydrogen bond C) triple covalent bond D) single covalent bond E) polar covalent bond 13) ______ 14) Elements that have atoms with full outer shells of electrons A) will form many compounds. B) will normally form anions. C) are inert. D) frequently form hydrogen bonds. 14) ______ E) will normally form cations. 15) Which one of the following statements is not correct about the reaction H2 + Cl2 → 2 HCl? A) B) C) D) E) 15) ______ One molecule of hydrogen contains 2 atoms. Two molecules of HCl are formed in the reaction. HCl is the product. This reaction is an example of a decomposition reaction. H2 and Cl2 are the reactants. 16) AB → A + B is to decomposition as A + B → AB is to A) metabolism. B) synthesis. C) exchange. D) combustion. E) replacement. 16) ______ 17) The reaction N2 + 3 H2 → 2 NH3 is an example of a(n) 17) ______ A) B) C) D) E) decomposition reaction. exchange reaction. synthesis reaction. metabolic reaction. enzyme reaction. 18) The reaction A + B → AB + energy is an example of a(n) A) endergonic reaction. B) exergonic reaction. C) equilibrium reaction. D) exchange reaction. E) decomposition reaction. 18) ______ 19) Chemical reactions that require an input of energy, such as heat, are said to be A) exergonic. B) endergonic. C) at equilibrium. D) activated. E) neutral. 19) ______ 20) All of the following are true concerning enzymes, except that they A) function as biological catalysts. B) lower the activation energy required for a reaction. C) become a part of the reaction's product. D) are proteins. E) affect only the rate of a chemical reaction. 20) ______ 21) Substrate molecules bind to enzymes at the ________ sites. A) active B) carboxyl group C) reactant D) amino group E) neutral zone 21) ______ 22) All of the compounds that can be synthesized or broken down by chemical reactions inside the body are called A) nutrients. B) enzymes. C) metabolites. D) organic compounds. E) inorganic compounds. 22) ______ 23) Each of the following is an example of an inorganic compound, except A) acids. B) bases. C) glucose. D) salts. E) water. 23) ______ 24) Which of the following statements about water is not correct? A) contains hydrogen bonds B) is composed of polar molecules C) has a relatively low heat capacity D) can be considered a "universal solvent" E) is responsible for about 2/3 of the mass of the human body 24) ______ 25) During ionization, water molecules disrupt the ionic bonds of a solute and a mixture of ions is produced. These ions are called A) anti-ions. B) dissociates. C) electrolytes. D) anions. E) cations. 25) ______ 26) Oppositely charged ions in solution are prevented from combining by A) the high heat capacity of water. B) radicals. C) hydration spheres. D) hydrogen bonding. E) water's nonpolar nature. 26) ______ 27) A solution containing equal numbers of hydrogen ions and hydroxide ions is A) ionated. B) acidic. C) basic. D) neutral. E) alkaline. 27) ______ 28) Which of the following substances would be least acidic? A) white wine, pH = 3 B) tomato juice, pH = 4 C) urine, pH = 6 D) stomach secretions, pH = 1 E) lemon juice, pH = 2 28) ______ 29) If a substance has a pH that is greater than 7, it is A) alkaline. B) acidic. C) a salt. D) a buffer. E) neutral. 29) ______ 30) An important buffer in body fluids is A) H2O. 30) ______ B) NaOH. C) NaHCO3. D) NaCl. E) HCl. 31) In the body, inorganic compounds A) can make up proteins. B) are important nutrients. C) are structural components of cells. D) can serve as buffers. E) both A and D 31) ______ 32) Inorganic compounds that are soluble and whose ions will conduct an electrical current are called A) covalent bonds. B) polar covalent molecules. C) hydrophobic. D) hydration spheres. E) electrolytes. 32) ______ 33) Carbohydrate molecules A) contain the genetic information found in cells. B) are the body's most readily available source of energy. C) form the regulatory molecules known as enzymes. D) are composed of C, H, O, and N atoms. E) are integral molecules of the cell membrane. 33) ______ 34) The most important metabolic fuel molecule in the body is A) sucrose. B) glucose. C) protein. D) vitamins. E) starch. 34) ______ 35) Molecules that have the same molecular formula but different structural formulas are called A) isotopes. B) isomers. C) isozymes. D) isomonomers. E) isotypes. 35) ______ 36) A polysaccharide that is formed in liver and muscle cells to store glucose is A) cellulose. B) glycogen. C) sucrose. D) fructose. E) starch. 36) ______ 37) The group of organic compounds containing carbon, hydrogen, and oxygen in a near 1:2:1 ratio is defined as a A) nucleic acid. B) lipid. C) protein. D) carbohydrate. E) both C and D 37) ______ 38) Lipids A) form essential structural components of cells. B) help to maintain body temperature. C) provide roughly twice the energy as carbohydrates. D) all of the above E) B and C only 38) ______ 39) A fatty acid that contains three double covalent bonds in its carbon chain is said to be A) monounsaturated. B) saturated. C) carboxylated. D) polyunsaturated. E) hydrogenated. 39) ______ 40) Most of the fat found in the human body is in the form of A) phospholipids. B) triglycerides. C) steroids. D) monoglycerides. E) prostaglandins. 40) ______ 41) A type of lipid that is produced by nearly every tissue in the body and that acts as a local regulator of metabolism are the A) phospholipids. B) prostaglandins. C) glycolipids. D) steroids. E) monoglycerides. 41) ______ 42) Cholesterol, phospholipids, and glycolipids are examples of A) prostaglandins. B) structural lipids. C) dietary fats. D) lipid drugs. E) steroids. 42) ______ 43) You would expect a peptide bond to link A) a cholesterol molecule and a fatty acid molecule. B) two amino acids. C) two simple sugars. D) a fatty acid and a glycerol molecule. E) two nucleotides. 43) ______ 44) Each amino acid differs from another in the A) number of peptide bonds in the molecule. B) size of the amino group. C) number of central carbon atoms. D) number of carboxyl groups. E) nature of the R group. 44) ______ 45) In proteins the alpha-helix and pleated sheet are examples of a ________ structure of a protein. A) quaternary B) secondary C) primary D) tertiary E) pentanary 45) ______ 46) Proteins have very complex shapes. Interactions between globular or fibrous polypeptide chains result in which type of structure? A) quaternary B) secondary C) primary D) pentagonal E) tertiary 46) ______ 47) Glycoproteins and proteoglycans are combinations of proteins and A) carbohydrates. B) fatty acids. C) nucleic acids. D) lipids. E) none of the above 47) ______ 48) Molecules that store and process genetic information are the A) carbohydrates. B) steroids. C) proteins. D) nucleic acids. E) lipids. 48) ______ 49) Nucleic acids are composed of units called A) pyrimidines. B) fatty acids. C) amino acids. D) purines. E) nucleotides. 49) ______ 50) A nucleotide consists of A) a five-carbon sugar and a nitrogenous base. B) a five-carbon sugar, a nitrogenous base, and a phosphate group. C) a phosphate group and a nitrogenous base. D) a five-carbon sugar and an amino acid. E) a five-carbon sugar and phosphate group. 50) ______ 51) According to the rules of complementary base pairing, a nucleotide containing the base cytosine would pair with a nucleotide containing the base A) uracil. B) adenine. C) guanine. D) thymine. E) cytosine. 51) ______ 52) The most important high-energy compound in cells is A) adenosine triphosphate. B) ribonucleic acid. C) adenosine monophosphate. D) deoxyribonucleic acid. E) adenosine diphosphate. 52) ______ 53) The bond between sodium and chloride in the compound sodium chloride (NaCl) is A) an ionic bond. B) a nonpolar covalent bond. C) a double ionic bond. D) a double covalent bond. E) a single covalent bond. 53) ______ 54) When atoms complete their outer electron shell by sharing electrons, they form A) hydrogen bonds. B) ionic bonds. C) cations. D) covalent bonds. E) anions. 54) ______ 55) Hydrophilic molecules readily associate with A) water molecules. B) lipid molecules. C) hydrophilic molecules. D) A and B E) all of the above 55) ______ 56) Carbohydrates, lipids, and proteins are classified as A) acids. B) bases. C) organic molecules. D) salts. E) inorganic molecules. 56) ______ 57) If an isotope of oxygen has 8 protons, 10 neutrons, and 8 electrons, its mass number is A) 16. B) 26. C) 8. D) 12. E) 18. 57) ______ 58) Of the following choices, the pH of the least acidic solution is A) 1.0. B) 6.0. C) 4.5. D) 7.0. 58) ______ E) 2.3. 59) Of the following items, which has the greatest mass on Earth? A) football B) baseball C) soccer ball D) bowling ball E) basketball 59) ______ 60) Electrons have a ________ charge; protons have a ________ charge; and neutrons have a ________ charge. A) positive; negative; negative B) negative; neutral; positive C) negative; positive; neutral D) negative; positive; positive E) negative; neutral; neutral 60) ______ 61) Identify cations from the following: A) Na+ B) ClC) K+ D) A and B E) A and C 61) ______ 62) An anion would best be represented by which of the following? A) K+ B) Na+ C) Cl- 62) ______ D) A and B E) A and C 63) A needle floating on the surface of a glass of water best illustrates A) anion action. B) surface tension. C) cation action. D) chemical tension. E) subatomic particles. 63) ______ 64) An example of an organic substance is A) sodium. B) oxygen. C) nitric oxide (NO). D) table sugar. E) table salt. 64) ______ 65) An example of an inorganic substance is 65) ______ A) B) C) D) E) fructose. glycogen. cholesterol. lipid. water. 66) In hydrolysis reactions, compounds react with A) carbon causing decomposition. B) water causing synthesis. C) glucose causing decomposition. D) water causing decomposition. E) hydrogen causing decomposition. 66) ______ 67) In dehydration reactions, compounds A) convert water molecules to hydrogen and oxygen. B) convert hydrogen and oxygen to water. C) lose water molecules. D) gain water molecules. E) gain electrons. 67) ______ 68) The body is approximately two-thirds water. Which property applied to changing water temperatures keeps the body temperature stabilized? A) lubrication B) reactivity C) thermal inertia D) surface tension E) kinetic energy 68) ______ 69) If a molecule has two equal and opposite electrically charged poles separated by a short distance, it is said to be A) colloid. B) hydrophilic. C) hydrophobic. D) tripolar. E) dipolar. 69) ______ 70) In an aqueous solution, cations move toward A) sodium. B) hydrogen ions. C) water. D) anions. E) potassium. 70) ______ 71) In an aqueous solution, sodium would move toward A) sodium. B) potassium. C) water. D) chloride. E) A and B 71) ______ 72) The chemical symbol indicating concentration is represented as A) (). B) [ ]. C) {}. D) <>. E) ||. 72) ______ 73) Which has the greater concentration of hydrogen ions, a substance with a pH of 5 or a substance with a pH of 4? A) A pH of 4 is greater. B) A pH of 5 is greater. C) They are both equal; 4 and 5 are relative values. D) A and B E) none of the above 73) ______ 74) Of the list below, which has the greatest concentration of hydroxide ions? A) one with a pH of 10 B) one with a pH of 7 C) one with a pH of 2 D) one with a pH of 13 E) one with a pH of 1 74) ______ 75) Which pH is closest to neutral pH? A) pH 6 B) pH 5 C) pH 4 75) ______ D) pH 3 E) pH 2 76) A functional group is best described as groupings of A) elements that occur in a salt. B) amino acids in a protein. C) atoms that occur in low pH. D) elements that occur in high pH. E) atoms that occur repeatedly, such as carboxyl groups and amino groups. 76) ______ 77) A side chain is a group of A) amino acids in a protein. B) atoms attached to an atom in a principal chain or ring in an amino acid. C) elements in a protein. D) proteins in an amino acid. E) compounds in an amino acid. 77) ______ 78) A side chain is often represented by the letter(s) ________ within a structural formula. A) R B) DNA C) RNA D) C E) S 78) ______ 79) The term ________ means each enzyme catalyzes only one type of reaction. A) micelle B) inertia C) peptide D) specificity E) saturation 79) ______ 80) The maximum rate of reaction is termed A) synthesis. B) saturation limit. C) dehydration. D) hydrolysis. E) reversible. 80) ______ 81) The average time between synthesis and recycling is known as A) metabolism. B) turnover rate. C) specificity. D) catabolism. E) anabolism. 81) ______ 82) Continuous removal and replacement of cells in a biological system is termed A) anabolic turnover. B) metabolic turnover. C) catabolic turnover. D) metabolism. E) A and C 82) ______ 83) Identify the product formed from the phosphorylation of ADP. A) deoxyribonucleic acid B) adenosine triphosphate C) adenosine diphosphate D) adenine E) ribose 83) ______ 84) ADP + P →. A) ATP B) 2ADP C) adenine D) ADP E) DNA 84) ______ 85) The phosphorylation of AMP forms A) 2ATP. B) ribose. C) ATP. D) 2AMP. E) ADP. 85) ______ 86) Adenine and guanine are A) purines represented by T and C. B) pyrimidines represented by A and G. C) pyrimidines represented by T and C. D) carbohydrates represented by A and G. E) purines represented by A and G. 86) ______ 87) Dissolved gases are required in biological systems for A) storage of energy. 87) ______ B) C) D) E) serving as structural components of bone. serving as catalysts. chemical messengers. cellular metabolism. 88) Human red blood cells are removed and replaced every 120 days. This is an example of A) surface tension. B) metabolic turnover. C) thermal inertia. D) functional groups. E) specificity. 88) ______ 89) What element is the most plentiful in the human body? A) carbon B) sulfur C) oxygen D) sodium E) potassium 89) ______ 90) What element is the second most abundant in the human body? A) nitrogen B) carbon C) hydrogen D) oxygen E) calcium 90) ______ 91) From the following group, indicate one containing all trace elements. A) sulfur, chlorine, oxygen B) silicon, fluorine, tin C) boron, oxygen, carbon D) cobalt, calcium, sodium E) selenium, hydrogen, calcium 91) ______ 92) The molecule NO is known as A) noxious oxygen. B) nitrate oxide. C) nitric oxygen. D) noxious oxide. E) nitric oxide. 92) ______ 93) The molecule CO2 is known as 93) ______ A) B) C) D) E) carbon oxide. carbon dioxide. carbonated oxygen. carbonized oxygen. carbon monoxide. 94) The molecule H2 is known as A) hydro. B) helium. C) hydrogen. 94) ______ D) hydroxide. E) helios. 95) The molecule O2 is known as A) B) C) D) E) 95) ______ oxide. organic. oxygen. B and C none of the above 96) The basic units of matter include ________ or ________. A) neutrons; electrons B) cells; tissues C) protons; neutrons D) atoms; elements E) protons; electrons 96) ______ 97) H2O is an example of a(n) A) sodium molecule. B) glucose molecule. C) covalent formula. D) ionic formula. E) molecular formula. 97) ______ 98) A(n) ________ accepts hydroxide ions in water and a(n) ________ releases hydrogen ions in water. A) base; acid B) acid; base C) molecule; acid D) compound; element E) element; compound 98) ______ 99) A nanometer is A) 10-12 meter. 99) ______ B) 10-6 meter. C) 10-8 meter. D) 10-9 meter. E) 10-10 meter. 100) An excess of hydrogen ions in the body fluids can have disastrous results because A) excess hydrogen ions can change the shape of large complex molecules, rendering them nonfunctional. B) excess hydrogen ions can disrupt tissue functions. C) excess hydrogen ions can break chemical bonds. D) all of the above E) A and B only 100) _____ 101) Artificial sweeteners A) are inorganic sugar substitutes. B) produce the same number of calories as the equivalent amount of 101) _____ sucrose. C) are generally 100 or more times sweeter than sucrose. D) are always some form of carbohydrate. E) are naturally similar to sugars. 102) Alaska Natives have a lower incidence of heart disease even though their diets are high in fat and cholesterol. This may be due to the large amount of ________ in their diets. A) steroids B) omega-3 fatty acids C) triglycerides D) prostaglandins E) oleic acid 102) _____ 103) If an element is composed of atoms with an atomic number of 6 and a mass number of 14, then a neutral atom of this element contains A) 6 neutrons. B) 14 protons. C) 8 electrons. D) 6 protons. E) 14 electrons. 103) _____ 104) One mole of any element A) has the same mass. B) has the same number of atoms. C) has the same number of electrons. D) has the same weight. E) all of the above 104) _____ 105) When electrons are transferred from one atom to another, and the two atoms unite as a result of the electrostatic attraction, A) an ion is formed. B) an ionic bond is formed. C) a hydrogen bond is formed. D) a covalent bond is formed. E) a molecule is formed. 105) _____ 106) Calcium atoms have two electrons in the outermost shell. As a result, you would expect calcium to form ions with a charge of A) -2. B) -1. C) 0. D) +2. E) +1. 106) _____ 107) Magnesium atoms have two electrons in the outermost shell and chlorine atoms have seven. The compound magnesium chloride would contain A) 1 magnesium and 2 chlorine. B) 2 magnesium and 7 chlorine. C) 2 magnesium and 1 chlorine. D) 1 magnesium and 1 chlorine. E) impossible to tell without more information 107) _____ 108) Each of the following statements concerning hydrogen bonds is true, except one. Identify the exception. 108) _____ A) Hydrogen bonds can occur within a single molecule. B) Hydrogen bonds can form between neighboring molecules. C) Hydrogen bonds are important forces for holding large molecules together. D) Hydrogen bonds are responsible for many of the unique properties of water. E) Hydrogen bonds are strong attractive forces between hydrogen atoms and negatively charged atoms. 109) In the reaction listed below, what coefficient needs to be added to balance the equation? 6 CO2 + 6 H2O → C6H12O6 + ________ O2 A) 6 B) 10 C) 2 D) 4 109) _____ E) 8 110) Nonpolar organic molecules are good examples of A) hydrophobic compounds. B) molecules that will dissociate when placed into water. C) electrolytes. D) solutes. E) hydrophilic compounds. 110) _____ 111) An inorganic compound, when placed in water, dissociates 99 percent forming hydrogen ions and anions. This substance would be A) a strong base. B) a strong acid. C) a salt. D) a weak base. E) a weak acid. 111) _____ 112) When a small amount of hydrochloric acid is added to a solution of Na2HPO4, the pH of the solution does not change. The pH does not 112) _____ change when a small amount of NaOH is added either. Based on these observations, all of the following are true concerning the compound Na2HPO4, except A) Na2HPO4 is able to accept extra hydrogen ions from the HCl. B) Na2HPO4 acts as a buffer. C) Na2HPO4 is able to donate hydrogen ions to the OH- from NaOH. D) Na2HPO4 is a salt formed from reacting a strong base with a weak acid. E) Na2HPO4 adsorbs excess H+ and OH- directly onto the surface of its crystalline structure. 113) Fructose A) is a hexose. B) is an isomer of glucose. C) is found in male reproductive fluids. D) all of the above E) A and B only 113) _____ 114) When two monosaccharides undergo a dehydration synthesis, A) hydrolysis occurs. B) a starch is formed. 114) _____ C) a disaccharide is formed. D) a new monosaccharide is formed. E) a polysaccharide is formed. 115) A shortage of cholesterol in the body would interfere with the formation of A) glycogen. B) sex hormones. C) proteins. D) nucleic acids. E) both A and C 115) _____ 116) How would the lack of a cofactor for an enzyme affect that enzyme's function? A) The enzyme would function more quickly. B) The enzyme's function would not be altered. C) The enzyme would not be able to function. D) The enzyme would cease to function after reaching a maximum rate. E) The enzyme would function more slowly. 116) _____ 117) The nucleic acid RNA A) contains the cell's genetic information. B) is double stranded. C) contains the pyrimidine uracil in place of thymine. D) contains the pentose deoxyribose. E) is restricted to the nucleus. 117) _____ 118) You would expect to find proteoglycan molecules A) acting as receptors on the surface of cell membranes. B) in the secretions coating the respiratory tract. C) functioning as hormones from the pancreas. D) acting as antibodies to viruses. E) functioning as enzymes in the stomach. 118) _____ SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question. 119) A(n) ________ is a substance that consists entirely of atoms with 119) ____________ the same atomic number. 120) The center of an atom is called the ________. 120) ____________ 121) Electrons whirl around the center of the atom at high speed forming a(n) ________. 121) ____________ 122) Electrons in an atom occupy an orderly series of electron shells or ________. 122) ____________ 123) A(n) ________ is a combination of two or more atoms and has different physical and chemical properties than its individual atoms. 123) ____________ 124) Ions with a positive charge are called ________. 124) ____________ 125) Ions with a negative charge are called ________. 125) ____________ 126) In a(n) ________ chemical bonds between atoms are broken as atoms are rearranged in new combinations to form different chemical substances. 126) ____________ 127) Chemical reactions that release energy are called ________. 127) ____________ 128) Chemical reactions that require energy are called ________. 128) ____________ 129) ________ control the rate of chemical reactions that occur in the human body. 129) ____________ 130) In living cells, complex reactions proceed in a series of interlocking steps called a(n) ________. 130) ____________ 131) ________ molecules are compounds that contain carbon as the primary structural atom. 131) ____________ 132) ________ compounds do not contain carbon as the primary structural atom. 132) ____________ 133) A(n) ________ is a homogeneous mixture containing a solvent and a solute. 133) ____________ 134) ________ are soluble inorganic compounds whose ions will conduct an electric current in solutions. 134) ____________ 135) Molecules that readily dissolve in water are called ________. 135) ____________ 136) Molecules that do not dissolve in water are called ________. 136) ____________ 137) The ________ of a solution is the negative logarithm of the hydrogen ion concentration expressed in moles per liter in the solution. 137) ____________ 138) ________ are compounds that in solution maintain pH within given limits. 138) ____________ 139) All fatty acids contain an arrangement of atoms called the ________ at one end of the chain. 139) ____________ 140) In water, large numbers of fatty acids tend to form droplets called ________. 140) ____________ 141) ________ are lipid molecules that form biological membranes. 141) ____________ 142) The molecule DNA contains a five-carbon sugar called ________. 142) ____________ 143) The molecule RNA contains a five-carbon sugar called ________. 143) ____________ 144) The purines found in DNA are ________ and ________. 144) ____________ 145) The pyrimidine bases found in DNA are ________ and ________. 145) ____________ 146) A(n) ________ is a covalent bond that stores an unusually large amount of energy. 146) ____________ 147) In the process of ________ a phosphate group is attached to a molecule. 147) ____________ 148) The hydrolysis of ATP yields the molecule ________. 148) ____________ 149) The ________ of a radioactive substance is the time required for a 50 percent reduction in the rate of radiation emission. 149) ____________ 150) Identify the three components of a nucleotide. 150) ____________ 151) Explain the role of water molecules in polysaccharide formation. 151) ____________ 152) What role do buffer systems play in the human body? 152) ____________ ESSAY. Write your answer in the space provided or on a separate sheet of paper. 153) Why is it life-threatening to have a high fever? 154) How does the DNA molecule control the appearance and function of a cell? 155) The element sulfur has an atomic number of 16 and an atomic weight of 32. How many neutrons are in the nucleus of a sulfur atom? If sulfur forms covalent bonds with hydrogen, how many hydrogen atoms can bond to one sulfur atom? 1) 2) 3) 4) 5) 6) 7) 8) 9) 10) 11) 12) 13) 14) 15) 16) 17) 18) 19) 20) 21) 22) 23) 24) 25) 26) 27) 28) 29) 30) 31) 32) 33) 34) 35) 36) 37) 38) 39) 40) 41) 42) 43) 44) 45) 46) 47) 48) 49) 50) 51) B D E D B A C E B C A B E C D B C B B C A C C C C C D C A C D E B B B B D E D B B B B E B A A D E B C 52) 53) 54) 55) 56) 57) 58) 59) 60) 61) 62) 63) 64) 65) 66) 67) 68) 69) 70) 71) 72) 73) 74) 75) 76) 77) 78) 79) 80) 81) 82) 83) 84) 85) 86) 87) 88) 89) 90) 91) 92) 93) 94) 95) 96) 97) 98) 99) 100) 101) 102) 103) A A D A C E B D C E C B D E D C C E D D B A D A E B A D B B B B A E E E B C B B E B C C D E A D D C B D 104) 105) 106) 107) 108) 109) 110) 111) 112) 113) 114) 115) 116) 117) 118) 119) 120) 121) 122) 123) 124) 125) 126) 127) 128) 129) 130) 131) 132) 133) 134) 135) 136) 137) 138) 139) 140) 141) 142) 143) 144) 145) 146) 147) 148) 149) 150) 151) 152) B B D A E A A B E E C B C C B element nucleus electron cloud energy levels compound cations anions chemical reaction exergonic endergonic Enzymes pathway Organic Inorganic solution Electrolytes hydrophilic hydrophobic pH Buffers carboxylic acid group micelles Structural lipids (or phospholipids) deoxyribose ribose adenine; guanine thymine; cytosine high-energy bond phosphorylation ADP half-life pentose; phosphate group; nitrogenous base Water molecules are released in the dehydration synthesis of polysaccharides. Buffer systems maintain pH within normal limits by removing or replacing hydrogen ions as needed. 153) A high body temperature can be life-threatening because the heat can cause certain proteins, such as vital enzymes, to become denatured. When this occurs, the proteins beco me nonfunctional and if they catalyze reactions that are necessary for life, life will cease. 154) The DNA molecule controls the manufacture of enzymes and structural proteins. By controlling the manufacture of structural proteins, the DNA is able to influence the physical appearance of a cell. By controlling the production of enzymes, the DNA is able to control all aspects of cellular metabolism and thus control the activity and biological functions of the cell. 155) The number of neutrons in an atom is equal to the atomic weight minus the atomic number. Thus, sulfur has 32 - 16 = 16 neutrons. The atomic number indicates the number of protons, so a neutral sulfur atom contains 16 protons plus 16 electrons to balance the protons electrically. The electrons would be distributed as follows: 2 in the first level, 8 in the second level, and the remaining 6 in the third level. To achieve a full 8 electrons in the third (outermost) level, the sulfur atom can accept 2 electrons in an ionic bond or can share 2 electrons in a covalent bond. Because hydrogen atoms can share one electron in a covalent bond, the sulfur atom can form two covalent bonds with hydrogen, one with each of two hydrogen atoms.