Exam 1: Practice Questions

a

A carbon atom has 6 electrons however, its valency is 4. This is because the carbon atom ________. a) has only 2 electrons in its first shell and 4 in the second shell b) donates its 2 electrons to another atom c) shares its 2 electrons and bonds with another atom d) has 4 electrons in its first shell and 2 in the second shell

b

About 25 of the 92 natural elements are known to be essential to life. Which 4 of these 25 elements make up approximately 96% of living matter? a) carbon, oxygen, phosphorus, hydrogen b) carbon, hydrogen, nitrogen, oxygen c) carbon, sodium, hydrogen, nitrogen d) oxygen, hydrogen, calcium, nitrogen

c

Based on both graphs, what condition(s) are most deadly for both colors of mice? a) dark-colored soil b) no moonlight c) high contrast between the mouse and its background d) full moonlight

c

Chemists assign atoms to chemical elements by counting their ________. a) neutrons b) isotopes d) protons e) electrons

a

In this molecule, what type of bond is found between the oxygen and hydrogens? a) polar covalent b) hydrophilic c) nonpolar covalent d) ionic e) hydrophobic

a

The brackets are indicating a(n) _____ bond. a) hydrogen b) single (nonpolar) covalent c) ionic d) polar covalent e) hydrophobic

b

A carbon atom is most likely to form what kind of bond(s) with other atoms? a) ionic bonds, covalent bonds, and hydrogen bonds b) covalent c) ionic d) hydrogen

a

A food company hydrogenated a barrel of fat. The treatment ... a) made the fat less fluid. b) made the fat less saturated. c) lengthened the fat tails. d) put more bends (kinks) in the fat tails. e) Both (a) and (d).

c

A neutral atom has two, eight, eight electrons in its first, second, and third energy levels. This information ________. a) does not tell us about the size of the element b) does not tell us about the chemical properties of the element c) does not tell us about the atomic mass of the element d) does not tell us about the atomic number of the element

c

A nucleotide is composed of a(n) _____. a) glycerol, a nitrogen-containing base, and a five-carbon sugar b) phosphate group, a nitrogen-containing base, and a hydrocarbon c) phosphate group, a nitrogen-containing base, and a five-carbon sugar d) sulfhydryl group, a nitrogen-containing base, and a five-carbon sugar e) amino group, a nitrogen-containing base, and a five-carbon sugar

c

A phrase that applies to covalent bonding and not other kinds of bonds is ... a) paired electrons. b) charge attraction. c) electron-sharing. d) great strength. e) All of the above.

e

A(n) _____ bond joins these two oxygen atoms. a) quadruple covalent b) single covalent c) ionic d) hydrogen e) double covalent

a

A(n) _____ refers to two or more atoms held together by covalent bonds. a) molecule b) shell c) ion d) community e) isotope

d

An atom has 6 electrons, 6 protons, and 6 neutrons. You can tell that this atom belongs to the element _____ because _____________________. a) N; it has 6 protons. b) N; it has 6 electrons. c) O; its mass number is 12. d) C; it has 6 protons. e) C; it has 6 electrons.

d

An atom has 8 protons, 8 neutrons, and 8 electrons. Another isotope of the same element might have ... a) 7 electrons. b) mass number 16, atomic number 7. c) 9 protons. d) 10 neutrons. e) All of the above.

b

An ion with six protons, seven neutrons, and a charge of 2+ has an atomic number of ________. a) five b) six c) seven d) four

b

Carbon-14 dating works for fossils up to about 75,000 years old. Most dinosaurs went extinct 65.5 million years ago. Can 14C be used to date dinosaur bones? a) Yes, the bones continued to take in 14C, even after the dinosaur died. b) No, the 14C present in the dinosaur when it died would decay too much to be measured after 65.5 million years. c) No, 14C can only be used to date dinosaur teeth, which are much stronger than bones. d) Yes, the bones contained 14C when the dinosaur died so it can be measured to determine the fossil's age.

b

Chemical equilibrium is reached when _____. a) all of the reactants are converted to products b) the forward and reverse reactions occur at the same rate so that the concentrations of reactants and products remain the same c) the reverse reaction begins to occur the rate at which matter is destroyed and d) the rate at which it is created offset each other e) matter is conserved

b

Dissolving is best described as ... a) a separation of molecules into neutral atoms. b) a mingling of molecules and/or ions. c) breaking covalent bonds. d) a change from a solid to a liquid. e) molecules breaking into ions.

e

Dr. Jones says an atom has 3 electrons in the first shell and four electrons in the second shell. Someone should tell Dr. Jones that ... a) the first shell must fill before the second shell can have electrons. b) the second shell should have 8 electrons. c) the second shell can't have 4 electrons. d) no shell can hold more than 2 electrons. e) the first shell shouldn't have 3 electrons.

c

Elements found on the left side of the periodic table contain outer shells that are _____; these elements tend to form _____ in solution. a) almost full; cations b) almost full; anions c) almost empty; cations d) almost empty; anions

a

For lipids to be fluid at room temperature, they should have ________. a) a higher number of cis double bonds b) a longer carbon chain c) a higher number of glycerol molecules d) single bonds only

c

Glycogen is _____. a) a transport protein that carries oxygen b) a source of saturated fat c) a polysaccharide found in animals d) the form in which plants store sugars e) a polysaccharide found in plant cell walls

c

How does 0.5 M sucrose (molecular mass 342) solution compare to 0.5 M glucose (molecular mass 180) solution? a) Sucrose has 171 mg/L, whereas glucose has 90 mg/L. b) Sucrose has 171 molecules, whereas glucose has 90. c) Both have 3.01 × 1023 molecules. d) Both have 6.02 × 1023 molecules.

c

How does a scientific theory differ from a scientific hypothesis? a) Hypotheses are usually an explanation for a more general phenomenon; theories typically address more specific issues. b) Confirmed theories become scientific laws; hypotheses become theories c) Theories are usually an explanation for a more general phenomenon; hypotheses typically address more specific issues. d) Theories are proposed to test scientific hypotheses.

b

How does the pH of the solution on the right compare with that of the solution on the left? a) Both of these solutions are equally acidic. b) the solution on the right is basic relative to the solution on the left. c) Both of these solutions are equally basic. d) The solution on the right is neutral relative to the solution on the left. e) The solution on the right is acidic relative to the solution on the left.

c

How many atoms in the pictured molecule can form hydrogen bonds with water molecules? a) 7 b) 2 c) 5 d) 8 e) 3

a

How many dark brown mice were caught in the dark-colored soil enclosure on a moonlit night? a) 12 b) 20 c) 28 d) 37

a

How many electrons are involved in a triple covalent bond? a) 6 b) 3 c) 9 d) 12

a

How many grams of the compound in the figure are required to make 1 liter of a 0.5 M solution? (Note: The atomic masses, in daltons, are approximately 12 for carbon, 1 for hydrogen, and 16 for oxygen.) a) 30 b) 120 c) 60 d) 90

d

How many light brown mice were caught in the dark-colored soil enclosure on a moonlit night? a) 12 b) 18 c) 26 d) 28

c

How much of 0.5 M glucose (molecular mass 180) is needed to provide 100 mg of glucose? a) 10 mL b) 0.11 mL c) 1.11 mL d) 100 mL

b

Hydrogen bonds ... a) are covalent bonds. b) can form between H and N. c) share electrons between the two bonded atoms. d) occur within a water molecule. e) All of the above.

e

Identify the level(s) of protein structure present in this molecule. a) primary b) secondary c) tertiary d) quaternary e) all of the above

d

If a DNA double helix is 100 nucleotide pairs long and contains 25 adenine bases, how many guanine bases does it contain? a) 50 b) 25 c) 150 d) 75 e) 200

e

If a strand of DNA has the nitrogen base sequence 5'-ATTTGC-3', what will be the sequence of the matching strand? a) 3'-ATTTGC-5' b) 3'-UAAACG-5' c) 3'-TUUUCG-5' d) 3'-GCAAAT-5' e) 3'-TAAACG-5'

c

In a neutral solution the concentration of _____. a) hydrogen ions is less than the concentration of hydroxide ions b) hydrogen ions is greater than the concentration of hydroxide ions c) hydrogen ions is equal to the concentration of hydroxide ions d) water molecules is less than the concentration of hydroxide ions e) water molecules is less than the concentration of hydrogen ions

c

In fat synthesis,________and fatty acids combine to make fats plus________. a) esters; water b) glucose; phosphate c) glycerol; water d) esters; phosphate e) phosphate; glycerol

c

In the molecule below, how many atoms could make hydrogen bonds with water? a) 5 b) 7 c) 10 d) 12

b

In the reaction that builds a fat,________ groups react with ________ groups. a) sulfhydryl; carboxyl b) hydroxyl; carboxyl c) hydroxyl; phosphate d) phosphate; amino e) carboxyl; amino

a

Is a dark brown mouse on dark-colored soil more likely to escape predation under a full moon or with no moon? What data support your answer? a) Under a full moon; the owl caught more dark mice when there was no moon (about 20) than when there was a full moon (about 12). b) Under no moon; the owl caught more dark mice when there was no moon (about 20) than when there was a full moon (about 12). c) Under no moon; the owl caught more light mice when there was a full moon (about 17) than when there was no moon (about 11). d) Under a full moon; the owl caught more dark mice when there was no moon (about 37) than when there was a full moon (about 19).

d

Is a light brown mouse on light-colored soil more likely to escape predation under a full moon or with no moon? What data support your answer? a) Under a full moon; the owl caught more dark mice when there was no moon (about 37) than when there was a full moon (about 19). b) Under no moon; the owl caught more light mice when there was a full moon (about 28) than when there was no moon (about 26). c) Under a full moon; the owl caught more dark mice when there was no moon (about 20) than when there was a full moon (about 12). d) Under no moon; the owl caught more light mice when there was a full moon (about 18) than when there was no moon (about 11).

c

Liquid water ________. a) is nonpolar b) has a specific heat lower than that of most other substances c) has a heat of vaporization higher than that of most other substances d) is less dense than ice

b

Low humidity in the atmosphere on a hot day ________. a) does not help in cooling because water evaporates from the skin faster b) helps in cooling because water evaporates from the skin faster c) helps in cooling because skin absorbs water from the atmosphere d) does not help in cooling because skin absorbs water from the atmosphere

a

Many of water's emergent properties, such as its cohesion, its high specific heat, and its high heat of vaporization, result from the fact that water molecules _____. See Concept 3.2 (Page 45) a) are attracted to each other by partial negative and positive charges on the oxygen and hydrogen atoms, respectively b) tend to repel each other c) are very small d) are in constant motion e) are extremely large

b

Now take a look at the data on both graphs for light brown mice, shown as white bars on the graphs. How many light brown mice were caught in the light-colored soil enclosure on a moonlit night? a) 11 b) 18 c) 26 d) 28

d

Now think about the data from the viewpoint of the owl's hunting success. Combining the data shown in both graphs, estimate the total number of mice caught in moonlight versus no-moonlight conditions. a) moonlight: about 86 caught; no moonlight: about 86 caught b) moonlight: about 95 caught; no moonlight: about 77 caught c) moonlight: about 83 caught; no moonlight: about 89 caught d) moonlight: about 77 caught; no moonlight: about 95 caught

c

Now you will look at data from two different enclosures: one with light-colored soil (left), and one with dark-colored soil (right). Use both graphs to answer the next few questions about the capture of dark brown mice, shown as brown bars in the graphs. How many dark brown mice were caught in the light-colored soil enclosure on a moonlit night? a) 12 b) 17 c) 19 d) 37

d

On a moonlit night, would a light brown mouse be more likely to escape predation by owls on dark- or light-colored soil? What data support your conclusion? a) On dark-colored soil; fewer light brown mice were caught on dark soil than on light soil under a full moon. b) On light-colored soil; fewer light brown mice were caught under no moon than under a full moon. c) On dark-colored soil; fewer dark brown mice were caught on dark soil than on light soil under a full moon. d) On light-colored soil; fewer light brown mice were caught on light soil than on dark soil under a full moon.

e

Polar attractions are ... a) forces between atoms with partial charges. b) weaker than covalent bonds. c) important because they are numerous. d) (a) and (b) are true. (c) is false. e) (a), (b), and (c) are correct

a

Radioactive decay is likely to occur when ... a) an atom has too many neutrons. b) an atom has too many electrons. c) atoms collide with one another. d) protons break into neutrons and electrons. e) an electron hits the nucleus.

b

Radioactive uranium-235 has a half-life of 704 million years. If it was incorporated into dinosaur bones, could it be used to date the dinosaur fossils? a) Yes, but only for dinosaurs that lived more than 704 million years ago. b) Yes, after 65.5 million years only about one tenth of the 235U would have decayed, leaving plenty to measure in the fossils. c) No, only about one tenth of the 235U would have decayed after 65.5 million years, not leaving enough to measure in the fossils. d) No, the dinosaurs went extinct too recently to use a radioisotope with a half-life of 704 million years.

a

Rank, from low to high, the pH of blood, stomach acid, and urine. a) stomach acid, urine, blood b) urine, blood, stomach acid c) stomach acid, blood, and urine d) blood, urine, and stomach acid

c

Research indicates that ibuprofen, a drug used to relieve inflammation and pain, is a mixture of two enantiomers; that is, molecules that _____. a) have identical chemical formulas but differ in the branching of their carbon skeletons b) differ in the location of their double bonds c) are mirror images of each other d) differ in the arrangement of atoms around their double bonds

d

So far you've looked at each color of mice separately. Next, consider the two colors of mice together when looking at the graphs. What combination of independent variables led to the highest predation level in enclosures with light-colored soil? a) light brown coat with no moon b) dark brown coat with full moon c) light brown coat with full moon d) dark brown coat with no moon

d

The bars on the graphs show the numbers of mice that were caught, but keep in mind that mice that were not caught by the owl escaped predation. On a moonlit night, would a dark brown mouse be more likely to escape predation by owls on dark- or light-colored soil? What data support your conclusion? a) On light-colored soil; fewer dark brown mice were caught on dark soil than on light soil under a full moon. b) On dark-colored soil; fewer light brown mice than dark brown mice were caught on light soil under no moon. c) On light-colored soil; the lowest level of predation was light brown mice on light soil. d) On dark-colored soil; fewer dark brown mice were caught on dark soil than on light soil under a full moon.

b

The graph shows data from the light-colored soil enclosure. There is one dependent variable and more than one independent variable on the graph. What are the independent variables, the variables that were manipulated by the researcher? a) the presence or absence of moonlight and the number of mice caught b) mouse coat color and the presence or absence of moonlight c) the color of the soil and the presence or absence of moonlight d) mouse coat color and the number of mice caught

d

The graph you constructed so far applies to decay of any radioisotope. To calibrate it specifically to 14C, you need to calculate how many years must pass to reach the amount of remaining isotope for each point of the half-life curve. To calibrate the x-axis for 14C decay, you have to convert half-lives to number of years. Recall that 14C has a single half-life of 5,730 years. How many years make up 5 half-lives for 14C? a) 3.13 × 10-2 years b) 1,146 years c) 5,730 years d) 28,650 years

b

The highlighted part of this molecule is derived from ... a) fatty acid. b) glycerol. c) aniline. d) guaiacol. e) cholesterol.

a

The kind and number of bonds an atom can form depends on ________. a) its electron configuration b) the number of particles in its nucleus c) its atomic mass d) its atomic number

b

The mass number of an atom is 15, and its atomic number is 7. The atom probably has... a) at least 15 electrons. b) 8 neutrons in the nucleus. c) 7 electrons in the nucleus. d) about as much mass in electrons as in protons. e) 7 units of negative charge in the nucleus.

c

The molar mass of glucose is 180 grams per mole (g/mol). Which of the following procedures should you carry out to make a 1 M solution of glucose? In 0.8 liter (L) of water, dissolve ________. a) 180 g of glucose, and then add 0.2 L more of water b) 18 g of glucose, and then add more water until the total volume of the solution is 1 L c) 180 g of glucose, and then add more water until the total volume of the solution is 1 L d) 1 g of glucose, and then add more water until the total volume of the solution is 1 L

e

The most unsaturated fats have ... a) the fewest double bonds. b) the shortest hydrocarbon tails. c) the highest ratio of H to C. d) the longest hydrocarbon tails. e) the most double bonds.

a

The open spaces in water's crystal structure make it possible for ... a) aquatic life to exist at the North Pole. b) water to have a low boiling point. c) life to occur in hot springs. d) Both (b) and (c). e) (a), (b), and (c).

a

The partial negative charge in a molecule of water occurs because _____. a) the electrons shared between the oxygen and hydrogen atoms spend more time around the oxygen atom nucleus than around the hydrogen atom nucleus b) the oxygen atom donates an electron to each of the hydrogen atoms c) one of the hydrogen atoms donates an electron to the oxygen atom d) the oxygen atom has two pairs of electrons in its valence shell that are not neutralized by hydrogen atoms

d

The presence of many C-C and C-H bonds causes fats to be ... a) rich in energy. b) insoluble in water. c) low in energy. d) Both (a) and (b). e) Both (b) and (c).

d

The tendency of an atom to pull electrons toward itself is referred to as its _____. a) tonicity b) polarity c) ionic potential d) electronegativity e) covalency

a

The two strands of a DNA double helix are held together by _____ that form between pairs of nitrogenous bases. a) hydrogen bonds b) covalent bonds c) S—S bonds d) hydrophilic interactions e) ionic bonds

b

The unequal sharing of electrons within a water molecule makes the water molecule _____. a) change easily from a liquid to gaseous form b) polar c) hydrophobic d) ionic e) have a low surface tension

a

This atom can form up to _____ single covalent bond(s). a) 4 b) 0 c) 3 d) 1 e) 2

c

Though you add heat, the temperature of boiling water remains constant because ... a) water has a constant boiling temperature. b) it takes energy to circulate water. c) it takes energy to break hydrogen bonds. d) it takes energy to break covalent bonds. e) None of the above. The temperature rises during boiling.

a

To act as an effective coolant in a car's radiator, a substance has to have the capacity to absorb a great deal of heat. You have a reference book with tables listing the physical properties of many liquids. In choosing a coolant for your car, which table would you check first? a) specific heat b) heat of vaporization c) pH d) density at room temperature

d

Triglycerides vary with respect to the number of ... a) hydrocarbon tails. b) C atoms in the tails. c) double bonds in the tails. d) Both (b) and (c). e) All of the above.

a

True or false? Enzymes in the digestive tract catalyze hydrolysis reactions. a) True b) False

d

Two atoms always represent the same element if they have ... a) the same mass number. b) the same number of electrons. c) the same number of shells. d) the same number of protons. e) the same number of particles in the nucleus.

c

Two moles of the compound in the figure would weigh how many grams? (Note: The atomic masses, in daltons, are approximately 12 for carbon, 1 for hydrogen, and 16 for oxygen.) a) 90 b) 30 c) 120 d) 60

d

Under which conditions would a dark brown mouse be most likely to escape predation at night? a) on light-colored soil with no moon b) on dark-colored soil with no moon c) on light-colored soil with full moonlight d) on dark-colored soil with full moonlight

a

Under which conditions would a light brown mouse be most likely to escape predation at night? a) on light-colored soil with no moon b) on dark-colored soil with no moon c) on light-colored soil with full moon light d) on dark-colored soil with full moon light

a

Van der Waals interactions may result when _____. a) electrons are not symmetrically distributed in a molecule b) two polar covalent bonds react c) a hydrogen atom loses an d) molecules held by ionic bonds react with water

d

Water has surface tension because ... a) cohesion forces are weaker at the surface. b) molecules at the surface make more hydrogen bonds. c) there is positive pressure inside the water mass. d) hydrogen bonds between surface water molecules resist being stretched. e) water tends to evaporate from the surface.

d

Water is a source of ______________ for chemical reactions in cells. a) hydrogen atoms b) oxygen atoms c) energy d) Both (a) and (b) e) (a), (b), and (c).

c

What combination of independent variables led to the highest predation level in enclosures with dark-colored soil? a) dark brown coat with no moon b)dark brown coat with full moon c) light brown coat with full moon d) light brown coat with no moon

b

What could happen if a mutation in a gene caused a hydrophobic amino acid in a polypeptide to be replaced by a hydrophilic amino acid? a) The shape of the protein would not be affected if only one amino acid in the primary structure is changed. b) The new amino acid would not form the same interactions with hydrophobic R groups, and the protein's shape would likely be affected. c) There would be no effect as long as the protein had quaternary structure, because primary structure does not affect that level. d) The hydrophilic amino acid could not form the proper peptide bond in its new location, so both the shape and function of the protein would be affected.

d

What do DNA, proteins, and fats have in common? a) They contain nitrogen. b) They contain phosphorus. c) They are polar. d) They contain carbonyl groups. e) They are polymers.

d

What is the arrow pointing to? a) hydroxide ion b) hydronium ion c) electron d) hydrogen ion e) water molecule

a

What is the arrow pointing to? a) hydroxide ion b) proton c) hydronium ion d) water e) hydrogen ion

d

What is the dependent variable, the response to the variables being tested? a) the color of the soil b) the mouse coat color c) the presence or absence of moonlight d) the number of mice caught

267

What is the mass number of an ion with 107 electrons, 159 neutrons, and a +1 charge?

a

What is the maximum number of covalent bonds that an oxygen atom with atomic number 8 can make with hydrogen? a) 2 b) 1 c) 4 d) 6

b

What name is given to the bond between water molecules? a) hydrophobic b) hydrogen c) single (nonpolar) covalent d) ionic e) polar covalent

a

What process exerts the pull on water molecules that is relayed from leaf to root via cohesion? a) evaporation b) gravity c) antigravity d) precipitation

d

What type of bond is joining the two hydrogen atoms? a)ionic b) hydrophilic c) hydrophobic d) covalent e) hydrogen

b

Which condition is optimal for predation by the owl on mice? a) The moon light has no effect on predation success. b) Dark nights are better for hunting. c) Moonlit nights are better for hunting.

d

Which factor is important in making it possible to cool yourself by sweating? Think carefully! a) Molecules collide with varied angles and speeds. b) Hydrogen bonds are relatively weak. c) Water has more energy at the body surface. d) Both (a) and (b). e) (a), (b), and (c).

c

Which molecule is a nucleotide? a) The amino acid glycine b) Deoxyribose e) ATP

b

Which monomers make up RNA? a) Amino acids b) Nucleotides c) Polymers d) Simple sugars

c

Which of the following best summarizes the relationship between dehydration reactions and hydrolysis? a) Hydrolysis reactions create polymers and dehydration reactions create monomers. b) Dehydration reactions eliminate water from membranes; hydrolysis reactions add water to membranes. c) Dehydration reactions assemble polymers; hydrolysis reactions break polymers apart. d) Dehydration reactions and hydrolysis reactions assemble polymers from monomers.

a

Which of the following correctly describes chemical equilibrium? a) Forward and reverse reactions continue with no net effect on the concentrations of the reactants and products. b) There are equal concentrations of products and reactants while forward and reverse reactions continue. c) There are equal concentrations of reactants and products, and the reactions have stopped. d)Concentrations of products are higher than the concentrations of the reactants.

a

Which of the following effects can occur because of the high surface tension of water? a) A raft spider can walk across the surface of a small pond. b) Lakes cannot freeze solid in winter, despite low temperatures. c) Sweat can evaporate from the skin, helping to keep people from overheating. d) Organisms can resist temperature changes, although they give off heat due to chemical reactions.

a

Which of the following helps most to explain why water has a high specific heat? a) A water molecule can make 4 hydrogen bonds. b) The water molecule has exceptionally strong covalent bonds. c) Water temperature is exceptionally sensitive to heat. d) Both (a) and (b). e) Both (b) and (c).

a

Which of the following is not attached to the central carbon atom in an amino acid? a) An oxygen b) A side chain ("R group") c) An amino functional group d) A carboxyl functional group

b

Which of the following is the best description of an atom's physical structure? a) An atom is a solid mass of material. b) Atoms are little bubbles of space with mass concentrated at the center of the bubble. c) The particles that form an atom are equidistant from each other. d) Atoms are little bubbles of space with mass concentrated on the outside surface of the bubble.

b

Which of the following is true of carbon? a) It can form a maximum of three covalent bonds with other elements. b) It can form both polar and nonpolar bonds. c) It is highly electronegative. d) It forms only polar molecules.

b

Which of the following statements about the formation of polypeptides from amino acids is true? a) A bond can form between any carbon and nitrogen atom in the two amino acids being joined. b) A bond forms between the carboxyl functional group of one amino acid and the amino functional group of the other amino acid. c) The reaction occurs through the addition of a water molecule to the amino acids. d) Polypeptides form by condensation or hydrolysis reactions.

b

Which of the following statements correctly describes cis-trans isomers? a) They have the same chemical properties. b) They have variations in arrangement around a double bond. c) They have an asymmetric carbon that makes them mirror images. d) They have different molecular formulas.

a

Which of the following statements is an accurate description of proteins? a) The primary structure of a protein is the order of amino acids in a polypeptide, as coded for in the DNA of a gene. b) The 20 amino acids found in proteins differ in the composition of their R groups, which may be either polar or charged. c) Secondary structures, which include the alpha helix or beta pleated sheet, are held together by interactions between R groups. d) Tertiary structure is the overall shape of a polypeptide, which may be stabilized by hydrophobic interactions, hydrogen bonds, ionic bonds, and peptide bonds. e) Quaternary structure is only found in proteins that have four identical polypeptide subunits.

a

Which of the following statements is true about buffer solutions? a)They maintain a relatively constant pH when either acids or bases are added to them. b) They fluctuate in pH when either acids or bases are added to them. c) They maintain a constant pH of 7. d) They maintain a constant pH when acids are added to them but not when bases are added to them.

b

Which of the functional groups shown above is most likely to gain a proton and become positively charged? a) The carboxyl group is most likely to gain a proton. b) The amino group is most likely to gain a proton. c) The hydroxyl group is most likely to gain a proton.

d

Which of these is a polysaccharide? a) galactose b) sucrose c) glucose d) cellulose e) lactose

a

Which part of an amino acid is always acidic? a) Carboxyl functional group b) Amino functional group c) Side chain ("R group") d) None of the above

d

Which polymers are composed of amino acids? a) Carbohydrates b) Nucleic acids c) Monomers d) Proteins

a

Which statement about weak bonds is correct? a) Weak bonds are transient and easily reversible. b) Weak bonds are less important to living things than strong covalent bonds. c) Weak chemical bonds form only between atoms of similar electronegativity.

e

Which statement helps to explain why ice is less dense than liquid water? a) Water molecules make hydrogen bonds at definite angles. b) Cold molecules move less than warm molecules. c) Hydrogen bonds lengthen in the cold. d) All of the above. e) Both (a) and (b).

b

Which statement is true of atoms? a) Protons attract other protons. b) Electrons determine the atom's size. c) Most of an atom's volume is filled with matter. d) Protons repel electrons. e) All of the above.

d

Which statement is true of the atom shown in the diagram? a) The atom has more than one valence electron. b) An electron will move from the outer to the inner shell. c) The atom is in the excited state. d) All of the above. e) None of the above.

b

Which statement is true of the energy levels of electrons in shells? a) Electrons must lose energy to move from the first to the second shell. b) The valence shell has higher energy than other occupied shells. c) All the electrons in an atom have similar amounts of energy. d) All of the above. e) None of the above.

c

Which statement must be mentioned in explaining why amphipathic molecules line up at a water surface? a) Polar groups repel water. b) Nonpolar groups repel water. c) Polar groups attract one another. d)Nonpolar groups attract one another. e) All of the above.

c

Why doesn't oil mix with water? a) Nonpolar molecules repel water molecules. b) Polar molecules repel nonpolar molecules. c) Polar molecules attract one another. d) Nonpolar molecules attract one another. e) Both (a) and (d).

b

Why is carbon so important in biology? a)It is a common element on Earth. b) It can form a variety of carbon skeletons and host functional groups. c) It bonds to only a few other elements. d) It has very little electronegativity, making it a good electron donor.

b

Why isn't this insect drowning? a) The insect is very light. b) Surface tension. c) The insect is flying just above the water surface. d) The insect is swimming. e) It is difficult to change the temperature of water.

b

You are asked to indicate the type and number of atoms in a molecule. Which representation would work best? a) space-filling model b) molecular formula c) ball-and-stick model d) structural formula

a

You have just sequenced a new protein found in mice and observe that sulfur-containing cysteine residues occur at regular intervals. What is the significance of this finding? a) Cysteine residues are involved in disulfide bridges that help form tertiary structure. b) Cysteine residues are required for the formation of α-helices and β-pleated sheets. c) It will be important to include cysteine in the diet of the mice. d) Cysteine causes bends, or angles, to occur in the tertiary structure of proteins.

b

_____ is the most abundant organic compound on Earth. a) Lactose b) Cellulose c) Glucose d) Glycogen e) Starch

d

glucose + glucose —> _____ by _____. a) sucrose + water ... dehydration synthesis b) lactose + water ... hydrolysis c) cellulose + water ... hydrolysis d) maltose + water ... dehydration synthesis e) starch + water ... dehydration synthesis