Deck 5: The Chemistry of Life

Question 1

In the illustration below, a positive ion is surrounded by water molecules.
The water molecules orient as shown because the slightly _____ in the water molecules are attracted to the positive charge of the ion.

A)negative hydrogen atoms
B)positive hydrogen atoms
C)negative oxygen atoms
D)positive oxygen atoms

Answer 1

C

Question 2

Individual water molecules orient toward each other because of the _____ bonds that form between them.

A)covalent
B)hydrogen
C)peptide
D)ionic

Answer 2

B

Question 3

The strongest possible chemical link between two atoms is a(n)

A)covalent bond.
B)hydrogen bond.
C)noncovalent bond.
D)ionic bond.

Answer 3

A

Question 4

A proton has _____ charge.

A)no
B)a neutral
C)a negative
D)a positive

Question 5

O₂, also termed atmospheric oxygen, is considered to be a molecule but not a compound; why not?

A)It contains no covalent bonds.
B)It contains a double covalent bond, but not a single covalent bond.
C)To be considered a compound there must be a minimum of three atoms; atmospheric oxygen is too small.
D)Compounds are defined as molecules constructed from two or more different elements.

Question 6

How many different elements would be needed to construct a molecule of C₈H₁₀N₄O₂?

A)4
B)8
C)12
D)24

Question 7

Chemists often represent the structure of atoms using p, n, and e to indicate the numbers of protons, neutrons, and electrons; which atom would have an atomic weight of 30?

A)10 p, 10 n, 10 e
B)15 p, 15 n, 15 e
C)15 p, 0 n, 15 e
D)0 p, 15 n, 15 e

Question 8

Which of the following combinations of atoms would form ionic bonds?

A)H+ and O
B)Na+ and K+
C)Na+ and Cl-
D)PO4- and I2-

Question 9

An atom of the element with the atomic number of 11 (which can form an ion)always contains 11 _____.

A)neutrons
B)nuclei
C)electrons
D)protons

Question 10

How many atoms are present in a single molecule of C₈H₁₀N₄O₂?

A)4
B)8
C)12
D)24

Question 11

Radioisotopes are useful in scientific research and medicine because they

A)have a different number of protons than other isotopes of the same element.
B)give off high-energy radiation that can be detected by film and specialized scanning machines.
C)have the same atomic mass as other isotopes of the same element.
D)all of the above

Question 12

Oil and water do not mix together well because

A)water is polar and oil is nonpolar.
B)only identical molecules of the same chemical can easily mix together.
C)water has hydrogen bonds and oil is polar.
D)water and oil are covalently bonded together.

Question 13

How many hydrogen atoms are in a molecule of C₈H₁₀N₄O₂?

A)8
B)10
C)20
D)24

Question 14

The smallest unit of a chemical element that displays the properties of that element is a(n)

A)amino acid.
B)molecule.
C)atom.
D)bond.

Question 15

Examine the illustration below, a representation of a sodium ion with a charge of +1. Based on the information provided determine the proton number for this atom.

A)8
B)9
C)10
D)11

Question 16

Ionic bonds

A)result from the sharing of electrons between atoms.
B)form only between polar molecules.
C)form between atoms that develop opposite charges.
D)result from the natural repulsion that develops between protons.

Question 17

The figure below shows two hydrogen atoms.
How many covalent bonds will form between these two atoms?

A)one
B)two
C)three
D)none, these atoms will form an ionic bond.

Question 18

The outer electron shell of a nitrogen atom can hold up to eight electrons, but contains only five. As a result, nitrogen can form _____ covalent bonds.

A)zero
B)one
C)three
D)eight

Question 19

You are given an unknown substance and asked to determine whether it is polar or nonpolar. The easiest way to do this would be to

A)determine whether the compound is held together by hydrogen bonds.
B)determine the number of electrons in the compound's outer shell.
C)mix the compound with an ionic substance to see whether its bonds can withstand the pressure.
D)determine whether the compound dissolves in water.

Question 20

Electrons are found

A)in the nucleus of an atom.
B)only in complex molecules.
C)in one or more shells that surround the atom's nucleus.
D)in both the nucleus and inner shell of an atom.

Question 21

Macromolecules are typically formed by repetitively adding small monomers together; which macromolecule is properly matched with the appropriate monomer?

A)polypeptide-amino acid
B)nucleic acid-amino acid
C)polysaccharide-nucleotide
D)triglyceride-cholesterol

Question 22

In the equation 3H₂ + N₂ à 2NH₃, how many molecules of hydrogen gas (H₂)are present?

A)2
B)3
C)6
D)12

Question 23

In organic compounds, carbon atoms are bound to each other by

A)ionic bonds.
B)polar bonds.
C)hydrogen bonds.
D)covalent bonds.

Question 24

After adding a small amount of Solution A to Solution B, the pH of Solution B declines from 8 to 3. Solution A must contain

A)a salt.
B)an acid.
C)water only.
D)a base.

Question 25

Chemical reactions do not change the identity of the participating atoms; all atoms present at the beginning of the reaction must be present at the end. Balance the chemical reaction by indicating the number of molecules necessary for each reactant and product: _____Cl₂ + _____ NaBr = _____Br₂ + _____NaCl.

A)1; 1; 1; 1
B)1; 2; 1; 1
C)1; 2; 1; 2
D)2; 2; 1; 2

Question 26

In the equation, 2 H₂O₂ à 2 H₂O + O₂, the H₂O₂ molecules are the _____ and the H₂O + O₂ molecules are the _____.

A)products; products
B)reactants; products
C)products; reactants
D)reactants; reactants

Question 27

A solution with a pH of _____ is _____ times more acidic than a solution with a pH of _____.

A)3; 10,000; 7
B)12; 100; 10
C)7; 1,000; 9
D)4; 10; 3

Question 28

One of the symptoms of kidney disease is the presence of proteins in a patient's urine. To quickly test for kidney disease using a urine sample, a doctor might add a chemical that causes a color change when

A)nitrogen, but not oxygen, is present.
B)nitrogen, but not phosphorus, is present.
C)only oxygen and hydrogen are present.
D)only carbon and hydrogen are present.

Question 29

Pure water has a pH of 7. The inside of a cell is also about pH 7. This might be so because

A)buffers work best when the pH is close to 7.
B)humans are largely made up of water by weight.
C)most of the chemical reactions that occur in humans can proceed optimally at pH 7.
D)ionic bonds cannot form at pH 7.

Question 30

The carbon dioxide you breathe out is carried to the lungs in the blood. Carbon dioxide, when dissolved in water, is an acid. How does the body prevent your blood from becoming too acidic on the way to your lungs?

A)Buffers in the blood release OH- ions to make the blood more basic.
B)Buffers in the blood accept H+ ions to make the blood less acidic.
C)Buffers in the blood release H+ to make the blood more basic.
D)Buffers in the blood accept OH- to make the blood less acidic.

Question 31

An acid is a polar substance that dissolves in water and

A)becomes nonpolar.
B)leaves behind an OH- ion.
C)accepts hydrogen ions from the solution.
D)donates hydrogen ions to the solution.

Question 32

Based only on the illustration below it could be predicted that ice floats on liquid water because

A)the crystal structure of ice is more regular than that seen in liquid water.
B)the distance between water molecules in ice is greater than in liquid water.
C)the cool temperature of ice reduces the extent of molecular motion relative to liquid water.
D)when ice forms the hydrogen bond in the water molecule becomes nonpolar; ice behaves like oil.

Question 33

Which of the following levels of protein structure involves more than one polypeptide chain?

A)primary structure
B)secondary structure
C)tertiary structure
D)quaternary structure

Question 34

A solution with a pH of 3 is

A)acidic.
B)nonpolar.
C)basic.
D)neutral.

Question 35

A molecule with the general formula CH₂O is a(n)

A)protein.
B)carbohydrate.
C)amino acid.
D)nucleic acid.

Question 36

The chemical reaction that represents the combustion of glucose is C₆H₁₂O₆ + O₂ à CO₂ + H₂O; _____ are the reactants.

A)CO2 and H2O
B)O2 and H2O
C)C6H12O6 and O2
D)C6H12O6 and CO2

Question 37

The sugar glucose has an important role

A)in the formation of proteins.
B)in short-term energy storage.
C)in the formation of membranes.
D)as a building block of nucleotides.

Question 38

Of the following pH values, which indicates the most basic pH?

A)3
B)7
C)8
D)10

Question 39

A molecule composed of amino acids is a

A)nucleotide.
B)lipid.
C)carbohydrate.
D)protein.

Question 40

Fevers in young children are a particular concern because oxygen is less effectively transported by hemoglobin at high temperature. How might this be explained?

A)The hemoglobin becomes denatured and cannot transport the oxygen.
B)The oxygen becomes denatured and cannot bind to the hemoglobin.
C)Oxygen has too much thermal energy to be bound by hemoglobin.
D)Oxygen evaporates at high temperature and is not available for binding with hemoglobin.

Question 41

We use soap to clean ourselves better than we could with water alone. Soaps contain phospholipids that are responsible for the cleansing action. Which of the following statements is the most likely explanation for how soaps work?

A)Phospholipids are ions and therefore mix with both the water and oily dirt.
B)Phospholipids are completely hydrophilic, and therefore oily dirt takes the place of the phospholipid molecules that would be dissolved in the rinse water.
C)The phospholipid tail attaches to the oily dirt while the phospholipid head interacts with the rinse water and carries the dirt (and soap) away with it.
D)The nonpolar fatty acid chains that make up the heads of the phospholipid are hydrophilic, and thus are repelled by the water.

Question 42

An atom that becomes charged due to the gain or loss of an electron is called a(n)____________________.

Question 43

A scientist observed a chemical that changes to bright red in the presence of organic compounds containing nitrogen and phosphorus. To test this chemical, a set of test tubes each containing a purified sample of one of the following organic compounds is prepared. The chemical is then added to each tube. Which test tube will always turn bright red?

A)the tube containing nucleic acids
B)the tube containing proteins
C)the tube containing carbohydrates
D)the tube containing phospholipids

Question 44

The figure below shows the structural and space-filling models for stearic acid and oleic acid.
Although the two fatty acids have the same number of carbon atoms, they have different three-dimensional configurations; oleic acid has a slight bend near the middle. As a result,

A)a pure sample of oleic acid would be more liquid than a pure sample of stearic acid.
B)stearic acid would be classified as an unsaturated fatty acid.
C)you would be more likely to find stearic acid in the form of an oil than in the form of a fat.
D)oleic acid would be classified a saturated fatty acid.

Question 45

Oxygen has six electrons in its outer shell that can hold up to eight electrons. As a result, oxygen will commonly form ____________________ covalent bonds.

Question 46

You purchase a laundry product that claims to use natural enzymes to remove stains from clothing. After spilling grape juice on your favorite shirt, you apply the product and wash your shirt (following the directions, of course). When you pull the shirt out of the washer, the stain is still there! Which of the following might explain why the stain remover did not work?

A)The stain remover and the grape juice are both hydrophilic, so the enzymes could not interact with the stain.
B)The pH of the water in your house is too basic or acidic for the enzymes to work properly.
C)Before you got home from the store, you stopped at the mall and left your stain remover in the trunk of your car on a hot day, denaturing the enzymes.
D)Both B and C are possible explanations.

Question 47

Which of the following is not a role of fatty acids in living organisms?

A)energy storage
B)storage of genetic information
C)membrane construction
D)building blocks of fats

Question 48

When you place a piece of red meat on a hot barbeque, it slowly changes from soft to firm. Meat is primarily made of proteins. Which of the following might account for the change in texture during cooking?

A)The heat causes the cells in the meat to produce more protein.
B)The heat causes chemical bonds to form between the proteins and nucleic acids in the meat.
C)The heat from the barbeque converts proteins into lipids.
D)The addition of heat causes proteins to lose their three-dimensional shape and link together.

Question 49

Nucleotides

A)are the building blocks of proteins.
B)are involved in every chemical reaction in the cell.
C)form physical structures such as hair.
D)are the building blocks of nucleic acids.

Question 50

An oil is a lipid that is _____ at room temperature.

A)liquid
B)saturated
C)supersaturated
D)solid

Question 51

The process of partial hydrogenation turns liquid plant lipids into semisolid lipids by

A)adding antioxidants that prevent lipid oxidation.
B)creating hydrocarbon chains that are more kinked than those in natural fats.
C)substituting nitrogen for carbon in fatty acid chains.
D)removing double bonds and adding hydrogen to the fatty acid chains of plant lipids.

Question 52

____________________ molecules are nonpolar molecules that are repelled by water.

Question 53

The uncharged component in the core of an atom is a(n)____________________.

Question 54

When phospholipids are added to water, they arrange themselves so that

A)their hydrophobic tails are on the inside of a lipid droplet.
B)their hydrophilic tails are on the outside of a lipid droplet.
C)their hydrophobic heads are facing the water.
D)both A and C

Question 55

One function of nucleotides is energy transfer. Carbohydrates can be used to store energy. These related processes are important because

A)if we could not store and transfer energy, we would have to match our energy input (eating) exactly to our energy requirements, even while sleeping.
B)there are not enough kinds of amino acids for proteins to be used as energy storage molecules.
C)energy transfer and storage are processes that are unique to humans, and therefore are used to determine the classification of people.
D)energy transfer is how we take the energy we gather from photosynthesis and transfer it into water molecules for later use when we need energy.

Question 56

The sum of an atom's protons and neutrons is its ____________________.

Question 57

In water, phospholipids arrange themselves such that

A)their fatty acid head groups are facing the water.
B)their hydrophobic tails are kept away from the water.
C)saturated fatty acids face the water while unsaturated fatty acids are separated from the water.
D)the charged atoms on their fatty acid chains can interact directly with the water molecules.

Question 58

Trans fats have been linked to a variety of undesirable health complications that have historically been associated with saturated fats; what do the two types of molecules share in common that may account for their health impacts?

A)Both molecules form solid assemblies at body temperature and clog small blood vessels.
B)Both molecules are rich in hydrogen that can easily form hydrogen ions and lower the pH to harmful values.
C)Both molecules are linear; for reasons not currently understood linear fatty acids appear to be more difficult to metabolize and have high biological activities.
D)Both molecules are rapidly converted to signal molecules called prostaglandins, creating discordant signaling within the body.

Question 59

Cholesterol is commonly found in the cell membranes of warm-blooded animals because

A)excess dietary cholesterol is stored in cell membranes.
B)cholesterol is involved in the muscle contractions needed to move an animal around its environment.
C)it prevents the cell membrane from becoming too flexible at body temperature.
D)warm-blooded animals tend to consume large amounts of cholesterol-rich foods.

Question 60

ATP is a universal fuel for living organisms. The energy that ATP molecules deliver in chemical reactions is stored in

A)covalent bonds between the molecule's phosphate groups.
B)covalent bonds between the molecule's sugar and phosphate groups.
C)hydrogen bonds between the bases of two of these molecules.
D)ionic bonds between the molecule's sugar and base.

Question 61

Most living organisms consist of more than 70 percent ____________________ by weight.

Question 62

Most lipids contain one or more of the long, hydrophobic hydrocarbon chains known as ____________________.

Question 63

An atom is in its most stable state when all its electron shells are filled to capacity.

Question 64

The monomers in proteins are ____________________.

Question 65

The number of electrons surrounding an atom's core never changes.

Question 66

A ____________________ is a compound that maintains the pH of a solution by taking up or releasing hydrogen ions.

Question 67

In addition to cardiovascular complication trans fats have recently been suggested as a contributing factor in ____________________.

Question 68

All the isotopes of a particular element have the same number of protons.

Question 69

A group of monomers bonded together form a ____________________.

Question 70

Lipids with a four-ring structure are called ____________________.

Question 71

Covalent bonds contain ions.

Question 72

____________________ are types of proteins that speed up the rate of chemical reactions in the cell.

Question 73

Using hydrolysis, a total of ____________________ water molecules would be required to completely separate the polymer below into individual monomers.

Question 74

Molecules with an uneven distribution of charge are described as ____________________.

Question 75

The number that represents neutrality on the pH scale is ____________________.

Question 76

The predominant atom in living systems is ____________________.

Question 77

The figure below shows the chemical structure and space-filling models for stearic acid and oleic acid.

The reason oleic acid is slightly bent (as compared to stearic acid)is that it contains a ____________________ between two of its carbon atoms.

Question 78

The monomers linked together in DNA are called ____________________.

Question 79

____________________ are a type of organic compound that plays roles in both heredity and the energy delivery in cells.

Question 80

____________________ are the most hydrophobic of the four classes of organic compounds because they are made of hydrocarbon chains that repel water.