Chapter 2 The Chemistry of Microbiology
2.1 Multiple Choice Questions
1) Which of the following does not contribute significantly to the mass of an atom?
A) electron
B) neutron
C) element
D) proton
E) isotope
2) Matter composed of a single type of atom is known as a(n)
A) element.
B) mineral.
C) molecule.
D) compound.
E) electron.
3) A stable atom has ________ in its valence shell.
A) 4 electrons
B) 2 neutrons
C) 8 electrons
D) 8 protons
E) 10 electrons
4) Which parts of the atoms interact in a chemical reaction?
A) protons
B) neutrons
C) ions
D) electrons
E) isotopes
5)
The atomic mass of this stable isotope atom (Figure 2.1) is
A) 4.
B) 6.
C) 10.
D) 12.
E) cannot be determined from the available information
6) The valence of an atom represents its
A) ability to interact with other atoms.
B) electronegativity.
C) radioactivity.
D) ability to attract electrons.
E) ability to interact with water.
7) The type(s) of bond produced when atoms share electrons equally is/are
A) a nonpolar covalent bond.
B) a hydrogen bond.
C) an ionic bond.
D) a polar covalent bond.
E) both polar covalent and ionic bonds.
8) The type(s) of bond produced when atoms with somewhat different electronegativities share
electrons is/are
A) a nonpolar covalent bond.
B) a polar covalent bond.
C) an ionic bond.
D) a hydrogen bond.
E) both nonpolar covalent and ionic bonds.
9) The carbon atoms in organic compounds typically form ________ with other atoms.
A) nonpolar covalent bonds
B) polar covalent bonds
C) ionic bonds
D) hydrogen bonds
E) either ionic or hydrogen bonds
10) Unstable isotopes can be useful
A) catalysts.
B) in medical diagnosis.
C) in vitamins.
D) in the formation of hydrogen bonds.
E) as buffers.
11) Which of the following is an INCORRECT pairing?
A) electrolytes; anions
B) synthesis; endothermic
C) hydrolysis; hydrogen bonds
D) catabolism; exothermic
E) dehydration; anabolism
12) A compound that dissociates in water to produce ________ is called a salt.
A) hydrogen ions
B) anions
C) hydroxyl ions
D) cations
E) anions and cations
13) Which of the following is a property of water?
A) It has a high capacity for heat.
B) It is not a common reactant in metabolic reactions.
C) It is not a good solvent.
D) It is liquid in a very narrow temperature range.
E) It is a nonpolar molecule.
14) An acid dissociates in water to release
A) hydrogen ion(s).
B) cation(s).
C) hydroxyl group(s).
D) anion(s).
E) both anions and hydrogen ions.
15) The reverse of a dehydration synthesis reaction is a(n) ________ reaction.
A) anabolic
B) exchange
C) hydrolytic
D) endothermic
E) metabolic
16) A weak acid may function as a
A) transfer group.
B) buffer.
C) hydroxyl donor.
D) cation.
E) salt.
17) Which of the following is NOT a characteristic of saturated fats?
A) They are usually solid at room temperature.
B) They contain at least one double bond.
C) They are found in animals.
D) Their fatty acids pack tightly together.
E) They are a form of stored energy.
18) Which of the following is NOT a characteristic of phospholipids?
A) They are found in cellular membranes.
B) They can form micelles and bilayers.
C) They contain fatty acids that associate with water.
D) They contain a hydrophilic phosphate “head.”
E) They contain two fatty acids and a phosphate functional group.
19) Organisms use carbohydrates in all of the following ways EXCEPT
A) as a component of cell walls.
B) as a long-term energy source.
C) as a short-term energy source.
D) to keep membranes flexible at low temperatures.
E) as a building block of DNA and RNA molecules.
20) Nucleic acids, proteins, and complex carbohydrates are all produced by
A) hydrolytic reactions.
B) dehydration synthesis.
C) exchange reactions.
D) hydrogen bonding.
E) catabolic reactions.
21) Which of the following is an example of a polysaccharide?
A) glycogen
B) glucose
C) fructose
D) deoxyribose
E) sucrose
22) Which of the following statements about proteins is FALSE?
A) They are composed of amino acids.
B) They have multiple levels of structural organization.
C) They can be hydrophobic, hydrophilic, or both.
D) Their primary function is energy storage.
E) They are formed by dehydration synthesis reactions.
23) All of the following are components of an amino acid EXCEPT a(n)
A) carboxyl group.
B) pentose group.
C) amino group.
D) α-carbon.
E) R group.
24) Which of the following is found in nucleic acids?
A) amines
B) carboxylic acid
C) purines
D) glycerol
E) R group
25) Hydrogen bonds are found in all of the following EXCEPT
A) between phosphates in ATP.
B) in α-helices.
C) between water molecules.
D) in the DNA double helix between nucleotides.
E) between the R groups of amino acids in proteins.
26) Tertiary and quaternary structure of proteins involves ________ bonds.
A) hydrogen
B) ionic
C) polar covalent
D) nonpolar covalent
E) ionic, hydrogen, polar, and nonpolar covalent
27) Which of the following are examples of pyrimidines?
A) uracil and adenine
B) cytosine and guanine
C) thymine and adenine
D) thymine and guanine
E) cytosine and thymine
28) All of the following bases are found in RNA molecules EXCEPT
A) adenine.
B) thymine.
C) uracil.
D) cytosine.
E) guanine.
29) The double-strands of DNA result from the formation of ________ between the bases.
A) covalent bonds
B) peptide bonds
C) ionic bonds
D) hydrogen bonds
E) α−1,4 bonds
30) Which of the following would NOT normally be found as a component of a cell’s nucleic
acids?
A) adenine deoxyribonucleotides
B) thymine deoxyribonucleotides
C) uracil deoxyribonucleotides
D) cytosine ribonucleotides
E) adenine ribonucleotides
31) All of the following are associated with ATP molecules EXCEPT
A) a long-term energy supply.
B) high-energy bonds.
C) a recyclable energy supply.
D) formation of coenzymes.
E) three phosphate groups.
32) Which of the following statements concerning nucleic acids is CORRECT?
A) Nucleic acid strands are held together by hydrogen bonds between adjacent carbohydrates.
B) Cellular DNA is double stranded.
C) All viruses have DNA genomes.
D) The nucleic acid polymer is composed of peptide bonds.
E) There are three naturally occurring purines in nucleic acids.
33) Which of the following is an INCORRECT pairing?
A) primary structure; amino acid sequence
B) secondary structure; disulfide bridges
C) tertiary structure; covalent bonds
D) quaternary structure; two or more polypeptides
E) secondary structure; β-pleated sheets
34) Proteins contain both acidic and basic R groups and can, therefore, function as
A) energy storage macromolecules.
B) structural macromolecules.
C) buffers.
D) catalysts.
E) genetic material.
35) A(n) ________ is a compound that dissolves into anions and cations in water.
A) acid
B) buffer
C) base
D) salt
E) catalyst
36) Cell walls containing ________ provide the best protection from drying.
A) polysaccharides
B) triglycerides
C) waxes
D) peptidoglycan
E) sterols
37) A(n) ________ is an arrangement of atoms found in a variety of macromolecules.
A) buffer
B) isotope
C) salt
D) stereoisomer
E) functional group
38) Decomposition reactions are commonly ________ reactions.
A) endothermic
B) exchange
C) exothermic
D) anabolic
E) dehydration
39) Lipids found in the cytoplasmic membranes of all eukaryotic cells are
A) polyunsaturated fats.
B) phospholipids.
C) steroids.
D) waxes.
E) triglycerides.
40) A protein is a ________ of amino acids.
A) monomer
B) polymer
C) bilayer
D) solution
E) decomposition product
41) DNA is composed of repeating units of sugars, phosphates, and nucleic acids. This is an
example of a
A) polymer.
B) monomer.
C) salt.
D) micelle.
E) lipid.
42) An unbranched polymer composed of simple sugars is a(n)
A) protein.
B) triglyceride.
C) starch.
D) glycoprotein.
E) amino acid.
43) Anna is conducting an experiment using a pH indicator that is red at low pH, green at
neutral pH and purple at high pH. She starts with a green solution. When she adds compound X
to her solution it turns purple. Then she adds compound Z to the solution and it turns green. She
adds more Z, the solution remains green. These observations suggest X is ________ and Z is
________.
A) a base; a buffer
B) an acid; a base
C) a base; a strong acid
D) an acid; a buffer
E) a buffer; a base
44) Two molecules react to produce two products, one of which is water. What type of reaction
is likely to be involved?
A) a decomposition reaction
B) a hydrolysis reaction
C) an exchange reaction
D) a synthesis reaction
E) The answer cannot be determined from the available information.
45) Which of the following is an organic compound?
A) adenine
B) carbon dioxide
C) molecular oxygen
D) sodium chloride
E) water
46) Which of the following is found in RNA but not DNA?
A) adenine
B) cytosine
C) deoxyribose
D) guanine
E) uracil
2.2 True/False Questions
1) The smallest chemical units of matter are elements.
2) The side groups of amino acids can interact with each other and with other molecules.
3) A molecule composed of carbon and hydrogen is a compound.
4) The electron shells of atoms hold eight electrons each.
5) Hydrogen bonds are stronger then covalent bonds.
6) An organic molecule with the chemical formula C4H5O1N3 is probably a pyrimidine.
7) Denaturation of a protein is always permanent.
8) The long-term chemical energy storage molecules in plants are steroids.
9) Dehydration synthesis is a common feature of polymer production in cells.
10) Salts are produced from exchange reactions in which acids and bases neutralize each other.
2.3 Short Answer Questions
1) Radioactive iodine is sometimes used to treat thyroid cancer. This is an example of the use
of (isotopes/elements/radiation) in medical treatment.
2) A(n) (nonpolar/polar/ionic/hydrogen) bond is one in which electrons are shared equally
between atoms.
3) Cell surface markers composed of both carbohydrate and lipid molecules are known as
(glycoproteins/glycolipids/LPS).
4) An atom or molecule becomes a(n) (anion/ion/cation) when it loses an electron to a more
electronegative molecule.
5) A chemical reaction in which a water molecule is a reactant is known as a
(dehydration/hydrolysis) reaction.
6) When a base dissolves in water it releases a(n) (electron/cation/hydrogen ion).
7) The folding of a polypeptide into a three-dimensional shape is its
(secondary/tertiary/quaternary) structure.
8) The DNA double helix is held together by (covalent/ionic/hydrogen) bonds.
9)
Figure 2.2 depicts the (primary/secondary/tertiary) structure of a protein.
10) A(n) (catalyst/enzyme) is any molecule that speeds up a chemical reaction.
11) The monomer of a nucleic acid is called a (nucleoside/nucleotide/base).
12) A nitrogenous base composed of two rings is a (purine/pyrimidine/ribose).
13) Jim adds an acid to a solution, but finds the pH has not changed afterward. This suggests
the solution contains a(n) (anion/buffer/salt).
14) A saturated fatty acid contains (no/one/multiple) double bonds.
15) The (atoms/isotopes/stereoisomers) of an element vary in the number of neutrons in the
nucleus.
2.4 Essay Questions
1) Compare and contrast synthesis reactions with decomposition reactions.
2) Discuss the importance of hydrogen bonds in the chemistry of the cell.
3) Max is exploring the properties of various compounds. Some of his explorations involve the
use of a pH indicator that is red at low pH, yellow-green at neutral pH and blue to purple at
high pH. He sets up several tubes containing water and the pH indicator and then begins to add
some of the compounds he is characterizing in various combinations. His results are shown on
the following table.
Compound None 1 × L 1 × M 2 × M 5 × M 1 × N 1 × L + 1 × M 1 × L + 5 ×
M 1 × L + 1 × M + 1 × N
Color Green Red Green Blue Purple Green Red Green Green
What can Max conclude about his compounds based on these results? Describe the likely
events in terms of hydrogen and hydroxyl ions.
4) Describe the chemical properties of phospholipids that account for their behavior in water.
5)
Consider the structure of thymine, shown on the left in Figure 2.3 above, and compare to the
structure of pyrimidine X on the right. What would be the impact if X is incorporated into the
structure of a DNA strand in place of thymine?