Biochemistry Unit Practice Test
Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
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1. About 25 of the 92 natural elements are known to be essential to life. Which four of these 25 elements make up approximately 96% of
living matter?
a. carbon, sodium, chlorine, nitrogen
b. carbon, sulfur, phosphorus, hydrogen
c. oxygen, hydrogen, calcium, sodium
d. carbon, hydrogen, nitrogen, oxygen
e. carbon, oxygen, sulfur, calcium
2. What is the approximate atomic mass of an atom with 16 neutrons, 15 protons, and 15 electrons?
a. 15 daltons
b. 16 daltons
c. 30 daltons
d. 31 daltons
e. 46 daltons
3. The nucleus of a nitrogen atom contains 7 neutrons and 7 protons. Which of the following is a correct statement concerning nitrogen?
a. The nitrogen atom has a mass number of approximately 7 daltons and an atomic mass of 14.
b. The nitrogen atom has a mass number of approximately 14 daltons and an atomic mass of 7.
c. The nitrogen atom has a mass number of 14 and an atomic mass of 7 grams.
d. The nitrogen atom has a mass number of 7 grams and an atomic number of 14.
e. The nitrogen atom has a mass number of 14 and an atomic mass of approximately 14 daltons.
4. Calcium has an atomic number of 20 and an atomic mass of 40. Therefore, a calcium atom must have
a. 20 protons.
b. 40 electrons.
c. 40 neutrons.
d. A and B only
e. A, B, and C
5. Different atomic forms of an element contain the same number of protons but a different number of neutrons. What are these different
atomic forms called?
a. ions
b. isotopes
c. neutronic atoms
d. isomers
e. radioactive atoms
6. How do isotopes of the same element differ from each other?
a. number of protons
b. number of electrons
c. number of neutrons
d. valence electron distribution
e. amount of radioactivity
7. Which of the following best describes the relationship between the atoms described below?
Atom 1
Atom 2
a.
b.
c.
d.
e.
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They are isomers.
They are polymers.
They are isotopes.
They contain 1 and 3 protons, respectively.
They each contain 1 neutron.
8. 3H is a radioactive isotope of hydrogen. One difference between hydrogen-1 ( H) and hydrogen-3 ( H) is that hydrogen-3 has
a. one more neutron and one more proton than hydrogen-1.
b. one more proton and one more electron than hydrogen-1.
c. one more electron and one more neutron than hydrogen-1.
d. two more neutrons than hydrogen-1.
e. two more protons than hydrogen-1.
9. Two isotopes of the same element will have different numbers of
a. protons.
b. neutrons.
c. electrons.
d. protons and neutrons.
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e. neutrons and electrons.
Atoms whose outer electron shells contain eight electrons tend to
a. form ionic bonds in aqueous solutions.
b. form covalent bonds in aqueous solutions.
c. be stable and chemically nonreactive, or inert.
d. be unstable and chemically very reactive.
e. be isotopes and very radioactive.
What are the chemical properties of atoms whose valence shells are filled with electrons?
a. They form ionic bonds in aqueous solutions.
b. They form covalent bonds in aqueous solutions.
c. They are stable and chemically unreactive or inert.
d. They exhibit similar chemical behaviors.
e. C and D only
Use the information extracted from the periodic table in the figure below to answer the following questions.
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How many electrons does nitrogen have in its valence shell?
a. 2
b. 5
c. 7
d. 8
e. 14
How many electrons does phosphorus have in its valence shell?
a. 1
b. 2
c. 3
d. 4
e. 5
How many neutrons are present in the nucleus of a phosphorus atom?
a. 8
b. 15
c. 16
d. 31
e. 46
The atomic number of each atom is given to the left of each of the elements below. Which of the atoms has the same valence as
carbon (
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C)?
a. 7nitrogen
b. 9fluorine
c. 10neon
d. 12magnesium
e. 14silicon
What is the valence of an atom with six electrons in its outer electron shell?
a. 1
b. 2
c. 3
d. 4
e. 5
What is the maximum number of covalent bonds an element with atomic number 8 can make with hydrogen?
a. 1
b. 2
c. 3
d. 4
e. 6
A molecule of carbon dioxide (CO2) is formed when one atom of carbon (atomic number 6) is covalently bonded with two atoms of
oxygen (atomic number 8). What is the total number of electrons that must be shared between the carbon atom and the oxygen atoms
in order to complete the outer electron shell of all three atoms?
a. 1
b. 2
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c. 3
d. 4
e. 5
A polar covalent bond can form when
a. there is the loss of one or more electrons from one atom to another atom of the same molecule.
b. there is the gain of one or more electrons from one atom to another atom of the same molecule.
c. one of the atoms has a greater affinity for electrons than the other atom of the same molecule.
d. one of the atoms has a greater affinity for neutrons than the other atom of the same molecule.
e. two atoms of a molecule attract electrons equally.
Results from a transfer of electron(s) between atoms.
a. nonpolar covalent bond
b. polar covalent bond
c. ionic bond
d. hydrogen bond
e. hydrophobic interaction
Van der Waals interactions result when
a. hybrid orbitals overlap.
b. electrons are not symmetrically distributed in a molecule.
c. molecules held by ionic bonds react with water.
d. two polar covalent bonds react.
e. a hydrogen atom loses an electron.
The slight negative charge at one end of one water molecule is attracted to the slight positive charge of another water molecule. What
is this attraction called?
a. a covalent bond
b. a hydrogen bond
c. an ionic bond
d. a hydrophilic bond
e. a hydrophobic bond
An example of a hydrogen bond is the bond between
a. C and H in methane (CH4).
b. the H of one water molecule and the O of another water molecule.
c. Na+and Cl- in salt.
d. the two hydrogen atoms in a molecule of hydrogen gas (H2).
e. Mg+and Cl- in MgCl2.
Water is able to form hydrogen bonds because
a. oxygen has a valence of 2.
b. the water molecule is shaped like a tetrahedron.
c. the bonds that hold together the atoms in a water molecule are polar covalent bonds.
d. the oxygen atom in a water molecule has a weak positive charge.
e. each of the hydrogen atoms in a water molecule is weakly negative in charge.
Which of the following is possible due to the high surface tension of water?
a. Lakes don't freeze solid in winter, despite low temperatures.
b. A water strider can walk across the surface of a small pond.
c. Organisms resist temperature changes, although they give off heat due to chemical reactions.
d. Water can act as a solvent.
e. The pH of water remains exactly neutral.
Temperature usually increases when water condenses. Which behavior of water is most directly responsible for this phenomenon?
a. the change in density when it condenses to form a liquid or solid
b. reactions with other atmospheric compounds
c. the release of heat by the formation of hydrogen bonds
d. the release of heat by the breaking of hydrogen bonds
e. the high surface tension of water
Hydrophobic substances such as vegetable oil are
a. nonpolar substances that repel water molecules.
b. nonpolar substances that have an attraction for water molecules.
c. polar substances that repel water molecules.
d. polar substances that have an affinity for water.
e. charged molecules that hydrogen-bond with water molecules.
How many molecules of glycerol (C3H8O3) would be present in 1 L of a 1 M glycerol solution?
a. 1
b. 14
c. 92
d. 1 107
e. 6.02 1023
Recall that when sodium chloride (NaCl) is placed in water the component atoms of the NaCl crystal dissociate into individual sodium
ions (Na+) and chloride ions (Cl-). In contrast, the atoms of covalently bonded molecules (e.g, glucose, sucrose, glycerol) do not
generally dissociate when placed in aqueous solution. Which of the following solutions would be expected to contain the greatest
concentration of particles (molecules or ions)?
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a. 0.5 M NaCl
b. 0.5 M glucose
c. 1.0 M NaCl
d. 1.0 M glucose
e. 1.0 M MgCl2
When sodium chloride (NaCl) is placed in water the component atoms of the NaCl crystal dissociate into individual sodium ions (Na+)
and chloride ions (Cl-). In contrast, the atoms of covalently bonded molecules (e.g., glucose, sucrose, glycerol) do not generally
dissociate when placed in aqueous solution. Which of the following solutions would be expected to contain the greatest number of
particles (molecules or ions)?
a. 1 L of 0.5 M NaCl
b. 1 L 0.5 M glucose
c. 1 L of 1.0 M NaCl
d. 1 L of 1.0 M glucose
e. C and D only
What would be the pH of a solution with a hydrogen ion [H+] concentration of 10-8 M?
a. pH 2
b. pH 4
c. pH 6
d. pH 8
e. pH 10
If the pH of a solution is increased from pH 5 to pH 7, it means that the
a. concentration of H+ is 2 times greater than what it was at pH 5.
b. concentration of H+ is 2 times less than what it was at pH 5.
c. concentration of OH- is 100 times greater than what it was at pH 5.
d. concentration of OH- is 100 times less than what it was at pH 5.
e. concentration of H+ is 100 times greater and the concentration of OH- is 100 times less than what they were at
pH 5.
One of the buffers that contribute to pH stability in human blood is carbonic acid H 2CO3. Carbonic acid is a weak acid that when
placed in an aqueous solution dissociates into a bicarbonate ion (HCO 3-) and a hydrogen ion (H+) Thus,
H2CO3
HCO3- + H+
If the pH of the blood increases, one would expect
a. a decrease in the concentration of H2CO3 and an increase in the concentration of H 2O.
b. an increase in the concentration of H2CO3 and a decrease in the concentration of H2O.
c. a decrease in the concentration of HCO3- and an increase in the concentration of H 2O.
d. an increase in the concentration of HCO3- and a decrease in the concentration of H 2O.
e. a decrease in the concentration of HCO3- and an increase in the concentration of both H2CO3and H2O.
Use the figure below to answer the following question.
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Observe the structures of glucose and fructose. These two molecules are
a. geometric isotopes.
b. enantiomers.
c. geometric isomers.
d. structural isomers.
e. nonisotopic isomers.
Use the figure below to answer the following questions.
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Which of the structures is an impossible covalently bonded molecule?
a. A
b. B
c. C
d. D
e. E
Use the figure below to answer the following questions.
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Which is a hydroxyl functional group?
a. Group A
b. Group B
c. Group C
d. Group D
e. Group E
Which is a carbonyl functional group?
a. Group A
b. Group B
c. Group C
d. Group D
e. Group E
Which is a functional group that helps stabilize proteins by forming covalent cross-links within or between protein molecules?
a. Group A
b. Group B
c. Group C
d. Group D
e. Group E
Which is an acidic functional group that can dissociate and release H+ into a solution?
a. Group A
b. Group B
c. Group C
d. Group D
e. Group E
Use the molecules shown in the figure below to answer the following questions.
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Which molecule is water-soluble because it has a hydroxyl functional group?
a. Molecule A
b. Molecule B
c. Molecule C
d. Molecule D
e. Molecule E
Which molecules contain a carbonyl group?
a. A and B
b. B and C
c. C and D
d. D and E
e. E and A
Which molecule can increase the concentration of hydrogen ions in a solution and is therefore an organic acid?
a. Molecule A
b. Molecule B
c. Molecule C
d. Molecule D
e. Molecule E
Which of the following is not one of the four major groups of macromolecules found in living organisms?
a. glucose
b. carbohydrates
c. lipids
d. proteins
e. nucleic acids
A molecule with the chemical formula C16H32O16 is probably a
a. carbohydrate.
b. lipid.
c. protein.
d. nucleic acid.
e. hydrocarbon.
Which of the following are polysaccharides?
a. glycogen
b. starch
c. chitin
d. A and B only
e. A, B, and C
What is the molecule illustrated in the figure below?
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a. a saturated fatty acid
b. an unsaturated fatty acid
c. a polyunsaturated triacylglyceride
d. a trans polyunsaturated triacylglyceride
e. a steroid similar to cholesterol
The molecule shown in the figure below is a
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a. polysaccharide.
b. polypeptide.
c. saturated fatty acid.
d. triacylglycerol.
e. unsaturated fatty acid.
The hydrogenation of vegetable oil would result in which of the following?
a. a decrease in the number of carbon-carbon double bonds in the oil (fat. molecules
b. an increase in the number of hydrogen atoms in the oil (fat. molecule
c. the oil (fat. being a solid at room temperature
d. A and C only
e. A, B, and C
The chemical reaction illustrated in the figure below results in the formation of a (an)
a. ionic bond.
b. peptide bond.
c. glycosidic linkage.
d. ester linkage.
e. phosphodiester linkage.
The bonding of two amino acid molecules to form a larger molecule requires which of the following?
a. removal of a water molecule
b. addition of a water molecule
c. formation of an ionic bond
d. formation of a hydrogen bond
e. both A and C
Use the figure below to answer the following questions.
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Which bond is closest to the C-terminus of the molecule?
a. Bond A
b. Bond B
c. Bond C
d. Bond D
e. Bond E
Which bonds are created during the formation of the primary structure of a protein?
a. peptide bonds
b. hydrogen bonds
c. disulfide bonds
d. phosphodiester bonds
e. A, B, and C
What maintains the secondary structure of a protein?
a.
b.
c.
d.
e.
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peptide bonds
hydrogen bonds
disulfide bonds
ionic bonds
phosphodiester bonds
The
helix and the
pleated sheet are both common polypeptide forms found in which level of protein structure?
a. primary
b. secondary
c. tertiary
d. quaternary
e. all of the above
The tertiary structure of a protein is the
a. bonding together of several polypeptide chains by weak bonds.
b. order in which amino acids are joined in a polypeptide chain.
c. unique three-dimensional shape of the fully folded polypeptide.
d. organization of a polypeptide chain into an á helix or â pleated sheet.
e. overall protein structure resulting from the aggregation of two or more polypeptide subunits.
A strong covalent bond between amino acids that functions in maintaining a polypeptide's specific three-dimensional shape is a (an)
a. ionic bond.
b. hydrophobic interaction.
c. van der Waals interaction.
d. disulfide bond.
e. hydrogen bond.
At which level of protein structure are interactions between the side chains (R groups. most important?
a. primary
b. secondary
c. tertiary
d. quaternary
e. all of the above
The R group or side chain of the amino acid serine is –CH2-OH. The R group or side chain of the amino acid alanine is –CH3. Where
would you expect to find these amino acids in a globular protein in aqueous solution?
a. Serine would be in the interior, and alanine would be on the exterior of the globular protein.
b. Alanine would be in the interior, and serine would be on the exterior of the globular protein.
c. Both serine and alanine would be in the interior of the globular protein.
d. Both serine and alanine would be on the exterior of the globular protein.
e. Both serine and alanine would be in the interior and on the exterior of the globular protein.
The globular protein transthyretin results from the aggregation of four polypeptide subunits. Each of the subunits is a polypeptide
chain with an
helix region. Which structure(s) must the transthyretin protein have?
a. primary structure
b. primary and secondary structure
c. primary, secondary, and tertiary structure
d. primary, secondary, tertiary, and quaternary structure
e. primary, secondary, tertiary, quaternary, and alpha structure
All of the following molecules are proteins except
a. hemoglobin.
b. transthyretin.
c. collagen.
d. lysozyme.
e. glycogen.
What is the term used for a change in a protein's three-dimensional shape or conformation due to disruption of hydrogen bonds,
disulfide bridges, or ionic bonds?
a. hydrolysis
b. stabilization
c. destabilization
d. renaturation
e. denaturation
Which of the following are nitrogenous bases of the purine type?
a. cytosine and guanine
b. guanine and adenine
c. adenine and thymine
d. thymine and uracil
e. uracil and cytosine
In the double helix structure of nucleic acids, cytosine hydrogen bonds to
a. deoxyribose.
b. ribose.
c. adenine.
d. thymine.
e. guanine.
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The structural feature that allows DNA to replicate is the
a. sugar-phosphate backbone.
b. complementary pairing of the nitrogenous bases.
c. disulfide bonding (bridging) of the two helixes.
d. twisting of the molecule to form an á helix.
e. three-component structure of the nucleotides.
The following questions are based on the 15 molecules illustrated below. Each molecule may be used once, more than once, or not at
all.
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Which of the following combinations could be linked together to form a nucleotide?
a. 1, 2, and 11
b. 3, 7, and 8
c. 5, 9, and 10
d. 11, 12, and 13
e. 12, 14, and 15
Which of the following molecules contain(s) an aldehyde type of carbonyl functional group?
a. 1
b. 4
c. 8
d. 10
e. 1 and 4
Which of the following molecules is a saturated fatty acid?
a. 1
b. 5
c. 6
d. 8
e. 9
Which of the following molecules is a purine type of nitrogenous base?
a. 2
b. 3
c. 5
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d. 12
e. 13
Which of the following molecules is the pentose sugar found in RNA?
a. 1
b. 4
c. 6
d. 12
e. 13
Which of the following molecules consists of a hydrophilic "head" region and a hydrophobic "tail" region?
a. 2
b. 5
c. 7
d. 9
e. 11
Which of the following statements is false?
a. 1 and 4 could be joined together by a glycosidic linkage to form a disaccharide.
b. 9 and 10 could be joined together by ester bonds to form a triacylglycerol.
c. 2 and 7 could be joined together to form a short peptide.
d. 2, 7, and 8 could be joined together to form a short peptide.
e. 14 and 15 could be joined together to form a polypeptide.