Proteins Flashcards
1
Q
Which of the following are considered the most important biological compound?
a. vitamins
b. carbohydrates
c. lipids
d. proteins
A
d. proteins
2
Q
What are the basic structural units of proteins?
a. amino acids
b. monosaccharides
c. triglycerides
d. fatty acids
A
a. amino acids
3
Q
Which of the following is a function of proteins?
a. catalysis
b. movement
c. storage
d. all of these
A
d. all of these
4
Q
Which of the following is a structural protein?
a. cellulose
b. collagen
c. hemoglobin
d. insulin
A
b. collagen
5
Q
Which of the following proteins is associated with the movement of muscles?
a. actin
b. ferritin
c. hemoglobin
d. insulin
A
a. actin
6
Q
Which of the following proteins is associated with the storage of iron?
a. actin
b. ferritin
c. hemoglobin
d. insulin
A
b. ferritin
7
Q
Which of the following proteins is a hormone?
a. casein
b. hemoglobin
c. insulin
d. all of these
A
c. insulin
8
Q
- Identify a statement that is true of the functions of proteins.
a. Ferritin, a protein that is found in the liver, stores iron in the body.
b. Hemoglobin, a protein, carries oxygen from cells to the lungs.
c. Antigens are proteins that are produced by the body to counteract antibodies.
d. Keratin forms the skeletal muscles of the body.
A
a. Ferritin, a protein that is found in the liver, stores iron in the body.
9
Q
Which of the following proteins can assist in blood clotting?
a. insulin
b. erythropoietin
c. fibrinogen
d. ferritin
A
c. fibrinogen
10
Q
Which of the following statements is true of the water solubility of proteins?
a. Both fibrous and globular proteins are insoluble in water.
b. Both fibrous and globular proteins are soluble in water.
c. Fibrous proteins are insoluble in water.
d. Globular proteins are insoluble in water.
A
c. Fibrous proteins are insoluble in water.
11
Q
Which of the following proteins stimulates the formation of red blood cells in the body?
a. fibrinogen
b. collagen
c. casein
d. erythropoietin
A
d. erythropoietin
12
Q
Which of the following is not a fibrous protein?
a. actin
b. collagen
c. keratin
d. None, they are all fibrous proteins.
A
a. actin
13
Q
Which of the following is an achiral amino acid?
a. proline
b. glycine
c. alanine
d. arginine
A
b. glycine
14
Q
How many naturally occurring amino acids are commonly found in proteins?
a. 10
b. 20
c. 25
d. 100
A
b. 20
15
Q
Which of the following amino acids contains nitrogen in its side chain?
a. cysteine
b. glycine
c. proline
d. leucine
A
c. proline
16
Q
What is the most important aspect of an amino acid’s side chain?
a. its polarity
b. its shape
c. its size
d. none of these
A
a. its polarity
17
Q
Which of the following amino acid side chains is hydrophobic?
a. acidic
b. basic
c. polar but neutral
d. none of these
A
d. none of these
18
Q
Which of the following amino acid side chains is hydrophobic?
a. acidic
b. nonpolar
c. polar but neutral
d. none of these
A
b. nonpolar
19
Q
Which of the following amino acid side chains is hydrophilic?
a. acidic
b. basic
c. polar but neutral
d. all of these
A
d. all of these
20
Q
Which of the following amino acids is not optically active?
a. alanine
b. glycine
c. tryptophan
d. none, all of these are optically active
A
b. glycine
21
Q
Which of the following statements is true of all amino acids?
a. All amino acids have a D-isomer.
b. All amino acids have an L-isomer.
c. The amino group is attached to the carbon atom of the carboxyl group.
d. The amino group and the carbon of the carboxyl group are attached to the same carbon atom.
A
d. The amino group and the carbon of the carboxyl group are attached to the same carbon atom.
22
Q
Which of the following pair of amino acids has sulfur-containing side chains?
a. cysteine and glycine
b. cysteine and methionine
c. histidine and methionine
d. phenylalanine and tryptophan
A
b. cysteine and methionine
23
Q
Which of the following is a β-hydroxy-α-amino acid?
a. asparagine
b. serine
c. tryptophan
d. none of these
A
b. serine
24
Q
Which of the following amino acids has a hydroxyl side chain?
a. asparagine
b. glutamine
c. threonine
d. none of these
A
c. threonine
25
Which of the following pair of amino acids has nonpolar side chains?
a. cysteine and glycine
b. cysteine and methionine
c. histidine and methionine
d. phenylalanine and tryptophan
d. phenylalanine and tryptophan
26
Which of the following pair of amino acids has polar but neutral side chains?
a. cysteine and methionine
b. cysteine and serine
c. histidine and methionine
d. phenylalanine and tryptophan
27
Which of the following pair of amino acids has basic side chains?
a. cysteine and glycine
b. cysteine and methionine
c. histidine and lysine
d. phenylalanine and tryptophan
c. histidine and lysine
28
Which of the following statements is true of zwitterions?
a. They are positively charged.
b. They are negatively charged.
c. They are electrically neutral.
d. They are made up of basic amino acids.
29
Which of the following explains the unusually high melting points of amino acids?
a. their unusually high molecular weights
b. the polarity of their side chains
c. the presence of nitrogen atoms in their side chains
d. their existence as zwitterions in polar solvents
30
Which of the following is true of amino acids that are dissolved in water?
a. They exist in an un-ionized form at high pH.
b. They exist in an un-ionized form at low pH.
c. They exist in an un-ionized form only at a specific pH.
d. They do not exist in an un-ionized form at any pH.
d. They do not exist in an un-ionized form at any pH.
31
What is the approximate isoelectric point (pI) of most amino acids?
a. 3
b. 6
c. 7
d. 10
32
Which of the following amino acids has the lowest pI?
a. arginine
b. cysteine
c. glycine
d. glutamic acid
d. glutamic acid
33
Which of the following amino acids has the highest pI?
a. arginine
b. cysteine
c. glycine
d. glutamic acid
34
Which of the following statements is true of the isoelectric point of amino acids?
a. It is the same for all amino acids.
b. It is the pH at which an amino acid conducts electricity.
c. It is the pH at which an amino acid has equal numbers of positive and negative charges.
d. All of these statements are true.
35
Which of the following is true of an amino acid at a pH below its isoelectric point?
a. It will have a negative charge.
b. It will be electrically neutral.
c. It will have a positive charge.
d. It is impossible to predict the charge of an amino acid.
36
Which of the following is true of an amino acid at a pH above its isoelectric point?
a. It will have a negative charge.
b. It will be electrically neutral.
c. It will have a positive charge.
d. It is impossible to predict the charge of an amino acid.
a. It will have a negative charge.
37
What determines the functions of amino acids?
a. their molecular weight
b. their side chain
c. both molecular weight and side chain
d. neither molecular weight nor side chain
b. their side chain
38
Which of the following amino acids can be easily dimerized?
a. alanine
b. cysteine
c. glycine
d. methionine
39
Which of the following contains a disulfide bond?
a. alanine
b. cysteine
c. cystine
d. methionine
40
Which of the following diseases is associated with lower-than-normal levels of L-dopa?
a. Alzheimer's disease
b. Schizophrenia
c. Parkinson's disease
d. Bipolar disorder
41
Which of the following types of chemical reaction is involved in the conversion of dopamine to epinephrine?
a. addition
b. reduction
c. decarboxylation
d. methylation
42
What type of chemical reaction is involved in the formation of cystine from cysteine?
a. addition
b. reduction
c. oxidation
d. substitution
43
What type of chemical reaction is involved in the conversion of cystine to cysteine?
a. addition
b. reduction
c. oxidation
d. substitution
44
How many essential amino acids have acidic side chains?
a. 1
b. 2
c. 3
d. 4
45
How many essential amino acids have basic side chains?
a. 1
b. 2
c. 3
d. 4
c. 3
46
Which of the following amino acids has an imidazole group side chain?
a. lysine
b. tryptophan
c. histidine
d. tyrosine
47
Which amino acid can be found in proteins in both its protonated and unprotonated forms?
a. alanine
b. glycine
c. histidine
d. phenylalanine
c. histidine
48
Serotonin, a neurotransmitter, has a calming effect. Which of the following amino acids is the precursor of serotonin?
a. arginine
b. glutamic acid
c. isoleucine
d. tryptophan
49
Which of the following neurotransmitters is associated with manic-depressive schizophrenia?
a. adrenaline
b. norepinephrine
c. serotonin
d. none of these
c. serotonin
50
Which of the following amino acids has a guanidino group in its side chain?
a. asparagine
b. glutamic acid
c. arginine
d. none of these
c. arginine
51
Which of the following amino acids absorbs UV radiation at 280 nm?
a. phenylalanine
b. tryptophan
c. tyrosine
d. all of these
52
Which of the following amino acids absorbs UV radiation at 280 nm?
a. arginine
b. alanine
c. leucine
d. tyrosine
d. tyrosine
53
What is the chemical name of serotonin?
a. 5-hydroxyphenylalanine
b. 5-hydroxytryptamine
c. 3-hydroxytyrosine
d. 3-hydroxyvaline
b. 5-hydroxytryptamine
54
From which amino acid is tyrosine usually derived?
a. cysteine
b. phenylalanine
c. tryptophan
d. valine
55
Neurotransmitters known as catecholamines are formed from which amino acid?
a. cysteine
b. threonine
c. tyrosine
d. valine
c. tyrosine
56
Which pair of the amino acids is the precursors of norepinephrine and epinephrine?
a. aspartic acid and glutamic acid
b. cysteine and methionine
c. isoleucine and leucine
d. phenylalanine and tyrosine
57
Which of the following amino acids is occasionally found in proteins?
a. asparagine
b. hydroxyproline
c. proline
d. serine
58
Which of the following amino acids functions as a hormone?
a. leucine
b. lysine
c. thyroxine
d. tyrosine
c. thyroxine
59
Which of the following amino acids contains iodine atoms in its structure?
a. leucine
b. lysine
c. thyroxine
d. tyrosine
60
Which protein contains both hydroxylysine and hydroxyproline?
a. actin
b. collagen
c. fibrinogen
d. hemoglobin
b. collagen
61
How are the dipeptides Ala—Gly and Gly—Ala related to each other?
a. They are the same compound.
b. They have the same properties.
c. They are constitutional isomers.
d. They are mirror images.
62
What is a residue?
a. An amino acid that has been severed from a protein
b. Any individual amino acid in a protein or a polypeptide
c. The portion of a protein that remains after one amino acid has been removed from its C-terminus
d. The portion of a protein that remains after one amino acid has been removed from its N-terminus
63
Identify the correct naming convention followed while naming a protein or polypeptide.
a. The convention of naming proteins is different from that of polypeptides.
b. They are named starting from the C-terminus residue to the N-terminus residue.
c. They are named starting from the middle toward both ends.
d. They are named starting from the N-terminus residue to the C-terminus residue.
64
64
What is the direction of protein synthesis?
a. from the C-terminus to the N-terminus
b. from the middle toward both the ends
c. from the N-terminus to the C-terminus
d. The direction varies from one protein to another.
c. from the N-terminus to the C-terminus
65
65
66
67
68
How are amino acids primarily linked in a protein?
a. by peptide bonds
b. by hydrogen bonds
c. by ester bonds
d. by ionic bonds
69
70
Which of the following is true of the atoms in a protein's backbone unit?
a. All of them are in a straight line.
b. All of them are in the same plane.
c. All of them have tetrahedral geometry.
d. None of these are correct.
71
What is the conformation of the peptide bond that is present between the amino acids in a protein?
a. planar
b. chair
c. bent
d. nonplanar
a. planar
72
At which pH does a protein have a net positive charge?
a. at its isoelectric point
b. never
c. at the pH above its isoelectric point
d. at the pH below its isoelectric point
73
At which pH does a protein have a net negative charge?
a. at its isoelectric point
b. never
c. at the pH above its isoelectric point
d. at the pH below its isoelectric point
c. at the pH above its isoelectric point
74
At which pH does a protein have the lowest solubility?
a. at a very low pH
b. at a neutral pH of 7
c. at a very high pH
d. at its isoelectric point
75
Which of the following statements is true of the polarity of proteins?
a. All proteins are acidic.
b. All proteins are basic.
c. All proteins are neutral.
d. The polarity of a protein depends on its side chains
d. The polarity of a protein depends on its side chains
76
Which of the following defines the primary structure of a protein?
a. the geometric arrangement of the backbone atoms of a protein
b. the geometric arrangement of the side chains of a protein
c. the sequence of the amino acids in a protein
d. all of the above
c. the sequence of the amino acids in a protein
77
How many different dipeptides can be made from 20 amino acids?
a. 20
b. 40
c. 200
d. 400
78
How are the two chains of insulin linked?
a. by peptide bonds
b. by ester bonds
c. by hydrogen bonds
d. by disulfide bonds
d. by disulfide bonds
79
How many different tripeptides can be made from 20 amino acids?
a. 60
b. 400
c. 6840
d. 8000
d. 8000
80
How many amino acids are present in human insulin, which is a hormone that regulates blood glucose?
a. 51
b. 104
c. 30
d. 21
81
How many different tripeptides can be made from glycine, alanine, and valine if the tripeptide contains each amino
acid only once?
a. 3
b. 6
c. 18
d. 36
b. 6
82
How many different tripeptides can be made from glycine and valine?
a. 4
b. 6
c. 8
d. 12
83
Which of the following is true of the relationship between the primary structure and the function of a protein?
a. A change in one amino acid always affects the function of a protein.
b. A change in one amino acid may or may not affect the function of a protein.
c. A change in one amino acid never affects the function of a protein.
d. The primary structure of a protein and its function are not related.
84
How many amino acid residues are present in both vasopressin and oxytocin?
a. 5
b. 7
c. 9
d. 11
c. 9
85
Hydroxyurea is used to treat and control the symptoms of _____.
a. malaria
b. diabetes
c. sickle cell anemia
d. phenylketonuria
86
Individuals with the genes for sickle cell anemia are resistant to which of the following diseases?
a. flu
b. malaria
c. polio
d. sleeping sickness
87
Which of the following is a type of secondary structure that is found in proteins?
a. α-helix
b. β-pleated sheet
c. both α-helix and β-pleated sheet
d. neither α-helix nor β-pleated sheet
88
Which of the following is a type of secondary structure that is found in proteins?
a. α-pleated sheet
b. β-helix
c. both α-pleated sheet and β-helix
d. neither α-pleated sheet nor β-helix
89
Which of the following is true of protein secondary structures?
a. They are the linear sequences of amino acids.
b. They are the repetitive conformations of the protein backbone.
c. They are held together by strong van der Waals forces of attraction.
d. They include parallelly arranged β-pleated sheets only.
90
Which of the following secondary structures is maintained by both intermolecular or intramolecular hydrogen bonds?
a. α-helix
b. β-pleated sheet
c. a hairpin turn
d. all of these
b. β-pleated sheet
91
Which of the following proteins has a predominant α-helix structure?
a. keratin
b. fibroin
c. both keratin and fibroin
d. neither keratin nor fibroin
a. keratin
92
Which of the following proteins has a predominant β-pleated sheet structure?
a. keratin
b. fibroin
c. both keratin and fibroin
d. neither keratin nor fibroin
93
Which of the following proteins has an extended helix secondary structure?
a. collagen
b. keratin
c. silk
d. none of these
94
Which amino acid accounts for about 33% of the collagen structure?
a. alanine
b. glycine
c. valine
d. lysine
95
Which of the following amino acids is not found in collagen?
a. glycine
b. hydroxyproline
c. proline
d. None, they are all found in collagen.
96
vWhich of the following defines the tertiary structure of proteins?
a. It is the sequence of amino acid in proteins.
b. It refers to the repetitive conformations of the protein backbone.
c. It is the overall 3-D conformation of a polypeptide chain and the interactions of the side chains.
d. It is the interaction between the subunits of a protein that has more than one polypeptide chain.
97
Which of the following interactions is not associated with the stabilization of the tertiary structure of a protein?
a. covalent bonding
b. hydrogen bonding
c. hydrophobic interactions
d. None, they are all associated with the tertiary structure.
98
In the tertiary structure of proteins, which amino acid is involved in the formation of covalent bonds?
a. alanine
b. aspartic acid
c. cysteine
d. tryptophan
99
Which of the following pair of amino acids can form hydrogen bonds?
a. alanine and glutamic acid
b. aspartic acid and lysine
c. leucine and phenylalanine
d. serine and tyrosine
d. serine and tyrosine
100
Which of the following pair of amino acids can form a salt bridge?
a. alanine and glutamic acid
b. aspartic acid and lysine
c. leucine and phenylalanine
d. serine and tyrosine
101
Which of the following pair of amino acids develops hydrophobic interactions?
a. alanine and glutamic acid
b. aspartic acid and lysine
c. leucine and phenylalanine
d. serine and tyrosine
c. leucine and phenylalanine
102
Which of the following defines the quaternary structure of proteins?
a. It is the sequence of amino acids in proteins.
b. It refers to repetitive conformations of the protein backbone.
c. It is the overall 3-D conformation of a polypeptide chain and the interactions of the side chains.
d. It is the interaction between the subunits of a protein that has more than one polypeptide chain.
d. It is the interaction between the subunits of a protein that has more than one polypeptide chain.
103
Which of the following proteins assists other proteins in attaining their proper secondary and tertiary structures?
a. insulin
b. chaperones
c. prions
d. myosin
b. chaperones
104
Which of the following amino acids are linked via metal ions?
a. arginine and glutamic acid
b. glutamic acid and aspartic acid
c. isoleucine and lysine
d. phenylalanine and alanine
105
How many polypeptide chains are present in hemoglobin?
a. one
b. two
c. three
d. four
106
Which phenomenon is exhibited during the binding of oxygen to hemoglobin?
a. negative cooperativity
b. metallic interaction
c. positive cooperativity
d. hydrophobic interaction
107
How does fetal hemoglobin differ from adult hemoglobin?
a. Fetal hemoglobin does not have α-chains.
b. Fetal hemoglobin does not have β-chains.
c. Fetal hemoglobin does not have γ-chains.
d. Fetal hemoglobin does not differ from adult hemoglobin.
c. Fetal hemoglobin does not have γ-chains.
107
Which of the following proteins contains a prosthetic group?
a. collagen
b. hemoglobin
c. insulin
d. none of these
108
Identify the protein whose complete tertiary structure was determined for the first time by X-ray crystallography.
a. collagen
b. insulin
c. hemoglobin
d. myoglobin
d. myoglobin
109
What is the shape of the oxygen-binding curve of myoglobin?
a. parabolic
b. sigmoidal
c. sinusoidal
d. hyperbolic
110
Which of the following is an allosteric protein?
a. hemoglobin
b. myoglobin
c. both hemoglobin and myoglobin
d. neither hemoglobin nor myoglobin
111
Which of the following structures contains hemoglobin that is 100% saturated with oxygen?
a. capillaries of active muscles
b. alveoli of the lungs
c. hepatocytes of the liver
d. cells of the intestinal tract
b. alveoli of the lungs
112
Which of the following denaturing agents affects disulfide bonds?
a. detergent
b. heat
c. heavy metals
d. urea
c. heavy metals
112
Which level of a protein structure is not affected by denaturation?
a. primary
b. secondary
c. tertiary
d. quaternary
113
Which of the following denaturing agents opens up the hydrophobic regions of a protein?
a. detergents
b. heat
c. heavy metals
d. urea
114
Which of the following regions of proteins are affected by the denaturing agent urea?
a. hydrogen bonds
b. disulfide bonds
c. hydrophobic regions
d. salt bridges
114
Why is 70% ethanol used to sterilize skin before injections instead of 95% ethanol?
a. 70% ethanol kills bacteria by denaturing their surface proteins.
b. 70% ethanol penetrates bacteria and kills them by coagulating their proteins.
c. 70% ethanol can kill bacteria without damaging their structures.
d. None of these are correct.
115
Identify the disease that is caused by conformational change in the α-helical content of the normal prion protein.
a. Mad cow disease
b. Scrapie disease
c. Creutzfeld-Jakob disease
d. All of these
d. All of these
116
Which of the following statements is true of the structure of myoglobin?
a. It is a fibrous protein molecule.
b. It consists of two polypeptide chains of 175 amino acids.
c. It has a prosthetic group called the heme group.
d. It has eight β-pleated sheet regions.
c. It has a prosthetic group called the heme group.
117
Which of the following amino acids plays a vital role in the interaction between the heme group and bound oxygen in
hemoglobin?
a. methionine
b. lysine
c. histidine
d. tryptophan
118
What is an apoprotein?
a. the prosthetic part of a protein
b. a polypeptide chain with a prosthetic group
c. a polypeptide chain without a prosthetic group
d. all of these
119
Identify the statement that is true of the heme group of hemoglobin.
a. The heme group contains an iron ion in its Fe3+ oxidation state.
b. The porphyrin part of the heme group consists of four pyrrole rings.
c. The pyrrole rings are linked together to form a tetrahedral structure.
d. The iron ion in the heme group has eight coordination sites.
120
Besides oxygen, which of the following gases can bind to the heme group of hemoglobin?
a. sulfur dioxide
b. chlorine
c. carbon monoxide
d. argon
121
Why is carbon monoxide poisonous in larger quantities?
a. because it enhances the binding of oxygen to the heme group
b. because it decreases the synthesis of hemoglobin in the bone marrow
c. because it disrupts the final step of the electron transport chain
d. because it disrupts the process of gluconeogenesis in the body
122
123
Which of the following chemical interactions is associated with the treatment of heavy metal poisoning?
a. hydrogen bonding
b. covalent bonding
c. a hydrophobic interaction
d. salt bridges
e. a metal ion coordination
124
Proteins are polymers in which:
a. Unbranched chains of amino acids are present.
b. Branched chains of amino acids are present.
c. Both unbranched and branched chains of amino acids are present.
d. Alternating amino acid and glucose monomer units are present.
a. Unbranched chains of amino acids are present.
125
Which of the following statements concerning proteins is incorrect?
a. The amino acids in a protein can be polar, nonpolar, or neutral in nature.
b. All proteins contain the elements C, H, O, and N.
c. All proteins are made of amino acids.
d. The amino acids in a protein are linked by ionic bonds.
126
Which of the following statements concerning standard amino acids is incorrect?
a. There are four main categories of amino acids.
b. They are all alpha-amino acids.
c. None of the standard amino acids are chiral.
d. Each of them has an amino group and a carboxyl group.
c. None of the standard amino acids are chiral.
127
How do the standard amino acids differ from one another?
a. in whether or not the amino group is chiral
b. in whether or not the carboxyl group is chiral
c. in the number of chiral carbon atoms between the carboxyl group and the amino group
d. in the identity of the R group (side chain)
128
128
Which of the following sets of elements is a possible composition for a standard amino acid?
a. carbon, hydrogen, oxygen, and sulfur
b. carbon, hydrogen, nitrogen, and sulfur
c. carbon, hydrogen, and nitrogen
d. carbon, hydrogen, oxygen, nitrogen, and sulfur
d. carbon, hydrogen, oxygen, nitrogen, and sulfur
129
130
131
The joining together of two amino acids to form a dipeptide involves the reaction between
a. two amide groups
b. an amino group and an alpha-carbon
c. an amino group and a carboxyl group
d. an alpha-carbon and a hydroxyl group
c. an amino group and a carboxyl group
132
133
How many peptide linkages are present in a tripeptide?
a. two
b. three
c. four
d. five
a. two
134
In the tetrapeptide Phe-Gln-Trp-His, the C-terminal amino acid is
a. Phe
b. Gln
c. Trp
d. His
