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General, Organic, and Biological Chemistry, 4e (Timberlake)
Chapter 19 Amino Acids and Proteins
19.1 Multiple-Choice Questions
- Which of the following is NOT a function of proteins?
A) provide structural components
B) stores the genetic information of a living organism
C) movement of muscles
D) catalyze reactions in the cells
E) transport substances through the bloodstream
Answer: B
Objective: 19.
Global Outcomes: GO
- Collagen, a protein found in tendons and cartilage, would be classified as a __________
protein.
A) catalytic
B) structural
C) transport
D) storage
E) hormone
Answer: B
Objective: 19.
Global Outcomes: GO
- Wool is primarily made up of
A) protein.
B) carbohydrate.
C) globin.
D) triacylglycerols.
E) enkephalin.
Answer: A
Objective: 19.
Global Outcomes: GO
- Sucrase, the protein that facilitates the hydrolysis of sucrose, would be classified as a
__________ protein.
A) transport
B) hormonal
C) catalytic
D) structural
E) contractile
Answer: C
Objective: 19.
Global Outcomes: GO
1
- The structural formulas of amino acids are the same EXCEPT for the
A) carboxyl group.
B) alpha carbon.
C) amino group.
D) side (R) group.
E) hydrogen bonding.
Answer: D
Objective: 19.
Global Outcomes: GO
- The following amino acid R group chain is
A) polar.
B) hydrophobic.
C) hydrophilic.
D) acidic.
E) basic.
Answer: B
Objective: 19.
Global Outcomes: GO
- Which of the following would be most likely to be deficient in at least one essential amino
acid?
A) eggs
B) milk
C) beans
D) steak
E) ham
Answer: C
Objective: 19.
Global Outcomes: GO
- Amino acids that are not synthesized in the body and must be obtained from the diet are called
A) essential.
B) polar.
C) nonpolar.
D) complete.
E) incomplete.
Answer: A
Objective: 19.
Global Outcomes: GO
2
- A basic amino acid has an R group that contains
A) an amine group.
B) a carboxyl group.
C) a methyl group.
D) an alcohol group.
E) a thiol group.
Answer: A
Objective: 19.
Global Outcomes: GO
- At a pH > 9, the zwitterion of glycine (pI=6.0) will have
A) a net positive charge.
B) a net negative charge.
C) an overall charge of zero.
D) low solubility in water.
E) a negative charge on the nitrogen.
Answer: B
Objective: 19.
Global Outcomes: GO
- At a pH < 5, the zwitterion for alanine (pI = 6) will have
A) a net positive charge.
B) a net negative charge.
C) an overall charge of zero.
D) low solubility in water.
E) a negative charge on the carboxyl group.
Answer: A
Objective: 19.
Global Outcomes: GO
4
- What is the structural formula of glutamic acid (pI = 3.2) at pH = 1?
A)
B)
C)
D)
E)
Answer: E
Objective: 19.
Global Outcomes: GO
- Consider a mixture of the amino acids lysine (pI = 9.7), tyrosine (pI = 5.7), and glutamic acid
(pI = 3.2) at a pH 5.7 that is subjected to an electric current. __________ will migrate towards
the positive electrode(+).
A) Lysine
B) Tyrosine
C) Glutamic acid
D) All of the amino acids
Answer: C
Objective: 19.
Global Outcomes: GO
5
high pH?
A)
B) -CH
OH
C) -CH
D)
E)
Answer: A
Objective: 19.
Global Outcomes: GO
7
- Which of the following is the correct structure for Ser-Ala-Asp? The appropriate side chains
look like this.
Ala: - CH 3
; Ser: - CH 2
OH; Asp:
A)
B)
C)
D)
E)
Answer: E
Objective: 19.
Global Outcomes: GO
8
- Which of the following shows all of the tripeptides that can be formed from one molecule
each of lysine (Lys), threonine (Thr), and histidine (His)?
A) Lys-Thr-His
B) Lys-Thr-His, Lys-His-Thr, His-Thr-Lys, His-Lys-Thr, Thr-Lys-His, Thr-His-Lys
C) Lys-Thr-His, Lys-His-Thr, His-Lys-Thr, Thr-His-Lys
D) Lys-Thr-His, Lys-His-Thr, His-Lys-Thr
E) Lys-Thr-His, Lys-His-Thr
Answer: B
Objective: 19.
Global Outcomes: GO
- A peptide bond contains which kind of functional group?
A) alcohol
B) amine
C) amide
D) carboxylic acid
E) ketone
Answer: C
Objective: 19.
Global Outcomes: GO
- A chain made of more than 50 amino acids is usually referred to as a(n)
A) peptide.
B) protein.
C) enzyme.
D) globulin.
E) hormone.
Answer: B
Objective: 19.
Global Outcomes: GO
- Which of the following is an example of a secondary protein structure?
A) dipeptide
B) triglyceride
C) a helix
D) amino acid
E) fatty acid
Answer: C
Objective: 19.
Global Outcomes: GO
10
- The α helix of the secondary structure of a protein is held together by __________ between
two widely separated parts of a protein chain.
A) hydrogen bonds
B) disulfide bridges
C) salt bridges
D) hydrophilic interactions
E) hydrophobic interactions
Answer: A
Objective: 19.
Global Outcomes: GO
- In the β -pleated sheet secondary structure of a protein, two or more amino acid sequences in
separate parts of the protein are held together
A) in a coil, by hydrogen bonding.
B) in random order, due to hydrophobic interactions.
C) in a triple helix.
D) in a double helix.
E) in a zig-zag conformation, by hydrogen bonding.
Answer: E
Objective: 19.
Global Outcomes: GO
- Enkephalins are polypeptides that have
A) a sweet taste.
B) a bitter taste.
C) extra caloric value.
D) pain-killing properties.
E) hormone activity.
Answer: D
Objective: 19.
Global Outcomes: GO
- Enkephalins, naturally produced opiates in the body, are found in
A) muscles and bone tissue.
B) brain and kidney tissue.
C) thalamus and spinal cord tissue.
D) heart and lung tissue.
E) pancreas and liver tissue.
Answer: C
Objective: 19.
Global Outcomes: GO
11
- Hemoglobin is an example of a protein with
A) primary structure only.
B) two protein chains held together.
C) a globular structure.
D) primarily a β -pleated sheet structure.
E) primarily an α helix structure.
Answer: C
Objective: 19.
Global Outcomes: GO
- The heme in hemoglobin is a(n)
A) protein chain.
B) small molecule within a protein.
C) helix area in the hemoglobin molecule.
D) pleated sheet area in the hemoglobin molecule.
E) oxygen molecule within the hemoglobin molecule.
Answer: B
Objective: 19.
Global Outcomes: GO
- Within hemoglobin, the heme functions as
A) a disulfide bridge.
B) an oxygen carrier.
C) a reducing agent.
D) an α subunit.
E) one of the four protein subunits.
Answer: B
Objective: 19.
Global Outcomes: GO
- Hemoglobin has a total of __________ protein chains in its quaternary structure.
A) one
B) two
C) three
D) four
E) five
Answer: D
Objective: 19.
Global Outcomes: GO
13
- The fibrous protein responsible for the structure of hair and wool is
A) keratin.
B) collagen.
C) endorphin.
D) myosin.
E) casein.
Answer: A
Objective: 19.
Global Outcomes: GO
- Which R group would most likely be found in a hydrophobic area of the tertiary structure of
a globular protein?
A) -CH
OH
B) - CH
COO
C)
D) - CH
CH
CH
CH
N
H
E)
Answer: C
Objective: 19.
Global Outcomes: GO
- What type of interaction would you expect between the following R groups in the tertiary
structure of a protein?
A) disulfide bonds
B) salt bridges
C) hydrogen bonds
D) hydrophobic interactions
E) peptide bonds
Answer: B
Objective: 19.
Global Outcomes: GO
14
- Acids and bases denature a protein by disrupting
A) peptide bonds and ionic bonds.
B) amide bonds and alkene bonds
C) hydrophobic interactions and peptide bonds.
D) ionic bonds and hydrophobic interactions.
E) ionic bonds and hydrogen bonds.
Answer: E
Objective: 19.
Global Outcomes: GO
- Heat denatures a protein by disrupting
A) ionic bonds and peptide bonds.
B) hydrophobic bonds and hydrogen bonds.
C) peptide bonds and hydrophobic bonds.
D) disulfide bonds and peptide bonds.
E) hydrogen bonds and disulfide bonds.
Answer: B
Objective: 19.
Global Outcomes: GO
- Denaturation of a protein
A) changes the primary structure of a protein.
B) disrupts the secondary, tertiary, or quaternary structure of a protein.
C) is always irreversible.
D) hydrolyzes peptide bonds.
E) can only occur in a protein with quaternary structure.
Answer: B
Objective: 19.
Global Outcomes: GO
- One heavy metal that can cause denaturation of a protein is
A) silver.
B) sodium.
C) barium.
D) iron.
E) calcium.
Answer: A
Objective: 19.
Global Outcomes: GO
16
- Heavy metals denature proteins by
A) releasing amino acids.
B) disrupting hydrophobic interactions.
C) changing the pH of the protein solution.
D) changing the temperature of the protein solution.
E) disrupting disulfide bonds.
Answer: E
Objective: 19.
Global Outcomes: GO
- An acid can denature a protein by
A) agitating the protein chains.
B) disrupting hydrogen bonds between R groups chains.
C) disrupting hydrophobic interactions within a protein chain.
D) removing helping molecules such as heme.
E) breaking disulfide bridges.
Answer: B
Objective: 19.
Global Outcomes: GO
19.2 Bimodal Questions
- Immunoglobulin, a protein that stimulates immune responses, would be classified as a
__________ protein.
A) transport
B) structural
C) storage
D) protection
E) catalytic
Answer: D
Objective: 19.
Global Outcomes: GO
- What amino acids have polar R groups that are attracted to water?
A) hydrophilic
B) hydrophobic
C) nonpolar
D) aromatic
E) hydrocarbon
Answer: A
Objective: 19.
Global Outcomes: GO
17
- In an enzyme, the polypeptide chain folds into a compact shape known as the __________
structure.
A) pleated
B) primary
C) secondary
D) tertiary
E) quaternary
Answer: D
Objective: 19.
Global Outcomes: GO
- When two protein chains combine to form an active protein, the structural level is
__________.
A) pleated
B) primary
C) secondary
D) tertiary
E) quaternary
Answer: E
Objective: 19.
Global Outcomes: GO
- Hydrophobic interactions help to stabilize the __________ structure(s) of a protein.
A) primary
B) secondary
C) secondary and tertiary
D) tertiary and quaternary
E) secondary and quaternary
Answer: D
Objective: 19.
Global Outcomes: GO
- What process occurs when heat, acids, bases, and heavy metal ions cause a loss of biological
function of a protein?
A) denaturation
B) saponification
C) hydrogenation
D) amidation
E) esterification
Answer: A
Objective: 19.
Global Outcomes: GO
19
- In digestion, proteins are broken down into amino acids by a(n) __________ reaction.
A) saponification
B) reduction
C) hydrolysis
D) oxidation
E) denaturation
Answer: C
Objective: 19.
Global Outcomes: GO
19.3 Short Answer Questions
- Collagen can be classified as a __________ protein.
Answer: structural
Objective: 19.
Global Outcomes: GO
- The protein that transports oxygen in the blood is __________.
Answer: hemoglobin
Objective: 19.
Global Outcomes: GO
- Proteins that stimulate immune response are known as __________.
Answer: immunoglobulins
Objective: 19.
Global Outcomes: GO
- Amino acids that are not synthesized in the body but must be ingested with the diet are called
__________ amino acids.
Answer: essential
Objective: 19.
Global Outcomes: GO
- A zwitterion of any amino acid has a net charge of __________.
Answer: zero
Objective: 19.
Global Outcomes: GO
- The isoelectric point for any amino acid is the pH at which the amino acid has a net charge of
__________.
Answer: zero
Objective: 19.
Global Outcomes: GO
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