Deck 19: Amino Acids and Proteins

Question 1

Wool is primarily made up of

A) protein.
B) carbohydrate.
C) globin.
D) triacylglycerols.
E) enkephalin.

Answer 1

protein.

Question 2

The side chain for histidine is classified as a __________ R group.

A) basic
B) neutral
C) acidic
D) nonpolar
E) polar

Answer 2

basic

Question 3

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 3

an amine group.

Question 4

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.

Question 5

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

Question 6

The following amino acid R group chain is

A) polar.
B) hydrophobic.
C) hydrophilic.
D) acidic.
E) basic.

Question 7

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 remain stationary.

A) Lysine
B) Tyrosine
C) Glutamic acid
D) All of the amino acids

Question 8

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.

Question 9

The R group for serine is -CH₂OH. As a zwitterion, serine has the structural formula

A)
B)
C)
D)
E)

Question 10

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

Question 11

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

Question 12

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

Question 13

Collagen, a protein found in tendons and cartilage, would be classified as a __________ protein.

A) catalytic
B) structural
C) transport
D) storage
E) hormone

Question 14

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.

Question 15

In a typical amino acid zwitterion, the carboxylate end is

A) positively charged.
B) negatively charged.
C) neutral.
D) soluble in a nonpolar solvent.
E) attached to an amine.

Question 16

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.

Question 17

Methionine is an amino acid that contains

A) a sulfur atom.
B) a chlorine atom.
C) a sodium atom.
D) a phenyl ring.
E) a heterocyclic ring.

Question 18

What is the structural formula of glutamic acid (pI = 3.2) at pH = 1?

A)
B)
C)
D)
E)

Question 19

Glycine is the only naturally occurring amino acid that is

A) negatively charged.
B) positively charged.
C) neutral.
D) in the L- form.
E) achiral.

Question 20

A completely vegetarian diet will contain all the essential amino acids if it includes

A) wheat and rice.
B) rice and beans.
C) almonds and walnuts.
D) corn and beans.
E) wheat and corn.

Question 21

The peptide bonds that combine amino acids in a protein are

A) ester bonds.
B) ether bonds.
C) amide bonds.
D) glycosidic bonds.
E) sulfide bonds.

Question 22

Which of the following functional groups of an amino acid would be in the ionized state at high pH?

A) $\begin{array} { c } \mathrm { O } \\\| \\- \mathrm { COH }\end{array}$
B) -CH?OH
C) -CH₃
D) $\begin{array} { c } \mathrm { O } \\\| \\- \mathrm { CNH } _ { 2 }\end{array}$
E)

Question 23

The interactions that are important in the secondary structure of a protein are

A) hydrogen bonds.
B) hydrophobic interactions.
C) disulfide bonds.
D) salt bridges.
E) peptide bonds.

Question 24

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.

Question 25

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.

Question 26

Which of the following is the correct structure for Ser-Ala-Asp? The appropriate side chains look like this. Ala: - CH₃; Ser: - CH?OH; Asp: $$\begin{array} { c } \mathrm { O } \\\mathrm { || } \\- \mathrm { CH } _ { 2 } \mathrm { COH }\end{array}$$

A)
B)
C)
D)
E)

Question 27

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

Question 28

In the peptide Ala-Try-Gly-Phe, the N-terminal amino acid is

A) alanine.
B) phenylalanine.
C) tryptophan.
D) aspartic acid.
E) glycine.

Question 29

Which of the following shows all of the tripeptides that can be formed from one molecule each of glycine (Gly), valine (Val), and leucine (Leu)?

A) Gly-Val-Leu, Gly-Leu-Val, Val-Leu-Gly, Val-Gly-Leu, Leu-Gly-Val, Leu-Val-Gly
B) Gly-Val-Leu, Gly-Leu-Val, Leu-Gly-Val
C) Val-Gly-Leu, Gly-Val-Leu, Gly-Leu-Val, Leu-Gly-Val
D) Val-Gly-Leu, Gly-Leu-Val
E) Gly-Val-Leu

Question 30

Enkephalins are polypeptides that have

A) a sweet taste.
B) a bitter taste.
C) extra caloric value.
D) pain-killing properties.
E) hormone activity.

Question 31

A peptide bond contains which kind of functional group?

A) alcohol
B) amine
C) amide
D) carboxylic acid
E) ketone

Question 32

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

Question 33

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

Question 34

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.

Question 35

In insulin, two peptide chains are held together in a single unit by

A) disulfide bridges.
B) hydrogen bonds.
C) salt bridges.
D) a prosthetic group.
E) a β-pleated sheet.

Question 36

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.

Question 37

The secondary structure of collagen is distinguished by

A) single α helix strands.
B) double α helix strands.
C) many α helixes wound into fibrils.
D) a braided triple helix.
E) many glycoside links.

Question 38

Which of the following is a secondary protein structure?

A) α helix
B) Ser-Met-Ala-Gly-Ile
C) disulfide bond
D) salt bridges
E) hydrophobic interactions

Question 39

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.

Question 40

In the peptide Ser-Cys-Ala-Gly, the C-terminal end is

A) serine.
B) serotonin.
C) glycine.
D) glycerine.
E) alanine.

Question 41

In sickle-cell anemia, the hemoglobin molecules

A) come apart into separate chains.
B) enlarge to twice normal size.
C) clump together into insoluble fibers.
D) dissolve in the plasma.
E) undergo crenation.

Question 42

The peptide hormone that regulates uterine contractions during labor is __________.

A) oxytocin
B) vasopressin
C) myoglobin
D) an endorphin
E) an enkephalin

Question 43

Disulfide bonds in a protein chain connect

A) an amine and a carboxylic acid group.
B) an alcohol and a carboxylic acid group.
C) tryptophan and alanine residues.
D) two cysteine residues.
E) two asparagine residues.

Question 44

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.

Question 45

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

Question 46

The fibrous protein responsible for the structure of hair and wool is

A) keratin.
B) collagen.
C) endorphin.
D) myosin.
E) casein.

Question 47

One heavy metal that can cause denaturation of a protein is

A) silver.
B) sodium.
C) barium.
D) iron.
E) calcium.

Question 48

The function of myoglobin is to

A) carry vitamins in the blood.
B) carry oxygen in the blood.
C) support the skeletal muscles.
D) carry oxygen in the muscle.
E) provide strength in cartilage.

Question 49

Consider the R groups of the following amino acids: cysteine: -CH₂SH; alanine: - 3CH3; serine: -CH₂OH
The name for the dipeptide shown below is __________.

A) alanyl-cysteine
B) alanyl-serine
C) seryl-alanine
D) seryl-cysteine
E) serine-alanine

Question 50

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.

Question 51

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.

Question 52

Hemoglobin has a total of __________ protein chains in its quaternary structure.

A) one
B) two
C) three
D) four
E) five

Question 53

What kinds of interactions are NOT part of tertiary protein structure?

A) peptide bonds
B) disulfide bonds
C) hydrophilic interactions
D) salt bridges
E) hydrophobic interactions

Question 54

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? $\begin{array} { l } + \\\mathrm { N }\end{array}$ H₃
E)


$\begin{array} { c } \mathrm { O } \\\mathrm { || } \\- \mathrm { CH } _ { 2 } { \mathrm { C } } \mathrm { NH } _ { 2 }\end{array}$

Question 55

At what pH would you expect valine, an amino acid with a neutral R group, to be in the zwitterionic form?

A) 1
B) 4
C) 7
D) 10
E) 14

Question 56

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.

Question 57

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.

Question 58

What amino acids have polar R groups that are attracted to water?

A) hydrophilic
B) hydrophobic
C) nonpolar
D) aromatic
E) hydrocarbon

Question 59

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.

Question 60

Immunoglobulin, a protein that stimulates immune responses, would be classified as a __________ protein.

A) transport
B) structural
C) storage
D) protection
E) catalytic

Question 61

The protein that transports oxygen in the blood is __________.

Question 62

The isoelectric point for any amino acid is the pH at which the amino acid has a net charge of __________.

Question 63

Insulin is a transport protein.

Question 64

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

Question 65

Hemoglobin is a transport protein.

Question 66

The dipeptide abbreviated as Gly-Lys is the same as the dipeptide abbreviated as Lys-Gly.

Question 67

Electrophoresis is a laboratory technique for separating amino acids using their different __________.

Question 68

In digestion, proteins are broken down into amino acids by a(n) __________ reaction.

A) saponification
B) reduction
C) hydrolysis
D) oxidation
E) denaturation

Question 69

When two protein chains combine to form an active protein, the structural level is __________.

A) pleated
B) primary
C) secondary
D) tertiary
E) quaternary

Question 70

Amino acids that are not synthesized in the body but must be ingested with the diet are called __________ amino acids.

Question 71

Proteins that stimulate immune response are known as __________.

Question 72

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

Question 73

Sickle-cell anemia is caused by a change in the primary structure of a subunit of the hemoglobin protein.

Question 74

A zwitterion of any amino acid has a net charge of __________.

Question 75

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

Question 76

Zwitterions have an overall positive charge.

Question 77

The peptide sequence Gly-Gly-Gly gives the primary structure of a tripeptide.

Question 78

Write the zwitterion of glycine.

Question 79

Circle the peptide bond in this structure.

Question 80

Collagen can be classified as a __________ protein.