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WKU Biochemistry Ch.2 Quiz

Total questions: 67

Worksheet time: 34mins

Name
Class
Date
1.

What are proteins polymers of?

a)

Nucleic acids

b)

α-amino acids

c)

Fatty acids

d)

Monosaccharides

2.

What functional group is represented by -COOH?

a)

Amino group

b)

Hydroxyl group

c)

Carboxylic acid group

d)

Phosphate group

3.

Which of the following is a characteristic of α-amino acids?

a)

They contain only an amino group.

b)

They contain only a carboxylic acid group.

c)

They contain both an amino group and a carboxylic acid group attached to the same carbon.

d)

They contain neither an amino group nor a carboxylic acid group.

4.

What is the general structure of an α-amino acid as depicted in the image?

a)

R-CH(NH2)-COOH

b)

R-CH2-COOH

c)

R-CH(OH)-COOH

d)

R-CH3-COOH

5.

What is the standard designation used in organic chemistry to differentiate amino acids like cysteine?

a)

L/D designation

b)

R/S designation

c)

A/B designation

d)

E/Z designation

6.

How many chiral amino acids are designated as L in biochemistry?

a)

18

b)

19

c)

20

d)

21

7.

Which amino acid is an exception by having an R designation in the standard R/S system?

a)

Glycine

b)

Alanine

c)

Cysteine

d)

Lysine

8.

What does the Henderson-Hasselbalch equation relate to in chemistry?

a)

The ratio of the concentration of an acid to its conjugate base

b)

The rate of a chemical reaction

c)

The energy change in a thermodynamic process

d)

The equilibrium constant for a gas-phase reaction

9.

In the Henderson-Hasselbalch equation, what does "p" represent?

a)

The power of the concentration

b)

The negative logarithm

c)

The pressure of the system

d)

The product of the concentrations

10.

Which of the following is the correct expression for the Henderson-Hasselbalch equation?

a)

pH = pK_a + log([A-]/[HA])

b)

pH = pK_a - log([A-]/[HA])

c)

pH = pK_a / log([A-]/[HA])

d)

pH = pK_a * log([A-]/[HA])

11.

If you know the pH and pK_a of a solution, what can you determine?

a)

The temperature of the solution

b)

The ratio of [A-] to [HA]

c)

The molecular weight of the solute

d)

The viscosity of the solution

12.

What happens to the ratio of [A-] to [HA] when the pH is equal to the pKa of the amino acid group?

a)

[A-]/[HA] = 10

b)

[A-]/[HA] = 100

c)

[A-]/[HA] = 1

d)

[A-]/[HA] = 0

13.

If the pH is one unit above the pKa of an amino acid group, approximately what percentage of the amino acid exists in the deprotonated [A-] form?

a)

50%

b)

91%

c)

99%

d)

99.9%

14.

What is the ratio of [A-] to [HA] if the pH is two units above the pKa of the amino acid group?

a)

[A-]/[HA] = 1

b)

[A-]/[HA] = 10

c)

[A-]/[HA] = 100

d)

[A-]/[HA] = 1000

15.

At a pH three units above the pKa, what is the approximate percentage of the amino acid in the [A-] form?

a)

50%

b)

91%

c)

99%

d)

99.9%

16.

What is the dominant form of an amino acid group when the pH is below its pKa?

a)

Deprotonated form

b)

Protonated form

c)

Neutral form

d)

Zwitterionic form

17.

If the pH is 2 units below the pKa of an amino acid group, approximately what percentage of the group is in the protonated [HA] form?

a)

91%

b)

99%

c)

50%

d)

99.9%

18.

For a basic amino acid group such as –NH2, what should be used instead of pKa to determine the ionization state?

a)

pKb of the conjugate acid

b)

pKa of the conjugate base

c)

pKa of the conjugate acid

d)

pKb of the conjugate base

19.

What is the approximate pKa value of the -COOH group on an alpha carbon?

a)

9.8

b)

7.0

c)

2.3

d)

3.0

20.

At pH 7, the -COOH group on an alpha carbon is predominantly in what state?

a)

Protonated (-COOH) form

b)

Deprotonated (-COO-) form

c)

Neutral

d)

Protonated (-NH3+) form

21.

What is the approximate pKa value of the -NH2 group on an alpha carbon?

a)

2.3

b)

7.0

c)

9.8

d)

4.0

22.

At pH 7, the -NH2 group on an alpha carbon is nearly how many units below the pKa?

a)

4 units

b)

2 units

c)

3 units

d)

5 units

23.

At pH 7, the -NH2 group on an alpha carbon is predominantly in what state?

a)

Deprotonated (-NH2) form

b)

Protonated (-NH3+) form

c)

Neutral

d)

Deprotonated (-COO-) form

24.

How many unique R groups are commonly observed in most proteins?

a)

10

b)

20

c)

30

d)

40

25.

What is the common form of abbreviation for most amino acids?

a)

2-letter abbreviations

b)

1-letter abbreviations

c)

3-letter abbreviations

d)

Full names only

26.

Which of the following amino acids is an exception to the rule where the 3-letter abbreviation is the first three letters of its name?

a)

Val

b)

Leu

c)

Ile

d)

Met

27.

1-letter abbreviations for amino acids typically represent what?

a)

The least abundant amino acids

b)

The most abundant amino acids

c)

The amino acids with the simplest structures

d)

The amino acids with the most complex structures

28.

What characteristic defines aliphatic amino acids?

a)

They contain aromatic hydrocarbon chains.

b)

They are non-aromatic hydrocarbon chains.

c)

They are only found in essential amino acids.

d)

They include a ring structure in their side chains.

29.

Which of the following amino acids is the simplest in structure?

a)

Alanine

b)

Valine

c)

Glycine

d)

Leucine

30.

What is the one-letter abbreviation for Alanine?

a)

G

b)

A

c)

V

d)

L

31.

Which amino acid has a β carbon in its side chain?

a)

Glycine

b)

Alanine

c)

Valine

d)

All of the above

32.

Which of the following amino acids is classified as an aliphatic amino acid?

a)

Tyrosine

b)

Leucine

c)

Phenylalanine

d)

Tryptophan

33.

What is the one-letter abbreviation for Isoleucine?

a)

A

b)

I

c)

L

d)

M

34.

Which amino acid has a sulfur atom in its side chain?

a)

Proline

b)

Leucine

c)

Methionine

d)

Isoleucine

35.

Proline is unique among the amino acids shown because its side chain is linked to the:

a)

Amino group

b)

Carboxyl group

c)

Alpha carbon

d)

Nitrogen in the amino group

36.

Which of the following amino acids is not considered an aromatic amino acid?

a)

Phenylalanine

b)

Tyrosine

c)

Tryptophan

d)

Lysine

37.

At what wavelength do aromatic amino acids typically absorb ultraviolet radiation?

a)

~250 nm

b)

~280 nm

c)

~300 nm

d)

~350 nm

38.

What is the one-letter abbreviation for Tyrosine?

a)

F

b)

Y

c)

W

d)

T

39.

Which aromatic amino acid contains a hydroxyl group (-OH) in its side chain?

a)

Phenylalanine

b)

Tyrosine

c)

Tryptophan

d)

Methionine

40.

What is the approximate pKa value of tyrosine?

a)

2

b)

10

c)

7.4

d)

12

41.

The acidity of tyrosine is due to which of the following factors?

a)

Resonance stability of positive charge

b)

Inductive effect of the amino group

c)

Resonance stability of negative charge

d)

Hydrophobic interaction

42.

Which amino acid is represented by the one-letter code 'S'?

a)

Threonine

b)

Cysteine

c)

Serine

d)

Alanine

43.

What functional group is present in the side chain of Cysteine?

a)

Hydroxyl (-OH)

b)

Methyl (-CH3)

c)

Sulfhydryl (-SH)

d)

Carboxyl (-COOH)

44.

Which amino acid has a side chain with a methyl group (CH3) as part of its structure?

a)

Serine

b)

Threonine

c)

Cysteine

d)

Glycine

45.

Which amino acid is represented by the abbreviation 'Tyr' in phosphorylation diagrams?

a)

Threonine

b)

Serine

c)

Tyrosine

d)

Tryptophan

46.

What is the abbreviation for Threonine as shown in the phosphorylation diagram?

a)

Ser

b)

Thr

c)

Tyr

d)

Trp

47.

Which amino acid is represented by the abbreviation 'Ser' in phosphorylation diagrams?

a)

Serine

b)

Threonine

c)

Tyrosine

d)

Tryptophan

48.

What is the approximate pKa value of Cysteine (Cys) as compared to Serine (Ser)?

a)

5.5

b)

8.5

c)

10.5

d)

12.5

49.

Which amino acid is capable of forming disulfide bonds?

a)

Serine (Ser)

b)

Glycine (Gly)

c)

Alanine (Ala)

d)

Cysteine (Cys)

50.

Between Serine (Ser) and Cysteine (Cys), which is more nucleophilic?

a)

Serine (Ser)

b)

Cysteine (Cys)

c)

Both are equally nucleophilic

d)

Neither is nucleophilic

51.

What is formed when two cysteine molecules become oxidized to form a covalent bond between their sulfur atoms?

a)

Hydrogen bond

b)

Ionic bond

c)

Disulfide bond

d)

Peptide bond

52.

In the formation of a disulfide bond, what happens to the cysteine molecules?

a)

They gain electrons (are reduced)

b)

They lose protons (are deprotonated)

c)

They gain protons (are protonated)

d)

They lose electrons (are oxidized)

53.

What is the name of the molecule formed when two cysteine molecules are linked by a disulfide bond?

a)

Cysteine

b)

Methionine

c)

Cystine

d)

Alanine

54.

What is the pKa value of Lysine as shown in the image?

a)

~10.8

b)

~12.5

c)

~6

d)

~9.5

55.

Which basic amino acid has a pKa value of approximately 12.5?

a)

Lysine

b)

Arginine

c)

Histidine

d)

Aspartic acid

56.

What is the one-letter abbreviation for Histidine?

a)

K

b)

R

c)

H

d)

L

57.

Which basic amino acid is represented by the one-letter abbreviation 'K'?

a)

Lysine

b)

Arginine

c)

Histidine

d)

Glutamine

58.

What is the approximate pKa value of Aspartate (Asp) and Glutamate (Glu)?

a)

2

b)

4

c)

7

d)

9

59.

Which amino acid is represented by the single-letter code 'D'?

a)

Asparagine

b)

Glutamine

c)

Aspartate

d)

Glutamate

60.

Which of the following amino acids is NOT acidic?

a)

Aspartate (Asp)

b)

Glutamate (Glu)

c)

Asparagine (Asn)

d)

Glutamine (Gln)

61.

What is the single-letter code for Glutamine?

a)

A

b)

E

c)

N

d)

Q

62.

What do pK_a values refer to in the context of amino acids?

a)

The strength of an amino acid as an acid or base when it is part of a protein

b)

The strength of an amino acid as an acid or base when it is in its "free" form, not in a protein

c)

The pH level at which an amino acid becomes neutral

d)

The temperature at which an amino acid changes its structure

63.

How much can pK_a values vary in a protein due to factors like hydrogen bonding and hydrophobicity?

a)

1-2 units

b)

3-4 units

c)

5-6 units

d)

7-8 units

64.

What effect does a hydrophobic environment have on the pK_a of amino acids in proteins?

a)

It does not affect the pK_a values

b)

It lowers the pK_a of acidic and raises the pK_a of basic amino acids

c)

It raises the pK_a of acidic and lowers the pK_a of basic amino acids

d)

It equalizes the pK_a values of all amino acids

65.

What is the pKa value of the carboxyl group of lysine?

a)

2.2

b)

9.1

c)

10.5

d)

10.0

66.

At pH 10.0, which group on lysine is most likely to be deprotonated?

a)

Carboxyl group

b)

Amino group (backbone)

c)

Amino group (side chain)

d)

All of the above

67.

Which of the following represents the dominant form of lysine at pH 10.0?

Carboxyl Group = 2.2

Backbone = 9.1

SideChain = 10.5

Normal pH is 7.0

a)

A

b)

B

c)

C

d)

D

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