West Los Angeles College » Chemistry » Chem 221 - Biochemistry for Science Majors » Fall 2021

Chem 221 - Biochemistry for Science Majors » Fall 2021 » L4 Amino Acids and Proteins

Need help with your exam preparation?

Existing Quiz Clients Login here

Question #1

The chirality of an amino acid results from the fact that its α carbon:

A. is symmetric

B. is a carboxylic acid

C. is bonded to four different chemical groups

D. is in the L absolute configuration in naturally occurring proteins

E. has no net charge

Question #2

Amino acids are ampholytes because they can function as either a(n):

A. standard or a nonstandard monomer in proteins

B. neutral molecule or an ion

C. polar or a nonpolar molecule

D. acid or a base

E. transparent or a light-absorbing compound

Question #3

Titration of valine by a strong base, for example NaOH, reveals two pK's. The titration reaction occurring at pK2 (pK2 = 9.62) is:

A. —COOH + —NH2 → —COO– + —NH2+

B. —COOH + OH– → —COO– + H2O

C. —NH2 + OH– → —NH– + H2O

D. —NH3+ + OH– → —NH2 + H2O

E. —COO– + —NH2+ → —COOH + —NH2

Question #4

For amino acids with neutral R groups, at any pH below the pI of the amino acid, the population of amino acids in solution will have:

A. no net charge

B. positive and negative charges in equal concentration

C. no charged groups

D. a net negative charge

E. a net positive charge

Question #5

The formation of a peptide bond between two amino acids is an example of a(n) ______________ reaction.

A. group transfer

B. cleavage

C. isomerization

D. oxidation reduction

E. condensation

Question #6

At the isoelectric pH of a tetrapeptide:

A. there are four ionic charges

B. the total net charge is zero

C. only the amino and carboxyl termini contribute charge

D. the amino and carboxyl termini are not charged

E. two internal amino acids of the tetrapeptide cannot have ionizable R groups

Question #7

A prosthetic group is:

A. a nonidentical subunit of a protein with many identical subunits

B. a part of the protein that is not composed of amino acids

C. synonymous with “protomer”

D. a fibrous region of a globular protein

E. a subunit of an oligomeric protein

Question #8

Which one of the following amino acids contains an aromatic group?

A. Phenylalanine

B. Arginine

C. Leucine

D. Methionine

E. Glycine

Question #9

An essential amino acid is one that

A. the body can synthesize under essential conditions

B. the body cannot synthesize

C. is essential to flagella motion

D. is essentially easy to synthesize

Question #10

Which of the following pairs of amino acids would carry a negative charge on their side chain at pH 8.0?

A. Aspartate & Glutamate

B. Asparagine & Glutamine

C. Leucine & Glycine

D. Histidine & Lysine

Question #11

How many different standard amino acids are there?

A. 20

B. 100

C. an infinite number

D. 3

Question #12

Of the 20 standard amino acids, only ___________ is not optically active (nonchiral). The reason is that its side chain ___________.

A. glycine; is a hydrogen atom

B. alanine; is a simple methyl group

C. lysine; contains only nitrogen

D. proline; forms a covalent bond with the amino group

E. glycine; is unbranched

Question #13

Which of the following is an amino acid?

A. Serine

B. Alanine

C. Proline

D. Glycine

Question #14

A protease

A. is also called a peptidase or proteinase

B. increases the rate of proteolysis

C. cleaves proteins by the addition of a molecule of water to a peptide bond

D. is an enzyme that catalyzes proteolysis, the breakdown of proteins into smaller polypeptides or single amino acids

E. All the above statements are correct

Question #15

Proteases

A. Cleave peptide bonds

B. Produce amino acids or short peptides

C. cleaves disulfide bonds

D. three of the choices are correct

E. Degrade proteins

Question #16

Chose the best true statement

A. Proteases can cleave at specific points in the peptide chain

B. Proteases are involved in many biological functions, including digestion of eaten proteins, and protein catabolism

C. Two of the statement are incorrect

D. Proteases are involved in anabolism

E. Cleave all peptide bonds

Question #17

The fully protonated form of histidine has a ____________charge.

A. +2

B. +3

C. +1

D. +4

Question #18

Which of the following amino acids has a net negative charge at physiologic pH (~7.4)?

A. Histidine

B. Lysine

C. Glutamic Acid

D. Asparagine

Question #19

Based on the pKa values given in the attached table (see canvas tables), in there any amino acid among the ones in the list below that could serve as a buffer at pH 8.0?

A. Leucine

B. Histidine

C. Glutamic acid

D. Cysteine

E. Tyrosine

Question #20

At pH = 0, the net charge on glutamic acid is:____________

A. -1

B. 0

C. +1

D. +2

Question #21

At pH = 13, the net charge on lysine is:____________

A. +3

B. +2

C. +1

D. -1

Question #22

What is the charge of the dipeptide Ala-Lys a pH = 12?

A. +2

B. -1

C. +1

D. 0

Question #23

The lowest charge possible for glutamic acid is

A. -2

B. -1

Question #24

The charge of cysteine at pH below 2 is

A. -1

B. -2

C. 0

D. +1

Question #25

The charge of glutamic acid at pH > 10 is

A. +2

B. -2

C. +1

D. 0

Need help with your exam preparation?

Existing Quiz Clients Login here