Chem 221 - Biochemistry for Science Majors » Fall 2021 » L4 Amino Acids and Proteins
Need help with your exam preparation?
Get Answers to this exam for $6 USD.
Get Answers to all exams in [ Chem 221 - Biochemistry for Science Majors ] course for $25 USD.
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.
has no net charge
C.
is a carboxylic acid
D.
is bonded to four different chemical groups
E.
is in the L absolute configuration in naturally occurring proteins
Question #2
Amino acids are ampholytes because they can function as either a(n):
A.
transparent or a light-absorbing compound
B.
standard or a nonstandard monomer in proteins
C.
neutral molecule or an ion
D.
polar or a nonpolar molecule
E.
acid or a base
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.
—NH2 + OH– → —NH– + H2O
B.
—COOH + OH– → —COO– + H2O
C.
—NH3+ + OH– → —NH2 + H2O
D.
—COOH + —NH2 → —COO– + —NH2+
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.
a net negative charge
B.
positive and negative charges in equal concentration
C.
a net positive charge
D.
no net charge
E.
no charged groups
Question #5
The formation of a peptide bond between two amino acids is an example of a(n) ______________ reaction.
A.
condensation
B.
isomerization
C.
cleavage
D.
oxidation reduction
E.
group transfer
Question #6
At the isoelectric pH of a tetrapeptide:
A.
two internal amino acids of the tetrapeptide cannot have ionizable R groups
B.
only the amino and carboxyl termini contribute charge
C.
there are four ionic charges
D.
the amino and carboxyl termini are not charged
E.
the total net charge is zero
Question #7
A prosthetic group is:
A.
a part of the protein that is not composed of amino acids
B.
a subunit of an oligomeric protein
C.
synonymous with “protomer”
D.
a fibrous region of a globular protein
E.
a nonidentical subunit of a protein with many identical subunits
Question #8
Which one of the following amino acids contains an aromatic group?
A.
Arginine
B.
Leucine
C.
Glycine
D.
Phenylalanine
E.
Methionine
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.
Leucine & Glycine
C.
Histidine & Lysine
D.
Asparagine & Glutamine
Question #11
How many different standard amino acids are there?
A.
an infinite number
B.
3
C.
20
D.
100
Question #12
Of the 20 standard amino acids, only ___________ is not optically active (nonchiral). The reason is that its side chain ___________.
A.
glycine; is unbranched
B.
glycine; is a hydrogen atom
C.
alanine; is a simple methyl group
D.
lysine; contains only nitrogen
E.
proline; forms a covalent bond with the amino group
Question #13
Which of the following is an amino acid?
A.
Glycine
B.
Alanine
C.
Serine
D.
Proline
Question #14
A protease
A.
All the above statements are correct
B.
increases the rate of proteolysis
C.
is also called a peptidase or proteinase
D.
is an enzyme that catalyzes proteolysis, the breakdown of proteins into smaller polypeptides or single amino acids
E.
cleaves proteins by the addition of a molecule of water to a peptide bond
Question #15
Proteases
A.
Produce amino acids or short peptides
B.
cleaves disulfide bonds
C.
Cleave peptide bonds
D.
three of the choices are correct
E.
Degrade proteins
Question #16
Chose the best true statement
A.
Proteases are involved in anabolism
B.
Cleave all peptide bonds
C.
Proteases are involved in many biological functions, including digestion of eaten proteins, and protein catabolism
D.
Two of the statement are incorrect
E.
Proteases can cleave at specific points in the peptide chain
Question #17
The fully protonated form of histidine has a ____________charge.
A.
+1
B.
+4
C.
+2
D.
+3
Question #18
Which of the following amino acids has a net negative charge at physiologic pH (~7.4)?
A.
Lysine
B.
Glutamic Acid
C.
Histidine
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.
Tyrosine
C.
Histidine
D.
Glutamic acid
E.
Cysteine
Question #20
At pH = 0, the net charge on glutamic acid is:____________
A.
+2
B.
+1
C.
-1
D.
0
Question #21
At pH = 13, the net charge on lysine is:____________
A.
+1
B.
+3
C.
-1
D.
+2
Question #22
What is the charge of the dipeptide Ala-Lys a pH = 12?
A.
-1
B.
+2
C.
0
D.
+1
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.
+1
C.
-2
D.
0
Question #25
The charge of glutamic acid at pH > 10 is
A.
0
B.
+1
C.
+2
D.
-2
Need help with your exam preparation?
Get Answers to this exam for $6 USD.
Get Answers to all exams in [ Chem 221 - Biochemistry for Science Majors ] course for $25 USD.
Existing Quiz Clients Login here