Question 1

Of the 20 standard amino acids, only _____ is not optically active. The reason is that its side chain _____.

Accepted Answer

A)  alanine; is a simple methyl group 
B)  glycine; is a hydrogen atom 
C)  glycine; is unbranched 
D)  lysine; contains only nitrogen 
E)  proline; forms a covalent bond with the amino group 
A)  alanine; is a simple methyl group 
B)  glycine; is a hydrogen atom 
C)  glycine; is unbranched 
D)  lysine; contains only nitrogen 
E)  proline; forms a covalent bond with the amino group B

Question 2

Which two amino acids differ from each other by only one atom?

Accepted Answer

A)  Ser and Thr 
B)  Leu and Ile 
C)  Ala and Ser 
D)  Asp and Asn 
E)  Ser and Cys 
A)  Ser and Thr 
B)  Leu and Ile 
C)  Ala and Ser 
D)  Asp and Asn 
E)  Ser and Cys E

Question 3

Which statement is TRUE about the pKa values for ionizable R-group of amino acids within a polypeptide?

Accepted Answer

A)  The pKa values for R-groups do not change from free amino acids. 
B)  The pKa values for R-groups are 1 pH unit higher than free amino acids. 
C)  The pKa values for R-groups are 1 pH unit lower than free amino acids. 
D)  The pKa values for R-groups vary depending on the local environment of the side chain. 
E)  The pKa values for R-groups depend on how close the R-group is to the N- or C-terminus of the polypeptide. 
A)  The pKa values for R-groups do not change from free amino acids. 
B)  The pKa values for R-groups are 1 pH unit higher than free amino acids. 
C)  The pKa values for R-groups are 1 pH unit lower than free amino acids. 
D)  The pKa values for R-groups vary depending on the local environment of the side chain. 
E)  The pKa values for R-groups depend on how close the R-group is to the N- or C-terminus of the polypeptide. D

Question 4

Which compound is a side-product of a peptide bond formation?

Accepted Answer

A)  water 
B)  phosphate 
C)  ammonium 
D)  carboxylic acid 
E)  None of the answers is correct. 
A)  water 
B)  phosphate 
C)  ammonium 
D)  carboxylic acid 
E)  None of the answers is correct.

Question 5

A biochemist is attempting to separate a DNA-binding protein (protein X) from other proteins in a solution. Only three other proteins (A, B, and
C) are present. The proteins have the following properties:
pI
(isoelectric
Size
Bind to
point)
Mr
DNA?
protein A
7.4
82,000
yes
protein B
3.8
21,500
yes
protein C
7.9
23,000
no
protein X
7.8
22,000
yes
What type of protein separation techniques might she use to separate:
(a) protein X from protein A?
(b) protein X from protein B?
(c) protein X from protein C?

Accepted Answer

To separate protein X from the other pro

Question 6

A polypeptide is hydrolyzed, and it is determined that there are 3 Lys residues and 2 Arg residues (as well as other residues). How many peptide fragments can be expected when the native polypeptide is incubated with the proteolytic enzyme trypsin?

Accepted Answer

Trypsin is a proteolytic enzyme that spe

Question 7

Distinguish between homologs, paralogs, and orthologs as classes of related proteins.

Accepted Answer

Homologs, paralogs, and orthologs are te

Question 8

At pH 7.0, converting a glutamic acid to $\gamma$-carboxyglutamate, will have what effect on the overall charge of the protein containing it?

Accepted Answer

A)  It will become more negative 
B)  It will become more positive. 
C)  It will stay the same. 
D)  There is not enough information to answer the question. 
E)  The answer depends on the salt concentration. 
A)  It will become more negative 
B)  It will become more positive. 
C)  It will stay the same. 
D)  There is not enough information to answer the question. 
E)  The answer depends on the salt concentration.

Question 9

According to the diagram, at pH 1, what is the average net charge on this amino acid?

Accepted Answer

A)  + 1 
B)  + 0.5 
C)  0 
D)  -0.5 
E)  -1 
A)  + 1 
B)  + 0.5 
C)  0 
D)  -0.5 
E)  -1

Question 10

If the average molecular weight of the 20 standard amino acids is 138, why do biochemists divide a protein's molecular weight by 110 to estimate its number of amino acid residues?

Accepted Answer

The average molecular weight of the 20 s

Question 11

The protein bovine serum albumin (BSA), has a MW of about 66,400. Using the Lambert-Beer Law, calculate the concentration of a sample of BSA with an absorbance at 280 nm of 1.3, assuming the molar extinction coefficient at 280 nm is 43,824 M-1cm-1.

Accepted Answer

A)  0.51 mg/mL 
B)  0.86 mg/mL 
C)  1.97 mg/mL 
D)  2.56 mg/mL 
E)  3.78 mg/mL 
A)  0.51 mg/mL 
B)  0.86 mg/mL 
C)  1.97 mg/mL 
D)  2.56 mg/mL 
E)  3.78 mg/mL

Question 12

In a highly basic solution, pH = 13, the dominant form of glycine is:

Accepted Answer

A)  NH2-CH2-COOH. 
B)  NH2-CH2-COO-. 
C)  NH2-CH3+-COO-. 
D)  NH3+-CH2-COOH. 
E)  NH3+-CH2-COO-. 
A)  NH2-CH2-COOH. 
B)  NH2-CH2-COO-. 
C)  NH2-CH3+-COO-. 
D)  NH3+-CH2-COOH. 
E)  NH3+-CH2-COO-.

Question 13

All of the amino acids that are found in proteins, except for proline, contain a(n) _____ group.

Accepted Answer

A)  amino 
B)  carbonyl 
C)  carboxyl 
D)  ester 
E)  thiol 
A)  amino 
B)  carbonyl 
C)  carboxyl 
D)  ester 
E)  thiol

Question 14

For the study of a protein in detail, an effort is usually made to first:

Accepted Answer

A)  conjugate the protein to a known molecule. 
B)  determine its amino acid composition. 
C)  determine its amino acid sequence. 
D)  determine its molecular weight. 
E)  purify the protein. 
A)  conjugate the protein to a known molecule. 
B)  determine its amino acid composition. 
C)  determine its amino acid sequence. 
D)  determine its molecular weight. 
E)  purify the protein.

Question 15

Describe two major differences between chemical synthesis of polypeptides and synthesis of polypeptides in the living cell.

Accepted Answer

The two major differences between chemic

Question 16

According to the diagram, which pH is the one at which this amino acid will have a net charge of 0?

Accepted Answer

A)  11 
B)  6 
C)  1.5 
D)  1 
E)  0.5 
A)  11 
B)  6 
C)  1.5 
D)  1 
E)  0.5

Question 17

The peptide alanylglutamylglycylalanylleucine has:

Accepted Answer

A)  a disulfide bridge. 
B)  five peptide bonds. 
C)  four peptide bonds. 
D)  no free carboxyl group. 
E)  two free amino groups. 
A)  a disulfide bridge. 
B)  five peptide bonds. 
C)  four peptide bonds. 
D)  no free carboxyl group. 
E)  two free amino groups.

Question 18

Define the primary structure of a protein.

Accepted Answer

The primary structure of a protein refer

Question 19

Identify the pair of peptides below that CANNOT be distinguished by tandem mass spectrometry.

Accepted Answer

A)  VTSPLYANEGK and VTCPLYANEGK 
B)  VTSPLYANEGK and VTSPLYADEGK 
C)  VTSPLYANEGK and VTSPIYANEGK 
D)  VTSPLYANEGK and VSTPLYANEGK 
E)  All of the answer choices are correct. 
A)  VTSPLYANEGK and VTCPLYANEGK 
B)  VTSPLYANEGK and VTSPLYADEGK 
C)  VTSPLYANEGK and VTSPIYANEGK 
D)  VTSPLYANEGK and VSTPLYANEGK 
E)  All of the answer choices are correct.

Question 20

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

Accepted Answer

A)  acid or a base. 
B)  neutral molecule or an ion. 
C)  polar or a nonpolar molecule. 
D)  standard or a nonstandard monomer in proteins. 
E)  transparent or a light-absorbing compound. 
A)  acid or a base. 
B)  neutral molecule or an ion. 
C)  polar or a nonpolar molecule. 
D)  standard or a nonstandard monomer in proteins. 
E)  transparent or a light-absorbing compound.

Exam 3: Amino Acids, Peptides, and Proteins

Of the 20 standard amino acids, only _____ is not optically active. The reason is that its side chain _____.

Which two amino acids differ from each other by only one atom?

Which statement is TRUE about the pKa values for ionizable R-group of amino acids within a polypeptide?

Which compound is a side-product of a peptide bond formation?

A polypeptide is hydrolyzed, and it is determined that there are 3 Lys residues and 2 Arg residues (as well as other residues). How many peptide fragments can be expected when the native polypeptide is incubated with the proteolytic enzyme trypsin?

Distinguish between homologs, paralogs, and orthologs as classes of related proteins.

At pH 7.0, converting a glutamic acid to γ\gammaγ -carboxyglutamate, will have what effect on the overall charge of the protein containing it?

According to the diagram, at pH 1, what is the average net charge on this amino acid?

If the average molecular weight of the 20 standard amino acids is 138, why do biochemists divide a protein's molecular weight by 110 to estimate its number of amino acid residues?

The protein bovine serum albumin (BSA), has a MW of about 66,400. Using the Lambert-Beer Law, calculate the concentration of a sample of BSA with an absorbance at 280 nm of 1.3, assuming the molar extinction coefficient at 280 nm is 43,824 M-1cm-1.

In a highly basic solution, pH = 13, the dominant form of glycine is:

All of the amino acids that are found in proteins, except for proline, contain a(n) _____ group.

For the study of a protein in detail, an effort is usually made to first:

Describe two major differences between chemical synthesis of polypeptides and synthesis of polypeptides in the living cell.

According to the diagram, which pH is the one at which this amino acid will have a net charge of 0?

The peptide alanylglutamylglycylalanylleucine has:

Define the primary structure of a protein.

Identify the pair of peptides below that CANNOT be distinguished by tandem mass spectrometry.

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

The Foundations of Biochemistry

Water

The Three-Dimensional Structure of Proteins

Protein Function

Enzymes

Carbohydrates and Glycobiology

Nucleotides and Nucleic Acids

DNA-Based Information Technologies

Lipids

Biological Membranes and Transport

Biosignaling

Bioenergetics and Biochemical Reaction Types

Glycolysis, Gluconeogenesis, and the Pentose Phosphate Pathway

Principles of Metabolic Regulation

The Citric Acid Cycle

Fatty Acid Catabolism

Amino Acid Oxidation and the Production of Urea

Oxidative Phosphorylation and Photophosphorylation

Carbohydrate Biosynthesis in Plants and Bacteria

Lipid Biosynthesis

Biosynthesis of Amino Acids, Nucleotides, and Related Molecules

Hormonal Regulation and Integration of Mammalian Metabolism

Genes and Chromosomes

DNA Metabolism

RNA Metabolism

Protein Metabolism

Regulation of Gene Expression

Filters

Of the 20 standard amino acids, only _ is not optically active. The reason is that its side chain _.

Which statement is TRUE about the pK_a values for ionizable R-group of amino acids within a polypeptide?

At pH 7.0, converting a glutamic acid to $\gamma$ -carboxyglutamate, will have what effect on the overall charge of the protein containing it?

The protein bovine serum albumin (BSA), has a MW of about 66,400. Using the Lambert-Beer Law, calculate the concentration of a sample of BSA with an absorbance at 280 nm of 1.3, assuming the molar extinction coefficient at 280 nm is 43,824 M^-¹cm^-¹.