Question 1

Amino acids found in meteorites and near stars are

Accepted Answer

A)  D isomers only. 
B)  L isomers only. 
C)  Both D and L isomers. 
D)  not isomers. 
A)  D isomers only. 
B)  L isomers only. 
C)  Both D and L isomers. 
D)  not isomers. C

Question 2

An amino acid with two chiral carbon atoms

Accepted Answer

A)  is unstable. 
B)  can exist in 4 forms all of which are superimposable. 
C)  can form three possible stereoisomers. 
D)  can form four possible stereoisomers. 
E)  can form five possible stereoisomers. 
A)  is unstable. 
B)  can exist in 4 forms all of which are superimposable. 
C)  can form three possible stereoisomers. 
D)  can form four possible stereoisomers. 
E)  can form five possible stereoisomers. D

Question 3

The amino acids in polypeptide chains which contain sulfur S) are

Accepted Answer

A)  cysteine, cystine, and methionine. 
B)  cystine. 
C)  methionine only. 
D)  cysteine only. 
E)  cysteine and methionine. 
A)  cysteine, cystine, and methionine. 
B)  cystine. 
C)  methionine only. 
D)  cysteine only. 
E)  cysteine and methionine. E

Question 4

In gel electrophoresis the molecules with the highest molecular weight migrate the farthest from the starting wells.

Accepted Answer

A) True 
 B)False

Question 5

All 20 common amino acids have an amino group and a carboxyl group bonded to the same carbon atom.

Accepted Answer

A) True 
 B)False

Question 6

What is the purpose of SDS in SDS-PAGE?

Accepted Answer

A)  to selectively bind the target protein 
B)  to maintain buffer pH in the gel 
C)  to cause the separation to be on the basis of molecular weight only 
D)  to initiate polymerization of acrylamide to form a gel 
A)  to selectively bind the target protein 
B)  to maintain buffer pH in the gel 
C)  to cause the separation to be on the basis of molecular weight only 
D)  to initiate polymerization of acrylamide to form a gel

Question 7

Glycine is not a stereoisomer because

Accepted Answer

A)  it has no chiral carbon. 
B)  it does not form enantiomers. 
C)  it does not exist in two non-superimposable mirror-image forms. 
D)  All of the above 
E)  A and B only 
A)  it has no chiral carbon. 
B)  it does not form enantiomers. 
C)  it does not exist in two non-superimposable mirror-image forms. 
D)  All of the above 
E)  A and B only

Question 8

The ionic charges associated with a protein molecule are .

Accepted Answer

A)  mostly contributed by the side chains of constituent amino acids 
B)  determined by the contribution from the α-carboxyl group, α-amino group and side chain of every amino acid in the protein 
C)  contributed by only the N-terminal and C-terminal residues 
D)  independent of the amino acid composition and depend only on pH 
A)  mostly contributed by the side chains of constituent amino acids 
B)  determined by the contribution from the α-carboxyl group, α-amino group and side chain of every amino acid in the protein 
C)  contributed by only the N-terminal and C-terminal residues 
D)  independent of the amino acid composition and depend only on pH

Question 9

A mixture of two proteins with the same pI and molecular weights MW) of 10,000 and 15,000 daltons, respectively, are applied to a gel filtration column. What happens during elution?

Accepted Answer

A)  Both elute together. 
B)  The one with MW of 10,000 elutes first. 
C)  The one with MW of 15,000 elutes first. 
D)  More information is needed about the specificity of the column matrix to tell what happens. 
A)  Both elute together. 
B)  The one with MW of 10,000 elutes first. 
C)  The one with MW of 15,000 elutes first. 
D)  More information is needed about the specificity of the column matrix to tell what happens.

Question 10

All 20 common amino acids exist in nature equally as both the D and L stereoisomers.

Accepted Answer

A) True 
 B)False

Question 11

The isoelectric point of amino acids is the average of the values pKCOOH + pKNH2.

Accepted Answer

A) True 
 B)False

Question 12

Amino acids with non-ionizable side chains are zwitterions when they are .

Accepted Answer

A)  in any solution 
B)  at physiological pH, pH = 7.4 
C)  in acidic solutions only 
D)  in alkaline solutions only 
E)  All of the above 
A)  in any solution 
B)  at physiological pH, pH = 7.4 
C)  in acidic solutions only 
D)  in alkaline solutions only 
E)  All of the above

Question 13

According to the Henderson-Hasselbalch equation, when the concentrations of proton acceptor and proton donor are the same, then

Accepted Answer

A)  the carboxylic acid is totally neutralized. 
B)  only salt forms are present. 
C)  pH = pKa. 
D)  pKa = log[proton acceptor]/[proton donor]. 
A)  the carboxylic acid is totally neutralized. 
B)  only salt forms are present. 
C)  pH = pKa. 
D)  pKa = log[proton acceptor]/[proton donor].

Question 14

Concentrations of some proteins cannot be estimated by UV spectrophotometry because they are

Accepted Answer

A)  high in non-absorbing amino acids. 
B)  low in tryptophan and tyrosine. 
C)  low in protein. 
D)  high in aromatic amino acids. 
A)  high in non-absorbing amino acids. 
B)  low in tryptophan and tyrosine. 
C)  low in protein. 
D)  high in aromatic amino acids.

Question 15

What information can be gained by comparing the sequences of proteins that have the same or similar function in different species?

Accepted Answer

A)  to determine evolutionary relationships and relatedness of species 
B)  to determine sequences that are conserved among species since they are likely to be important to the function and stability of the proteins 
C)  to locate highly variable residues which contribute little to the structure and function of the protein 
D)  All of the above 
A)  to determine evolutionary relationships and relatedness of species 
B)  to determine sequences that are conserved among species since they are likely to be important to the function and stability of the proteins 
C)  to locate highly variable residues which contribute little to the structure and function of the protein 
D)  All of the above

Question 16

For the amino acid lysine, the Henderson-Hasselbalch equation can be applied to ionization groups).

Accepted Answer

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

Question 17

Asparagine and glutamine are both amides of aspartic acid and because they have uncharged sidechains are often found on the interior of proteins.

Accepted Answer

A) True 
 B)False

Question 18

Most proteins contain an approximately equal amount of each of the standard amino acids.

Accepted Answer

A) True 
 B)False

Question 19

The RS system of nomenclature describes

Accepted Answer

A)  amino acids not easily described by the DL system. 
B)  the way the R groups are arranged. 
C)  the chiral carbon centers of amino acids. 
D)  the strength of the chemical groups in amino acids. 
A)  amino acids not easily described by the DL system. 
B)  the way the R groups are arranged. 
C)  the chiral carbon centers of amino acids. 
D)  the strength of the chemical groups in amino acids.

Question 20

The last common ancestor of modern organisms must have used

Accepted Answer

A)  both D and L amino acids. 
B)  D amino acids. 
C)  L amino acids. 
D)  either D or L amino acids. 
A)  both D and L amino acids. 
B)  D amino acids. 
C)  L amino acids. 
D)  either D or L amino acids.

Exam 3: Amino Acids and the Primary Structures of Proteins

Amino acids found in meteorites and near stars are

An amino acid with two chiral carbon atoms

The amino acids in polypeptide chains which contain sulfur S) are

In gel electrophoresis the molecules with the highest molecular weight migrate the farthest from the starting wells.

All 20 common amino acids have an amino group and a carboxyl group bonded to the same carbon atom.

What is the purpose of SDS in SDS-PAGE?

Glycine is not a stereoisomer because

The ionic charges associated with a protein molecule are .

A mixture of two proteins with the same pI and molecular weights MW) of 10,000 and 15,000 daltons, respectively, are applied to a gel filtration column. What happens during elution?

All 20 common amino acids exist in nature equally as both the D and L stereoisomers.

The isoelectric point of amino acids is the average of the values pKCOOH + pKNH2.

Amino acids with non-ionizable side chains are zwitterions when they are .

According to the Henderson-Hasselbalch equation, when the concentrations of proton acceptor and proton donor are the same, then

Concentrations of some proteins cannot be estimated by UV spectrophotometry because they are

What information can be gained by comparing the sequences of proteins that have the same or similar function in different species?

For the amino acid lysine, the Henderson-Hasselbalch equation can be applied to ionization groups).

Asparagine and glutamine are both amides of aspartic acid and because they have uncharged sidechains are often found on the interior of proteins.

Most proteins contain an approximately equal amount of each of the standard amino acids.

The RS system of nomenclature describes

The last common ancestor of modern organisms must have used

Introduction to Biochemistry

Water

Proteins: Three-Dimensional Structure and Function

Properties of Enzymes

Mechanisms of Enzymes

Coenzymes and Vitamins

Carbohydrates

Lipids and Membranes

Introduction to Metabolism

Glycolysis

Gluconeogenesis, the Pentose Phosphate Pathway, and Glycogen Metabolism

The Citric Acid Cycle

Electron Transport and Oxidative Phosphorylation

Photosynthesis

Lipid Metabolism

Amino Acid Metabolism

Nucleotide Metabolism

Nucleic Acids

Dna Replication, Repair, and Recombination

Transcription and Rna Processing

Protein Synthesis

Recombinant Dna Technology

Filters

The isoelectric point of amino acids is the average of the values pK_COOH+ pK_NH₂.