Question 1

Histidine has pKa values of 1.8, 6.0 R-group and 9.3 . At pH 8.0, the net charge on histidine is

Accepted Answer

A)  positive. 
B)  negative. 
C)  neutral uncharged. 
D)  insufficient information to tell. 
A)  positive. 
B)  negative. 
C)  neutral uncharged. 
D)  insufficient information to tell.

Question 2

At the isoelectric pH of an amino acid which has two pKa values the net charge is

Accepted Answer

A)  0.5. 
B)  1. 
C)  0. 
D)  -1. 
A)  0.5. 
B)  1. 
C)  0. 
D)  -1.

Question 3

All amino acids have mirror-image pairs designated D and L.

Accepted Answer

A) True 
 B)False

Question 4

Which is used as the basis of separation of proteins by affinity chromatography?

Accepted Answer

A)  The net charge and pI of the protein at the pH of the column. 
B)  The proteinʹs molecular weight. 
C)  The proteinʹs density. 
D)  The selective binding of the protein to a ligand on the column matrix. 
A)  The net charge and pI of the protein at the pH of the column. 
B)  The proteinʹs molecular weight. 
C)  The proteinʹs density. 
D)  The selective binding of the protein to a ligand on the column matrix.

Question 5

A mixture of four proteins X, Y, Z and N is applied to a gel-filtration column. Given the information supplied, which will elute first? $\begin{array}{|c|c|}
\hline \text { Protein } & \text { Molecular Weight g/mol) } \
\hline X & 35,000 \
\hline Y & 26,000 \
\hline Z & 146,000 \
\hline \mathrm{N} & 26,000 \
\hline
\end{array}$

Accepted Answer

A)  Z 
B)  Y and N elute together 
C)  X 
D)  cannot answer without information about the isoelectric point 
A)  Z 
B)  Y and N elute together 
C)  X 
D)  cannot answer without information about the isoelectric point

Question 6

The pKaʹs of the side chain group and the α-carboxyl group of glutamate are 4.1 and 2.1, respectively. Which statement accounts for this difference?

Accepted Answer

A)  The side chain has more possible resonance structures. 
B)  The α-carboxyl group has less steric hindrance and is therefore ionized more easily. 
C)  The side chain is a different functional group than the α-carboxyl group. 
D)  The α-carboxyl group is closer to the α-amino group than the side chain is. 
A)  The side chain has more possible resonance structures. 
B)  The α-carboxyl group has less steric hindrance and is therefore ionized more easily. 
C)  The side chain is a different functional group than the α-carboxyl group. 
D)  The α-carboxyl group is closer to the α-amino group than the side chain is.

Question 7

Iodoacetate is used to acetylate sulfhydryl groups to prevent their oxidation to disulfides.

Accepted Answer

A) True 
 B)False

Question 8

An amino acid named for a plant from which it was first isolated is

Accepted Answer

A)  proline. 
B)  methionine. 
C)  threonine. 
D)  asparagine. 
A)  proline. 
B)  methionine. 
C)  threonine. 
D)  asparagine.

Question 9

The hydropathy of amino acids can help determine the folding of protein chains.

Accepted Answer

A) True 
 B)False

Question 10

Arginine is the most basic of the 20 amino acids because its side chain is under most cell conditions.

Accepted Answer

A)  very highly charged 
B)  hydrophobic 
C)  titrated 
D)  protonated 
E)  negatively charged 
A)  very highly charged 
B)  hydrophobic 
C)  titrated 
D)  protonated 
E)  negatively charged

Question 11

Which amino acids are linked in phenylalanylglycine?

Accepted Answer

A)  phenyline, alanine and glycine 
B)  phenol, alanine and glycine 
C)  phenylalanine and glycine 
D)  phenol, adenine and glycine 
A)  phenyline, alanine and glycine 
B)  phenol, alanine and glycine 
C)  phenylalanine and glycine 
D)  phenol, adenine and glycine

Question 12

The purpose of adding ammonium sulfate to a solution containing proteins is to cause fractionation by precipitating the less soluble proteins.

Accepted Answer

A) True 
 B)False

Question 13

Disulfide bridges can form in proteins .

Accepted Answer

A)  only between cysteine residues side-by-side in the protein sequence 
B)  between cysteine residues that are close in three-dimensional space, but not necessarily close in the primary structure 
C)  between two cystine residues in proteins 
D)  between any two methionines or cysteines 
A)  only between cysteine residues side-by-side in the protein sequence 
B)  between cysteine residues that are close in three-dimensional space, but not necessarily close in the primary structure 
C)  between two cystine residues in proteins 
D)  between any two methionines or cysteines

Question 14

Which will react with amino acids to yield derivatives that can be detected by monitoring the absorbance at 254 nm?

Accepted Answer

A)  PITC 
B)  SDS 
C)  CNBr 
D)  HCl 
A)  PITC 
B)  SDS 
C)  CNBr 
D)  HCl

Question 15

A sequence of amino acids with a relatively high hydropathy is very likely to function by

Accepted Answer

A)  being at the active site of an enzyme. 
B)  being embedded in a cell membrane. 
C)  making a protein soluble. 
D)  being on the protein surface. 
A)  being at the active site of an enzyme. 
B)  being embedded in a cell membrane. 
C)  making a protein soluble. 
D)  being on the protein surface.

Question 16

The peptide bond is which of the following?

Accepted Answer

A)  an amide bond 
B)  an ester bond 
C)  an ether bond 
D)  an amine bond 
A)  an amide bond 
B)  an ester bond 
C)  an ether bond 
D)  an amine bond

Question 17

Ultraviolet (UV) light can be used to estimate concentrations of proteins in solutions because tryptophan and tyrosine absorb light at a wavelength of 280 nm.

Accepted Answer

A) True 
 B)False

Question 18

What is the net charge on the tripeptide Gly-Arg-Lys at pH 7? The table below gives the pKa?s of the ionizable groups on the free amino acids. $\begin{array}{|l|c|c|c|}
\hline \text { Free amino acid } & \begin{array}{c}
\mathrm{pKa} \text { of } \
\alpha \text {-Carboxyl group }
\end{array} & \begin{array}{c}
p \mathrm{k} \text { of } \
\alpha \text {-amino group }
\end{array} & \begin{array}{c}
\mathrm{pK} \mathrm{a} \text { of side } \
\text { chain }
\end{array} \
\hline \text { Glycine } & 2.4 & 9.8 & \cdots \
\hline \text { Arginine } & 1.8 & 9.0 & 12.5 \
\hline \text { Lysine } & 2.2 & 9.1 & 10.5 \
\hline
\end{array}$

Accepted Answer

A)  -1 
B)  0 
C)  +1 
D)  +2 
A)  -1 
B)  0 
C)  +1 
D)  +2

Question 19

Uncharged R groups of amino acids are not polar.

Accepted Answer

A) True 
 B)False

Question 20

The isoelectric point of alanine is pH = 6.15. It is mixed with proline pHCOOH = 2.0; pHNH2 = 10.6), and the mixture is placed in an electric field at pH 6.15. Which statement is true?

Accepted Answer

A)  The two amino acids will be separated. 
B)  The two amino acids will not be separated. 
C)  Neither amino acid will move in the electric field. 
D)  Both amino acids will move from the origin and be separated. 
A)  The two amino acids will be separated. 
B)  The two amino acids will not be separated. 
C)  Neither amino acid will move in the electric field. 
D)  Both amino acids will move from the origin and be separated.

Exam 3: Amino Acids and the Primary Structures of Proteins

Histidine has pKa values of 1.8, 6.0 R-group and 9.3 . At pH 8.0, the net charge on histidine is

At the isoelectric pH of an amino acid which has two pKa values the net charge is

All amino acids have mirror-image pairs designated D and L.

Which is used as the basis of separation of proteins by affinity chromatography?

A mixture of four proteins X, Y, Z and N is applied to a gel-filtration column. Given the information supplied, which will elute first? Protein Molecular Weight g/mol) X 35,000 Y 26,000 Z 146,000 26,000

The pKaʹs of the side chain group and the α-carboxyl group of glutamate are 4.1 and 2.1, respectively. Which statement accounts for this difference?

Iodoacetate is used to acetylate sulfhydryl groups to prevent their oxidation to disulfides.

An amino acid named for a plant from which it was first isolated is

The hydropathy of amino acids can help determine the folding of protein chains.

Arginine is the most basic of the 20 amino acids because its side chain is under most cell conditions.

Which amino acids are linked in phenylalanylglycine?

The purpose of adding ammonium sulfate to a solution containing proteins is to cause fractionation by precipitating the less soluble proteins.

Disulfide bridges can form in proteins .

Which will react with amino acids to yield derivatives that can be detected by monitoring the absorbance at 254 nm?

A sequence of amino acids with a relatively high hydropathy is very likely to function by

The peptide bond is which of the following?

Ultraviolet (UV) light can be used to estimate concentrations of proteins in solutions because tryptophan and tyrosine absorb light at a wavelength of 280 nm.

What is the net charge on the tripeptide Gly-Arg-Lys at pH 7? The table below gives the pKa?s of the ionizable groups on the free amino acids. Free amino acid of \alpha -Carboxyl group p of \alpha -amino group of side chain Glycine 2.4 9.8 \@cdots Arginine 1.8 9.0 12.5 Lysine 2.2 9.1 10.5

Uncharged R groups of amino acids are not polar.

The isoelectric point of alanine is pH = 6.15. It is mixed with proline pHCOOH = 2.0; pHNH2 = 10.6), and the mixture is placed in an electric field at pH 6.15. Which statement is true?

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

Histidine has pK_avalues of 1.8, 6.0 R-group and 9.3 . At pH 8.0, the net charge on histidine is

At the isoelectric pH of an amino acid which has two pK_avalues the net charge is

The pK_aʹs of the side chain group and the α-carboxyl group of glutamate are 4.1 and 2.1, respectively. Which statement accounts for this difference?

What is the net charge on the tripeptide Gly-Arg-Lys at pH 7? The table below gives the pK_a?s of the ionizable groups on the free amino acids. Free amino acid of \alpha -Carboxyl group p of \alpha -amino group of side chain Glycine 2.4 9.8 \@cdots Arginine 1.8 9.0 12.5 Lysine 2.2 9.1 10.5

The isoelectric point of alanine is pH = 6.15. It is mixed with proline pH_COOH= 2.0; pH_NH2 = 10.6), and the mixture is placed in an electric field at pH 6.15. Which statement is true?