Question 1

Which of the following is a characteristic of stereoisomers?

Accepted Answer

A) A diastereomer is a non-superimposable mirror image. 
B) An enantiomer is a superimposable mirror image. 
C) Diastereomers rotate plane-polarized light in equal magnitude but opposite directions. 
D) Diastereomers have different melting points 
A) A diastereomer is a non-superimposable mirror image. 
B) An enantiomer is a superimposable mirror image. 
C) Diastereomers rotate plane-polarized light in equal magnitude but opposite directions. 
D) Diastereomers have different melting points D

Question 2

At what pH is the cysteine side-chain sulfhydryl group 11% dissociated if its pKₐ value is 8.32?

Accepted Answer

A) 3.2 
B) 7.4 
C) 8.5 
D) 10.2 
A) 3.2 
B) 7.4 
C) 8.5 
D) 10.2 B

Question 3

Glutamic acid has pKₐ's at 2.2,4.3,and 9.7.What is the isoelectric point for glutamic acid?

Accepted Answer

A) 3.25 
B) 4.3 
C) 5.4 
D) 7.0 
A) 3.25 
B) 4.3 
C) 5.4 
D) 7.0 A

Question 4

Which of the following is an intrinsic property of the commonly occurring 20 amino acids?

Accepted Answer

A) asymmetrical a-carbon 
B) the inability to polymerize 
C) polarity 
D) non-chirality 
A) asymmetrical a-carbon 
B) the inability to polymerize 
C) polarity 
D) non-chirality

Question 5

Which of the following amino acids has a side-chain pKₐ near neutrality and therefore plays an important role as proton donor and acceptor in many enzyme-catalyzed reactions?

Accepted Answer

A) histidine 
B) cysteine 
C) aspartic acid 
D) arginine 
A) histidine 
B) cysteine 
C) aspartic acid 
D) arginine

Question 6

Which of the following amino acid derivatives is correctly derived from its corresponding commonly occurring amino acid?

Accepted Answer

A) GABA is a neurotransmitter derived from aspartic acid. 
B) Histamine is a neurotransmitter derived from proline. 
C) Epinephrine is a hormone derived from tyrosine. 
D) Serotonin is a neurotransmitter derived from phenylalanine. 
A) GABA is a neurotransmitter derived from aspartic acid. 
B) Histamine is a neurotransmitter derived from proline. 
C) Epinephrine is a hormone derived from tyrosine. 
D) Serotonin is a neurotransmitter derived from phenylalanine.

Question 7

Which of the following amino acids most likely to be present if the pI of a peptide is 4.6?

Accepted Answer

A) glutamic acid 
B) histidine 
C) arginine 
D) cysteine 
A) glutamic acid 
B) histidine 
C) arginine 
D) cysteine

Question 8

Which of the following has partial double-bond character?

Accepted Answer

A) hydrogen bond 
B) peptide bond 
C) phosphoanhydride bond 
D) van der Waals bond 
A) hydrogen bond 
B) peptide bond 
C) phosphoanhydride bond 
D) van der Waals bond

Question 9

Which of the following amino acids has more than 1 chiral carbon?

Accepted Answer

A) serine 
B) lysine 
C) threonine 
D) cysteine 
A) serine 
B) lysine 
C) threonine 
D) cysteine

Question 10

Histidine has pKₐ values of 1.8,6.0,and 9.2.At which of the following pH values would histidine be found with a net negative charge?

Accepted Answer

A) 1.0 
B) 4.0 
C) 8.0 
D) 11.0 
A) 1.0 
B) 4.0 
C) 8.0 
D) 11.0

Question 11

The amino and carboxyl groups of amino acids react in a head-to-tail fashion and forming a covalent linkage.What is this linkage typically referred to as?

Accepted Answer

A) an aromatic bond 
B) a phosphoanhydride bond 
C) a peptide bond 
D) a hydrogen bond 
A) an aromatic bond 
B) a phosphoanhydride bond 
C) a peptide bond 
D) a hydrogen bond

Question 12

Which of the following does NOT react with the -SH group on cysteine?

Accepted Answer

A) N-ethylmaleimide 
B) benzaldehyde 
C) acrylonitrile 
D) iodoacetate 
A) N-ethylmaleimide 
B) benzaldehyde 
C) acrylonitrile 
D) iodoacetate

Question 13

Of the following four amino acids which one absorbs light most strongly between 250 and 300 nm?

Accepted Answer

A) histidine 
B) phenylalanine 
C) tryptophan 
D) tyrosine 
A) histidine 
B) phenylalanine 
C) tryptophan 
D) tyrosine

Question 14

Which of the following is a property of ninhydrin?

Accepted Answer

A) It produces a yellow product upon reaction with histidine. 
B) It can be used to detect the location of amino acids following SDS-PAGE. 
C) It produces a green product upon reaction with alanine. 
D) It reacts with an amino acid by oxidatively deaminating its amino group. 
A) It produces a yellow product upon reaction with histidine. 
B) It can be used to detect the location of amino acids following SDS-PAGE. 
C) It produces a green product upon reaction with alanine. 
D) It reacts with an amino acid by oxidatively deaminating its amino group.

Question 15

What is the pH of a serine solution in which the a-NH₃⁺ group,which has a pKₐ 9.2,is one-third dissociated?

Accepted Answer

A) 8.7 
B) 8.9 
C) 9.0 
D) 9.5 
A) 8.7 
B) 8.9 
C) 9.0 
D) 9.5

Question 16

Which of the following is a feature of L-isoleucine?

Accepted Answer

A) It has four stereoisomers. 
B) L-allo-leucine would be its diastereomer. 
C) It contains a total of 2 symmetric carbons. 
D) Using the (R,S)system,it can also be named as (3S,2S)-isoleucine. 
A) It has four stereoisomers. 
B) L-allo-leucine would be its diastereomer. 
C) It contains a total of 2 symmetric carbons. 
D) Using the (R,S)system,it can also be named as (3S,2S)-isoleucine.

Question 17

Which of the following amino acids is classified as a basic amino acid?

Accepted Answer

A) leucine 
B) aspartic acid 
C) asparagine 
D) lysine 
A) leucine 
B) aspartic acid 
C) asparagine 
D) lysine

Question 18

What effect does the presence of the α-COO- group of an amino acid have on the pKₐ value of its α-NH₃⁺ group?

Accepted Answer

A) The pKa value increases by >2 pH units. 
B) The pKa value decrease by > 2 pH units. 
C) The pKa value increases by ~1.5 pH units. 
D) The pKa value decrease by ~ 1.5 pH units. 
A) The pKa value increases by >2 pH units. 
B) The pKa value decrease by > 2 pH units. 
C) The pKa value increases by ~1.5 pH units. 
D) The pKa value decrease by ~ 1.5 pH units.

Question 19

Which of the following results from resonance in peptide bonds?

Accepted Answer

A) a C?-carbon that is out of the coplanar group of atoms 
B) unrestricted rotation in the peptide backbone at the N-C? bond and C?-Co bond 
C) approximately 40% double-bond character 
D) Co-N bond distance that is longer than normal,but shorter than C=N bonds 
A) a C?-carbon that is out of the coplanar group of atoms 
B) unrestricted rotation in the peptide backbone at the N-C? bond and C?-Co bond 
C) approximately 40% double-bond character 
D) Co-N bond distance that is longer than normal,but shorter than C=N bonds

Question 20

Based on their properties,which amino acids are correctly classified?

Accepted Answer

A) Alanine and valine are neutral,nonpolar amino acids. 
B) Aspartic acid and asparagine are acidic amino acids. 
C) Serine and glutamine are polar,charged amino acids. 
D) Lysine and arginine are basic,uncharged amino acids. 
A) Alanine and valine are neutral,nonpolar amino acids. 
B) Aspartic acid and asparagine are acidic amino acids. 
C) Serine and glutamine are polar,charged amino acids. 
D) Lysine and arginine are basic,uncharged amino acids.

Exam 4: Amino Acids

Which of the following is a characteristic of stereoisomers?

At what pH is the cysteine side-chain sulfhydryl group 11% dissociated if its pKₐ value is 8.32?

Glutamic acid has pKₐ's at 2.2,4.3,and 9.7.What is the isoelectric point for glutamic acid?

Which of the following is an intrinsic property of the commonly occurring 20 amino acids?

Which of the following amino acids has a side-chain pKₐ near neutrality and therefore plays an important role as proton donor and acceptor in many enzyme-catalyzed reactions?

Which of the following amino acid derivatives is correctly derived from its corresponding commonly occurring amino acid?

Which of the following amino acids most likely to be present if the pI of a peptide is 4.6?

Which of the following has partial double-bond character?

Which of the following amino acids has more than 1 chiral carbon?

Histidine has pKₐ values of 1.8,6.0,and 9.2.At which of the following pH values would histidine be found with a net negative charge?

The amino and carboxyl groups of amino acids react in a head-to-tail fashion and forming a covalent linkage.What is this linkage typically referred to as?

Which of the following does NOT react with the -SH group on cysteine?

Of the following four amino acids which one absorbs light most strongly between 250 and 300 nm?

Which of the following is a property of ninhydrin?

What is the pH of a serine solution in which the a-NH₃⁺ group,which has a pKₐ 9.2,is one-third dissociated?

Which of the following is a feature of L-isoleucine?

Which of the following amino acids is classified as a basic amino acid?

What effect does the presence of the α-COO- group of an amino acid have on the pKₐ value of its α-NH₃⁺ group?

Which of the following results from resonance in peptide bonds?

Based on their properties,which amino acids are correctly classified?

The Facts of Life: Chemistry Is the Logic of Biological Phenomena

Water: the Medium of Life

Thermodynamics of Biological Systems

Proteins: Their Primary Structure and Biological Functions

Proteins: Secondary, tertiary, and Quaternary Structure

Carbohydrates and the Glycoconjugates of Cell Surfaces

Lipids

Lipid Biosynthesis

Membranes and Membrane Transport

The Reception and Transmission of Extracellular Information

Enzymes Kinetics and Specificity

Mechanisms of Enzyme Action

Enzyme Regulation

Molecular Motors

Nutrition and the Organization of Metabolism

Glycolysis

The Tricarboxylic Acid Cycle

Electron Transport and Oxidative Phosphorylation

Photosynthesis

Gluconeogenesis, glycogen Metabolism, and the Pentose Phosphate Pathway

Fatty Acid Catabolism

Nitrogen Acquisition and Amino Acid Metabolism

Nucleotides and Nucleic Acids

Structure of Nucleic Acids

Synthesis and Degradation of Nucleotides

Recombinant Dna: Cloning and Creation of Chimeric Genes

DNA Metabolism: Replication, recombination, and Repair

Transcription and the Regulation of Gene Expression

Protein Synthesis

Post-Transcriptional Regulation of Gene Expression

Completing the Protein Life Cycle: Folding, processing, and Degradation

Metabolic Integration and Organ Specialization

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