Question 1

Even though mass spectrometry has been in use for over a hundred years,it had only limited use with proteins until the 1980s because

Accepted Answer

A) not many proteins had been discovered and purified before the 1980s. 
B) it was not possible to disperse charged proteins into a gaseous stream of particles. 
C) many proteins are difficult or impossible to crystallize. 
D) proteins decompose too quickly into their component amino acids. 
A) not many proteins had been discovered and purified before the 1980s. 
B) it was not possible to disperse charged proteins into a gaseous stream of particles. 
C) many proteins are difficult or impossible to crystallize. 
D) proteins decompose too quickly into their component amino acids.

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

Which shows a proper peptide bond?

Accepted Answer

A)    
B)    
C)    
D)    
A)    
B)    
C)    
D)

Question 4

Amino acids are neutral at the isoelectric pH.

Accepted Answer

A) True 
 B)False

Question 5

Fossil dating by amino acid racemization measured

Accepted Answer

A) the amount of a D-amino acid present. 
B) the amount of an L-amino acid present. 
C) the amounts of both D and L forms of an amino acid present. 
D) the total of all amino acids present. 
A) the amount of a D-amino acid present. 
B) the amount of an L-amino acid present. 
C) the amounts of both D and L forms of an amino acid present. 
D) the total of all amino acids present.

Question 6

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 7

The twenty standard amino acids are the only amino acids found in living organisms.

Accepted Answer

A) True 
 B)False

Question 8

At neutral pH,the net charge of serine is

Accepted Answer

A) positive. 
B) negative. 
C) zero. 
D) None of the above. 
A) positive. 
B) negative. 
C) zero. 
D) None of the above.

Question 9

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 10

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 11

The distribution of amino acids in a protein often cannot be determined precisely by acid hydrolysis.Why?

Accepted Answer

A) The side chains of asparagine and glutamine are also hydrolyzed. 
B) The amine groups on lysine and arginine neutralize much of the acid. 
C) The side chain of phenylalanine is almost totally destroyed by acid hydrolysis. 
D) All of the above. 
A) The side chains of asparagine and glutamine are also hydrolyzed. 
B) The amine groups on lysine and arginine neutralize much of the acid. 
C) The side chain of phenylalanine is almost totally destroyed by acid hydrolysis. 
D) All of the above.

Question 12

The RS system of nomenclature describes

Accepted Answer

A) the relative sizes of molecules. 
B) the way the amino acid side chains are arranged. 
C) the absolute configuration about chiral carbon centers . 
D) the strength of the chemical groups in amino acids. 
A) the relative sizes of molecules. 
B) the way the amino acid side chains are arranged. 
C) the absolute configuration about chiral carbon centers . 
D) the strength of the chemical groups in amino acids.

Question 13

Basic amino acids are ________ (positive,negative)at pH 7 and acidic R group amino acids are ________ (positive,negative)at pH 7.

Accepted Answer

A) negative;positive 
B) negative;negative 
C) positive;negative 
D) positive;positive 
A) negative;positive 
B) negative;negative 
C) positive;negative 
D) positive;positive

Question 14

Which amino acid is ideal for the transfer of protons within the catalytic site of enzymes due to the presence of significant amounts of both the protonated and deprotonated forms of its side chain at biological pH?

Accepted Answer

A) Lysine. 
B) Asparagine. 
C) Tyrosine. 
D) Cysteine. 
E) Histidine. 
A) Lysine. 
B) Asparagine. 
C) Tyrosine. 
D) Cysteine. 
E) Histidine.

Question 15

Uncharged R groups of amino acids are not polar.

Accepted Answer

A) True 
 B)False

Question 16

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 17

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.

Question 18

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 19

Although the hydroxyl groups in serine and threonine are uncharged,they can react within active sites of some enzymes ________.

Accepted Answer

A) precisely because they are uncharged 
B) because the hydroxyl group is polar 
C) because the hydroxyl group is small and fits into the site 
D) All of the above 
A) precisely because they are uncharged 
B) because the hydroxyl group is polar 
C) because the hydroxyl group is small and fits into the site 
D) All of the above

Question 20

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

Accepted Answer

A) True 
 B)False

Exam 3: Amino Acids and the Primary Structures of Proteins

Even though mass spectrometry has been in use for over a hundred years,it had only limited use with proteins until the 1980s because

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

Which shows a proper peptide bond?

Amino acids are neutral at the isoelectric pH.

Fossil dating by amino acid racemization measured

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

The twenty standard amino acids are the only amino acids found in living organisms.

At neutral pH,the net charge of serine is

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

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

The distribution of amino acids in a protein often cannot be determined precisely by acid hydrolysis.Why?

The RS system of nomenclature describes

Basic amino acids are ________ (positive,negative)at pH 7 and acidic R group amino acids are ________ (positive,negative)at pH 7.

Which amino acid is ideal for the transfer of protons within the catalytic site of enzymes due to the presence of significant amounts of both the protonated and deprotonated forms of its side chain at biological pH?

Uncharged R groups of amino acids are not polar.

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

An amino acid with two chiral carbon atoms

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

Although the hydroxyl groups in serine and threonine are uncharged,they can react within active sites of some enzymes ________.

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

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 Atp Synthesis

Photosynthesis

Lipid Metabolism

Amino Acid Metabolism

Nucleotide Metabolism

Nucleic Acids

DNA Replication, repair, and Recombination

Transcription and RNA Processing

Protein Synthesis

Filters

Basic amino acids are (positive,negative)at pH 7 and acidic R group amino acids are (positive,negative)at pH 7.