Biochem Test 2

Front 1

What are the non-polar (hydrophobic) amino acids?

Back 1

Luecine, Proline, Mehionine, Tryptophan, Alanine, Valine, Phenylalanine, Isoleucine

Front 2

What are the polar (hydrophilic) uncharged amino acids?

Back 2

Glycine, Serine, Threonine, Cysteine, Asparagine, Glutamine, Tyrosine, Histidine

Front 3

What are the acidic amino acids?

Back 3

Aspartic, Glutamic

Front 4

What are the basic amino acids?

Back 4

Lysine, Arginine

Front 5

What amino acids is not an alpha-amino acid?

Back 5

proline

Front 6

Which two groups of an amino acid react to form a peptide bond?

Back 6

the alpha-amino gropu and the alpha-carboxyl group

Front 7

Understanding the unique characteristic behaviour of amino acid side-chains is important because:

Back 7

1) chemical reactivity of some can be used ot modify proteins in specific ways
2) chemical and physical propreties of some allow detections and quantification
3) chemical and physical properties of some bestow propteins with specific biological functions

Front 8

Ninhydrin is used to detect and quantify a-amino acids. Reactions with ninhydrin results in:

Back 8

deamination and decarboxylation

Front 9

Which amino acid lacks a chiral center?

Back 9

glycine

Front 10

Which amino acids absorb light at 250-280 nm?

Back 10

arginine, lysine & histidine

Front 11

Which amino acid has two chiral centers?

Back 11

L-Threonine

Front 12

For all amino acids except one, the L-configuration corresponds to the S-configuration. Which one has the R-configuration?

Back 12

L-Cysteine

Front 13

amino acids are always what configuration

Back 13

L-amino acids

Front 14

Amino acids join via

Back 14

peptide bonds which release water

Front 15

What contributes to protein folding?

Back 15

aliphatic and aromatic R-group containing amino acids

Front 16

At neutral pH, amino acids are

Back 16

zwitterions - bipolar ions

Front 17

What is the pH of a glutamic acid solution if the α p g
carboxyl is 1/4 dissociated?

Back 17

pH = 2 + log10 [1]/[3]
pH = 2 + (-0.477)
pH = 1.523

Front 18

What is the pH of a lysine solution if the side p y
chain amino group is 3/4 dissociated?

Back 18

pH = 10.5 + log [3]/[1]
pH = 10.5 + (0.477)
pH = 10 977 = 11

Front 19

The first amino acid that is eluted is

Back 19

the lowest postitive charge; the higher the charge the greater affinity and the slower the elution

Front 20

What must the elution tube contain for the elution to work?

Back 20

salt

Front 21

Which pairs of amino acid side chains might you expect to find in a salt bridge in a protein at pH 7.0?

Back 21

Aspartate & Arginine

Front 22

The 20 common amino acids found in proteins are usually the L enantiomers. The exception is:

Back 22

Glycine

Front 23

At pH 7.0 which of the following amino acid side chains would you expect to be protonated?

Back 23

Arginine

Front 24

The pKa of the side chain of histidine is 6.0. At pH 7.0 what is the ratio of positively charged histidine side chains to neutral side chains?

Back 24

1:10

Front 25

Which of the following amino acid side chains reacts chemically with DTNB and p-HydroxyMercuriBenzoate

Back 25

Cysteine

Front 26

If a mixture of Glutamic acid (side chain pKa = 4.3) and Aspartic acid (side chain pKa = 3.9), at pH 4.0 are separated by using anion exchange chromatography at pH 4.0, what will happen?

Back 26

Both will stick but using a salt gradient will elute the glutamate before the aspartate

Front 27

In water the pKa of the side chain of glutamic acid is 4.3. If the local dielectric constant of the medium was changed to that of hexane (dielectric constant 1.9) the pKa would

Back 27

Increase

Front 28

Which of the following amino acids has two chiral centers?

Back 28

Isoleucine

Front 29

Which of the following amino acids is not found occasionally in proteins?

Back 29

Ornithine

Front 30

The green fluorescent properties of GFP (green Fluorescent Protein) result from:

Back 30

A chromophore formed autocatalytically involving a particular sequence of amino acids in the protein

Front 31

The color formed when ninhydrin is used to detect and quantitate amino acids

Back 31

Is a derivative containing two ninhydrin moieties formed by reaction with released ammonia during the reaction

Front 32

Peptide bond formation is

Back 32

a dehydration reaction

Front 33

In a peptide bond

Back 33

-the C-Co-N-C configuration is trans; the six atoms are co-planar; there is rotation about C-R, C-Co and C-N bonds; rotation about Co-N is restricted; there is a distinct polarity

Front 34

As a first approximation proteins can be assigned to one of three classes on the basis of shape and solubility. These are:

Back 34

fibrous, globular, membrane

Front 35

Through H-bond interactions between adjacent amino acids residues the polypeptide chain can arrange itself into characteristic helical or pleated segments. This is a definition of the

Back 35

secondary structure

Front 36

The secondary, tertiary and quaternary structures of proteins are stabilized principally by

Back 36

H-bonds; electrostatic interactions; van der Waals forces; hydrophobic interactions

Front 37

In general protein solubility is influenced by:

Back 37

pH; amino acid sequence; polarity of solvent

Front 38

The effect of ionic strength on protein solubility is attributed to:

Back 38

the decrease in electrostatic interactions between protein molecules; The increase in charge-counter ion interactions; competition between the protein and the salt ions for water of solution

Front 39

The first step in determining the amino acid composition of a protein involves hydrolyzing the protein in 6NHCl at 110C for 24, 48 and 72 h. This procedure:

Back 39

slowly destroys Ser and Thr, but their original concentration is estimated by extrapolation to zero time from their concentrations at 24, 48 and 72 h.

Front 40

The complex amino acid mixture in a protein hydrolysate is separated using:

Back 40

ion-exchange chromatography

Front 41

Comparing the amino acid composition of different proteins allows the following generalizations:

Back 41

each of the 20 naturally occurring amino acids is usually represented at least once.

Front 42

Determining the amino acid sequence of a protein (its primary structure) involves both chemical and enzymatic strategies. A procedure for the cleavage of disulfide bonds is:

Back 42

reduction with 2-mercaptoethanol or dithiothreitol (DTT) followed by alkylation with iodoacetate.

Front 43

Determining the amino acid sequence of a protein (its primary structure) involves both chemical and enzymatic strategies in seven basic steps. A procedure for determining the N-terminal amino acid is:

Back 43

specific hydrolysis with cyanogen bromide (CNBr) to yield a sulfonium ion that undergoes rapid intramolecular rearrangement to form the iminolactone

Front 44

Determining the amino acid sequence of a protein (its primary structure) involves both chemical and enzymatic strategies in seven basic steps. A procedure for determining the C-terminal amino acid is:

Back 44

specific hydrolysis with carboxypeptidase using an automated protocol

Front 45

Determining the amino acid sequence of a protein (its primary structure) involves both chemical and enzymatic strategies in seven basic steps. A chemical procedure for specifically cleaving next to Met residues is:

Back 45

specific hydrolysis with cyanogen bromide (CNBr) to yield a sulfonium ion that undergoes rapid intramolecular rearrangement to form the iminolactone

Front 46

What is the order of procedures for determining the position of disulfide bonds?

Back 46

hydrolysis with enzymes such as trypsin; electrophoresis; oxidation with performic acid; electrophoresis; sequencing with phenylisothiocyanate (Edman degradation)

Front 47

Homologous proteins are those with:

Back 47

the same function in different organisms; different functions but similarities in sequence and tertiary structures; the same function and a high degree of sequence similarity; positions in the primary sequence where the same amino acid always occurs; positions in the primary sequence where the same type of amino acid always occurs

Front 48

Procedure/s used for the separation of proteins based on solubility is/are:

Back 48

ammonium sulfate precipitation

Front 49

Procedure/s used for the separation of proteins based on activity or function is/are:

Back 49

affinity chromatography

Front 50

Procedure/s used for the separation of proteins based on net charge is/are:

Back 50

isoelectric focusing

Front 51

Procedure/s used for the separation of proteins based on mass is/are:

Back 51

size exclusion chromatography; sodium dodecylsulfate-polyacrylamide gel electrophoresis

Front 52

Procedure/s used for the separation of proteins based on charge and mass is/are:

Back 52

electrophoresis

Front 53

Procedure/s used for the separation of proteins based on mass and/or density is/are:

Back 53

ultracentrifugation