PS2 Exam 1 half

All of the amino acids EXCEPT ____ have both free α-amino and freeα-carboxyl groups.

-aspartic acid

-asparagine

-proline

-lysine

-valine

proline

The side chain groups of amino acids are bonded to which carbon?

-The α-carbon.

-The β-carbon.

-The carbonyl carbon.

-Different amino acids have their side chains attached to different carbons.

The α-carbon.

The amino acids which occur in proteins

-are all of the L- form.

-are all of the D- form.

-can be either the L- or D- form.

-do not have L- and D- forms.

are all of the L- form.

Which amino acid has a benzene-like ring?

-Glutamic Acid

-Histidine

-Isoleucine

-Serine

-Tyrosine

Tyrosine

T/F: Thr and Ser both have hydroxyls as side chains.

True

Which of the following can be considered a unique characteristic of histidine?

-Its side chain is attached to the alpha carbon

-It has a basic side chain

-It has a side chain that is chemically basic but has an acidic pKa

-It is technically an "imino" acid

It has a side chain that is chemically basic but has an acidic pKa

The pKa values of the alpha carboxyl groups of common amino acids are around

-pH 2, 5, 7, 9

2

The pKa values of the amino groups of common amino acids

-occur at very low pH values

-occur in a range from pH 9 to pH 11

-all occur at pH 8

-all occur above pH 12

occur in a range from pH 9 to pH 11

What is the predominant form of the amino acid abbreviated R at pH 7?

positive

What is the predominant form of the amino acid abbreviated E at pH 7?

negative

The collective group of all the proteins is called the:

-protosome, proteome, genome, prion, liposome

proteome

The net charge of the peptide Arg-Phe-Gly-Lys-Glu at pH 7 is:

+1

Which of the following characteristics is consistent with the description of a fibrous protein, but not a globular protein?

-water insoluble

-dissolved in biological fluids

-high content of polar amino acids

-low tensile strength

-often function as transport proteins

water insoluble

Proteins with charges can be separated by _______ chromatography.

-exclusion, size, affinity, ion exchange, gel

ion exchange

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

=1, 4, 8, 11, none

11

 The peptide bond has partial ____ character.
-hydrogen bond

-van der Waals bond

-double bond

-triple bond

-all of the above

double bond

 Proteins with two different polypeptide chains are:
-monomeric proteins.

-trimeric proteins.

-homodimeric proteins.

-heterodimeric proteins.

-none of the above.

heterodimeric proteins.

 A common reaction of two cysteine residues in proteins results in the formation of ____.
-thioester bonds

-disulfide bonds

-dithiol bonds

-thioether bonds

-none of the above

disulfide bonds

α-Helix and β-strand are components of ____ structure
-primary, secondary, tertiary, quaternary, all are true

secondary

 Which of the following levels of protein structure is correctly defined?
-secondary: hydrogen bond arrangement of polar R-groups

-quaternary: order of amino acid residues in the peptide chain

-primary: interaction between subunits of a protein

-none of the above are correct

-tertiary: three dimensional arrangement of all atoms in a single peptide

tertiary: three dimensional arrangement of all atoms in a single peptide

 After treating a protein with trypsin, which of the following techniques could be used to determine its identity by peptide mass fingerprinting?
-NMR, MALDI-TOF mass spectrometer, HPLC, gel electrophoresis, none of the above

MALDI-TOF mass spectrometer

 The C-terminal residue of a polypeptide can be determined by first cleaving the polypeptide with:
-chymotrypsin

-carboxypeptidase

-trypsin

-CNBr

-none of the above

carboxypeptidase

 A hydrophobic interaction might occur within a protein between which of the following amino acid pairs?
-Ser/Ile

-Val/Leu

-Tyr/Cys

-Lys/Asn

-His/Val

Val/Leu

 Secondary and higher orders of structure are determined by all EXCEPT:
-hydrophobic interactions.

-ionic bonds.

-van der Waals forces.

-hydrogen bonds.

-peptide bonds.

peptide bonds.

In electrophoresis experiments

-the separation must be carried out in bright light

-the polarity of substances to be separated is more important than their charge or size

-the sample can be badly degraded as a result of the separation

-an electric field must be applied to the mixture to be separated

an electric field must be applied to the mixture to be separated

The peptide bond

-is planar

-can be written as a resonance hybrid

-is the basis of protein structure.

-all of the above

all of the above

Quaternary structure is associated with

-the overall shape of the polypeptide chain

-the sum of secondary and tertiary interactions

-simple proteins with only one subunit

-the relative orientation of one polypeptide to another polypeptide in a multisubunit protein

the relative orientation of one polypeptide to another polypeptide in a multisubunit protein

 Fibrous proteins, such as collagen, have which one of the following properties?
-Highly soluble in water.

-Their hydrophilic residues are directed into the interior of the protein.

-Exhibit enzymatic activity.

-Serve structural roles in the cell.

-Monomeric.

Serve structural roles in the cell.

 What is the overall net charge on the peptide lys-lys-ser-glu at pH 7.0?
=+2, +1, 0, -1, -2

+1

In affinity chromatography, a protein

-which binds to the ligand will remain on the column.

-which binds to the ligand will elute from the column.

-which is hydrophobic will remain on the column.

-which is hydrophilic will remain on the column.

which binds to the ligand will remain on the column