Proteins(1)

Question 1

the only common amino acid
that is not chiral

Answer 1

glycine

Question 2

formed by enzyme-facilitated reaction

Answer 2

Derived amino acids

Question 3

constituent of several proteins involved in
blood clotting.

Answer 3

γ-carboxyglutamic acid

Question 4

presence of P regulates the activity
of proteins.

Answer 4

O-phosphoserine -

Question 5

the amino acid sequence of the
polypeptide chain

Answer 5

primary structure

Question 6

a result of covalent bonding between the amino acids

Answer 6

peptide bonds

Question 7

translations of information contained in genes

Answer 7

Primary Structure

Question 8

involves heating in the presence of 6N HCl in a sealed tube at 110oC for 10 – 100 hrs. depending on the nature of the peptide or protein to be hydrolyzed
* the protein is completely hydrolyzed, but trp is destroyed completely and ser, thr, and tyr are partially destroyed.

Answer 8

Acid Hydrolysis

Question 9

• heating in the presence of 4N NaOH in a sealed tube at 10 – 100 hrs as in acid hydrolysis
• does not damage trp, but destroys arg, cys, cys-cys, thr, & ser; and some amino acids are partly deaminated
• more disadvantageous but since it does not destroy trp, it is used in the quantitative determination of this amino acid

Answer 9

Alkaline Hydrolysis

Question 10

cleaves external peptide bonds

Answer 10

*Exopeptidases

Question 11

• sequentially cleaves peptide bonds, beginning at the N- terminal end of the polypeptide.
• the liberated amino acids are identified one by one.

Answer 11

*Aminopeptidases

Question 12

the polypeptide chain is reacted with 1–fluoro–2,4–dinitrobenzene (DNFB). The resultant dinitrophenyl-amino acid or DNP-amino acid can be separated from the other amino acids by ion–exchange chromatography after the polypeptide is hydrolyzed because it is more soluble in nonpolar solvents

Answer 12

Sanger’s method

Question 13

uses phenylisothiocyanate (PITC),
(Edman’s reagent.) which combines with the N-terminal amino acid to yield a phenylthiohydantoin-compound (PTH-
compound). This can be identified by chromatography and extracted by organic solvent.

Answer 13

Edman degradation

Question 14

preferentially cleaves peptide bonds when an aromatic amino acid is the C–terminal residue.

Answer 14

Carboxypeptidase A

Question 15

cleaves basic amino acid residues. Because these enzymes sequentially cleave peptide bonds starting at the C–terminal residue, the first amino acid liberated is the C–terminal residue.

Answer 15

Carboxypeptidase B

Question 16

reacts with all amino acids whose carboxyl group bis bound in peptide linkage, creating amino acylhydrazides. Only the C-terminal amino acid is spared.

Answer 16

Hydrazine method

Question 17

-cleaves peptide bonds on the carboxyl side of the two strongly basic amino acids arg and lys.

Answer 17

Trypsin

Question 18

cleaves peptide bonds on the carboxyl side of
the three aromatic amino acids (phe, tyr, and trp).

Answer 18

Chymotrypsin

Question 19

cleaves on the carboxyl side of gly and ala

Answer 19

Elastase

Question 20

cleaves peptide bonds at the amino end of aromatic amino acids (phe, trp, tyr), acidic amino acids (asp, glu) and ile

Answer 20

Pepsin

Question 21

cleaves peptide bonds at the amino end of the
three aromatic amino acids, phe, tyr, trp; and amino acids with bulky nonpolar R groups, leu, ileu, and val.

Answer 21

Thermolysin

Question 22

specifically cleaves peptide bonds on the carboxyl side of methionine residues

Answer 22

Cyanogen Bromide (CNBr)

Question 23

most common type of secondary structure

Answer 23

a-Helix

Question 24

between the R groups of nonpolar amino
acids that are hydrophobic

Answer 24

Van der Waals forces

Question 25

between the polar R groups of the polar amino acids

Answer 25

Hydrogen bonds

Question 26

between the R groups of oppositely charged amino acids

Answer 26

Ionic bonds (salt bridges)

Question 27

between the thiol-containing amino acids. Two of the polar cysteines can be oxidized to a dimeric amino acid called cystine. The disulfide bond of cystine can be a cross-link between different proteins, or it can tie two segments within a protein together.

Answer 27

Covalent bonds

Question 28

- simple and regular linear structures - axial ration > 10 - serve mainly structural roles - low solubility in water or dilute salt solution

Answer 28

Fibrous porteins

Question 29

- compactly folded, approx. spherical shape - axial ratio < 10(but usually not > 3-4) - serve mainly functional roles (e.g. enzymes)

Answer 29

Globular proteins

Question 30

- found in membranes; frequently polyhelical structures - insoluble in water;

Answer 30

Membrane proteins

Question 31

occurs when there is a change that disrupts the interactions between R groups that stabilize the secondary, tertiary, or quaternary structure. However, the covalent amide bonds of the primary structure are not affected.

Answer 31

Denaturation of Proteins