Proteins(1) Flashcards

(31 cards)

1
Q

the only common amino acid
that is not chiral

A

glycine

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2
Q

formed by enzyme-facilitated reaction

A

Derived amino acids

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3
Q

constituent of several proteins involved in
blood clotting.

A

γ-carboxyglutamic acid

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4
Q

presence of P regulates the activity
of proteins.

A

O-phosphoserine -

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5
Q

the amino acid sequence of the
polypeptide chain

A

primary structure

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6
Q

a result of covalent bonding between the amino acids

A

peptide bonds

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7
Q

translations of information contained in genes

A

Primary Structure

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8
Q

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.

A

Acid Hydrolysis

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9
Q
  • 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
A

Alkaline Hydrolysis

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10
Q

cleaves external peptide bonds

A

*Exopeptidases

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11
Q
  • sequentially cleaves peptide bonds, beginning at the N- terminal end of the polypeptide.
  • the liberated amino acids are identified one by one.
A

*Aminopeptidases

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12
Q

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

A

Sanger’s method

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13
Q

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.

A

Edman degradation

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14
Q

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

A

Carboxypeptidase A

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15
Q

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.

A

Carboxypeptidase B

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16
Q

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

A

Hydrazine method

17
Q

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

18
Q

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

19
Q

cleaves on the carboxyl side of gly and ala

20
Q

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

21
Q

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.

22
Q

specifically cleaves peptide bonds on the carboxyl side of methionine residues

A

Cyanogen Bromide (CNBr)

23
Q

most common type of secondary structure

24
Q

between the R groups of nonpolar amino
acids that are hydrophobic

A

Van der Waals forces

25
between the polar R groups of the polar amino acids
Hydrogen bonds
26
between the R groups of oppositely charged amino acids
Ionic bonds (salt bridges)
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.
Covalent bonds
28
- simple and regular linear structures - axial ration > 10 - serve mainly structural roles - low solubility in water or dilute salt solution
Fibrous porteins
29
- compactly folded, approx. spherical shape - axial ratio < 10(but usually not > 3-4) - serve mainly functional roles (e.g. enzymes)
Globular proteins
30
- found in membranes; frequently polyhelical structures - insoluble in water;
Membrane proteins
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.
Denaturation of Proteins