Quiz 4

Question 1

The __ amino acids share a common structure but differ in their ____

Answer 1

20, side chains

Question 2

amino acids contain a central

Answer 2

tetrahedral a-carbon atom

Question 3

_____ link amino acid residues in a ______

Answer 3

peptide bonds, polypeptide

Question 4

some amino acid side chains contain ___ who’s ___ values may vary

Answer 4

ionizable groups ; pka

Question 5

all amino acids are built on a central

Answer 5

tetrahedral a-carbon

Question 6

The amino acid is tetrahedral

Answer 6

around the alpha carbon, except fir proline [and uncommon derivatives] , all of the amino acids commonly found in proteins possess this type of structure

Question 7

amino acids are sorted into groups based on their side chains

Answer 7

• non polar amino acids
• polar uncharged amino acids
• charged acidic amino acids
• charged basic amino acids1

Question 8

non polar amino acids

Answer 8

• leucine
• alanine
• proline
• valine
• methionine
• phenyl alanine
• isoleucine
• tryptophan

Question 9

polar amino acids

Answer 9

• glycine
• serine
• asparagine
• glutamine
• threonine
• cysteine
• tyrosine

Question 10

charged acidic amino acids

Answer 10

• aspartic acid
• glutamic acid

Question 11

charged basic amino acids

Answer 11

• lysine
• arginine
• histidine

Question 12

at neutral pH…

Answer 12

the a-carboxyl group and the a- amino group are charged

Question 13

a-carboxylic group pKa

Answer 13

2

Question 14

a-amino group pKa

Answer 14

9

Question 15

aspartic acid

Answer 15

Asp, D, pKa(B-carboxyl)= 3.9 (-) at pH 7

Question 16

glutamic acid

Answer 16

Glu, E, pKa(y-carboxyl)= 4.1(-) at pH 7

Question 17

histidine

Answer 17

His, H, pKa(imidazole)= 6.0 neutral at pH 7

Question 18

Cysteine

Answer 18

Cys, C, pKa(sulfhydryl SH)= 8.4 neutral at pH 7

Question 19

tyrosine

Answer 19

Tyr, Y, pKa(phenolic OH)=10.5 neutral at pH 7

Question 20

lysine

Answer 20

Lys, K, pKa(E-aminp)=10.5 (+) at pH 7

Question 21

arginine

Answer 21

Arg, R, pKa(guanidino group)=12.5 (+) at pH 7

Question 22

amino acids and many other biological compound are chiral molecules whose

Answer 22

configurations can be depicted by Fischer projections

Question 23

the amino acids in proteins all have the

Answer 23

L stereochemical configuration

Question 24

all amino acids [with the exception of glycine] are

Answer 24

chiral, not symmetric at the a carbon

Question 25

D,L nomenclature is based on

Answer 25

D- and L- glyceraldehyde

Question 26

Absorb UV

Answer 26

Tyr and Trp
- absorbance at 280 nm is a good diagnostic test for amino acids

Question 27

amino groups from Schiff bases and

Answer 27

amides

Question 28

carboxyl groups form amides and

Answer 28

esters

Question 29

edmans reagent

Answer 29

reacts with the a-amino group of an amino acid or peptide to produce a phenylthiohydantoin, or PTH derivative

Question 30

Lys residues can form

Answer 30

disulfides and can easily be alkylated

Question 31

edmans reagent react with the

Answer 31

N-terminal amino acid of a peptide or protein to form a cyclic thiazoline derivative that reacts in weak aqueous acid to yield a PTH-amino acid, plus the polypeptide with a new N-terminus

Question 32

GFP

Answer 32

green fluorescent protein is a naturally fluorescent protein , can be used to tag virtually any protein, structure or organelle.
- lies in center or b barrel protein structure