Experiment 6: Color Reactions of Amino Acids and Proteins

Question 1

Complex, high molecular weight biomolecules composed of amino acids joined together by peptide bonds.

Answer 1

Protein

Question 2

Give the 8 tests of Color Reactions of Amino Acids and Proteins

Answer 2

Biuret test, Ninhydrin test, Xanthoproteic test, Millon-Nasse test, Bromine Water test, Unoxidized Sulfur test, Sakaguchi test, Hopkins-Cole test

Question 3

Indicates the presence of peptide linkages.

Answer 3

Biuret Test

Question 4

What is the color of a positive Biuret test?

Answer 4

purplish-violet color

Question 5

Amino acids react with Ninhydrin (?)

Answer 5

Triketohydrindrene hydrate

Question 6

What is the color of a positive Ninhydrin test?

Answer 6

blue-purple color

Question 7

Amino acid + Ninhydrin = ____?

Answer 7

Ruhemann’s blue purple

Question 8

Positive for proteins and amino acids containing an AROMATIC SIDE CHAIN.

Answer 8

Xanthoproteic test

Question 9

What are the three aromatic side chains?

Answer 9

Phenylalanine, tyrosine and tryptophan

Question 10

What is the color of a positive Xanthoproteic test?

Answer 10

Yellow color

Question 11

Does not respond readily to the test and requires H2SO4 as catalyst because of the absence of an activating group in the ring.

Answer 11

Phenylalanine

Question 12

Phenolic group of tyrosine reacts to ______ test.

Answer 12

Millon-Nasse test

Question 13

What is the color of a positive Millon-Nasse test?

Answer 13

Old rose or pink to red complex

Question 14

Pyrrole ring of tryptophan undergoes halogenation with ______ test in the presence of amyl alcohol.

Answer 14

Bromine Water test

Question 15

What is the color of a positive Bromine Water test?

Answer 15

Pink or lavender color

Question 16

Sulfur containing amino acids: cysteine and cystine.

Answer 16

Unoxidized sulfur test

Question 17

What is the color of a positive Unoxidized sulfur test?

Answer 17

Brown-black precipitate of lead sulfate.

Question 18

Guanidium group of arginine in alkaline solution.

Answer 18

Sakaguchi test

Question 19

What is the color of a positive Sakaguchi test?

Answer 19

Orange or red color with a-naphtol and sodium hypobromine.

Question 20

Indole ring of tryptophan reacts with _______ test.

Answer 20

Hopkins-Cole test

Question 21

What is the color of a positive Hopkins-Cole test?

Answer 21

Violet to red purple color

Question 22

Give 5 apparatuses that was used.

Answer 22

Hot plate/stove, alcohol lamp, 600 ml beaker, 50 ml beaker, test tubes, test tube rack, 10 ml graduated cylinder, pipets, droppers, litmus paper, wire gauze

Question 23

1% solutions (Materials)

Answer 23

1% solution of egg albumin
1% casein
1% gelatin

Question 24

0.1% solutions (Materials)

Answer 24

TACT
Tryptophan
Arginine
Cystein
Tyrosine
Ninhydrin

Question 25

5%?

Answer 25

5% CuSO4 [Copper (II) Sulfate]

Question 26

10%

Answer 26

10% NaOH [Sodium Hydroxide]

Question 27

20%

Answer 27

20% NaOH [Sodium Hydroxide]

Question 28

Reagents (Materials)

Answer 28

Millon-Nasse Reagent
Bromine Water
Hopkins-Cole Reagent

Question 29

Others

Answer 29

N-amyl alcohol
A-naphtol solution
Distilled water
Litmus paper