A8 Color Reactions of Proteins and Amino Acids

Question 1

Which gas is liberated in the Ninhydrin solution?

Answer 1

Carbon dioxide

Question 2

A very dilute solution of CUSO4 is used in the Biuret test. why?

Answer 2

Cu2+ needs to be eliminated to produce color

Question 3

Why should excess bromine water be avoided in the test for free tryptophan?

Answer 3

Bromine water lessens the pink color produced

Question 4

Which test shows the hydrolytic reaction of a protein by trypsin?

Answer 4

Sakaguchi test

Question 5

Amino acids present in Gelatin

Answer 5

Cys Tyr his arg

Question 6

Amino acids present in Hair

Answer 6

cysteine

Question 7

Amino acids present in albumin

Answer 7

cys, tyr, trp, his. arg

Question 8

Amino acids present in casein

Answer 8

cys, tyr, trp, his. arg

Question 9

Amino acids present in Peptone

Answer 9

cys, tyr, trp, his. arg

Question 10

Ninhydrin test effect on Glycine Casein Albumin Gelatin Peptone

Answer 10

G PURPLE +

C BLUE -
A BLUE -

G PURPLE +
P PURPLE +

shows alpha - amino groups through liberation of CO2 |Ninhydrin

Question 11

Biuret test effect on Glycine Casein Albumin Gelatin Peptone

Answer 11

G BLUE +
C VIOLET +

A PINK -

G VIOLET +

P PINK -

NH4OH dissolves CH(OH2) to form the dark blue ion | urea

Question 12

Xanthoproteic Reaction effect on Tryptophan Tyrosine Casein Albumin Peptone

Answer 12

T Red Orange +
T Red Orange +

C Yellow
A Yellow
P Yellow

Nitration of benzene nucleus | Nitric acid

Question 13

Millon’s Reaction effect on Tyrosine Casein Albumin Gelatin Peptone

Answer 13

T Red Pink +
C Red Pink +
A Red Pink +

G Pink -
P Pink -

Good indication of the presence of Tyrosine | monohydroxybenzene

Question 14

Hopkin’s-Cole effect on Tryptophan Casein Albumin Gelatin Peptone

Answer 14

T Ring +
C Ring +
A Ring +

G No Ring -

P Ring +

Indole group condensese with aldehyde

Question 15

Pauly Reaction effect on Histidine Tyrosine Albumin Peptone Casein

Answer 15

ALL RED +

Diazobenzene sulfonic acid forms dyes

Question 16

Reduced Sulfur Reaction effect on Cysteine Casein Albumin Gelatin Hair

Answer 16

C Black

C Brown
A Brown
G Brown

H Black

Test for Cysteine

Question 17

Sakaguichi Reaction on Arginine Casein Albumin Gelatin Peptone

Answer 17

All Red Orange +