Module 5

Question 1

a chemical test that can be used to check for the presence of peptide bonds in each analyte

Answer 1

biuret test

Question 1

be used to gauge the amount of protein present in the analyte

Answer 1

biuret test

Question 2

this test, the presence of peptides results in the formation of pale purple colored (or mauve colored) coordination compounds of the copper(II) ion (when the solution is sufficiently alkaline)

Answer 2

biuret test

Question 3

Principle for Biuret Test

Answer 3

Alkaline CuSO4 reacts with compounds containing two or more peptide bonds to give a violet-colored product which is due to formation of co-ordination complex of cupric ions with un-shared electron pairs of peptide nitrogen and O2 of water.

Question 4

Reagents for Biuret Test

Answer 4

• 10% Sodium Hydroxide
• 0.5% Copper Sulfate

Question 5

Test Solutions for Biuret Test

Answer 5

Test Solutions for Biuret Test

• 5% Albumin
• 5% Arginine
• 5% Glycine
• Distilled Water

Question 6

What is the positive and Negative result for Biuret test?

Answer 6

Positive = Purple
Negative = Blue

Question 7

the only amino acid that give biuret test positive

Answer 7

Histidine

Question 8

What ions can interfere in a biuret test?

Answer 8

magnesium and ammonium ions

Question 9

True or false? Presence of magnesium and ammonium ions can be overcome by using excess alkali.

Answer 9

True

Question 10

 A high concentration of ammonium salts and bile pigments influences the reaction.
 It is not as sensitive as the Folin Lowry test

Answer 10

Limitations of the Biuret Test

Question 11

What are the functions of proteins?

Answer 11

Catalysis, Defense, Transport, Signaling, Movement, Structure

Question 12

Enzymes that speeds up chemical reaction

Answer 12

Catalysis

Question 13

Antibodies and complement proteins move the cell or molecules with the cell

Answer 13

Defense

Question 14

Protein binds and transport numerous small molecules and ions through the body

Answer 14

Transport

Question 15

Proteins that conveys signals between cells

Answer 15

Signaling

Question 16

Motor and contractile protein move the cells or molecules within the cell

Answer 16

Movement

Question 17

Structure proteins define cell shape and comprise body structures

Answer 17

Structure

Question 18

They are linear in shape

Answer 18

Fibrous Protein

Question 19

Spherical or globular in shape

Answer 19

Globular Protein

Question 20

composed only of amino acids

Answer 20

Simple Protein

Question 21

composed of amino and non
amino acid component

Answer 21

Conjugated Protein

Question 22

what are the three ways to classify proteins?

Answer 22

structure, composition and function

Question 23

is a biochemical test for the detection
of amino acids containing phenolic or indolic groups like phenylalanine, tyrosine, and tryptophan (aromatic amino acids)

Answer 23

Xanthoproteic test

Question 24

The test is named Xanthoproteic test due to the formation of a

Answer 24

yellow precipitate of xanthoproteic acid

Question 25

Concentrated nitric acid reacts with the phenyl ring to give a yellow-colored aromatic nitro compound. Addition of alkali at this point will deepen the color to ______.

Answer 25

orange

Question 26

What are the reagents for the Xanthoproteic test

Answer 26

* Nitric acid * 40% NaOH

Question 27

What are the test solutions for the Xanthoproteic

Answer 27

* 1% tyrosine * 1% tryptophan * 1% phenylalanine * 5% egg white * Distilled Water

Question 28

What is the result for a negative xanthoproteic test?

Answer 28

No dark yellow or orange color

Question 29

What is the result for a positive xanthoproteic test?

Answer 29

Dark yellow or orange color present

Question 30

The test allows the differentiation of aromatic amino acids from non-aromatic amino acids.

Answer 30

xanthoproteic test

Question 31

Why doesnt phenylalanine give a positive xanthoproteic test despite being an aromatic group containing amino acid?

Answer 31

phenylalanine has a highly stable phenyl group

Question 32

a chemical test performed to detect the presence of ammonia, primary/secondary amines, or α-amino acids.

Answer 32

Ninhydrin test

Question 33

This test involves the addition of ninhydrin reagent to the test sample that results in the formation of deep blue color, often termed as Ruhemann’s purple, in the presence of an amino group

Answer 33

Ninhydrin test

Question 34

what is the principle of the ninhydrin test

Answer 34

Amino acids with a free NH2 group and proteins containing free amino groups react with ninhydrin to give a purple-blue complex.

Question 35

In amino acids like proline and hydroxyproline, ninhydrin test yields an iminium salt which is

Answer 35

yellow-orange

Question 36

proteins with a free amino group like asparagine, react with the ninhydrin reagent to form a

Answer 36

brown colored product

Question 37

what are the reagents in a ninhydrin test

Answer 37

2% ninhydrin solution

Question 38

what is the test solutions for a ninhydrin test

Answer 38

* 1% alanine * 1% asparagine * Distilled Water

Question 39

what is the preparation of 2% ninhydrin solution

Answer 39

0.2g of ninhydrin in 10ml of acetone or ethanol

Question 40

* Also known as the glyoxylic acid reaction * Used for detecting the presence of tryptophan, the only amino acid containing an indole group. * The indole ring reacts with glyoxylic acid in the presence of a strong acid to form a violet cyclic product.

Answer 40

Hopkin's Cole test

Question 41

what is the principle of the Hopkins Cole test

Answer 41

tryptophan reacts with glyoxylic acid in the presence of a strong acid to form a violet cyclic product

Question 42

What is the negative and positive result for a hopkins cole test

Answer 42

Negative = no purple ring, tryptophan absent Positive = purple ring present, tryptophan present

Question 43

True or False? In the hopkins cole test compounds like nitrites, chlorates, nitrates, and excess chlorides prevent the formation of the condensation product.

Answer 43

True

Question 44

* a biochemical test consisting of colorimetric reaction for the detection and quantification of guanidinium groups. * used as a qualitative test for arginine that is either free or in protein. *a specific test for arginine where the guanidinium group of arginine reacts with 1-naphthol or α-naphthol to produce a colored product.

Answer 44

Sakaguchi test

Question 45

What are the reagents in the sakaguchi test

Answer 45

* 1% alpha naphthol * 10% Sodium hypobromite solution of bromine water * 40% NaOH

Question 46

what are the test solutions in the sakaguchi test

Answer 46

* 1% arginine * 1% glycine * 5% albumin * Distilled Water

Question 47

what is the positive and negative result for the sakaguchi test

Answer 47

Negative = No red color complex (arginine or guanidium compound absent) Positive = Presence of red colored complex (arginine or guanidium compound present)

Question 48

How can a sakaguchi test be made quantitative?

Answer 48

the addition of urea

Question 49

what can cause difficulties in the testing results of the sakaguchi test

Answer 49

some of the guanidium groups in the solution might be destroyed by the hypochlorite, resulting in difficulties in testing results