EXPERIMENT 1 Qualitative analysis of proteins

Question 1

building blocks of proteins.

Answer 1

amino acids

Question 2

polymers composed of amino acids linked together by a peptide or
amide bond.

Answer 2

proteins

Question 3

what reaction is used in forming peptide bonds

Answer 3

condensation/ dehydration

Question 4

yields the component amino acids.

Answer 4

complete hydrolysis

Question 5

link amino acids together.

Answer 5

peptide or amide bonds

Question 6

what maintain the structures.

Answer 6

diff types of intermolecular forces and peptide backbone

Question 7

what structure determines the biological activity

Answer 7

depends on the secondary and tertiary structures.

Question 8

associated with the alteration of the structures.

Answer 8

Protein denaturation

Changes in physical properties (precipitation or coagulation)
o Loss of biological activity

Question 9

Structures that can be broken down by protein denaturations

Answer 9

secondary to quaternary

Question 10

What structures can protein hydrolysis break

Answer 10

primary to quaternary

Question 11

Possible Causes of Denaturation:

Answer 11

Heat
o Light
o Chemical Reagents
▪ Alcohols
▪ Strong Acids and Bases
▪ Detergents
▪ Heavy Metal Ions: Hg(II), Pb(II)

Question 12

Derived from protein collagen, connective tissue protein by boiling with water.

Answer 12

Gelatin

Question 13

Difference between gelatin and collagen

Answer 13

Collagen: insoluble in water and resistant to animal digestive enzymes.
* Gelatin: easily digestible and soluble

Question 14

Enumerate tests and its components

Answer 14

Ninhydrin, Biuret, Sakaguchi, Hopkins Cole, Lead Sulfide, Heat coagulation

Question 15

the only amino acid containing the guanidine group.

Answer 15

arginine

Question 16

reacts with -naphthol in the presence of an oxidizing agent
(_____ and _____) to give a red-colored product.

Answer 16

bromine water, sodium hypochlorite; arginine

Question 17

how is glyoxylic acid prepared

Answer 17

prepared by reducing oxalic acid with magnesium power or
sodium amalgam NaHg

Question 18

The indole group of tryptophan reacts with glyoxylic acid in the presence of
cone ____ to give a purple color.

Answer 18

H2SO4

Question 19

Sulfur-Containing Amino Acid (Sulfhydryl or Thiol Group) – degraded in
strongly alkaline(NaOH) media to release sulfide ion (S2-) as _____

Answer 19

H2S (hydrogen sulfide)

Question 20

what react with lead (II) acetate to form a brownish-black
precipitate.

Answer 20

sulfide ions (S2-)

Question 21

will test positive due to the presence of keratin protein containing
cysteine residues

Answer 21

hair strand

Question 22

an irreversible process that occurs at the highest pH of
proteins.

Answer 22

Protein Coagulation

Question 23

in heat coagulation test, The lower portion of the solution functions as ___

Answer 23

a buffer.

Question 24

o Red color at pH ___ and below
o Orange color at around ___
o Yellow color at pH ____

Answer 24

4.4; 5.1; 6.2 and above

Question 25

N- acetylcysteine is negative in ninhydrin despite it havonmg NH group, why?

Answer 25

is negative in ninhydrin test since the amino group is acetylated (not free)

Question 26

Gelatin is deficient in ____ and ____ as it is a non-coagulable protein.

Answer 26

tryptophan and cysteine

Question 27

What sample test positive for ninhydrin

Answer 27

lahat except sa N- Accetylcysteine

Question 28

what sample test positive for Biuret

Answer 28

albumin and gelatin

Question 29

what sample test postive for Sakaguchi

Answer 29

albumin and arginine

Question 30

What sample test positive for hopkins cole

Answer 30

Albumin and tryptophan

Question 31

what sample test positive for lead sulfide

Answer 31

N-acetylcysteine, albumin

Question 32

what sample test positive for Heat coagulation

Answer 32

albumin