EXPERIMENT 1 Qualitative analysis of proteins Flashcards
building blocks of proteins.
amino acids
polymers composed of amino acids linked together by a peptide or
amide bond.
proteins
what reaction is used in forming peptide bonds
condensation/ dehydration
yields the component amino acids.
complete hydrolysis
link amino acids together.
peptide or amide bonds
what maintain the structures.
diff types of intermolecular forces and peptide backbone
what structure determines the biological activity
depends on the secondary and tertiary structures.
associated with the alteration of the structures.
Protein denaturation
Changes in physical properties (precipitation or coagulation)
o Loss of biological activity
Structures that can be broken down by protein denaturations
secondary to quaternary
What structures can protein hydrolysis break
primary to quaternary
Possible Causes of Denaturation:
Heat
o Light
o Chemical Reagents
▪ Alcohols
▪ Strong Acids and Bases
▪ Detergents
▪ Heavy Metal Ions: Hg(II), Pb(II)
Derived from protein collagen, connective tissue protein by boiling with water.
Gelatin
Difference between gelatin and collagen
Collagen: insoluble in water and resistant to animal digestive enzymes.
* Gelatin: easily digestible and soluble
Enumerate tests and its components
Ninhydrin, Biuret, Sakaguchi, Hopkins Cole, Lead Sulfide, Heat coagulation
the only amino acid containing the guanidine group.
arginine
reacts with -naphthol in the presence of an oxidizing agent
(_____ and _____) to give a red-colored product.
bromine water, sodium hypochlorite; arginine
how is glyoxylic acid prepared
prepared by reducing oxalic acid with magnesium power or
sodium amalgam NaHg
The indole group of tryptophan reacts with glyoxylic acid in the presence of
cone ____ to give a purple color.
H2SO4
Sulfur-Containing Amino Acid (Sulfhydryl or Thiol Group) – degraded in
strongly alkaline(NaOH) media to release sulfide ion (S2-) as _____
H2S (hydrogen sulfide)
what react with lead (II) acetate to form a brownish-black
precipitate.
sulfide ions (S2-)
will test positive due to the presence of keratin protein containing
cysteine residues
hair strand
an irreversible process that occurs at the highest pH of
proteins.
Protein Coagulation
in heat coagulation test, The lower portion of the solution functions as ___
a buffer.
o Red color at pH ___ and below
o Orange color at around ___
o Yellow color at pH ____
4.4; 5.1; 6.2 and above
N- acetylcysteine is negative in ninhydrin despite it havonmg NH group, why?
is negative in ninhydrin test since the amino group is acetylated (not free)
Gelatin is deficient in ____ and ____ as it is a non-coagulable protein.
tryptophan and cysteine
What sample test positive for ninhydrin
lahat except sa N- Accetylcysteine
what sample test positive for Biuret
albumin and gelatin
what sample test postive for Sakaguchi
albumin and arginine
What sample test positive for hopkins cole
Albumin and tryptophan
what sample test positive for lead sulfide
N-acetylcysteine, albumin
what sample test positive for Heat coagulation
albumin
