post lab discussion: exp. 1 Flashcards
What are the functional groups in a class of biological, important compounds, amino acids
Amino and carboxylic acids groups
The building blocks of proteins
Amino acids
The proteins are polymers composed of amino acids that are libnked together by a ….
Peptide bond (amide bond)
What type of reaction yields the component amino acids
Complete hydrolysis
How are peptide bonds formed
When there are 2 amino acids
Amino group from one amino acids
Carboxylic group from another
When reaction occur, peptide bond is formed
Peptide bond
O = C - NH
Type of categories of amino acids
Small
Nucleophilic
Hydrophobic
Aromatic
Amide
Basic
Acidic
Briefly explain the structures of proteins
Primary
-peptide bond
Secondary
-focus on 1-2 amino acids (hydrogen bonding btwn alpha and beta carbon)
Tertiary
-overall structure (ionic/ electrostatic attractions/ hydrogen bonding, disulfide bond)
Quaternary
-how subunits will react to one another (focus on subunits on how they react to alter one of the subunits)
What are the different types of intramolecular forces of attraction between R groups and the peptide backbone that maintain these structures
hydrogen bonding (H attach)
ionic bonding (+ve and -ve charged ions)
hydrophobic bonding (non polar R grps cluster tgt)
van der waals forces (weak forces that occur btwn closely packed atoms)
disulfide bonds (strong bond btwn 2 sulfur atoms of 2 cysteine aa)
The biological activity of a protein depends on what type of structures
Secondary and tertiary
Protein denaturation vs protein hydrolysis
Protein denaturation:
Associated with alteration of these structures (sec to quart)
Changes in physical properties (precipitation or coagulation)
Loss of biological activity
Protein hydrolysis:
From Pri to quart
it is derived from protein collagen, connective tissue protein by boiling with water
gelatin
(heart breaks down but doesn’t completely destroy the collagen —–> becomes gelatin)
difference between gelatin and collagen
collagen:
insoluble in water
resistant to animal digestive enzymes
basically its tough, indigestible
gelatin:
soluble
easily digestible (soft)
in lead sulfide test, why will hair strand test positive
due to the presence of Keratin protein which contain cysteine residues
heat coagulation performs what test
albumin
gelatin
all test except heat coagulation perform tests on glycine, arginine, tryptophan, NAC, albumin, gelatin
partially true
additional of strand of hair in lead sulfide test
chemical test for Ninhydrin
free NH2 groups
(16) ninhydrin in ethanol soln
= blue/violet
but proline is orange
chemical test for Biuret
protein peptide bond
(2) copper sulfate (CuSO4) in alkane medium
= blue/ violet
chemical test for Sakaguchi
arginine
3 α-naphthol in alkaline medium;
3 bromine-water -OA
= red
chemical test for Hopkins-cole
tryptophan
2ml Hopkins-cole reagent (glyoxylic acid + 1ml H2SO4)
= purple ring at the interphase of 2 layers (separates protein and H2SO4)
*glyoxylic acid reacts with indole group in the presence of H2SO4
*glycolic acid is prepared by reducing oxalic acid with magnesium powder or sodium amalgam
chemical test for Lead Sulfide
sulphur containing aa (cysteine, cystine and methionine)
lead acetate (4) Pb(CH3COOH) + (10) NaOH
= brownish-black ppt
*lead acetate test
*sulfide ions react w lead (II) acetate to form tht color
chemical test for Heat Coagulation
coagulable proteins (albumin and globulin)
1% acetic acids; methyl red indicator
= dense coagulum (cloudiness)
*lower portion of the solution function as a buffer
*process of coagulation by heat of proteins happens in 2 phases
1. denaturation/ agglutination
2. dissociation of the protein denatured in the form it is in
commonly used un detection of fingerprint
ninhydrin test
