post lab discussion: exp. 1

Question 1

What are the functional groups in a class of biological, important compounds, amino acids

Answer 1

Amino and carboxylic acids groups

Question 2

The building blocks of proteins

Answer 2

Amino acids

Question 3

The proteins are polymers composed of amino acids that are libnked together by a ….

Answer 3

Peptide bond (amide bond)

Question 4

What type of reaction yields the component amino acids

Answer 4

Complete hydrolysis

Question 5

How are peptide bonds formed

Answer 5

When there are 2 amino acids
Amino group from one amino acids
Carboxylic group from another
When reaction occur, peptide bond is formed

Question 6

Peptide bond

Answer 6

O = C - NH

Question 7

Type of categories of amino acids

Answer 7

Small
Nucleophilic
Hydrophobic
Aromatic
Amide
Basic
Acidic

Question 8

Briefly explain the structures of proteins

Answer 8

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)

Question 9

What are the different types of intramolecular forces of attraction between R groups and the peptide backbone that maintain these structures

Answer 9

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)

Question 10

The biological activity of a protein depends on what type of structures

Answer 10

Secondary and tertiary

Question 11

Protein denaturation vs protein hydrolysis

Answer 11

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

Question 12

it is derived from protein collagen, connective tissue protein by boiling with water

Answer 12

gelatin
(heart breaks down but doesn’t completely destroy the collagen —–> becomes gelatin)

Question 13

difference between gelatin and collagen

Answer 13

collagen:
insoluble in water
resistant to animal digestive enzymes
basically its tough, indigestible

gelatin:
soluble
easily digestible (soft)

Question 14

in lead sulfide test, why will hair strand test positive

Answer 14

due to the presence of Keratin protein which contain cysteine residues

Question 15

heat coagulation performs what test

Answer 15

albumin
gelatin

Question 16

all test except heat coagulation perform tests on glycine, arginine, tryptophan, NAC, albumin, gelatin

Answer 16

partially true
additional of strand of hair in lead sulfide test

Question 17

chemical test for Ninhydrin

Answer 17

free NH2 groups
(16) ninhydrin in ethanol soln
= blue/violet
but proline is orange

Question 18

chemical test for Biuret

Answer 18

protein peptide bond
(2) copper sulfate (CuSO4) in alkane medium
= blue/ violet

Question 19

chemical test for Sakaguchi

Answer 19

arginine
3 α-naphthol in alkaline medium;
3 bromine-water -OA
= red

Question 20

chemical test for Hopkins-cole

Answer 20

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

Question 21

chemical test for Lead Sulfide

Answer 21

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

Question 22

chemical test for Heat Coagulation

Answer 22

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

Question 23

commonly used un detection of fingerprint

Answer 23

ninhydrin test