Experiment #9: Amines, Amino Acids, And Proteins

Question 1

TERMINOLOGY:

Proteins with 1 peptide chain

Answer 1

Monomeric Proteins

Question 2

*

TERMINOLOGY:

Proteins with more than 1 polypeptide chain

Answer 2

Multimeric Proteins

Question 3

TERMINOLOGY:

Only one kind of polypeptide

Answer 3

Homomultimeric

Question 4

TERMINOLOGY:

Several different kinds of polypeptide chains

Answer 4

Heteromultimeric

Question 5

TERMINOLOGY:

Each amino acid in a peptide

Answer 5

Moiety or Residue

Question 6

TERMINOLOGY:

The residue having a free alpha amino group

Answer 6

n-terminal residue

Question 7

TERMINOLOGY:

The residue having a free carboxyl group

Answer 7

c-terminal residue

Question 8

SOLUBILITY OF AMINES IN WATER:

Small aliphathic amines whose carbon atoms are less than ________ are water soluble and their solutions gave a ____________ (ph less than 7) when tested with litmus paper

Answer 8

1. less than 5
2. basic response

Question 8

TRUE OR FALSE:
Solubility of Amines in Water:

As the number of C atom increase, solubility decreases

Answer 8

TRUE

Question 9

TRUE OR FALSE:
Solubility of Amines in Water:

Although most amines are not water soluble, amine salts are generally water soluble

Answer 9

TRUE

Question 10

TRUE OR FALSE:
Solubility of Amines in Water:

The more substituted or larger is the nonpolar group, the more soluble

Answer 10

FALSE; the more substituted/larger the nonpolar group, the less soluble

Question 11

TRUE OR FALSE:
Solubility of Amines in Water:

The more substituted the compound is, the more basic

Answer 11

TRUE

Question 12

IDENTIFICATION:
Solubility of Amines in Aqueous Acid:

Amines react with acids forming ____________________ ?

Answer 12

positively charged quaternary amines

Question 13

Generally used to detect the presence of free alpha amino groups in amino acids, polypeptides, and proteins

Answer 13

Ninhydrin Test

Question 13

What is the reagent for Ninhydrin Test?

Answer 13

Ninhydrin Solution

Question 14

What is the positive result for Ninhydrin Test?

Answer 14

Appearance of blue to violet colored spots

Question 14

The test is used to detect the presence of two or more peptide linkage in proteins and their larger hydrolytic products (proteoses and peptones)

Answer 14

Biuret Test

Question 15

What is the reagent of Biuret Test?

Answer 15

Alkaline Copper (II) Sulfate

Question 16

What is the positive result for Biuret Test?

Answer 16

Formation of violet-colored coordination complex due to the coordination of cuptic ions with the unshared electron pairs of the peptide

Question 17

What is the reagent for Reaction with Lead Acetate?

Answer 17

NaOH/Pb (CH3COO2)

Question 18

It is a test where the sulfur in sulfur-containing proteins and amino acids can be released as sulfides by the action of strong alkali

Answer 18

Reaction with Lead Acetate

Question 19

TRUE OR FALSE:

In Reaction with Lead Acetate, the sulfides can be precipitated by lead acetate

Answer 19

TRUE

Question 20

It is associated with the alteration of the secondary and tertiary structures of biological proteins which results in changes in physical properties and loss of biological activity

Answer 20

Protein Denaturation

Question 21

TRUE OR FALSE:

Amines are readily protonated by weak acids

Answer 21

FALSE; it is readily protonated by strong acids

Question 21

# * **TRUE OR FALSE:** Protein denaturation may be caused by the action of heat, light, alcohols, strong acids and bases, and other denaturing agents

Answer 21

TRUE

Question 22

This test is to classify amines where it treat amines with benzenesulfonyl in aqueous sodium hydroxide and then acidified with HCl

Answer 22

Hinsberg Test

Question 22

What is the positive result for Protein Denaturation?

Answer 22

Appearance of precipitation or coagulated product

Question 23

**IDENTIFICATION:** Amines that are insoluble in pure water will be soluble in acid due to the formation of an _________________?

Answer 23

Ammonium Chloride