Kuffour

Course Outline

• Protein - amino acids
• Synthetic Polymer
• Industrial Chemistry

Topic 1: Protein – amino acids

Objective At the end of the lesson, viewers would be able to:

• Identify the functional groups in amino acid.
• Classify amino acids based on the structure of side – chain radical
• Write the common name of a given structure of amino acid.

Amino acids They are organic compounds that contain at least one carboxylic (-COOH) and at least one amino group (-NH2). They have the general formula

Where R=H, alkyl or phenyl group.

Classification of amino acids Amino acids are based on

(a) Their structure

(b) acid- base properties

Classification based on their structure

Amino acids are distinguished by the structure of side – chain R-group. Amino acids are distinguished by the structure of side – chain (radical) R-group and also by their physico – chemical properties inherent in these radicals. The structural features of the side chain radicals are shown below.

1. Aliphatic unsubstitueted amino acid, their common name, their three-letter and one- letter code

Glycine (Gly) G

Alanine (Ala) A

2. Aliphatic substituted Amino acid

(a) Hydroxyamino acids

Serine (Ser) S

physical property	units	symbol
length	metre	m
mass	kilogram	kg

Theonine (Thr) T

(b) Carboxyamino acids

Aspartate (Asp) D

Glutamate (Glu) E

(c). Diamino acid

Lysine (Lys) K

Arginine (Arg) R

3.  Cyclic amino acids

(a). Aromatic amino acids

Phenylalanine (Phe) F

Tyrosine (Tyr) Y

(b) Heterocyclic amino acid

Tryptophan (Trp) W

Histidine (His) H

Classification based on Acid- based properties

Amino acids are classified into acid, base and neutral depending on the R-group.

Acidic amino acids Example: 1.

2.

(b) Basic amino acids Example: 1.

2.

(c) Neutral amino acids Example: alanine, glycine, phenylalanine, leucine.

Glycine (Gly) G

Alanine (Ala) A

Valine (Val) V

Phenylalanine (Phe) F

Nomenclature of proteins

Amino acids have three system of naming. These are:

• Common names.
• Three and one letter code.
• IUPAC system.

Common names All the amino acids have traditional names. These names are usually abbreviated with the first three letters or one capital letter. This system is still being used by chemist. For example, histidine (HIS) or H, and alanine (Ala) or A.

Summary

• Amino acids are organic compounds that contain at least one carbonyl group and at least one amino acid group.
• They are classified based on their structure as:

Aliphatic unsubstituted amino acid.

Aliphatic substituted amino acid.

They are classified based on their acid-base properties as:

• Acidic
• Basic
• Neutral

They have traditional names as well as IUPAC system of naming.

• The traditional names are represented by using three letters or one capital letter code.

PENFIELD

Q1. Give the structure of the amino acid represented as: a) F b) Val c) Gly

Q2. Give one structure of an amino acid that is: a) Acidic b) Basic c) neutral