TAlk chemistry WITH Cyprian

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LECTURE 7: PROTEINS — THE BUILDING BLOCKS OF LIFE

1. Introduction

Proteins are large, complex organic molecules made up of carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and sometimes sulphur (S) and phosphorus (P).

They are the body’s builders — responsible for growth, repair, and maintenance of tissues.

In short:
If carbohydrates give you energy, and lipids store it — proteins build you!

2. Composition of Proteins

Proteins are made up of smaller units called amino acids.
There are about 20 naturally occurring amino acids, and they link together through peptide bonds to form long chains.

Peptide bond:
Formed between the –COOH (carboxyl) group of one amino acid and the –NH₂ (amino) group of another, releasing a molecule of water (H₂O).

3. Classification of Proteins

(a) Simple Proteins

These yield only amino acids on hydrolysis.
Examples: Albumin (egg white), Globulin (blood plasma)

(b) Conjugated Proteins

Contain a non-protein part (called a prosthetic group).
Examples: Haemoglobin (iron-containing group), Glycoproteins

(c) Derived Proteins

Formed by the breakdown of simple and conjugated proteins.
Examples: Peptones, Proteoses

4. Levels of Protein Structure

1. Primary structure → Linear sequence of amino acids.

2. Secondary structure → Coiling or folding (e.g., alpha-helix, beta-sheet).

3. Tertiary structure → 3D arrangement of the chain.

4. Quaternary structure → Combination of multiple polypeptide chains (e.g., haemoglobin).

5. Functions of Proteins

Structural: Collagen (skin), Keratin (hair, nails).

Enzymatic: Enzymes speed up biochemical reactions.

Transport: Haemoglobin carries oxygen.

Hormonal: Insulin controls blood sugar.

Defensive: Antibodies fight infections.

Repair and Growth: Essential for tissue repair and muscle building.

6. Quick Recap

Proteins are made of amino acids joined by peptide bonds.

They have complex structures and perform diverse biological roles.

They’re essential for life — no protein, no you!

Quick Test

Which of the following elements is always present in proteins but not in carbohydrates or lipids?

A. Oxygen
B. Hydrogen
C. Nitrogen
D. Carbon

ISOLATED DIENES

An isolated diene is simply one in which the two C=C double bonds are separated by two or more single (σ) bonds ( sp³ hybridized carbon).

GENERAL FORMULA FOR DERIVING ISOLATED DIENES

C=C - (CH2)n - C=C
Where n can take positive integers beginning from 2, 3, 4 ....

There is no upper limit in IUPAC or organic chemistry theory on how many sp³ hybridized carbons (single-bonded carbons) can separate the two double bonds.

The only requirement is that they are not adjacent (so not conjugated or cumulated). Once the π-systems are too far apart to interact, the molecule remains isolated.

Example

1. 1,5-Hexadiene → 2 sp³ C in between (isolated)
CH₂=CH–CH₂–CH₂–CH=CH₂

2. 1,7-Octadiene → 4 sp³ C in between (still isolated)
CH₂=CH–(CH₂)₄–CH=CH₂

3. 1,9-Decadiene → 6 sp³ C in between (still isolated!)
CH₂=CH–(CH₂)₆–CH=CH₂

In all of these, π–π interaction is practically zero, so they’re isolated dienes.

Ndernen Richard
Kenneth Shater

What on earth is not chemistry ?