Lesson 7: Proteins

🧬 Definition of Proteins

Proteins are the most common (abundant) organic substances found in living cells.
They are made by joining together many smaller molecules called amino acids, like beads on a necklace.

So, proteins = polymers (chains) of amino acids.

Polymer means a large molecule made up of repeating small units (monomers).
In this case, the monomer is an amino acid.

👉 Analogy: Think of a protein like a train. Each amino acid is a train car, and all the cars linked together form a complete train — the protein.

📜 Historical Background

The word “Protein” was first used in 1838 by a scientist named J.J. Berzelius.
He used a Greek word “Proteios” which means “of first importance” or “first rank”, because proteins are very important for life.

🧠 Why are Proteins Important?

Proteins are like the workers and the bricks of a cell.

• They build structures in the body (like muscles, skin, hair, etc.).
• They help in performing functions (like digesting food, sending signals, fighting infections, etc.).

👉 Real-life example: If your body was a factory, proteins would be:

• The machines that do the work (like enzymes),
• The builders who make structures (like collagen),
• And the messengers who send instructions (like hormones).

🔗 Structure of Proteins

Protein as a Polymer

As we said, proteins are long chains of amino acids joined together.

• Some proteins are small – made of just a few amino acids.
• Some are very large – made of hundreds or even thousands of amino acids.

✅ Examples:

• Insulin (a hormone that controls blood sugar) has 51 amino acids.
• Hemoglobin (a protein in red blood cells that carries oxygen) has 574 amino acids.