🧩 Amino Acids – The Building Blocks
🔬 What is an Amino Acid?
An amino acid is a small molecule that works like a brick in a protein.
Each amino acid has 4 parts attached to a central carbon atom (called alpha carbon):
- An Amino group – NH₂
- A Carboxyl group – COOH
- A Hydrogen atom – H
- A Side group (R) – this part changes from one amino acid to another
👉 Mnemonic to remember parts of an amino acid:
“A C H R” = A Cat Has Rabbits
- A = Amino group (NH₂)
- C = Carboxyl group (COOH)
- H = Hydrogen (H)
- R = Side group (R)
🌈 Variety of Amino Acids
There are about 170 types of amino acids found in nature.
But only about 20 amino acids are commonly used by living organisms to make proteins.
These 20 amino acids are used in different combinations, just like letters in the alphabet make thousands of different words.
👉 Analogy: Think of amino acids like letters, and proteins like sentences. Just like you can make many different sentences from only 26 letters, your body can make thousands of proteins from only 20 amino acids!
🌟 Role of the R Group (Side Chain)
The R group is what makes each amino acid different from the others.
It’s like the personality of the amino acid.
✅ Examples:
- In glycine, the R group is just a hydrogen atom (H) – so it is the simplest amino acid.
- In alanine, the R group is a CH₃ (methyl group) – just one carbon with 3 hydrogens.
👉 Think of the R group as a custom accessory added to each amino acid – like putting a hat, scarf, or glasses on a person – it changes how they look and behave!