IB Biology Topic B1.2 Proteins Revision Notes (SL/HL)

All Amino Acids Share One Core Blueprint

There are 20 amino acids used to build proteins, and every one of them shares the same basic framework.
At the centre sits an alpha carbon, sometimes written as Cα.
Four different groups are bonded to this central carbon.
1. An amino group (-NH₂)
2. A carboxyl group (-COOH)
3. A hydrogen atom (H)
4. A variable side chain, called the R group
The first three groups are identical in all 20 amino acids.