Proteins are one of the most important biological molecules covered in the IB Biology syllabus. They form enzymes, structural components, hormones, transport channels, and so much more. But before proteins can perform their vast array of functions, they must be built from smaller units: amino acids. The bond that links amino acids together into polypeptides is known as a peptide bond, and understanding how this bond forms is essential for mastering biochemistry. Students often strengthen these fundamentals early in their revision, following the exam-focused guidance outlined in How to Pass IB Biology SL Exams (https://www.revisiondojo.com/blog/how-to-pass-ib-biology-sl-exams-proven-study-strategy) .
The Peptide Bond: A Covalent Link Between Amino Acids
The bond that holds amino acids together is called a peptide bond.
It is a covalent bond formed between:
- The carboxyl group (–COOH) of one amino acid
- The amine group (–NH₂) of another
This bond forms the backbone of all proteins, creating long chains called polypeptides. When many amino acids join, the resulting chain folds into a functional three-dimensional structure, ultimately becoming a fully formed protein.
Understanding this bonding process is crucial for both SL and HL students. The structural expectations and required depth differ slightly between levels, a distinction explained clearly in IB Biology HL vs SL: 7 Key Differences (https://www.revisiondojo.com/blog/ib-biology-hl-vs-sl-difficulty-7-key-differences-every-ib-student-must-know) .
How Peptide Bonds Form: Condensation Reaction
A peptide bond is formed through a condensation reaction, meaning a molecule of water is released when the bond is created.
