Foundation module · Level 1
No prior background assumed. Five lessons covering the vocabulary and the biology you need before reading anything else on this platform.
Lesson 01
Twenty standard amino acids make up the biological alphabet. Each has the same backbone and a different side chain, and it is the side chain that decides whether a position in a sequence is charged, water-attracting or water-repelling.
Nothing about a peptide can be understood without this: the properties of the parts determine the behaviour of the whole.
Lesson 02
When amino acids are joined by peptide bonds, the result is a chain. Roughly two to fifty residues is conventionally called a peptide; longer chains are called proteins. The order of residues is the sequence.
The sequence causes the chain to fold into a preferred shape. Shape determines which other molecules the peptide can recognise, which is why a single substitution can change function completely.
Lesson 03
Many peptides are signalling molecules. They bind a receptor — a protein that recognises a specific shape — and the binding event changes activity inside the cell.
Two terms describe how well this works. Affinity is how strongly the molecule binds its target. Selectivity is how many different targets it binds. High affinity with poor selectivity is not a useful result.
Lesson 04
The body produces peptides itself; these are endogenous. Peptides can also be assembled in a laboratory to a defined sequence; these are synthetic.
A synthetic peptide with the same sequence as an endogenous one is chemically the same molecule. That does not make its effects in a living system predictable, because dose, delivery, stability and context all differ.
Lesson 05
Much of the popular writing on peptides — including commercially published guides — presents mechanisms as outcomes. A binding result in a test tube is not an outcome in a person.
Where this platform draws on non-peer-reviewed sources, those statements are labelled as claims of the source. That distinction is the whole point of the evidence framework.
Next step
Each path builds on this module without repeating it.
Continue: stability and mechanisms
Half-life, degradation, receptor interaction and how mechanisms are actually tested.
OpenScientific glossary
Precise definitions for peptide, receptor, ligand, bioregulator, concentration and vial.
OpenEvidence framework
How every reference entry on this platform is classified.
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