What a pathway actually is
Enzymes, cofactors, and why one missing nutrient stalls a whole assembly line.
Almost nothing in your body happens in one step. Turning the sugar in an apple into usable energy, or an amino acid into a brain chemical, takes a chain of small chemical reactions — each one handing its product to the next. That chain is a *pathway*.
Think of it as a factory assembly line. Each station does one specific job, and the half-finished part moves down the belt. The line only runs as fast as its slowest — or most broken — station.
Each station on the line is run by an enzyme — a protein that speeds up one reaction. Many enzymes can't do the job bare-handed: they need a cofactor, a small helper molecule, often a vitamin or mineral. No tool, no work. That is the deep reason a micronutrient gap matters far more than its tiny dose suggests.
A vitamin or mineral you eat — say B6, magnesium, or iron. On its own it does nothing useful; its value is what it unlocks downstream.
One cofactor can be needed at many different stations across many different lines. Run low on it and you don't break one thing — you slow dozens of things a little, all over the body. That's why 'I'm just a bit low on magnesium' can show up as cramps AND poor sleep AND fatigue at once.
An enzyme needs a vitamin-derived cofactor to work. If that vitamin is in short supply, what happens to the pathway?