hydrolysis
/ hy-DROL-uh-sis /
If condensation is gluing two pieces together and squeezing out a drop of water, hydrolysis is the reverse: snip the bond and insert a water to fill the gap. The word itself means 'splitting by water,' and it is how cells take big molecules apart — to recycle them, to digest food, and to release stored energy.
In hydrolysis, a water molecule (H2O) is added across a bond, breaking one molecule into two. The water splits, donating a hydrogen (-H) to one fragment and a hydroxyl (-OH) to the other, exactly undoing what a condensation reaction did. Picture a protein chain being cut: a water slides in at a peptide bond, and the chain falls into two shorter pieces, each capped where the water joined. Although water is the reactant, hydrolysis at body temperature is far too slow to be useful on its own — so cells use enzymes (with names ending in -ase, like protease, nuclease, lipase) to speed specific cuts thousands of times over.
Hydrolysis is the demolition crew of biology. Your digestion is hydrolysis: enzymes split dietary proteins, starches, and fats into their building blocks so your body can absorb them. Inside cells, hydrolysis recycles worn-out molecules and, crucially, releases energy: splitting ATP by hydrolysis frees the energy that powers most of the cell's work. Build with condensation, demolish with hydrolysis — between the two, the cell endlessly remakes itself.
When you digest a steak, protease enzymes in your gut hydrolyze its proteins back into individual amino acids — each peptide bond broken by inserting one water — so the building blocks can be absorbed and reused.
Break a bond, add a water — condensation run in reverse.
Although hydrolysis releases energy and water is everywhere, biological bonds do not dissolve away on their own at any useful rate — they are kinetically stable, and it is enzymes that decide when and where a bond is actually cut.