-lysis

Quick Definition

Meaning: Decomposition or breaking down

Origin: Greek (lysis = a loosening)

Pronunciation: LYE-sis

Why It Matters

Students often confuse -lysis with -osis. The key difference: -lysis specifically implies a breaking apart or decomposition process, often via an external agent (electro-, hydro-, pyro-). -osis indicates a condition or state, not necessarily a decomposition. In lab contexts, when you see -lysis, think 'something is being broken down.' A common mistake in exams is writing 'hydrolysis' when the question describes a synthesis reaction. Remember: hydrolysis uses water to break a bond, while dehydration synthesis removes water to form a bond. These are opposites, and getting them backwards is one of the most frequent errors I see in first-year organic chemistry. The energy story matters too: hydrolysis reactions are typically exergonic (they release energy), which is why your body uses hydrolysis to break down ATP for energy. When you see -lysis on an exam, also check whether the question is asking about the mechanism (nucleophilic attack by water) or the outcome (the molecule split into two parts).

Examples

• Electrolysis
• Hydrolysis
• Pyrolysis
• Glycolysis

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