Cells store energy either as carbohydrates or lipids (fats and oils).
Carbohydrates provide for fast, short term energy. They are a key part of cellular respiration.
Lipids provide for long term energy storage because storing lipids is much more effective than storing carbs. One gram of lipid can store twice as much as one gram of carbs. So to access this energy storage, cells must conduct hydrolysis (inserting a hydrogen and a hydroxide group to split off the energy).
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