Many types of bonds can hold molecules together. Two amino acids will move towards each other and prepare to undergo a reaction. The carboxyl group of one molecule approaches the amino group of the other molecule. The carboxyl group loses a hydrogen and an oxygen, and the amino group loses a hydrogen. This releases a full molecule of water (H2O), classifying it as a condensation reaction. The hydrolysis that cleaves these bonds is essentially the opposite reaction, adding water instead of removing it.

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