Which two substances bind using a lock-and-key mechanism?
enzyme and substrate
reactant and substrate
substrate and product
reactant and product

The answer is the first option. Enzyme and substrate bind using a lock-and-key mechanism. Enzymes act on a specific substrate and a substrate needs a specific enzyme, this is what is called a lock-and-key mechanism. Enzymes and substtates are like a key and a lock, one is for each other.

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