Starch is broken down into by the enzyme

Starch is broken down into glucose by the enzyme amylase.

Explanation:

Starch is a polymer, a long chain of subunits of the sugar glucose. They join together to form a macromolecule. As it is, starch is 'too big' to enter cells to be processed to obtain energy; it must be broken down into its glucose subunits first.

Amylase is an enzyme present in the human saliva, among other places, and is responsible for breaking starch down so it can be transported inside cells as glucose, and then turned into energy by the cellular respiration.

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