In which part of the digestive system does a chemical change of the food first occur? mouth esophagus stomach liver

The answer is: the mouth.

Explanation:

Chemical digestion is the breakdown of food into small particles to subsequently go through the process of absorption and transport to cells.

The mouth secretes enzymes capable of breaking relatively strong intra-molecular bonds so that difficult-to-digest molecules turn into small, digestible molecules (Nutrients).

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.

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