A student investigated the chemical composition of three unknown food samples, P, Q, and R, by performing standard biochemical food tests. The observations are recorded in the table below:
| Food Sample | Biuret Test | Benedict's Test | Iodine Test | Ethanol Emulsion Test |
|---|---|---|---|---|
| P | Purple | Blue | Orange-brown | Clear |
| Q | Pale blue | Brick-red | Orange-brown | Clear |
| R | Pale blue | Blue | Blue-black | Cloudy emulsion |
The Biuret test confirms that food sample P contains protein molecules.
Describe how proteins are digested in the human body.
