How does food turn into food?

Answer 1

Food is broken down in a process called respiration. Enzymes are usually involved in the breakdown of food. Proteins are broken to amino-acids by protease, Carbohydrates broken down to simple sugars e.g fructose and glucose and Lipids (fats & oils) are broken down to fatty acids and glycerol by Lipase. Once they are broken down, they are taken to the cells where they're respired to produce Energy, Metabolic water and carbon-dioxide.

Answer 2

Heat denatures protein molecules, breaks long starch molecules into shorter starch molecules and sugar molecules, and melts fats. All of these effects make cooked food much easier to chew and digest, significantly increasing its nutritional value.

Also when cooked to a high enough temperature, potentially harmful bacteria, fungi, and parasites that may be living on or in the food are killed, reducing the chance of your food making you sick.