Mechanical digestion involves the physical breakdown of food through chewing and grinding, while chemical digestion relies on enzymes and acids to break foods down at a molecular level. Carbohydrates, proteins, and fats are the main macronutrients, with carbohydrates broken down for quick energy, proteins building muscles, and fats providing long-term storage. Enzymes aid the chemical breakdown of these macronutrients with carbohydrates being used first, then fats, and finally proteins if energy stores are depleted.

1. Mechanical Versus Chemical Mechanical: Breakdown by physical means Examples: Chewing, swallowing, fluid breakdown, mashing, grinding. Chemical: Breakdown by chemical means Examples: Enzymes in saliva, acids in stomach.

2. Carbohydrates: Long chains of sugars attached together, stored briefly in blood and broken down for energy

3. Proteins: Long chains of amino acids, stored in muscles.

4. Fats: Strings of individual fatty acids attached together, stored on top of muscles. Saturated: Maximum amount of hydrogen on fatty acids. Examples: Butter and solid fats Unsaturated: Multiple places where hydrogen is missing. (Better for you) Examples: oils and liquid fats

5. Enzymes: Chemicals that aid in breaking down carbohydrates, fats and proteins. Order of food breakdown Carbohydrates in blood (turned to fat if not used) Fat in body Proteins (muscle degeneration) Diets, do they work? Which ones?