Digestion et Composants Alimentaires

Study Notes

Digestion is the breakdown of large molecules into smaller nutrients that can be absorbed into the blood.
Digestion occurs in the mouth, esophagus, stomach, and small intestine.
Two types of digestion:
- Mechanical digestion: involves physical processes like chewing, churning, and mixing to break down food.
- Chemical digestion: involves enzymes breaking down food into smaller molecules.
Digestion in the mouth:
- Mechanical: chewing (mastication)
- Chemical: saliva (enzyme)
Digestion in the esophagus: mechanical
Digestion in the stomach: chemical (gastric juice)
Digestion in the small intestine: mechanical and chemical (intestinal juice)
Carbohydrates are sugars
Proteins are made of amino-acids
Fats are lipids
Different tests can be used to identify the presence of different nutrients. Different tests are listed in subsequent sections.

Water: Heating a food sample and observing the droplets of water that form indicates water is present.
Chlorides: Adding silver nitrate solution and observing a white precipitate confirms the presence of chlorides.
Calcium: Adding ammonium oxalate to food, then observing a white precipitate, confirms the presence of calcium.
Reducing sugars (like glucose): The Fehling test , where a brick-red precipitate forms after heating, indicates the presence of reducing sugars.
Starch: Adding iodine solution and observing a blue-black color change confirms the presence of starch.
Proteins: The Biuret test, where a violet color develops, confirms the presence of proteins.
Lipids: The Sudan III test which produces a reddish-orange color confirms the presence of lipids.
Coagulation: Observed for proteins. The test shows protein coagulation if the substance curdles (thickens) upon heating or acid addition confirming the presence of proteins.