- How does the food change in consistency and form?
As food enters the mouth, it goes through mechanical digestion and chemical digestion. Starting from the mouth, it is broken down into pieces by chewing using the teeth while the tongue mixes it with the saliva which breaks down carbohydrates into simpler sugars, forming a mass called bolus. When swallowed, it goes to the stomach where the walls contract and digestive enzymes are secreted turning the food into a semi-liquid substance called chyme, gastric juices also begin the chemical digestion of proteins. Chyme then moves to the small intestine for the absorption of nutrients, releasing bile and pancreatic enzymes such as lipases and proteases turning fats and proteins into fatty acids and amino acids.
2. How could the body absorb the nutrients from the foods we eat?
Nutrient absorption occurs in the small intestine where food particles are small enough for the body to absorb. When carbohydrates, proteins, and fats are turned into nutrients, they are absorbed into the blood or lymphatic vessels by both active and passive transport mechanisms traveling to the other tissues for their respective metabolic functions. These transport mechanisms include diffusion, facilitated diffusion, osmosis, and active transport. A brief description are as follows:
- Diffusion lets fatty acids and fat-soluble vitamins to move across epithelial cell membranes.
- Facilitated diffusion assists in moving glucose and amino acids through transport proteins without the use of energy.
- Osmosis regulates fluid balance in the bloodstream as nutrients are absorbed.
- Active transport transports essential nutrients through the body with the use of energy.