1. breakdown of food into a form that can be used by an organism for metabolism
1.1. 2 types of digestion
1.1.1. Chemical
1.1.1.1. process of breaking apart complex molecules into simple molecules
1.1.1.2. carried out by enzymes
1.1.1.2.1. greatly increase rate of breakdown
1.1.1.2.2. splits food molecules by hydrolysis
1.1.1.2.3. manufactured by specific cells in
1.1.1.2.4. large molecules can require multiple enzymes to completely breakdown
1.1.1.2.5. humans secrete more than 20 different digestive enzymes
1.1.2. Physical
1.1.2.1. physical process of making food smaller for digestion by chemicals
1.1.2.2. Examples
1.1.2.2.1. Chewing (teeth)
1.1.2.2.2. Muscle movement
1.1.2.2.3. stones inside a birds gizzard
2. If food is swallowed in large pieces, there is small SA for enzymes to break down
2.1. Digestion is faster if the food is smaller
3. Extracellular
3.1. cells release enzymes into the lumen
3.1.1. lumen = central cavity of the small intestine
3.1.2. splits food molecules into smaller molecules
3.1.2.1. molecules absorbed
3.2. Example:
3.2.1. sea stars turn their stomach inside out and release enzymes directly onto their prey
3.2.1.1. the release of enzymes is what signifies the extra (outside) cellular (cell) digestion
4. Intracellular
4.1. cells engulf small pieces of food
4.1.1. lysosomes fuse with vacuole and release enzymes
4.1.1.1. enzymes digest food INSIDE of cell
4.2. Organisms
4.2.1. Invertebrates
4.2.1.1. mussels
4.2.1.2. sea-jellies
4.2.1.3. flatworms