Physical digestion
Physical digestion
- Physical digestion breaks food into smaller pieces without changing the molecules.
- This gives a larger surface area for enzymes to work on.
- Teeth, the stomach and bile all help.
Practice
Physical digestion:
Physical digestion just makes pieces smaller (more surface area); chemical digestion changes the molecules.
Teeth
| Tooth | Job |
|---|---|
| incisors | bite and cut |
| canines | tear |
| premolars / molars | chew and grind |
- Tooth parts: hard enamel (the hardest material in the body) over dentine, a soft pulp (nerves/blood vessels), and cement fixing the root.
Practice
Which teeth are used for biting and cutting?
Incisors (front) bite and cut; canines tear; premolars and molars chew.
Practice
The hardest part of a tooth is the:
Enamel is the hard white outer layer — the hardest material in the body.
Stomach and bile
- The stomach wall is muscle that squeezes and mixes the food.
- Bile (made in the liver, stored in the gall bladder) emulsifies fat — breaks it into tiny droplets, giving a larger surface for lipase. Bile contains no enzymes.
Practice
Bile helps digest fat by:
Bile emulsifies fat (more surface area for lipase) but contains no enzymes itself.
You've got it
Key idea
- physical digestion = smaller pieces, more surface area (the molecules are unchanged)
- teeth: incisors cut, canines tear, premolars/molars chew; enamel is the hardest layer
- bile emulsifies fat (bigger surface for lipase) but contains no enzymes