Physical digestion
Introduced| English | Meaning |
|---|---|
| incisors/ɪnˈsaɪzəz/ | incisors |
| canines/ˈkeɪnaɪnz/ | canines |
| molars/ˈməʊləz/ | molars |
| emulsification/ɪˌmʌlsɪfɪˈkeɪʃn/ | The dispersal of one liquid as small droplets in another; in digestion, bile helps break large fat droplets into smaller ones. |
| lipase/ˈlɪpeɪs/ | The enzyme that digests lipids into fatty acids and glycerol. |
| physical digestion/ˈfɪzɪkl daɪˈdʒestʃn/ | physical digestion |
Breaking food apart — physically
- Before chemicals can act, big lumps of food must be broken into smaller pieces.
- This physical (mechanical) digestion doesn't change the food chemically — it just makes it smaller.
Which teeth are used for cutting?
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Incisors cut; canines tear; molars and premolars grind.
Chewing food into smaller pieces helps digestion because it:
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Smaller pieces give enzymes more surface to act on.
Teeth
- Incisors 门齿 cut, canines 犬齿 tear, premolars and molars 臼齿 grind.
- Chewing breaks food into smaller pieces with a larger surface area for enzymes.
Digestive enzymes break large molecules into small, soluble ones
Physical (mechanical) digestion
Physical digestion breaks food into smaller pieces WITHOUT changing it chemically — it just increases the surface area for enzymes.
Physical digestion changes the chemical structure of food molecules.
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Physical digestion only makes food smaller; enzymes do the chemical change.
The stomach
- The stomach's muscular walls churn food, mixing it with acid and enzymes.
- This continues the physical breakdown.
Bile emulsifies fat, which means it:
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Emulsification is physical: bigger surface area for lipase.
Breaking large fat droplets into smaller ones is called ______.
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Bile emulsifies fats to speed up lipase action.
Bile and emulsification 乳化
- Bile breaks large fat droplets into many tiny ones — emulsification.
- This greatly increases the fat's surface area for the enzyme lipase 脂肪酶.
Physical digestion 物理消化 doesn't change the molecules. Chewing and churning only make food smaller. The chemical change — breaking molecules into smaller ones — is done by enzymes (chemical digestion).
You've got it
- physical digestion makes food smaller without changing it chemically
- teeth cut/tear/grind; the stomach churns food
- bile emulsifies fats — increasing surface area for lipase