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
Write from bile and fat droplets
- Bile is added to a mixture of fat and water.
- The fat breaks into many tiny droplets.
What is this physical change called, and why does it help?
Smaller droplets give lipase more surface to work on.
What does bile do to fats?
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Bile is the emulsifier, and lipase does the chemical split.