Carbohydrates

Proteins

Lipids

Nucleic acids

Chemical digestion

Emulsification

Absorption

Peristalsis

Available in the soil only in small amounts 

Required by plants in small amounts 

Small molecules required by plants 

Useful, but not required by plants 

Lubrication of the food 

Beginning of protein digestion 

Breaking the food into small fragments 

All of the above do occur in the oral cavity 

Esophagus

Stomach

Small intestine

Large intestine