The first step of digestion

The idea

In the mouth, teeth crush food, saliva from the salivary glands wets it, and the enzyme salivary amylase breaks starch into simple sugar; enzymes are biological catalysts that break complex food into smaller molecules.

Chewing food

You chew your food before you swallow it.

Which of these do you think changes the food while it is in your mouth?

• Teeth, saliva and an enzyme
• Only the tongue
• Nothing, it stays the same until the stomach

Inside the mouth

Press Next step to follow the food.

Mouth work

In the mouth the teeth crush the food and saliva wets it. Saliva also holds an enzyme, salivary amylase, that begins to break starch down into simple sugar. Enzymes are biological catalysts that break complex food into smaller molecules.

In the mouth, teeth crush food, saliva from the salivary glands wets it, and the enzyme salivary amylase breaks starch into simple sugar; enzymes are biological catalysts that break complex food into smaller molecules.

Notes

In the mouth teeth crush food, saliva wets it, and salivary amylase breaks starch into simple sugar; enzymes are biological catalysts.

Check yourself

Which enzyme in saliva breaks down starch?

What does the breakdown of starch by salivary amylase give?

Saliva is secreted by the ...

Enzymes are ...

• Pepsin. Pepsin is the protein-digesting enzyme released by the gastric glands of the stomach.
• Salivary amylase — correct. Yes!
• Trypsin. Trypsin is in pancreatic juice and digests proteins.
• Amino acids. Amino acids come from the final digestion of proteins.
• Fatty acids and glycerol. Fatty acids and glycerol come from the final digestion of fats.
• Simple sugar — correct. Yes!
• salivary glands — correct. Yes!
• gastric glands. Gastric glands in the wall of the stomach release hydrochloric acid, pepsin and mucus.
• liver. The liver makes bile, which acts on fats in the small intestine.
• teeth that crush the food. Teeth crush the food; enzymes are biological catalysts.
• biological catalysts that break complex food into smaller molecules — correct. Yes!
• a fluid that only wets the food. Wetting the food is done by saliva. Enzymes are biological catalysts that break complex food into smaller molecules.