Digestion & Enzymes
Describe the organs of the human digestive system and how food is physically and chemically digested, including the role of enzymes as biological catalysts
What a learner can do afterwards
- Traces the journey of food from mouth to large intestine, naming each organ and its role
- Explains what enzymes do and names where they are produced (salivary glands, stomach, small intestine)
- Distinguishes physical digestion (chewing, churning) from chemical digestion
1 · Read
You already know the main stops food makes on its way through your body. Now look closer at how those stops release the nutrients that help you move and grow. Digestion happens in two ways: physical digestion, which breaks food into smaller pieces, and chemical digestion, which breaks food's molecules apart using enzymes.
Enzymes are proteins that speed up chemical reactions. In digestion, enzymes break big food molecules into small ones your body can absorb. Salivary glands start breaking down starch with an enzyme. The stomach makes an enzyme for protein. The small intestine makes enzymes and receives enzymes from the pancreas to finish starches, proteins, and fats. It then absorbs most of the small molecules for the body to use.
When you chew a piece of bread, your teeth physically tear it into smaller bits. At the same time, an enzyme in your saliva called amylase starts breaking the starch in the bread into sugar molecules. Physical and chemical digestion happen at the same time, in the same bite.
Check whether the food's size or its molecules are changing. Chewing and churning change size and shape, so they are physical. When enzymes change food into smaller molecules, the process is chemical.
Physical digestion breaks food into smaller pieces; chemical digestion, powered by enzymes made along the way, breaks it down into molecules your body can absorb.
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2 · Watch
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