Biology
Introducing enzymes
We are learning how to: • Describe the role of different enzymes in digestion. • Analyse a model of the digestive system. • Explain observations of a practical activity to explore the role of enzymes.
Enzymes are protein molecules that occur naturally in your body. Without enzymes, we could not live because they speed up many vital processes, such as digestion. Enzymes in digestion
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If you eat a pizza, you need to digest the starch in the bread and the protein in the cheese. The enzyme amylase, released in the mouth and the small intestine, digests the starch. Starch is broken down into smaller molecules of sugar (glucose). large starch molecule
enzyme cuts bonds
smaller glucose molecules
in mouth and small intestine FIGURE 1.2.11b: Amylase enzyme breaks down starch to glucose molecules.
Protein is broken down by a different enzyme into smaller molecules, called amino acids. This enzyme is released in the stomach and the small intestine. large protein molecule
different enzyme cuts bonds
FIGURE 1.2.11a: You need enzymes to digest your pizza.
smaller amino acid molecules
in stomach and small intestine FIGURE 1.2.11c: Protein molecules are broken down to smaller molecules.
Fats are digested by another enzyme, lipase. This enzyme is released in the small intestine. 1. What are starch and protein broken down into during digestion? 2. List where each of the three enzymes that digest starch, protein and fats is found. 3. A pizza also contains fats. Fats are digested to fatty acids and glycerol by the enzyme lipase. Draw a string of triangles to represent a fat molecule, and show what happens to it when it is digested.
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KS3 Science Book 1: Eating, Drinking and Breathing
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