Lesson #11: Enzymes in digestion

Objective:- Identify the main enzymes in digestion and their functions

Practical1. Label the boiling tubes A & B2. Fill each tubing with 8ml of starch.3. Wash one of the tubes very well and place it in boiling

tube A.4. Add 3ml of amylase solution in the other tube. Shake.

Wash very well and place in boiling tube B.5. Place both boiling tubes in the water bath for 30

minutes.6. Test the water in the boiling tube for starch and

glucose using iodine and benedict’s solution7. Record your results.

Digestive Enzymes• There are 3 main types of digestive enzymes:

Enzyme Reaction catalysed Where produced

Amylase Starch → sugars Salivary glands, pancreas, small intestine

Protease Proteins → amino acidsStomach, pancreas, small intestine

Lipase Lipids → fatty acids + glycerol Pancreas, small intestine

Digestive Enzymes

Amylase

StarchGlucose

Protease

ProteinAmino Acids

Digestive Enzymes

Glycerol

Fatty Acid

Fatty Acid

Fatty Acid

Glycerol

Fatty Acid

Fatty Acid

Fatty Acid

Lipase

Fat Fatty Acids and Glycerol

The enzyme fits over the substrate perfectly – like a key fits a lock.

It holds the starch molecule in place as a water molecule breaks the bond between two glucose particles

Starch molecule

Amylase enzyme

This continues until the molecule has been broken down completely

Chemical digestion:• Salivary amylase: starch maltose• Pepsin in stomach: protein peptides• Pancreatic amylase: starch maltose• Trypsin from the pancreas: protein peptides• Lipase from the pancreas: fats glycerol + fatty acids

Digestion Summary

What factors affect the rate of reaction of enzymes

• How do you think you can speed up the rate of an enzymic reaction?(Hint: It’s the same as any other reaction!)

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