(a) Activity: Take a small piece of bread and chew it for 2-3 minutes without swallowing. Initially it has no taste, but after some time it starts to taste sweet.
This happens because saliva contains an enzyme called salivary amylase (ptyalin) which breaks down starch present in the bread into simple sugars (maltose). This shows that saliva acts on the starch in food and begins its chemical digestion in the mouth.
(b) Bile juice is secreted by the liver and stored in the gall bladder. It does not contain any digestive enzymes but is important because it makes the acidic food coming from the stomach alkaline, so that pancreatic enzymes can act on it. It also helps in the emulsification of fats, breaking large fat globules into smaller droplets, which increases the surface area for enzyme action.
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