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Biology: Digestive System

This will cover:

Digestive System

Food Tests

Digestive Enzymes

The Digestive System:

Oesophagus/ Gullet (not on diagram):

Food chute from mouth to stomach

Slivery Glands:

Produce amylase enzymes to start breakdown of starch.

Stomach:

1. It pummels the food with its muscular walls

2. Produces protease enzymes

3. Releases hydrochloric acid to:

• Kill bacteria

• Give the right pH for protease to work (pH2)

Liver:

Where bile is stored which emulsifies fats and neutralizes stomach acid.

Pancreas:

Produces protease, amylase and lipase enzymes.

Gall Bladder:

Where bile is stored until injection into the intestine

Small Intestine:

1. Produces amylase, lipase and protease enzymes

2. Where food is absorbed into the blood

3. Long and folded to increase surface area. Finger like things called villi cover the inner surface to furtherly increase the surface area.

Large Intestine:

Where excess water is absorbed from the food.

Anus:

Where the faeces made up of mostly indigestible food leaves the body.

The food tests:

1. The iodine test for starch :: Turns blue or black

• Add some drops of brown iodine solution to the food

• If contains starch the iodine will turn either blue or black

2. The biuret test for protein :: turns CuSO4 purple

• Add sodium hydroxide (NaOH) solution to the food and shake with care

• Add some weak copper sulphate solution

• If the pale blue colour turns purple then protein is present

3. The Benedict's test for simple sugars :: an orange precipitate

• Add blue Benedict's solution to the food in a test tube

• If you get an orange precipitate then the food contains simple sugars

Digestive Enzymes:

Remember enzymes break large molecules into smaller ones.

There are three main enzymes to remember:

1. Amylase which converts starch into simple sugars

• Produced in the pancreas, small intestine and the salivary glands

2. Protease converts proteins into amino acids

• Produced in the pancreas, small intestine and stomach

3. Lipase converts fats into fatty acids and glycerol

• Produced in the pancreas and small intestine

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