1. Digestion

2. is the breakdown of food
It is essential that nutrients
from the food we eat…
…enter every cell of our body
Digestion
is the breakdown of food

3. Food is taken into the mouth
The Digestive System
Food is taken into the mouth
by eating

4. There are two types of digestion:
Chemical Digestion
Physical Digestion

5. Let’s take a close look at how this happens…
Open wide!

6. Physical Digestion (Mechanical)
Mouth
Physical Digestion (Mechanical)
Physical digestion is when the shape of food is changed
Physical Digestion happens in the mouth
Teeth cut and chew food into smaller pieces

7. Teeth 2 3 1 4

8. Teeth Incisor- cutting and biting
Canines- long, pointed teeth (fangs) for grip, stab and tear
Premolars- for crushing, chewing and grinding
Molars- for crushing, chewing and grinding

9. Food is broken down by enzymes
Chemical Digestion
Food is broken down by enzymes
from large molecules into smaller molecules
What are enzymes??

10. Chemical digestion happens in the mouth!
A liquid called saliva is made in our mouths
Saliva 1) helps to soften food,
2) it contains an enzyme called amylase
amylase
starch maltose ( a simple sugar)

11. The Mouth. Teeth break down food into small pieces.
Salivary glands make saliva.
Chewed food gets mixed with saliva which contains enzymes that start to digest starch to maltose.

12. Digestive System

13. Oesophagus Oesophagus
Oesophagus is a muscular tube
It forces food down using a wave of muscular action called peristalsis
Peristalsis

14. Mechanical digestion

15. Stomach A muscular bag that holds food for a few hours
Hydrochloric acid kills bacteria
Enzymes chemically digest the food
The stomach churns and mixes the food
Churning

16. Liver and Pancreas Liver Produces a liquid called bile.
- It helps to digest fats
Pancreas
Produces enzymes which pass from the pancreas into the small intestine.

17. Guess how long the small intestine is???
Produces many enzymes –breakdown food
Food passes into the bloodstream here – called absorption
Guess how long the small intestine is???

19. Large Intestine
Material entering the large intestine contains a lot of liquid
The large intestine absorbs water back into the bloodstream
The solid waste left is called faeces
Faeces are stored in the rectum and pass out the intestine
via the anus

20. Large Intestine
What would happen if liquid is not reabsorbed in the large intestine??
Diarrhoea
If too much water is taken back the waste becomes too solid and this leads to…
Constipation

22. Digestion summary

23. Digestive system diagram

24. Enzymes
An enzyme is a biological catalyst: it speeds up chemical reactions without the enzyme being used up itself

25. Enzymes – How they work! Enzymes Big Molecule of Starch (for example)
Introduce yellow and red sequence as a piece of protein made up of amino-acid building blocks.
Lots of molecules of maltose (a simple sugar)

26. Enzymes
Each enzyme has a special shape so that it can attach to the molecule that it acts on (the substrate)
The enzyme acts on the substrate to make a product

27. Enzymes An enzyme called amylase is found in Saliva! amylase
starch maltose ( a simple sugar)
Enzyme
The substrate
Product
Amylase
Starch
Maltose

28. Step one:
Leave test tube A and test tube B in a water bath at 37oC for ten minutes

29. Step two:
Test solution from each test tube for the presence of starch

30. Test each test tube for the presence of Maltose (a simple sugar)
Step three:
Test each test tube for the presence of Maltose (a simple sugar)
1. Add a few drops of Benedict's solution to each test tube
2. Heat test tubes in a boiling water bath for 3 minutes!