Digestion

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

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

There are two types of digestion: Chemical Digestion Physical Digestion

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

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

Teeth 2 3 1 4

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

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

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)

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.

Digestive System

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

Mechanical digestion

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

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.

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???

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

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

Digestion summary

Digestive system diagram

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

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)

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

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

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

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

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!