8A Food and Digestion © Tony P. Thould September 2000

National Curriculum Statements linked to Yr8 Food and Digestion 2a about the need for a balanced diet containing carbohydrates, proteins, fats, minerals, vitamins, fibre and water, and about foods that are sources of these 2b the principles of digestion, including the role of enzymes in breaking down large molecules into smaller ones 2c that the products of digestion are easily absorbed into the bloodstream and transported throughout the body, and that waste material is egested 2d that food is used as a fuel during respiration to maintain the body’s activity and as a raw material for growth and repair

DIGESTION The breaking down of complex foods into simple soluble substances

DIGESTION The ……………………. of …………… ……..into ……… ……… ………….

CARBOHYDRATES FATS PROTEINS Potatoes Rice Pasta Bread Butter Cream Fried Food Peanuts Meat Fish Soya Energy giving foods full of Starch Stored energy and insulation For growth and repair

VITAMINS MINERALS FIBRE Fresh fruit and vegetables Fresh fruit vegetables milk Cereals fruit vegetables Prevent deficiency diseases Provides bulk to move food along.

VITAMINS MINERALS FIBRE Prevent deficiency diseases Provides bulk to move food along.

Potatoes Rice Pasta Bread Butter Cream Fried Food Peanuts Meat Fish Soya E giving foods full of Starch Stored energy and For

CARBOHYDRATES FATS PROTEINS Potatoes Rice Pasta Bread Butter Cream Fried Food Peanuts Meat Fish Soya Amylase breaks down the Starch in these foods to Glucose sugar Lipase breaks down fats to Fatty Acids and Glycerol Protease breaks down Protein to Amino Acids

CARBOHYDRATES FATS PROTEINS Potatoes Rice Pasta Bread Butter Cream Fried Food Peanuts Meat Fish Soya A breaks down the Starch in these foods to Glucose sugar L breaks down fats to Fatty Acids and Glycerol P breaks down Protein to Amino Acids

CARBOHYDRATES FATS PROTEINS breaks down the Starch in these foods to Glucose sugar breaks down fats to Fatty Acids and Glycerol breaks down Protein to Amino Acids Amylase Lipase Protease

CARBOHYDRATES FATS PROTEINS breaks down the Starch in these foods to breaks down fats to breaks down Protein to A L P

FOOD GROUPS There are SEVEN main food groups :- Carbohydrates Fats Proteins Vitamins Minerals Water Fibre

FOOD GROUPS There are SEVEN main food groups :

A BALANCED DIET You must have the right amounts of all of the seven food groups in order to keep healthy Too much of one group or not enough of another or missing groups out from your diet will mean an unbalanced diet and ill health.

WHAT IS IN FOOD? There are tests that can be done on foods to find out which food groups are present in that food. IODINE is an orange/brown liquid that turns black when it reacts with Starch BIURET TEST involves adding the Biuret reagent to the food and then adding up to the same amount of Sodium Hydroxide to it. If a purple colour appears this means that the food contains proteins. BENEDICTS TEST tests for Reducing Sugar ( Glucose ). It is a blue liquid that when heated with a food solution turns green to orange to Brick red depending upon the amount of sugar present.

ENZYMES These rare chemicals made in the body whose job it is to breakdown the complex foods into simple soluble substances BD CF SSS The three different food groups each need their own special Enzymes to break them down from a complex food into a simple soluble substance

A SUMMARY OF DIGESTION

THE ENZYME AMYLASE Amylase will only break down Carbohydrates such as Starch Carbohydrates must end up as a simple soluble substance Enzymes are Catalysts made from Protein

Iodine is a chemical test for starch If a drop of Iodine, which is normally red brown in colour, is placed upon a substance that contains starch, the iodine will turn black. If the substance contains no starch the iodine stays the same colour I.e. red /brown.

A CHEMICAL TEST FOR STARCH IODINE is a red / brown liquid Starch

STARCH + AMYLASE EXPERIMENT Amylase is added to Starch solution, placed in a water bath at 37ºC A drop of this mixture removed every two minutes for 24 minutes and tested in a dimple tray with Iodine. WHAT RESULTS WOULD YOU EXPECT?

Iodine in a dimple tray at the start of the experiment with Starch + Amylase

How do you explain these results after 24mins.

THE ENZYME AMYLASE Amylase will only break down Carbohydrates such as Starch Carbohydrates must end up as a simple soluble substance Enzymes are Catalysts made from Protein

THE ENZYME AMYLASE Amylase will only break down C____________ such as Starch Carbohydrates must end up as a simple soluble substance such as G_________ Enzymes are C __________ made from Protein

STARCH IS A COMPLEX FOOD - it is too big to be absorbed and must be broken down by amylase into a simple soluble substance- glucose so that it can pass into the blood S T AR C H

STARCH IS A COMPLEX FOOD S T AR C H G G G G G G Enzymes are chemical scissors cutting up the large complex food molecules ( starch ) into a simple soluble substances ( Glucose )

STARCH IS A COMPLEX FOOD S T AR C H G G G G G G AMYLASE is the Enzyme that breaks down Starch into Glucose

S T AR C H G G G G G G Easily absorbed XXX The complex starch molecule is too big to pass into the blood vessel X

S T AR C H G GGG G XXX No starch gets into the blood and would pass out of the body unused X The soluble glucose is easily absorbed into the bloodstream and carried around the body.

BY NOW YOU SHOULD KNOW The definition of Digestion The main food groups, sources and uses What Enzymes are and what they do Three named Enzymes, what food group they act upon and what they break down the food into

THE DIGESTIVE SYSTEM Label in pencil any parts that you already know.

THE DIGESTIVE SYSTEM Salivary Glands Oesophagus Stomach Pancreas Colon Rectum Anus Appendix Ileum Duodenum Gall Bladder Liver Large Intestine Small Intestine ( Gullet )

THE DIGESTIVE SYSTEM

SGSG O S P C R A A I D GBGB L

Salivary Glands These make the liquid Saliva in the mouth. Just the thought of food can make these work - they make your mouth water - or drool like a dog waiting to be fed. Saliva moistens the food, lubricating it so that it is easier to swallow Saliva contains an Enzyme called Amylase which can break down the large molecules of Starch into soluble Glucose ready to be absorbed into the blood

THE DIGESTIVE SYSTEM Oesophagus or Gullet Food going down the Oesophagus into the stomach The food is forced down the Oesophagus by muscular contractions squeezing behind it. This is called Peristalsis

THE DIGESTIVE SYSTEM Stomach This is where Protein Digestion begins Hydrochloric acid and the Enzyme Pepsin ( Protease ) are made by cells in the Stomach wall. Together they make up Gastric Juice. Pepsin starts the break down of Proteins into Amino Acids which are soluble and easily absorbed into the blood.

THE DIGESTIVE SYSTEM Liver Gall Bladder Duodenum The Liver makes a liquid called Bile. This is stored in the Gall Bladder before passing down the tube - Bile Duct - into the Duodenum. Bile emulsifies Fats. This means that the fat is turned into small pieces. This gives the fat a larger surface area for the Enzyme Lipase to chemically attack it and break it down Bile also neutralises the acid stomach contents so that the Pancreatic enzymes can work in a neutral pH

THE DIGESTIVE SYSTEM Pancreas The Pancreas is an “ Enzyme Factory “ It makes lots of different Enzymes including Lipase, Amylase and Trypsin. These Enzymes pass down the tube - Pancreatic Duct - into the Duodenum Lipase breaks down the emulsified fats into Fatty Acids and Glycerol. These are soluble and are absorbed first into the Lymph System before going into the bloodstream through veins in the neck.

THE DIGESTIVE SYSTEM Ileum Duodenum The Duodenum and Ileum together make up the Small Intestine In the Duodenum all of the Enzymes from the Pancreas ( Pancreatic Juice ) digest the remaining complex foods into simple soluble substances before passing on into the Ileum

THE DIGESTIVE SYSTEM Ileum The simple soluble ( liquid ) food is now absorbed into the bloodstream For this to happen quickly the inner wall of the Ileum is tightly folded each fold is known as a Villus Villi increase the surface area of the inner wall of the Ileum They have a good blood supply ready to carry away the soluble food. Any undigested food carries on into the Large Intestine

THE DIGESTIVE SYSTEM Colon Rectum Anus Appendix The Colon, Appendix, Rectum and Anus together make up the Large Intestine The Appendix has no function Undigested remains pass out of the Anus - Egestion Excess water is absorbed back into the blood through the wall of the Colon. Lumps of undigested remains - Faeces - are stored in the Rectum

THE DIGESTIVE SYSTEM

BY NOW YOU SHOULD KNOW The main parts of the Digestive System The location of these parts in the body The main functions of these parts