Chapter 5 The Digestive System & Enzymes Objectives: Syllabus OB6Identify and locate the major parts of the digestive system including the mouth, oesophagus, stomach, liver, pancreas, small intestine and large intestine, and know their functions. OB7 Identify molars, premolars, canines and incisors, and describe their functions OB8 Investigate the action of amylase on starch; name the substrate, product and enzyme

Label the diagram of the human digestive system: Word Bank: stomach, small intestine, liver, large intestine, pancreas, oesophagus, mouth, rectum, anus, gall bladder

Diagram of the human digestive system PartFunction MouthPhysical digestion OesophagusPasses food to the stomach by peristalsis StomachPhysical and chemical digestion Small intestine (6 metres long) Chemical digestion and the absorption of nutrients into the blood PancreasContains digestive enzymes LiverProduces Bile (for the digestion of fats) Large intestineAbsorption of water from the food remains RectumThe remains of food and water is stored in the rectum.

Diagram of Digestive System

Two types of digestion: 1.Physical Digestion – where food is broken down by teeth and the muscles of the digestive system. 2.Chemical Digestion – food is broken down by special molecules called enzymes. Enzymes are chemicals that are found in every cell in the body. Enzymes speed up chemical reactions in cells. Enzymes are biological catalysts that speed up the digestion of food e.g. amylase

Amylase Amylase is an enzyme found in the mouth that breaks down starch e.g. in bread to maltose Substrate = the substance an enzymes breaks down e.g. starch Product = The substance formed when an enzyme reacts with a substance e.g. maltose

Enzymes are proteins which speed up chemical reactions without the enzymes being used up. The substance produced by an enzyme is called the product. The substance the enzyme acts on is called the substrate. The enzyme amylase acts on starch to produce a reducing sugar called maltose.

To investigate the action of amylase on starch: –If saliva (amylase) is added to a starch solution, the solution will turn red/yellow when iodine is later added. –If saliva is not added to a starch solution, the solution will turn blue-black when iodine is later added.

Experiment: To investigate the action of amylase on starch Test tube Contents at startTested for at end Resultconclusion AStarch + amylaseStarchNo starch presentStarch broken down by amylase BStarch + waterStarchStarch presentStarch not broken down CStarch + amylaseReducing Sugar Reducing sugar present Starch broken down to reducing sugar DStarch + waterReducing Sugar Reducing sugar absent Starch not broken down

Functions of the main parts of the digestive system or alimentary canal are as follows:  The mouth carries out physical digestion (using teeth) and chemical digestion (using the enzyme amylase).  The oesophagus moves food to the stomach by peristalsis.  The stomach has acid which softens food and kills bacteria.  Enzymes in the stomach break down food. The stomach churns food to cause physical digestion.  The liver makes bile which breaks down fats.  The pancreas makes enzymes which digest food.  The first part of the small intestine completes the breakdown of food.  The second part of the small intestine allows the food to be absorbed from the intestine into the bloodstream.  The large intestine takes water back into thebloodstream.  The rectum stores faeces.

Digestive System The digestive System is a long tube that stretches from the mouth to the anus. Consists of: (1) Mouth (2) Oesophagus (3) Stomach (4) Small Intestine (5) Large Intestine

Human Nutrition involves 4 stages 1. Eating – Food is taken into the mouth 2. Digestion – Food is broken down into smaller, soluble molecules 3. Absorption – The digested food is taken into the blood stream and carried to the cells where it is used. 4. Egestion - Getting rid of undigested waste as faeces

–The liver makes bile which breaks down fats. –The pancreas makes enzymes which digest food. –The first part of the small intestine completes the breakdown of food. –The second part of the small intestine allows the food to be absorbed from the intestine into the bloodstream. –The large intestine takes water back into thebloodstream. –The rectum stores faeces.

Teeth A full adult set of teeth contains 32 teeth ToothFunction IncisorsBiting and cutting CaninesGrasping and tearing PremolarsGrinding and crushing MolarsGrinding and crushing 1. The mouth The mouth is where digestion begins: Enzymes in saliva (amylase) break down starch to maltose Teeth physically break down food into smaller pieces

Diagram of the Tooth

3. Stomach Muscular bag which holds the food for 3-4 hours It releases enzymes and other digestive juices which chemically digest the food. The stomach muscles churn and mix the food HCl produced in the stomach kill bacteria in the food 4. Small Intestine More enzymes are added to complete breakdown of the food Digested food passes from the small intestine into the blood stream this is called absorption Undigested food is pushed into the large intestine.

5. Liver & Pancreas The liver and pancreas are two organs associated with digestion Liver has many functions including: The production of bile which contains enzymes to break down fat. The pancreas produces enzymes which break down food. 6. Large Intestine The large intestine reabsorbs water back into the blood stream. The faeces (waste material) is stored in the rectum and released from the body through the anus.

PartFunction Mouth Oesophagus Stomach Liver Pancreas Small Intestine Large Intestine Parts and functions of Digestive System

Exam Questions 2013 Honours J.C. Q2a