IGCSE Biology Year 10. Digestion. Name:

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1 IGCSE Biology Year 10 Digestion Name: Prepared by William Green DBGS 2010

2 Introduction You are a tube inside a tube 1. What is this inside tube called? 2. Imagine you swallow a small piece of metal. Will it become part of you? Why not? 3. What does absorb mean? 4. In which part of the gut does absorption take place? 5. Describe the wall of the small intestine 6. Explain why only small particles can pass through from the gut to the blood 7. What is digestion?

3 TASK: Copy and complete this diagram 8. What is the gut? 9. What happens to food that is not absorbed? 10. What are the parts of the gut?

4 Tour Itinerary Amylase Enzyme Mouth Teeth Oesophagus Protease, Pepsin Enzyme Enzymes and ph Stomach Small Intestine Pancreas Amylase, Protease, and Lipase Enzymes Large Intestine Rectum & Anus

5 Enzymes 1. As food moves into the mouth it is mixed with a sticky liquid called saliva. Saliva has two jobs a. b. 2. Enzymes are. They are made up of. Each for a specific. 3. Digestive enzymes the digestive process by in place. 4. Complete this diagram to show the enzyme:

6 5. The enzyme fits over the substrate perfectly, like. This means that there is only ONE enzyme for each substrate. 6. How many types of digestive enzymes are there? 7. breaks down into glucose. breaks protein down into. breaks down into and 8. Copy the diagrams to show the process on digestion by enzymes. Starch Protein Fat

7 9. Remember enzymes are proteins. What factors affect the rate of enzymes? 10. Enzymes catalyse all reactions of the body. This is referred to as. Metabolisms includes which complex molecules such as. Catabolism complex molecules such as.

8 Enzymes and Temperature Fill in the labels on the graph: Heat energy causes more between and Optimum temperature for humans is close to Enzymes (change shape) at high temperatures so rate falls. When enzymes denature, the active site (where the enzyme touches the substrate) changes shape and it can no longer fit the substrate. This is irreversible.

9 Enzymes and ph Optimum Varies from to Think of the two enzymes we have met so far (amylase and pepsin). Which one would work best in ph 1? Which would work best at ph 8? What happens if enzymes are put into the wrong ph?

10 Enzymes in Industry Describe how enzymes are used in industry. Use diagrams if you want to.

11 Swallowing and Peristalsis Watch the animation and answer these questions: 1. The tongue pushes food against the roof of the mouth to make a soft, rounded mass of food. What is it called? 2. Describe the function of the epiglottis. 3. Complete this diagram to show peristalsis: Circular muscles and longitudinal muscles squeeze bolus forward. Circular muscles and longitudinal muscles the bolus pass. Peristalsis is the same sort of movement you make when trying to squeeze toothpaste out of a toothpaste tube!!

12 The Stomach 1. Gastric processes When food enters the stomach the contracts behind so food does not move back up the oesophagus Firstly attacks microbes that may be swallowed. Secondly, the enzyme breaks down into Thirdly stomach muscles contract and relax to break down the food in to smaller pieces

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14 The duodenum The first part of the small intestine is called the duodenum. Food, still mixed with gastric juice is squirted into it from the stomach. The food is now a semi liquid, highly acidic mush. Fill in this flow chart to show what happens: Food leaves the stomach and enters the duodenum is squirted on to the food. (Bile is made in the and stored in the ) Bile neutralises the stomach acid and emulsifies the fat (breaks it down ) The food continues down, past the. Three enzymes made in the PANCREAS are squirted out on to the food: turns starch into turns protein into turns fat into and Liver Stomach Gall bladder Pancreas

15 Complete the flow chart Notice that the fat has not been chemically digested, only physically. The result is a over which the enzyme can attack the fat What are the three accessory glands?

16 The small intestine There are 3 enzymes produced by the duodenum. In the space below, explain what they are and what they do. Complete this sentence: The function of the small intestine is to the products of digestion into the. The molecules that can be absorbed are,, and. Complete this summary table and LEARN IT WELL!! Enzyme Substrate Product Where it is produced Amylase Pancreas Where it acts Duodenum Amino Acids Fat Pancreas

17 Absorption 1. As food continues along the intestine, more enzymes are added, until the parts of the food can be digested. This is the role of the last part of the small intestine called the? 2. To effectively absorb food, the small intestine needs to have This diagram shows the wall of the small intestine. Draw in the pathway the food takes: Outer wall Inner wall

18 (singular = villus) Villi Products of fat digestion, as well as tiny fat droplets enter a tube in the middle of the villus, called the lacteal. The lacteal forms part of the lymphatic system. Blood vessels from the ileum join up to form a large blood vessel called the hepatic portal vein which leads to the liver. What is the epithelium? Why does it have to be thin? What goes into the blood capillary? (2 things) Where do they go from here? What blood vessel takes them there?

19 Egestion Give an example of indigestible food Where does this type of food go after the small intestine? What happens in the colon? What do we call the solid waste that is formed? Where are faeces stored? What is egestion?

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21 A Tour through the Digestive system Complete the tour map

22 PROCESS ORGAN SECRETION FOOD WORKED ON ACTION Ingestion Mouth (Oral Cavity) Oesophagus Stomach Duodenum (small intestine) Ileum (small intestine) Large Intestine Anus Saliva Amylase Mucus Gastric Juice HCl Pepsin Bile (Liver) Pancreatic Juice Lipase Protease (Trypsin) Amylase Lipase Protease Amylase Prepared by William Green DBGS 2010