1. BIOLOGICAL CATALYSTS

2. FIND THE LINK… What do these images of a feeding flesh fly a flashing firefly! biological washing powder a jar of baby food have in common?

3. …… ENZYMES ! A.Biological washing powders contain hydrolytic enzymes to digest stains and clean our clothes. B. A flesh fly vomits digestive juices, enzymes, and saliva on a decaying caterpillar carcass which begins to break down and dissolve it. The fly can then suck up the liquid food with its mouth parts. C. Light is created when oxygen combines with a substance called luciferin in the presence of the enzyme luciferase. The rhythm and intensity of the flashes serve to identify males and females to each other. D. Enzymes are used to ‘pre-digest’ some of the larger food molecules in baby food making it easier for a baby’s digestive system to function.

4. PROPERTIES OF ENZYMES enzymes are biological catalysts controlling the chemical reactions that take place in all our body cells they speed up reactions but do not get used up themselves they are protein molecules made up of long chains of amino acids they are folded to produce a special shape vital for their function

5. How do enzymes work? The molecules that react in the enzyme-catalysed reaction are substrates Molecules produced in the reaction are products The active site is the part of the enzyme where the substrate fits and product forms Just like a key only fits into a specific lock, each enzyme has its own specific substrate. Once the reaction is complete and the required product has been produced, the enzyme is free to bind with more molecules of substrate. Each enzyme can be used many thousands of times.

6. Lock and Key Hypothesis

7. Induced Fit Hypothesis (this is extension work) This is similar to the ‘lock and key’ but it is thought that the enzyme changes shape slightly as substrate binds i.e. hand fitting into a glove

8. Factors affecting enzyme action Temperature pH Enzyme concentration Substrate concentration

9. Factors affecting enzyme action Temperature is important in all reactions. As the temperature increases, so does the rate of reaction. This is because heat energy causes more collisions between the particles in the enzyme and particles in the substrate. Very high temperatures damage or denature enzymes.denature Different enzymes work best at different pH values. The optimum pH for an enzyme depends on its site of action. For example, enzymes in the stomach have an optimum pH of about 2 because the stomach is acid, but intestinal enzymes have an optimum pH of about 7.5. Enzyme concentration. The more enzyme molecules, the more active sites for substrate molecules to react and make more products Substrate concentration. The more substrate molecules to react, the more product can be made

10. MEASUREMENT OF CARBON DIOXIDE 1.What is the purpose of the potassium hydroxide solution? 2.What does the indicator solution in flask B show? 3.How can you explain the change in flask D? 4.Suggest a suitable control investigation and explain your choice. 5.Suggest any visible change that might happen in flask C. Explain your answer.

12. Human Digestive System Can you name parts A-K? A B C D E F G H I J K

13. oesophagus Human Digestive System Now Annotate each label

14. Parts of the Digestive System A Mouth B Liver C Gall Bladder D Large intestine E Appendix F Anus G Rectum H Small intestine I Pancreas J Stomach K Oesophagus

15. Function of parts of the Digestive System A Mouth -food is ingested and mixed with saliva B Liver-produces bile which neutralises food, emulsifies fat C Gall Bladder-stores bile D Large intestine-reabsorbs water E Appendix-no known function in humans Other animals? F Anus –exit for undigested food (faeces) G Rectum –stores undigested food (faeces) H Small intestine - in the first part semi-liquid food is mixed with pancreatic juice & bile - in the second part digested food is mixed with intestinal juice & absorbed into the blood I Pancreas – produces pancreatic juice (containing enzymes, mucus & hydrogen carbonate ions) J Stomach – food mixed with acidic digestive juices K Oesophagus – carries food from mouth to stomach Using which method?

16. Types of enzyme 1.Enzymes can either be extracellular or intracellular 2.Digestive enzymes are extracellular enzymes - they control reactions that take place outside cells. 3.Those enzymes which control reactions inside cells are called (not surprisingly!) intracellular enzymes e.g. enzymes in respiration and photosynthesis

17. MODEL GUT EXPERIMENT 1.What is the test for Starch and Glucose? 2.What part does the visking tubing play? 3.Can you predict the results of this experiment? 4.Justify your prediction.

18. ROLE OF DIGESTIVE ENZYMES Copy and complete the table ENZYMEPRODUCTION SITE SUBSTRATE PRODUCT/S AND WHERE DIGESTION TAKES PLACE CONDITIONS AMYLASE (a carbohydrase) PROTEASE LIPASE

19. ROLE OF DIGESTIVE ENZYMES ENZYMEPRODUCTION SITE SUBSTRATE PRODUCT/S AND WHERE DIGESTION TAKES PLACE CONDITIONS AMYLASE (a carbohydrase) Salivary Glands Pancreas Small Intestine STARCHSUGARS in mouth &small intestines ALKALINE # no digestion takes place in the pancreas # PROTEASEStomach Small Intestine PROTEIN AMINO ACIDS in stomach & small intestines Stomach produces Hydrochloric ACID LIPASEPancreas Small Intestine LIPIDS (FATS & OILS) Fatty acids Glycerol in small intestines Bile produced (by liver) neutralises stomach acid to ALKALINE conditions in small intestines

20. MAKING USE OF ENZYMES IN THE HOME & INDUSTRY ENZYME Example WHAT DOES THE ENZYME DO? Protease Lipase Carbohydrase Isomerase

21. MAKING USE OF ENZYMES IN THE HOME & INDUSTRY ENZYME Example WHAT DOES THE ENZYME DO? Protease Used to pre-digest proteins during the manufacture of baby foods Lipase Used (together with protease) in biological detergents to digest the food stains into smaller, water soluble substances Carbohydrase Used to convert starch syrup, which is relatively cheap, into sugar syrup, which is more valuable - for example as an ingredient in sports drinks Isomerase Used to convert glucose syrup into fructose syrup (fructose is sweeter than glucose so it can be used in smaller amounts in slimming foods)