Science (Biology)

1. Science (Biology) Revision for Mid year Examination

2. Topics • Biological Molecules (Nutrients) • Enzymes • Nutrition in Man • Nutrition in Plants

3. Biological Molecules (Nutrients) • What are the components of the nutrients we need? Carbohydrate Fats Protein

4. Biological Molecules (Nutrients) • What are the function of these nutrients?

5. Biological Molecules (Nutrients) • How do we test for the nutrients? Food Test • Benedict’s Test • Starch Test • Emulsion Test • Biuret’s Test

6. Enzymes What are enzymes? Enzymes are biological catalysts that speed up the rate of reactionwithout themselves being chemically changed at the end of the reaction.

7. Enzymes Describe the effects of temperature on enzyme action. • At low temperature, enzymes are inactive. • Thus, little enzyme action. • As temperature increases, enzyme action also increases.

8. Enzymes • Enzymes work best at their optimum temperature • Beyond their optimum temperature, enzymes are denatured. • Thus, enzyme action decreases.

9. Enzymes Describe the effects of pH on enzyme action. • Enzymes work best at their optimumpH. • At extremechanges in pH, enzymes are denatured.

10. Enzymes Explain the effects of temperature on enzyme action. • At low temperature, enzymes have very little kinetic energy and are inactive. • They move slowly and collide less frequently with the substrate molecules. • Substrate molecules bind to enzymes’ active siteless frequentlylittle enzyme action

11. Enzymes • As temperature increases, enzymes gain more kinetic energy and moves around faster. • Thus, enzymes collide with the substrate moleculesmore frequently . • Substrate molecules bind to enzymes’ active sitemore frequently enzyme action increases.

12. Enzymes • Enzymes work best at their optimum temperature. • Beyond their optimum temperature, active sites of the enzymes are physically altered. • Enzymes lose its specificity and can no longer bind the substrate. • Enzymes are denatured enzyme action decreases.

13. Enzymes Describe / Explain how enzymes work. • Enzymes work based on the lock and key hypothesis. • Enzymes are like the lock and substrates are the keys. • Enzymes have active sites which have a specific shape complementary to its substrate.

14. Enzymes • Enzymes and substrate will collide. • Substrate will bind to the enzymes at the active site. • Products are then formed and released from the enzymes’ active site.

15. Enzymes • Enzymes remain chemically unchanged at the end of the reaction. - Enzymes can then be reused.

16. Nutrition in Man Describe / Explain the role of bile in digestion • bile is produced in the liver and secreted into the duodenum • bile emulsifies fats by breaking up fat droplets into smaller droplets • this increases the fats surface area for lipase to digest into fatty acids and glycerol

17. Nutrition in Man • Describe the parts played in the digestion of food by (i) the pancreas (ii) the liver The pancreas: • pancreas secretes pancreatic juice into the duodenum • pancreatic juice contains amylase, trysinand lipase for digestion • pancreatic amylase will digest starch to maltose • trypsin digests proteins to polypeptides • pancreatic lipase digests fats into fatty acids and glycerol

18. Nutrition in Man • the liver • the liver produces bile which aids in the digestion of fats • bile helps to emulsify the fats by breaking it up into smaller fat droplets • this increases the surface area for lipase to digest

19. Nutrition in Man • thus, lipase can digest fats faster • liver plays a part in assimilation of glucose and amino acids • excess glucose is converted into glycogen by the hormone insulin

20. Nutrition in Man • glycogen is stored in the liver • excess amino acids is deaminated whereby the amino group is removed • the remains of the amino acid is converted to glucose and excess glucose is converted to glycogen

21. Nutrition in Man • normal amounts of glucose and amino acids will leave the liver via the hepatic vein • the glucose is used for respiration to produce energy • the amino acids is used for growth, repair of worn out tissues and synthesis of protoplasm

22. Nutrition in Man Describe what happens to fats as they pass through the following regions of the alimentary canal: • the mouth cavity • the duodenum • the rest of the small intestine the mouth cavity no fat digestion occurs in the mouth due to absence of lipase

23. Nutrition in Man (ii) the duodenum • bile produced in the liver is secreted into the duodenum • bile emulsifies fats by breaking it up into smaller fat droplets • this increases the surface area for lipase to digest into fatty acids and glycerol

24. Nutrition in Man • the rest of the small intestine • in the ileum, the fatty acids and glycerol would be absorbed into the lacteals in the villi • villi are minute finger-like projections of the walls of the small intestinein the lacteal, fatty acids and glycerol recombines to form fats • fats will then be carried away by the lymphatic vessels

25. Describe / Explain how the small intestine is adapted to carry out absorption of nutrients The small intestine is adapted for absorption in three ways: • firstly, its inner walls are extensively folded to increase surface area for absorption  secondly, its wall bears numerous villi villi are minute finger-like projections that increases the surface area for absorption  thirdly, the small intestine is long and coiled to provide sufficient time for absorption

26. Describe / Explain how the villi is adapted to carry out its function/s • Main function of villi is absorption of digested food substances • Villi is richly supplied with blood capillaries and lacteals • Glucose and amino acids are absorbed into the blood capillaries

27. fats are absorbed into the lacteal • blood capillaries and lacteals carry away the absorbed food substances quickly • this maintains the concentration gradient for diffusion to occur • wall of the villi is also only one-cell thick • this provides a short diffusion distance for diffusion to occur faster