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Revision for Mid year Examination.  1)Biological Molecules (Nutrients) 2)Enzymes 3)Nutrition in Man 4)Nutrition in Plants Topics.

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Presentation on theme: "Revision for Mid year Examination.  1)Biological Molecules (Nutrients) 2)Enzymes 3)Nutrition in Man 4)Nutrition in Plants Topics."— Presentation transcript:

1 Revision for Mid year Examination

2  1)Biological Molecules (Nutrients) 2)Enzymes 3)Nutrition in Man 4)Nutrition in Plants Topics

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

4   What are the function of these nutrients? Biological Molecules (Nutrients)

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

6  What are enzymes? Enzymes are biological catalysts that speed up the rate of reaction without themselves being chemically changed at the end of the reaction. Enzymes

7  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. Enzymes

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

9  Describe the effects of pH on enzyme action.  Enzymes work best at their optimum pH.  At extreme changes in pH, enzymes are denatured. Enzymes

10  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 site less frequently  little enzyme action Enzymes

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

12   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. Enzymes

13  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. Enzymes

14  -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. Enzymes

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

16  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 Nutrition in Man

17   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, trysin and lipase for digestion  pancreatic amylase will digest starch to maltose  trypsin digests proteins to polypeptides  pancreatic lipase digests fats into fatty acids and glycerol Nutrition in Man

18  (ii)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 Nutrition in Man

19   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 Nutrition in Man

20   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 Nutrition in Man

21   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 Nutrition in Man

22  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 Nutrition in Man

23  (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 Nutrition in Man

24  (ii)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 intestine in the lacteal, fatty acids and glycerol recombines to form fats  fats will then be carried away by the lymphatic vessels Nutrition in Man

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


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