Presentation on theme: "Revision for Mid year Examination"— Presentation transcript:
1 Revision for Mid year Examination 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?CarbohydrateFatsProtein
4 Biological Molecules (Nutrients) What are the function of these nutrients?
5 Biological Molecules (Nutrients) How do we test for the nutrients?Food TestBenedict’s TestStarch TestEmulsion TestBiuret’s Test
6 Enzymes 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.
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 optimum pH.At extreme changes 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 site less frequently little enzyme action
11 EnzymesAs 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.
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 EnzymesEnzymes 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 duodenumbile emulsifies fats by breaking up fat droplets into smaller dropletsthis 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 liverThe pancreas:pancreas secretes pancreatic juice into the duodenumpancreatic juice contains amylase, trysin and lipase for digestionpancreatic amylase will digest starch to maltosetrypsin digests proteins to polypeptidespancreatic lipase digests fats into fatty acids and glycerol
18 Nutrition in Man the liver the liver produces bile which aids in the digestion of fatsbile helps to emulsify the fats by breaking it up into smaller fat dropletsthis 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 acidsexcess 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 removedthe remains of the amino acid is converted to glucose and excess glucose is converted to glycogen
21 Nutrition in Mannormal amounts of glucose and amino acids will leave the liver via the hepatic veinthe glucose is used for respiration to produce energythe amino acids is used for growth, repair of worn out tissues and synthesis of protoplasm
22 Nutrition in ManDescribe what happens to fats as they pass through the following regions of the alimentary canal:the mouth cavitythe duodenumthe rest of the small intestineno 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 duodenumbile emulsifies fats by breaking it up into smaller fat dropletsthis 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 villivilli are minute finger-like projections of the walls of the small intestine in the lacteal, fatty acids and glycerol recombines to form fatsfats 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 villivilli 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 substancesVilli is richly supplied with blood capillaries and lactealsGlucose 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 quicklythis maintains the concentration gradient for diffusion to occurwall of the villi is also only one-cell thickthis provides a short diffusion distance for diffusion to occur faster