Iodine is a test for starch while Benedict’s solution is a test for reducing sugars.
When solution A is tested by benidicts test, the clear blue solution changed to a little reddish and brick red precipitate is formed. this result show that solution A is a reducing sugar. When carried out iodine test with solution A, the colourless solution remain unchanged . this tell us that starch is absent is solution A.
When solution B is tested with Benedicts test, the clear blue solution remain unchanged, we can conclude that it is a non reducing sugar.When tested with iodine test, the colourless solution changed to dark blue colour. this show that starch is present in solution B. From the above test, we can conclude that solution B is a starch solution so we can use it to carry out the next test.
solution B , saliva and hydrochloric acid was used in the second test. The enzyme involed in this test is salivary amylase which can found in saliva. Salivary Amylase, is called ptyalin it’s to break down starch to sugar. Things we ate is broken down in mouth by amylase.
Amylase hydrolysed starch into a reducing sugar which can give beneduct test a positive result.Body temperature is the optimal temperature for the action of amylase. Enzymes are catalysts for any reactions. They provide an alternative way of lower activation energy to speed up the reaction.
When the temperature is low, the kinetic energy of substrate and enzyme is low, this take long time for both of the substance to bind together so the rate of reaction is low. When the temperature is high, the kinetic energy of the substance and enzyme is high too. The substrate and enzyme collide more often with each other. The rate of the both substance to bind is increase too.
When the temperature reach optimal, the kinetic energy and collision increase but the rate of the substrate-enzyme bind to form is decrease because the amino acid in the molecule vibrate strongly. When the temperature is too high and exceed the optimum temperature for the enzyme to react, the thermal energy will cause the enzyme to denature. The high temperature break the hydrogen bond which hold the tertiary and secondary structure of the enzyme, the enzyme lose its shape and the substrate cannot bind to the active site anymore.HCl is to catalyst the organic proses.
Starch is make up with a long chain of sugar molecules by glycosidic bond. The bond can be broken through hydrolysis to release glucose. The simple sugar, glucose can be separated by HCl. Hydrochloric acid add H+ in the solution and thus hydrolysis occur.
When Hcl add to solution B, it hydrolyse carbohydrate to sugar. And it give Benedict test a positive result meaning that redusing sugar is present. But the hydrolysis with hcl can only occur if the temperature is high enough for the reaction to occur.When the miture of solution B and Hcl was incubate at 37C the result remail unchanged because the starch molecule not been broken down yet.
When solution B mixed with same amout of saliva, and incubate at 37c for 5 mins, it change the clear blue solution to opaque green and red precipitate is formed. This result show that a small quantity of sugar is present in the solution. The amylase in saliva hydrolyse starch in solution B to a reducing sugar. After incubate a t the same temperature the same solution of solution b and saliva for 35mins, the clear blue solution change to opaque green which indicate that sugar is present.
This result means that a temp of 37 is suitable for amylase to hydrolyse the starch into glucose. Incubation of solution b plus hcl at 37c for 5mins give a negative result of Benedict test. The blue solution remain unchanged. there is no sugar present in the solution whch mean that hcl does not hydrolye starch in solution b .
after 35 mins of incubation of 37c, the bliue solution remain unchnage too. The starch does not be hydrolysed by hcl. This result show that the temperature is not suitable for hydrolysis between hcl and starch.