Iodine is used to test for the presence of starch and Benedict’s solution is used to test for the presence of reducing sugars.
When solution A is tested with Benedict’s test, the clear blue solution turns slightly reddish and a brick red precipitate is formed. This indicates that solution A is a reducing sugar. Additionally, when performing the iodine test with solution A, the colorless solution remains unchanged, indicating the absence of starch in solution A.
When testing solution B with Benedicts test, it remains clear and blue, indicating it is a non-reducing sugar. However, the iodine test causes the clear solution to turn dark blue, indicating the presence of starch in solution B. These tests confirm that solution B is a starch solution and suitable for further testing.
In the second test, saliva and hydrochloric acid were combined with solution B. The enzyme involved in this test is salivary amylase, also known as ptyalin, which can be found in saliva. Salivary amylase breaks down starch into sugar. This process occurs in the mouth through the action of amylase when we consume food.
Amylase is responsible for the breakdown of starch into a reducing sugar, leading to a positive result in the Benedict’s test. The ideal temperature for amylase activity is equivalent to body temperature. Enzymes act as catalysts for different reactions, providing a more efficient route to decrease activation energy and speed up the reaction.
The binding process between the substrate and enzyme is affected by temperature. When the temperature is low, both the substrate and enzyme have reduced kinetic energy, resulting in a slower binding time and a lower reaction rate. Conversely, at high temperatures, both the substrate and enzyme possess increased kinetic energy which leads to more frequent collisions and faster binding rates.
When the temperature reaches the optimal level, both kinetic energy and collision increase. However, the rate of substrate-enzyme binding decreases because of strong vibrations in the amino acid molecule. If the temperature becomes too high and exceeds the enzyme’s optimum temperature for reaction, thermal energy will cause denaturation of the enzyme. The high temperature disrupts hydrogen bonds that stabilize the enzyme’s tertiary and secondary structure, resulting in loss of shape and inability to bind to substrate’s active site. HCl functions as a catalyst for organic process.
Starch is composed of a lengthy string of sugar molecules connected by glycosidic bonds. Hydrolysis can break these bonds, freeing glucose. To separate the glucose, HCl can be added to the solution, as hydrochloric acid introduces H+ and aids in hydrolysis.
When solution B is treated with HCl, it causes the breakdown of carbohydrates into sugar and generates a positive outcome in the Benedict test, confirming the existence of reducing sugar. However, this hydrolysis process involving HCl can only happen at high temperatures that are suitable for the reaction to take place. When the combination of solution B and HCl is kept at 37°C for incubation, there is no change in the result since the starch molecule has not yet undergone decomposition.
When an equal amount of saliva is mixed with solution B and incubated at 37°C for 5 minutes, it leads to the formation of an opaque green color and a red precipitate in the clear blue solution. This outcome suggests that there exists a small quantity of sugar in the solution. Specifically, the amylase present in saliva breaks down the starch present in solution B into a reducing sugar. Subsequently, when this combination of solution B and saliva is incubated at the same temperature for 35 minutes, it causes the previously clear blue solution to turn opaque green, indicating the presence of sugar.
The outcome demonstrates that a temperature of 37°C is optimal for amylase to break down starch into glucose. After incubating solution B with HCl at 37°C for 5 minutes, the Benedict test yields a negative result. The blue solution remains unaltered, indicating the absence of sugar in the solution. This suggests that HCl does not break down the starch in solution B after 35 minutes of incubation at 37°C; the blue solution also remains unchanged. Consequently, HCl fails to hydrolyze the starch. These findings reveal that the temperature is not suitable for the hydrolysis of starch by HCl.
