The Effects of Substrate Concentration, Reaction Time and Enzyme Concentration on Enzyme Reactions
Corey von Ellm-St. Croix
Matthew Hrycyshyn & Saeideh Mayanloo
Biol 130L, Section 017
Wednesday, 9:30am-12:20pm, 151
November 09, 2011
A living system controls its activity through enzymes. Enzymes are made from hundreds or even thousands of amino acids connected in a very unique and specific order. Almost all enzymes are proteins, except for ribozymes. The chain of amino acids then folds into a unique shape. That shape not only allows the enzyme to carry out specific chemical reactions but to act as a very efficient catalyst. The enzyme speeds that reaction up tremendously. Each enzyme reacts with one specific reactant called a substrate that will form its products. The purpose of the experiments is to determine the effects of substrate concentration, reaction time and enzyme concentration on the direction of an enzyme reaction. Amylase is a digestive enzyme found in both the saliva and the small intestine. Salivary amylase is a hydrolytic reaction that breaks down starch molecules by systematically breaking off the maltose molecules from the ends of starch chains. The maltose is further broken down by another enzyme. Phosphorylase is an enzyme that systematically removes glucose molecules by consumes phosphoric acid to break the beta-1-4-glucosidic bonds in starch. The interaction of phosphate with the glucosidic bond results in the formation of glucose-1-phosphate and the loss of a chain unit in starch. In the reverse reaction the glucose part of glucose-1-phosphate is added as a new chain unit and phosphate is set free. This reversible enzymatic polymerization occurs with little change in free energy and therefor the reaction may choose to go either way.
Iodine Test is a test for the presence of starch in which the sample turns blue-black in color when a few drops of potassium iodide solution are placed on the sample. A negative iodine test is when the reaction remains yellow in colour. It is the reaction between iodine and the coiled polymer of glucose known as amylase in starch that causes the colour change. The reaction occurs when straight amylase chains form helices in which the iodine can pass inside. Glycogen also receives a colour change because it is a glucose polymer as well but its structure differentiates from starch which therefore forms a brown colour change. The iodine test does not work for mono or disaccharides because they are too small to capture the iodine. The Benedict’s test is used to detect the presence of reducing sugars. Reducing sugars are sugars with a free aldehyde or ketone group. The free reactive carbonyl group allows all monosaccharides to be reducing sugars. The same goes for disaccharides as some also contain the free reactive carbonyl group. The colour of precipitate formed when the Benedict’s test acquires a positive result depends on the concentration of reducing sugars present. A green colour change indicates that few reducing sugars are present. Orange indicates a higher concentration, red an even higher concentration and brown is the highest concentration colour change. A negative test for reducing sugar occurs when the Benedict’s solution remains its blue colour.
Materials and Method
Materials and Method found in 1119 BIOL 130, Department of Biology 2011 Cell Biology Laboratory Manual. University of Waterloo, Waterloo. Fall 2011. pp. 37-42. The procedure of the lab did not differ from that in the lab manual.
Iodine test: Table 1
Test Tube Number
| Results Through Experimentation
| 1 (10% salivary amylase solution)
2 (5% salivary amylase solution)
3 (2% salivary amylase solution)
4 (1% salivary amylase solution)
5 (1% starch suspension)
Table1: The table...
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