Enzymes: Enzyme and Salivary Amylase Solution

Topics: Enzyme, Starch, Amylase Pages: 16 (5032 words) Published: March 9, 2013

Enzymes are mainly proteins that catalyze biological reactions by accelerating the rate at which favorable chemical reactions proceed (Karp, 2008). Without enzymes, metabolic reactions would proceed too slowly to carry out regular metabolism. Each enzyme exhibits a great specificity for a particular reaction, therefore thousands of enzymes are required to mediate metabolism (Karp, 2008). The molecules upon which an enzyme act are called substrates. To accelerate the rate at which a reaction occurs, enzymes become intimately involved in the activities of the substrates by forming an substrate-enzyme complex. The complex eventually breaks down into the unaltered enzyme and the product (Matheson and Richardson, 1976). Essentially, this process can be expressed as follows: Substrate+Enzyme-->Substrate-Enzyme Complex-->Product+Enzyme (Karp, 2008). A number of factors including temperature, pH, enzyme concentration, substrate and product concentration, and activation energy effect the rate at which an enzyme converts the substrate into the product (Matheson and Richardson, 1976). Theoretically, all enzymemediated reactions should be reversible, but the direction of the reaction always depends on the conditions in which the reaction takes place (Karp, 2008). During the experiment, Investigating the Effects of Enzyme Concentration, Substrate Concentration, and Reaction Time on the Direction of Enzyme Reaction, two different enzymes were used to catalyze reactions. These reactions were used to investigate the effects of enzyme concentration, reaction time, and substrate concentration on the direction of enzyme reactions. The first reaction preformed during this experiment was catalyzed by a digestive enzyme secreted by the salivary glands in the mouth known as salivary amylase (Karp, 2008). The substrate for salivary amylase is starch, a polysaccharide composed of amylose and amylopectin (Cohen, 2007). Salivary amylase acts by


catalyzing the breakdown of starch into smaller polysaccharides and a disaccharide formed from two glucose molecules known as maltose (Cohen, 2007). The reaction is a hydrolysis reaction because it requires water to breakdown the substrate (Karp, 2008). Salivary amylase activity is optimal when a buffer is present to maintain a pH of 4.6-5.2 (Harrow and Mazur, 1958), and when a constant temperature of 37°C is maintained (Cohen, 2007). The first test preformed during this experiment was essentially a control test. In other words, each of the samples tested were expected to generate either a positive or negative result to act as a positive or negative treatment control respectively to maximize accuracy by minimizing the unintended influence of other variables in the experiment (Karp, 2008). The iodine test for starch was preformed on each of the following samples: 10% salivary amylase solution, 5% salivary amylase solution, 2% salivary amylase solution, 1% salivary amylase solution, and 1% starch suspension (made up in 0.25% NaCl; the chloride ions specifically activate salivary amylase). The iodine test for starch is a simple test in which a few drops of iodine are added to each sample. Iodine is normally yellow-brown in colour, but turns blue-black in the presence of starch (Lea, C. et al., 2000). This reaction is the result of the formation of polyiodide chains from the reaction of starch and iodine. The amylose, or straight chain portion of starch, forms helices where iodine molecules assemble, forming a dark blue-black color (The University of New Mexico, 2002).Therefore, a positive iodine test is evident in a colour change from yellow-brown to blue-black, and indicates the presence of starch. Conversely, a negative iodine test is evident in a stable yellow-brown colour, and indicates the absence of starch. The second test preformed during...
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