BIOS 2011 Lab 1 Enzymes

Thus there are many different kinds of enzymes needed

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Unformatted text preview: are so specific that they only catalyze one particular reaction using only one substrate (or pair of coupled substrates) and producing only one product (or pair of products). Thus there are many different kinds of enzymes needed to perform all the reactions necessary to maintain life. Many enzymes are named for the particular reaction they perform, including the enzymes in today’s lab: Succinic Dehydrogenase and α Amylase. The reason for enzyme specificity lies in the topology of each enzyme, or its shape. Every enzyme has a different 3D form that determines its function. The active site of the enzyme must have a shape that encourages substrate to bind to that part of the enzyme, which has been compared to key fitting into a lock. In many cases the enzyme responds to the binding of substrate by changing its conformation slightly to better hold onto its substrate, known as induced fit. Charge also plays an important role in enzyme ­substrate binding, as the amino acid residues in the active site also play a role in attracting the substrate. If the charges are not right, the active site would repel the substrate instead of binding to it. Within the active site specific amino acid residues are critical to the activity of the enzyme, performing sub ­reactions that are necessary for the enzyme’s catalytic effect. Many enzymes also require specific cofactors such as metal ions to be active. These cofactors must be present in the enzymes environment in the cell, or in the test tube. The pH environment for an enzyme can have a large effect on the shape and charge of an enzyme and thus affects the enzyme’s activity. Each enzyme has an optimum pH, a range in the pH scale where it performs its reaction with the highest rate. In this pH range the enzyme has the correct shape and its active site has the correct charges for full activity. When the pH is not optimum the shape of the active site has a less good fit for the enzyme, and the charges of the amino acid residues of the active site may also change. This reduces the attraction for the substrate or makes it harder to perform the chemistry needed to catalyze the reaction. So pH 2 Exercise 1 Enzymes ranges above or below optimum cause enzyme activity to drop, eventually going to zero at pHs very far from the optimum. Typically this produces a bell shaped curve on a graph of enzyme activity versus pH. You will explore this in today’s third experiment. Succinic Dehydrogenase and Competitive Inhibition: The number of substrates and products vary from enzyme to enzyme, so...
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