The internal energy of the molecules may include the translational energy, vibrational energy and rotational energy of the molecules, the energy involved in chemical bonding of the molecules as well as the energy involved in nonbonding interactions. Some of this heat may be converted into chemical potential energy. If this chemical potential energy increase is great enough some of the weak bonds that determine the three-dimensional shape of the active proteins may be broken. This could lead to a thermal denaturation of the protein and therefore inactivate the protein. Therefore too much heat can cause the rate of an enzyme-catalysed reaction to decrease because the enzyme or substrate becomes denatured and inactive.
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Diagram 1.1 the temperature optima of three different enzymes are depicted. You should note that the temperature optimum of each enzyme is different. .
The Curve in blue might represent an enzyme isolated from a shrimp that normally lives in the cold waters of Alaska. Thus its enzymes have evolved to work best at lower temperatures.
The curve in red might represent that obtained with porcine chymotrypsin.
Curve in green might represent the temperature optimum obtained with an enzyme isolated from bacteria that normally lives in the hot springs of Yellowstone National Park. Http://www.biology.arizona.edu/biochem/problem/energy-enzymes.09.t.html.
Affect of Substrate Concentration to enzyme activity.
Enzymes react uniquely to change in the concentration of reacting molecules. At very low substrate concentration, collisions between enzyme and substrate molecules are rare and reaction proceeds slowly. As the substrate concentration increases, their reaction rate at first increases proportionately as collisions between enzyme molecules and reactants become more frequent see diagram 1.2. When the enzymes begin to move towards the maximum rate at which they can unite with reactants and release products, the effects of increasing substrate concentration reduce.