ENZYMES

1. ENZYMES Lab 6

2. Objetives 1.- Be able to define the following terms in writing: a) catalyst e) enzyme specificity b) substrate f) enzyme-substrate complex c) end product g) inhibitor d) enzyme. • 2- Be able to describe enzyme specificity in terms of the lock and key theory. • 3- Be able to describe how temperature and pH change enzyme activity. (optional topics: concentration of the enzyme, concentration of the substrate, and inhibitors change enzyme activity).

3. Every living organism carries out a large number of chemical reactions. • It is essential for the life of the organism that these reactions occur at an extremely rapid rate and at a safe temperature. • All organisms utilize enzymes to speed up the rate of chemical reactions without increasing the temperature.

4. Enzymes do not start a reaction; they merely speed up the reaction that is already under way by reducing the need for large amounts of activation energy. Without this increased rate of reaction, life as it occurs on this earth would not be possible. Each reaction in a cell requires a specific enzyme to allow the reaction to proceed at the proper rate.

5. Since there are hundreds of different reactions necessary in the life of the cell, hundreds of different enzymes are present in the cell. In order for an enzyme to work in a reaction, it must fit with a substrate. Each type of enzyme has a specific physical shape that fits the physical shape of its substrate.

6. Enzymes are proteins, and the sequence of their amino acids is determined by the genetic code of DNA molecules. Most enzymes are specific in the type of chemical reactions that they control. When an enzyme substrate complex (see diagram exp 6 page 2). • The substrate is changed into the new end product, but the enzyme is not changed by the reaction. The shape of an enzyme is determined by the kind and sequence of amino acids that compose it. • Weak hydrogen bonds, which form between aminoacids of the chain, are responsible for the three-dimensional shape of the enzyme.

7. Catalytic cycle of an enzyme

8. Since these bonds are easily broken, the shape of the enzyme may be changed by changes in temperature and pH. Such changes inactivate the enzyme. Most enzymes function best in narrow temperature and pH ranges. The number of times that one molecule of enzyme can react with a substrate in a period of time is known as the turnover number

9. If a molecule has a shape that is almost the same as that of the normal substrate, this different molecule might combine with the enzyme. Such a molecule, because of its shape, will become stuck to the enzyme. • When the enzyme is attached to this molecule, the enzyme is not free to combine with the normal substrate molecule. The molecule attached to the enzyme is called an inhibitor. An inhibitor slows down the normal turnover number of an enzyme

10. Large molecules of fats, proteins, and carbohydrates must be broken down into smaller molecules to be used by a cell in cellular respiration or as building components for other molecules. • The degradation of large molecules into smaller molecules by the addition of water and the catalytic action of enzymes is called digestion. Thus, large molecules are digested into smaller molecules by enzymatic hydrolysis.

11. In this experiment, you will assess the effect of temperature and pH on the action of amylase. This enzyme accelerates the hydrolysis of starch, a polysaccharide, to maltose, a disaccharide and reducing sugar.