Discuss lock-and-key theory of enzyme-substrate interaction giving Essay

Discuss lock-and-key theory of enzyme-substrate interaction giving specific example to illustrate theory. Include the effects of substrate concentration, pH cha - Essay Example Enzymes have active sites which interact with the substrate. The structure of the active site is unique for that respective substrate. Just as a uniquely shaped key will only fit in to and open a matching lock, so it is with enzymes and their substrates. The wrong key may fit in to the lock, but nothing can happen because the match of shapes is not correct. This fit is so specific that the change in a single hydrogen atom in a molecule makes it lose its specificity to a particular enzyme. This means that it may not bind to the specific site and even if it does, the enzyme will be unable to do anything chemically to it. The substrate always fits into the enzymes active site and the active site is always a fold or groove in the enzyme. Enzymes are always larger than the substrate and they are flexible so that they can move and fold around the substrate (Refer to Figure.1). This is facilitated by the weak bonds that hold the enzyme in its functional shape. The union between an enzyme an d its substrate is called the enzyme -substrate complex. When a substrate is bound to the active site, particular chemical bonds of the substrate are weakened and the substrate bends. This lowers the activation energy to the point where the heat in the environment is sufficient to supply the activation energy to initiate the reaction (Chapter 7, Metabolism and Biochemistry). If the amount of the enzyme is kept constant and the substrate concentration is then gradually increased, the reaction velocity will increase until it reaches a maximum. After this point, increases in substrate concentration will not increase the velocity. This means that when this maximum velocity had been reached, all of the available enzyme has been converted to the enzyme-substrate complex (Refer to Figure.3). Michaelis developed a set of mathematical expressions to