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Unformatted text preview: Lecture 007 Enzymes: A Summary The spontaneity of a reaction is determined by G, in which if G < 0, a reaction is designated as non-spontaneous (requiring energy to proceed), and is also known as an endergonic reaction. If G > 0, a reaction is designated as spontaneous (doesnt require energy to proceed, however doesnt necessarily mean reaction will proceed rapidly), which is also known as an exergonic reaction. Enzymes act as biological catalysts, in that they make reactions go faster, however they cannot cause endergonic reactions to become spontaneous. Enzymes work by reducing the activation energy of a reaction. In a reaction, the activation energy is the energy required to start the reaction. This in effect acts very much like a barrier. The enzyme reduces the energy requirement to get to the transition state. Enzymes, being proteins, are given much of their function through tertiary and quaternary structure. Therefore the sequence and selection of amino acids in the protein does not dictate the function of the enzyme. The site of catalysis (where enzyme catalyzes reaction) is known as the active site. The site is a small, 3D cleft, functions on the idea of an induced fit, in that the substrate approaches the active site, and upon close proximity, the enzyme will fold to encompass the shape of the substrate. Enzymes work in the various ways to lower the activation energy 1. A conformational strain: by bringing the reacting molecules so close together, a collision is certain to occur. 2. Precise orientation of the substrates: the substrates bind at the active site of the enzyme so they collide at the correct site and at the correct angles....
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This note was uploaded on 04/04/2009 for the course BIOLOGY 1222 taught by Professor Haffie during the Spring '09 term at UWO.
- Spring '09