Enzymes I - LAB EXERCISE#6 Laboratory Safety Precautions Guaiacol is potentially toxic it may be irritating to skin eyes and mucous membranes

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1 LAB EXERCISE #6 Laboratory Safety Precautions : Guaiacol is potentially toxic; it may be irritating to skin, eyes, and mucous membranes. Hydroxylamine may be irritating to skin and eyes. Goggles must be worn for this lab. BACKGROUND ON ENZYMES Enzymes are: non-structural proteins operate in all living cells can be excreted from cells catalyze biochemical reactions are very specific catalysts can be extracted from tissues, purified and used for experiments and life as we know it could not existed if enzymes had not evolved Basic catalytic cycle 1. Every biological reaction is catalyzed by an enzyme. Some enzymes have much more complex cycles, needing cofactors and coenzymes. 2. Every step of every pathway is catalyzed by an enzyme which makes metabolism work: E + S ←→ ES E + P 3. The mechanism above is the simplest one possible for a one-substrate enzyme. First, the enzyme (E) must find the substrate (S) in solution and bind to it, forming the ES complex in which the substrate is bound at the active site (remember that substrates are specific for an enzyme's active site). The ES complex then converts the substrate to product and releases it. Real enzymes are more complicated and almost never proceed through just one enzyme-substrate-enzyme-product complex. There are often many steps involved. Look up "Glycolysis" in the Raven textbook. Although there may be many steps involved, the slowest step will determine the rate of the overall reaction . 4. All enzymes are affected by: pH, temperature, concentration of salts, and inhibitors, which change the shape of the active site. All enzymes have an active site where the substrate molecule fits and is changed. Active site has a very specific shape. Active site is very sensitive to changes in the cell environment. If the active site is altered in any way, then the rate of the reaction is changed. 5. All enzymes are affected by enzyme concentration, substrate concentration, and cofactor concentration, which affect the formation of the ES complex. 6. All these variables affect the rate of the catalytic cycle and so the rate of product formation. ACTIVATION ENERGY Enzyme kinetics is simply a specialized branch of chemical kinetics. As such, it is based on the kinetic theory of matter. In this theory, a solution is viewed as being made up of a group of molecules all moving at particular velocities . As they move about, they collide with each other, and each such collision involves a certain amount of energy. If the energy is sufficient, the molecule combines to form an activated intermediate sometimes referred to as the transition state . The energy that is required for the formation of this intermediate is the activation energy . If the collision does not involve sufficient energy no reaction occurs, i.e. the molecules just bounce off one another.
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2 Imagine drawing a line vertically from substrate (A) to the peak of the transition state in the above graph. This is
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This note was uploaded on 04/07/2008 for the course BIOSCI 0050 taught by Professor Carollafarve during the Fall '07 term at Pittsburgh.

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Enzymes I - LAB EXERCISE#6 Laboratory Safety Precautions Guaiacol is potentially toxic it may be irritating to skin eyes and mucous membranes

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