(d)+Denaturing

1. Define denaturation & explain its effect on proteins (including enzymes, which are proteins)

A protein consists of one or more chains of amino acids that fold into shapes held in place by chemical bonds. The bonds licking the amino acids are strong, covalent bonds. However, most of the bonds that maintain the 3-D shape of proteins are weak bonds that can be broken easily by chemicals or heat. When proteins get heated, they will vibrate violently and their weakest bonds will break, causing strings of amino acids to unravel. This process is called "denaturation" When these bonds break, the protein starts to unfold and loses some its properties. For example, denatured proteins usually becomes less soluble, which means it doen't dissolve in water as well.

Some effects that cause denaturation of proteins are Sometimes, high temperatures or extreme pH values affect the shape of an enzyme molecule and this process is called "denaturing". This will make enzyme less effective or even useless. media type="file" key="enzyme denaturation3.swf" align="center" width="360" height="270"
 * Heat (temperature)
 * pH
 * Exposed to UV light

Please right click and then click 'play' and 'loop' if the animation stops More information on Protein Denaturation in this link []

Enzymes are sensitive molecules. They often have a narrow range of conditions under which they operate properly.

- Enzyme concentration:



The rate of reaction is directly related to the enzyme concentration, they are linear; when the enzyme concentration increases then the rate of reaction increases.

- Substrate concentration: At lower substrate concentrations, the reaction rate is strictly proportional to the substrate concentration; but, once the substrate molecule concentrations increase beyond a certain level, there are no more binding sites available for them. This is called saturation, when enzymes catalyze as fast as they can, and reaction rates reaches its maximum potential. Without substrate, enzymes cannot function, and without the appropriate amount of substrate, the velocity of the reactions would take place very slowly.



- Temperature: Higher temperatures speed up all reactions, but few enzymes can tolerate temperatures higher than 50-60ºC. The rate at which enzymes are denatured increases with higher temperatures. For most of the enzymes associated with plant and animal metabolism, there is little activity at low temperature. As the temperature increases, so too does the enzyme activity, until the point is reached where the temperature is high enough to damage the enzyme’s structure



- pH (acidity / alkalinity) Like all proteins, enzymes are denatured by extremes of pH. Within these extremes, most enzymes are still influenced by pH. Each enzyme has a preferred pH range for optimum activity. Examples: Pepsin- stomach enzyme, Urease- catalyzes the hydrolysis of urea Optimum pH: Pepsin = 1, since it is a stomach enzyme and mostly contains acidic substances. Urease = 6-7, since urea is mostly water and toxic waste