Enzymes.docx

[Enzymes] \*\*Need to Know\*\*[\ ]-Enzymes are proteins and biological catalysts that speed up chemical reactions without being used up by the cell. Enzymes are specific, which means they only work on one substrate, producing one set of products.\ -Enzymes are made of long chains of amino acids join...

[Enzymes] \*\*Need to Know\*\*[\ ]-Enzymes are proteins and biological catalysts that speed up chemical reactions without being used up by the cell. Enzymes are specific, which means they only work on one substrate, producing one set of products.\ -Enzymes are made of long chains of amino acids joined together by peptide bonds. The chains of amino acids that form the enzyme are folded into a complex 3D shape.\ - Some enzymes need helper chemicals to attach to them in order to work properly. These helper substances are called co-enzymes. Co-enzymes are organic, non-protein molecules. Some vitamins, such as B1 and B6, act as co-enzymes.\ - Names for enzymes end in 'ase'. [Factors affecting enzyme activity]\*\*Be able to explain both\*\*[\ ]Enzymes are sensitive to their environmental conditions and can be seriously affected by pH and temperature. They are also affected by enzyme concentration, substrate concentration and the presence of inhibitors.\ - pH: Different enzymes work best within certain narrow pH ranges. Most work best at around neutral (amylase, pH 7). Pepsin, which is releases in the stomach to act on proteins, works best at around pH 2. Lipase works in the small intestine digesting fats and acts best at pH 10.\ - Temperature: Enzyme activity increases with temperature, up to around 40^o^C. Above 40^o^C enzymes rapidly denature (change shape) and do not work. The human temperature of 37^o^C is close to the optimum temperature, but it is also close to the temperature at which enzymes start to denature. If your temperature gets too high, enzymes are affected, particularly in the brain. This can cause seizure and fits. Plant enzymes prefer an optimum temperature of around 25^o^C. [Denatured Enzymes] Denatured means that an enzyme has lost its shape and therefore its activity. There are three main causes of enzymes/proteins becoming denatured.\ - Temperature above 40^o^C: At temperatures just above 40^o^C, the enzyme begins to lose its shape and its activity. If the temperature drops back down below 40^o^C, it will resume its shape and activity. Once the temperature rises above 50^o^C, the change becomes irreversible. For example, Albumen, a major constituent of egg whites, starts off as a clear runny jelly, but when denatured it becomes stiff and white.\ - Change in pH: Salivary amylase acts on starch in the mouth and begins the process of breaking it down into fructose. Optimum pH is 7---8 which is what is found in the mouth. Once the food reaches the stomach, the pH suddenly changes to a very acidic pH 1, which denatures the salivary amylase and stops carbohydrate digestion. Food, like beetroot, can be pickled by placing it in an acid medium (vinegar). The pH is around 3 and this denatures the enzymes in bacteria and fungi so they cannot survive. Benzoic acid preserves soft drinks.\ - Agitation: Shaking/beating can denature enzymes. When egg whites are beaten with sugar, the albumen is denatured to form microscopically small strands of solid protein that trap and bind the sugar. This makes it thick and viscous so that it can be shaped. [Active Site Theory] Active site is the place on the enzyme where its substrate fits and where the reaction takes place. The shape is so precise that only one substrate can fit.\ - As the substrate engages with the active site, its shape changes slightly and in many cases the shape of the enzyme also changes a little. The combination of the enzyme and the substrate is called the enzyme-substrate complex.\ - These changes make it easier for the products to form, lowering the activation energy. The products form a substrate-product complex from which the products are ejected. This allows the enzyme to regain its original shape and thus become free to collect a fresh substrate molecule.\ - If the product is more complex than the reactants, it is an anabolic reaction. Making muscle is anabolic.\ - If the products are smaller and less complex than the reactant, it is a catabolic reaction. Digestion is catabolic. A picture containing text, screenshot, font, diagram Description automatically generated(1)