Enzymes PDF

ENZYMES  Learning Outcomes Define enzymes Describe the characteristics of enzymes. Explain the mode of action of enzymes Explain enzyme action in terms of the ‘lock and key’ hypothesis Explain why enzyme is specific to its substrate using the “lock and key” hypothesis....

ENZYMES  Learning Outcomes Define enzymes Describe the characteristics of enzymes. Explain the mode of action of enzymes Explain enzyme action in terms of the ‘lock and key’ hypothesis Explain why enzyme is specific to its substrate using the “lock and key” hypothesis. Describe and explain the effects of temperature, pH, and substrate concentration and pH on the rate of enzyme-catalysed reactions. Explain “optimum temperature” and “optimum pH". Outline the commercial applications of enzymes. State the differences between anabolic and catabolic enzyme-catalysed reactions.* Outline how enzyme inhibitors work.* *Only for IP Enzymes are interesting! Bromelain is a mixture of enzymes found in pineapples (Ananas comosus) that digest protein. The truth is, pineapple hurts to eat because bromelain is digesting the tender skin inside of your mouth. The pineapple is eating you? https://melscience.com/US- en/articles/pineapples-can-eat-you-too/ ENZYMES Enzymes are proteins which speed up biochemical reactions that remain unchanged at the end of the reactions. Enzyme; Active Site; Substrate; Enzyme-substrate complex; product product Active site Characteristics of Enzymes Affected by temperature and pH Being proteins, they are sensitive to temperature and pH changes. They work efficiently within an optimal temperature and pH range. High temperatures and extreme pH values denature and inactivate the enzymes. Characteristics of Enzymes Needed only in small amounts, and not affected by the reactions they catalyse They are not used up in a reaction. The same enzyme molecule can process a large number of substrate molecules. Characteristics of Enzymes Highly specific They have specific sites called active sites which bind to specific substrates. substrate is ‘key’ enzyme is ‘lock’ http://g11-biob2-2011-12.wikispaces.com/file/view/lockandkey.gif/262021472/lockandkey.gif ‘lock-and-key’ hypothesis Factors affecting enzyme activity Temperature The optimum temperature is the temperature at which the enzyme catalyses a reaction at the maximum rate. Most enzymes in humans have an optimum temperature of about 37°C. optimal temperature rate of reaction temperature/°C Factors affecting enzyme activity pH The activity of enzymes is affected by the acidity or alkalinity of the solutions in which they act. A slight change in pH can affect the rate of enzyme-catalysed reactions as each enzyme functions optimally at a particular pH. At unsuitable pH values, ionic bonds within the enzyme can be disrupted and this changes the active site. Factors affecting enzyme activity pH Factors affecting enzyme activity Substrate concentration The rate of an enzyme-catalysed reaction increases in direct proportion to the substrate concentration until a maximum value. The rate then remains constant as the enzyme molecules are saturated, i.e., the substrate molecules have occupied all the active sites of the enzyme molecules. Factors affecting enzyme activity Substrate concentration Success Biology SPM Gan Wan Yeat Oxford Fajar Sdn.Bhd. 2010 Some commercial applications of enzymes Meat tenderiser (protease) Ice cream (lactase) Cereals (cellulase) Agar: from seaweed (cellulase) Use of the enzyme lactase in making of ice-cream Lactose crystallises and makes ice cream gritty. Converting it to glucose and galactose makes ice cream smoother. Some commercial applications of enzymes ▪ Removes starch from fabrics (amylase) ▪ Stain removers in detergents (protease, amylase) For IP/SBGE Anabolic Reactions These are chemical reactions in which simpler substances are combined to form more complex molecules. Anabolic reactions usually require energy. Biology Study Guide for HKDSEE Din-yan Yip Pauline Yip Times Publishing (HK)Ltd 2010 Catabolic Reactions These are chemical reactions that result in the breakdown of more complex organic molecules into simpler substances. Energy is usually released. Biology Study Guide for HKDSEE Din-yan Yip Pauline Yip Times Publishing (HK)Ltd 2010 Enzyme inhibitors Enzyme inhibitors interfere with enzyme catalysed reactions. Examples of these inhibitors are cyanide, cadmium, mercury, lead, arsenic, and carbon monoxide. http://www.youtube.com/watc h?v=PILzvT3spCQ http://karimedalla.wordpress.com