Transcript enzyme
Identifying and investigating the role of enzymes INVESTIGATING ENZYMES ENZYMES Enzymes speed up metabolic reactions by lowering energy barriers Enzymes are substrate specific The active site is an enzyme’s catalytic center A cell’s physical and chemical environment affects enzyme activity ENZYMES A catalyst is a chemical agent that changes the rate of a reaction without being consumed by the reaction An enzyme is a catalytic protein THE ACTIVATION ENERGY BARRIER Enzymes speed up metabolic reactions by lowering energy barriers Initial investment of energy for starting a reaction is known as activation energy Activation energy is energy required to break bonds THE ACTIVATION ENERGY BARRIER An enzyme speeds the reaction by reducing the uphill climb to the transition state ENZYMES AND ACTIVATION ENERGY Some chemical reactions that make life possible have activation energies that are too high Catalysts speed up the rate of chemical reactions Catalysts work by lowering a reaction’s activation energy Enzymes are proteins that act as biological catalysts ENZYMES ARE SUBSTRATE SPECIFIC Enzymes have an active site to match up with their substrate ENZYMES ARE SUBSTRATE SPECIFIC Enzyme Substrate(s) ---------> Product(s) For example, Sucrase Sucrose + H2O ---------> Glucose + Fructose ENZYMES ARE SUBSTRATE SPECIFIC An enzyme can distinguish its substrate from even closely related properties Each type of enzyme catalyzes a particular reaction For example, sucrase will act only on sucrose and will reject other disaccharides, such as maltose ENZYMES ARE SUBSTRATE SPECIFIC Active sites are restricted regions of the enzyme molecule that bind to the substrate The active site is typically a pocket or a groove on the surface of the protein ENZYMES ARE SUBSTRATE SPECIFIC Specificity of an enzyme is due to a compatible fit between the shape of its active site and the shape of the substrate The substrate binds to the active site to form an enzyme-substrate complex THE CATALYTIC CYCLE OF AN ENZYME Side chains (R groups) of amino acids make up the active site Side chains catalyze the conversion of substrate to product THE CATALYTIC CYCLE OF AN ENZYME After the conversion from substrate to product, the product departs from the active site After the cycle, the enzyme is then free to take another substrate molecule into its active site Enzymes emerge from the reaction in their original form THE CATALYTIC CYCLE OF AN ENZYME The rate at which a given amount of enzyme converts substrate to product is partly a function of the initial concentration of the substrate The more substrate molecules available, the more frequently they access the active sites of the enzyme molecules http://youtu.be/qhiG6_83pbc DENATURING Denaturing is the process of changing an enzyme’s shape because of high temperatures or extreme pH values Denaturing makes the enzyme less effective of even completely useless EFFECTS OF TEMPERATURE The velocity of enzymatic activity reaction increases with increasing temperature With increasing temperatures, substrates collide with active sites more frequently Beyond that temperature, bonds that stabilize active conformation become disrupted When this occurs, the protein molecule denatures EFFECTS OF TEMPERATURE Each enzyme has an optimal temperature at which its reaction rate is fastest This temperature allows the greatest number of molecular collisions without denaturing the enzyme EFFECTS OF PH The optimal pH values of most enzymes falls in the range of pH 6-8 ENZYME INHIBITORS Inhibitors slow down or stop the activity of an enzyme Inhibitors usually bond to the protein and change the shape of the enzyme, causing it to become ineffective ENZYME INHIBITORS Competitive inhibitors mimic the substrate and competes for the active site Competitive inhibitors reduce the productivity of enzymes by blocking substrates from entering active sites ENZYME INHIBITORS Non-competitive inhibitors do not directly compete with the substrate at the active site Noncompetitive inhibitors slow enzymatic reactions by binding to another part of the enzyme This alters the conformation of the enzyme so that the active site is no longer fully functional ENZYME INHIBITORS SALIVARY AMYLASE Enzyme that catalyzes the hydrolysis of starch into simpler compounds Present in human saliva If salivary amylase were not present, we would not be able to break down complex sugars into simpler compound sugars in our mouths, which would make digestion of sugars difficult PEPSIN (PROTEASE) Pepsin helps breakdown proteins like those in dairy, meat, nuts, and eggs Without pepsin, the body would be unable to breakdown proteins into their peptide amino acid parts LACTASE Found in the small intestine, liver, and kidney Breaks down the milk sugar and lactose into simpler sugars (glucose and galactose) Without lactase, the body is unable to breakdown milk products People without lactase are said to be lactose intolerant CATALASE Found throughout the body, usually in cell organelles called peroxisomes Breaks down hydrogen peroxide into water and oxygen Hydrogen peroxide is a waste product of cells, but is toxic to the body Without catalase, hydrogen peroxide would build up and cause cell and tissue damage http://youtu.be/BjEGUMd-_Gs