Lab 7 Enzyme Activity 1 What are enzymes A Enzymes are proteins 1 Proteins are made from a set of 20 amino acids 2 Each protein has a unique conformation 3 D shape because of the four levels of protein structure a Primary structure the sequence of amino acids like a string of pearls b Secondary structure the primary structure chain coils or folds into regular patterns helix or sheets c Tertiary structure irregular contortions because of bonding between side chains of the amino acids d Quaternary structure two or more contorted chains fit together into one large macromolecule 3 Proteins can denature pH or temperature can loosen up or break apart the protein makes the protein work less efficiently or not at all a Can be reversible if the protein gets back into its favorite environment b May not be reversible think about the white of an egg when it is cooked 4 Proteins are also used for all kinds of functions in a cell besides being an enzyme structural transport hormonal defensive etc B Enzymes are chemical reaction catalysts 1 Catalysts change the rate of a reaction without being consumed by the reaction a A chemical reaction starts with a reactant or reactants and ends up with a product or products 1 Given a set of conditions pH or temperature a reaction may not occur there is not enough activation energy in the environment or in the reactants to kick off the reaction 2 But under other conditions higher temperature for instance that same reaction would happen b Catalysts are reaction helpers 1 Catalysts lower the amount of energy needed for a reaction to proceed the activation energy 2 Activation energy is the energy required to break bonds in the reactant molecules An enzyme lowers the reaction energy giving the reactants the ability to reactant sooner and faster than without the enzyme s help Activation Energy Activation Energy without an enzyme Activation Energy with an enzyme Energy Reaction progress without enzyme Reaction progress with enzyme Progress of reaction 2 How does an enzyme work to change the activation energy of a reaction a The enzyme helps to break or form chemical bonds The method varies from reaction to reaction 1 The enzyme could line up the reactants in the proper orientation 2 The enzyme could put stress on the reactants and start breaking critical bonds in the reactants helping along the reaction 3 The enzyme could participate in the reaction process providing temporary bonds b An enzyme is a large macromolecule that accepts and holds the reactants of a chemical reaction in place until the products are formed Some terms to know Substrate the reactants in a chemical reaction Enzyme a protein that acts as a catalyst for a chemical reaction Active site the location on the enzyme where the substrate attaches It is uniquely shaped to accept the substrate s only Induced fit The enzyme accepts the substrate and in doing so changes its shape slightly to hold the substrate firmly This is called an induced fit the enzyme brings all the players in line and ready for the reaction to begin Here is a picture of the reaction of sucrose breaking apart into fructose and glucose An enzyme sucrase catalyzes this reaction Notice that the sucrase is unchanged at the end of the cycle and is ready to accept another sucrose molecule The reaction we re studying today Amylase Starch S U B S T R A T E Maltose E N Z Y M E P R O D U C T Amylase catalyzes the digestion of starch a polysaccharide into maltose a disachharide Your body uses this enzyme in saliva to predigest starch We will initiate the above reaction under different pH and temperature conditions 1 Your hypothesis 1 of them should predict which specific pH or which specific temperature will produce the most product How does your hypothesis relate to where the enzyme is usually found 2 The amount of product is an indication of how well the enzyme is catalyzing the reaction This would logically correspond to the optimal temperature and pH that least disturbs the conformation of the enzyme during its peak performance IN LAB TODAY WE WILL 1 Perform an experiment to test the effect of pH on amylase activity 1 2 the class a pH 4 5 6 7 8 9 b Using I2KI you will be able to determine when all of the starch has been digested i I2KI turns blue in the presence of starch ii Sample solutions every 10 seconds up to 7 minutes or until complete digestion 2 Perform an experiment to test the effect of temperature on amylase activity 1 2 the class a 4 C 22 C 37 C 80 C b Using I2KI you will be able to determine when all of the starch has been digested i I2KI turns blue in the presence of starch ii Sample solutions every 30 seconds up to 10 minutes or until complete digestion 3 Discuss what needs to be written in the lab report for this experiment