Energy and Chemical Reactions Energy can be stored or released in chemical reactions. In a chemical reaction bonds in molecules are broken between atoms and new ones are formed. In this process one or more substances are produced. Thousands of chemical reactions are occurring in your cells every second. When energy (heat) is added to a raw egg atoms and molecules and atoms are rearranged in egg. You notice that clear part of the egg becomes white.

Energy and Chemical Reactions Energy - Capacity of doing work; the ability to change or to move matter. Activation Energy - the amount of energy required to start a chemical reaction.

Energy and Chemical Reactions BIO BIT The production of light in bioluminescent organisms results from the conversion of chemical energy to light energy. Bioluminescence is found among some insects, mollusks, fish, ctenophores (comb jellies) and annelid worms. Some of the most dramatic light-producing creatures are found in marine environments.  Bioluminescence should not be confused with fluorescence, in which light from an outside source is stored and re-emitted.

Energy and Chemical Reactions A potential energy diagram displayed here presents relative potential energies ("internal" energies) of the chemicals believed to take part in the overall chemical reaction. When molecules have enough energy to collide effectively chemist say they form an Activated complex. The activated complex is placed at the top of the activation energy "hill".

Energy and Chemical Reactions Since reactions can be either exothermic or endothermic we have two general forms of this diagram. (a) In an exothermic reaction energy is given off: heat/ light. Reactants have more energy then products (b) In an endothermic reaction energy is absorbed: Icepacks. Products have more energy then Reactants.

Energy and Chemical Reactions Enzymes - substance that speeds up a chemical reaction. Active Sites – site on an enzyme that attaches to a substrate.

Energy and Chemical Reactions The activation energy is the extra energy needed to help the reactants to form into the products. We represent this activation energy as a hill between the reactants and products. The size of the hill is determined by the nature of the reactants involved. The presence of enzyme lowers the hill and allows for reactants to be turned into products easier than without the enzyme.

Energy and Chemical Reactions Another Way of Looking at an Enzyme Catalyzed Reaction The picture is an analogous way of thinking of how enzymes work. The enzyme lowers the EA barrier so the reactants can become products easier.

Energy and Chemical Reactions A glucose molecule approaches an enzyme and enters its active site. The conformation (shape) of the enzyme changes slightly so that no other substance can enter the active site while the enzyme is working on the glucose. In this example the substrate is broken down into two products. Observe how the shape of the active site is almost a perfect for the substrate that the enzyme acts on. Biochemists refer to this as specificity. For every substrate(s) there is one enzyme.

Energy and Chemical Reactions In an enzyme catalyzed reactions the substrate attaches to the enzyme at its active site. In the active site the substrate and the enzyme interact to form a complex that reduces the activation energy needed for the reaction to occur, making it more likely for a reaction to proceed. The enzyme, upon completion of the reaction releases the new product(s) from its active site. The freed up enzyme is now capable of repeating the process on a new substrate(s).

Energy and Chemical Reactions Enzyme Animations http://www.ccnmtl.columbia.edu/projects/biology/lecture7/lec7_01.htm (Two reactants, one product) http://www.stolaf.edu/people/giannini/flashanimat/enzymes/enzyme.swf (Change in Conformation) http://www.stolaf.edu/people/giannini/flashanimat/enzymes/transition%20state.swf (Energy Diagram) http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/activa2.swf (Activation Energy) http://www.stolaf.edu/people/giannini/flashanimat/enzymes/prox-orien.swf (Orientation and Collisions) http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/collis11.swf http://www.stolaf.edu/people/giannini/flashanimat/enzymes/chemical%20interaction.swf (In active site) http://www.stolaf.edu/people/giannini/flashanimat/enzymes/biochem.path.swf (Pathway) http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter8/animations.html# http://www.stolaf.edu/people/giannini/flashanimat/enzymes/allosteric.swf (Allosteric Enzyme) http://programs.northlandcollege.edu/biology/Biology1111/animations/enzyme.html

Energy and Chemical Reactions Example of Enzyme Activity Digestion

Energy and Chemical Reactions BIO BIT Why do some laundry detergents contain enzymes? Enzymes breakdown carbohydrates and proteins in common foods and blood - making the stains easier to remove. The enzymes are purified form mutant bacteria that can tolerate the high temperatures and alkaline conditions required for cleaning fabrics.

Energy and Chemical Reactions Two Models for Explaining how Enzymes Work on Their Substrate Lock – and – Key Model The specific action of an enzyme with a single substrate can be explained using a Lock and Key analogy. In this analogy, the lock is the enzyme and the key is the substrate. Only the correctly sized key (substrate) fits into the key hole (active site) of the lock (enzyme). Induced – Fit Model The induced-fit theory assumes that the substrate plays a role in determining the final shape of the enzyme and that the enzyme is partially flexible. This explains why certain compounds can bind to the enzyme but do not react because the enzyme has been distorted too much. Only the proper substrate is capable of inducing the proper alignment of the active site.

Energy and Chemical Reactions Lock and Key Theory:

Energy and Chemical Reactions Induced Fit Theory:

Energy and Chemical Reactions Directions: Identify; the enzyme, the substrate, the reactants, and the products. Enzyme: Substrate(s): Reactants: Products: Enzyme: Substrate(s): Reactants: Products:

Energy and Chemical Reactions Directions: Identify; the enzyme, the substrate, the reactants, and the products. Enzyme: Carbonic anhydrase Substrate(s): CO2 and H2O Reactants: CO2 and H2O Products: H+ and HCO3- Enzyme: Catalase (peroxidase) Substrate(s): H2O2 Reactants: H2O2 Products: O2 and H2O

Energy and Chemical Reactions Directions: Identify; the enzyme, the substrate, the reactants, and the products. Enzyme: Substrate(s): Reactants: Products:

Energy and Chemical Reactions Directions: Identify; the enzyme, the substrate, the reactants, and the products. Enzyme: Amylase Substrate(s): Amylose + (water) Reactants: Amylose + Water Products: Maltose

Energy and Chemical Reactions A change in pH can also affect enzyme activity. Each enzyme has an optimal pH range that helps maintain its normal configuration in an environment which it operates. A change in pH can alter the tertiary or quaternary structure of a protein. A denatured protein can not combine with a substrate.

Energy and Chemical Reactions A higher temperature generally results in an increase in enzyme activity. If the temperature rises beyond a certain point, however, the enzyme activity eventually levels out and then declines rapidly because the enzyme is denatured by heat. The enzyme shape changes during denaturation and can not catalyze the reaction.

Energy and Chemical Reactions IEC Classification of Enzymes  Group Name  Type of Reaction Catalyzed  Oxidases or Dehydrogenases  Oxidation-reduction reactions  Transferases Transfer of functional groups  Hydrolases Hydrolysis reactions  Lyases Addition to double bonds or its reverse  Isomerases Isomerization reactions  Ligases or Synthetases Formation of bonds with ATP cleavage Honors

Energy and Chemical Reactions Enzyme Regulation Competitive Inhibition -The inhibitor chemical and substrate both bind to the active site. Binding of the inhibitor prevents substrate binding. Honors

Energy and Chemical Reactions Enzyme Regulation Allosteric regulation is the regulation of an enzyme binding an effector molecule at the enzyme's allosteric site (that is, a site other than the enzyme's active site). Honors

Energy and Chemical Reactions Enzyme Regulation As the final product in a chemical pathway increases in concentration it will inhibit the first enzyme in the chemical pathway. Honors

Energy and Chemical Reactions Enzyme Regulation Effectors that enhance the protein's activity are referred to as allosteric activators. Honors

Energy and Chemical Reactions Enzyme Regulation Effectors that decrease the protein's activation are called allosteric inhibitors. Honors

Energy and Chemical Reactions Enzyme Regulation Noncompetitive Inhibition - Inhibitor and substrate bind to different sites. Binding distorts the enzyme and decreases the likelihood of substrate binding. Honors

Energy and Chemical Reactions Michaelis-Menten equation describes the kinetics (rate) of many enzymes. The speed V means the number of reactions per second that are catalyzed by an enzyme. Honors

Energy and Chemical Reactions To determine the maximum rate of an enzyme mediated reaction, the substrate concentration ([S]) is increased until a constant rate of product formation is achieved. Honors

Energy and Chemical Reactions Enzyme to Substrate Ratio If there is a high concentration of Enzyme and low concentration of Substrate the reaction will proceed at a fast rate. If there is a low concentration of Enzyme and high concentration of Substrate the reaction will proceed at a slow rate.