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Energy and Enzymes Energy in Living Systems Energy is the capacity to perform work Energy can be converted from one form to another 2 Energy in Living Systems KINETIC ENERGY is the energy of motion Includes light Includes heat 3 Energy in Living Systems POTENTIAL ENERGY is the energy stored in a location or structure 4 Energy in Living Systems POTENTIAL ENERGY is the energy stored in a location or structure Molecules have potential energy called CHEMICAL ENERGY 5 Energy in Living Systems Cells convert KINETIC ENERGY to POTENTIAL ENERGY and back. 6 Thermodynamics 1st law: Energy can be changed from one form to another, but cannot be created or destroyed. 7 Thermodynamics 2nd law: Energy transformations increase disorder, or entropy, and some energy is lost as heat 8 Laws of Thermodynamics in Organisms As energy is converted from one form to another, heat is lost Heat Chemical reactions Carbon dioxide Glucose ATP ATP Water Oxygen Energy for cellular work 9 Energy Flow Through Ecosystems Energy flows in one direction through ecosystem 10 Majority of Energy is from the SUN Amount of energy captured by plants influences the ecosystem 11 Energy Capture Energy flow: Sun producers consumers decomposers and Bacteria 12 Energy Flow Through Ecosystems Two ways for organisms to capture energy Producers - produce chemical energy from energy in sunlight 13 Energy Flow Through Ecosystems Two ways for organisms to capture energy Producers - produce chemical energy from energy in sunlight Consumers - consume other organisms for energy 14 Food webs - the reality **Arrows show energy flow, not who eats who 15 Food web creation http://www.gould.edu.au/foodwebs/kids_w eb.htm 16 Energy Pyramid Energy flows through food chain Most energy lost as metabolic heat Each step is a trophic level 17 Concentration of toxins As you go up the energy pyramid, toxins build up in bodies of animals “Bioaccumulation” and “biomagnification” Example: DDT Example: Mercury 18 Energy in Living Systems Metabolismis the sum of all chemical reactions in the body. Characteristic of Living Things Transfers energy and follows the laws of thermodynamics. Chemical Reactions store or release energy 19 Chemical Reactions Reactants interact, leading to products Atoms are rearranged, but the number of atoms stays constant on both sides of the equation H2 + O2 H2O REACTANTS PRODUCT Chemical reactions 2 H2 H H + O2 O O 2 H2O H H O H H REACTANTS? PRODUCTS? H H O 21 Chemical reactions 3 H2 H H + N2 N H N N H H H H 2 NH3 H REACTANTS? PRODUCTS? H H N H H 22 Types of Chemical Reactions Products Potential energy of molecules ENDERGONIC Require an input of energy from the surroundings Yield products rich in potential energy Example: photosynthesis Energy required Amount of energy required Reactants 23 EXERGONIC Release energy Yield products that contain less potential energy than their reactants Examples: cellular respiration, burning Potential energy of molecules Types of Chemical Reactions Reactants Energy released Amount of energy released Products 24 Using Energy from Food Energy transfer in cells must be controlled Reactions are carefully controlled 27 Uncontrolled Reaction Glucose and Oxygen react when exposed to a spark Energy is released all at once CO2 and H2O form 28 Controlled Reaction CO2 e– glucose oxygen H+ e– water Energy input used to split glucose Same overall reaction occurs, but in small steps Energy can be harnessed to do work in cell CO2 and H2O form 29 Enzymes Proteins Perform and control chemical reactions Why are enzymes important? Digestion Building / recycling cells Muscle contraction Everything that happens in your body 30 Enzymes 31 Enzyme Examples Lactase – cleaves lactose sugar DNA Polymerase – joins nucleotide monomers to make DNA polymer Luciferase – generates light in fireflies Amylase – breaks down starch during digestion Protease – breaks down proteins Cellulase – breaks down cellulose (bacterial enzyme found in ruminants) 32 Interesting Enzyme Example A Hope For Oil Spill Bioremediation ScienceDaily (May 17, 2005) — A recently published article in Environmental Microbiology reveals that indigenous microbiota of the Galician shore is readily able to degrade crude oil. What are the consequences of this discovery? 33 Enzymes “Catalysts” speed up a reaction, but aren’t used up Can be used over and over in the cell 34 Enzymes Enzymes are not altered in a reaction and can be used again (catalyst) Lew-Port Enzyme Animation 35 Reactions and Enzymes Some chemical reactions need a “jump start” in order to proceed Energy needed to jump start a reaction is called activation energy 36 Reactions and Enzymes Glucose contains energy in its bonds Energy is released when bonds are broken Small amount of energy must be expended to start reaction 37 Enzymes Work by lowering the activation energy. Reactants the enzyme acts upon are called substrates. H2O2H2O+ O2 substrate products “Gets turned into” Chemical Reaction Catalyzed by enzyme 38 Activation Energy EAwithout enzyme EAwith enzyme Reactants Net change in energy Products Progress of the reaction 41 Where does the energy come from? ATP is a form of chemical energy the cell can use ATP (adenosine triphosphate) powers nearly all forms of cellular work Where does the energy come from? ATP is composed of one adenine, one ribose, and three negatively charged phosphates The energy in an ATP molecule lies in the bonds between its phosphate groups How does ATP work? Adenosine Triphosphate Phosphate group P Adenine P P Adenosine diphosphate H2O P Hydrolysis Ribose ATP ADP P + P + Energy How does ATP work? Adenosine Triphosphate Phosphate group P Adenine P P Adenosine diphosphate H2O P Hydrolysis Ribose ATP ADP P + P + Energy How does ATP work? ATP powers cellular work through coupled reactions The bonds connecting the phosphate groups are broken by hydrolysis, an exergonic reaction (absorbs or releases energy?) Hydrolysis is coupled to an endergonic reaction through phosphorylation A phosphate group is transferred from ATP to another molecule ATP Chemical work Mechanical work Transport work Membrane protein P Motor protein Solute P Reactants P P P Product Molecule formed P Protein moved ADP + P Solute transported ATP regenerates The ATP cycle involves continual phosphorylation and hydrolysis ATP Energy from exergonic reactions Energy for endergonic reactions ADP + P Enzymes Very specific for reactions Three dimensional shape determines function (remember the World’s Largest Protein) Active site is region where the substrate binds 49 “Lock and Key” Easy version: Enzyme and substrate fit like a lock and key (shape) 50 “Lock and Key” Carboxypeptidase More complex version: polar/nonpolar, hydrogen bonds, shape, other interactions between atoms 51 Enzymes in Metabolism Metabolic pathways in the body usually involve several reactions. There may be several intermediates. Each intermediate has its own enzyme. E1 E2 E3 A (initial reactant) B (intermediates) C D (final product) 52 Wow! A single enzyme may act on thousands or millions of substrate molecules per second Animation – Campbell Ch 5: How Enzymes Work 53 Example Enzyme Reaction Enzyme available with empty active site Active site Glucose Substrate (sucrose) Enzyme (sucrase) Substrate binds to enzyme with induced fit Fructose H2O Products are released Substrate is converted to products 54 Cellular Environment Affects Enzymes Some enzymes require non-protein cofactors Metal ions, organic molecules called coenzymes Physical factors influence enzyme activity Temperature, salt concentration, pH 55 Enzyme Activity •Enzymes function best at one pH and temperature •What conditions do you think an enzyme would function best at? 56 Enzyme Activity Human Enzyme (37°C) Heat-Resistant Bacteria Enzyme (70°C) Trypsin (small intestine) Pepsin (stomach) 57 Altering Enzymes For all proteins: change of shape may change the function. Denatured = major change in structure due to external stress Breaks hydrogen bonds Temperature pH 58 Denaturation Of a protein DNA does it too! Animation:Egg White Denaturation 59 Enzyme Inhibitors A COMPETITIVE inhibitor takes the place of a substrate in the active site Substrate Active site Enzyme Normal binding of substrate Competitive inhibitor Noncompetitive inhibitor Enzyme inhibition 60 Enzyme Inhibitors A COMPETITIVE inhibitor takes the place of a substrate in the active site A NONCOMPETITIVE inhibitor alters an enzyme's function by changing its shape Substrate Active site Enzyme Normal binding of substrate Competitive inhibitor Noncompetitive inhibitor Enzyme inhibition 61 Enzyme Inhibitors Cyanide inhibits an enzyme involved with ATP production during cellular respiration 62 Enzyme Inhibitors Some pesticides irreversibly inhibit an enzyme crucial for insect muscle function 63 Enzyme Inhibitors Many antibiotics inhibit enzymes essential for diseasecausing bacteria 64 Enzyme Inhibitors Ibuprofen and aspirin inhibit enzymes involved in inducing pain 65 Enzyme activity #1 – to turn in Design an enzyme that could function in this environment Determine the organism it is found in Determine the substrate and draw the enzyme / substrate complex Give it an appropriate name Draw graphs of its activity at different pH and temperatures 66 Enzyme activity #2 – to turn in Pepsin cleaves proteins into their component amino acids during digestion Use ecology vocabulary to describe organisms that would produce high levels of pepsin Draw graphs of its activity at its optimum pH and temperatures 67