BIOL 1411 1ST Edition Lecture 10 Outline of Last Lecture 1 Extracellular signal transduction 2 Cell s response from signal 3 Direct cell cell interaction and communication Outline of Current Lecture 1 Energy transformation 2 Enzymes characteristics 3 How enzymes work Current Lecture Chapter 8 Energy Metabolism in Cells Biological Energy Transformations To be able to acquire and transform energy from one form to another is characteristic to life o KNOW THE ENERGY FORMS FROM THE BOOK Relating to cells particularly all energy transformations are linked to chemical transformations i e to cellular metabolism Anabolic Reactions o Simple molecules complex molecules o Energy input in required stored in chemical bonds Catabolic reactions o Complex molecules simpler molecules o Energy released from chemical bonds and used for any other energy requiring activities These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Energy transformations in living organisms follow the same laws of nature that nonliving things do such as the thermodynamics laws o 1st Law of Thermodynamics energy is neither created nor destroyed energy can be converted from one form to another but same amount of total energy remains o 2nd Law of Thermodynamics when energy is converted from one form to another some of that energy becomes unavailable to work no energy transformation is 100 percent efficient some energy is converted to a nonusable form associated with disorder or randomness entropy Entropy is increasing in the universe Total energy usable energy unusable energy entropy o Enthalpy H free energy G Entropy S o H G TS T absolute temp o G H TS Only free energy G can be used for cellular work Measurable changes in free energy G occur in chemical reactions o Reactants and products have different amounts of energy in their bonds o Expressed as delta G delta H T delta S o Exergonic Reaction Delta G is negative Free energy released Can occur spontaneously Complexity molecules simpler molecules catabolic Generates disorder o Endergonic Delta G positive Free energy is consumed Energy enters Include anabolic reactions Simple molecules complex molecules Is a localized decrease in entropy Will not occur spontaneously o If free energy is not available the reaction doesn t occur o Energy releasing reactions occur spontaneously and always increase disorder in the system Review of more chemical principles o Chemical reactions can happen to the right or left side of reaction o Concentrations of A and B determine which direction will be favored o Chemical equilibrium forward and reverse reactions occur at the same rate delta G 0 In living organisms rarely happens due to metabolic pathways Closed system o Every reaction has specific equilibrium point o Delta G related to equilibrium point further away from eq point the more free energy is released o Delta G near zero indicates readily reversible reactions Open system o Can do work as long as input balances output o Disequilibrium is maintained Living organisms are highly ordered o Built from complex macromolecules assembled into complex cells tissues organs and organ systems o These reactions are not thermodynamically favored Organisms don t violate the 2nd law of thermodynamics because living organisms must always have a constant supply of outside energy to maintain order open system o Photosynthetic organisms capture solar energy and convert it to chemical energy o Heterotrophs like us start with chemical energy from our photosynthetic coinhabitants o Endergonic reactions are coupled to exergonic reactions in ordered metabolic pathways ATP o Releases in large quantity when hydrolyzed to ADP and Pi o Delta G 7 3 kcal mol exergonic o ATP H2O ADP Pi free energy o Bioluminescence example fire fly Luciferin O2 ATP luciferase Oxyluciferin AMP PPi Light o ATP couples exergonic and endergonic reactions in cells Enzymes Characteristics of enzymes o Biological reactions require enzymes o Highly specific for their substrates o Substrates bind to active site of enzyme o 3 d shape determines the specificity lock and key analogy o How enzymes work o Enzyme substrate complex ES forms Held together by Hydrogen bonds electrical attraction or covalent bonds Enzyme E may change when bound to the substrate induced fit but returns to original form E S ES E P Can catalyze more of the same reactions with new substrate molecules o Enzymes lower the energy barrier for reactions Final equil Does not change Delta G doesn t change An uncatalyzed reaction has greater activation energy than does a catalyzed reaction No difference in free energy between catalyzed and uncatalyzed reactions o May use one or more mechanisms to catalyze a reaction Orienting substrates to react Inducing strain in the bonds of the substrates Temporarily adding chemical groups Acid base catalysis enzyme side chains transfer H to or from the substrate causing a covalent bond to break Covalent catalysis Functional group in a side chain bonds covalently with the substrate Metal ion catalysis Metals on side chains lose or gain electrons Some enzymes change shape when substrate binds to them Substrates bind to active site the two halves of the enzyme move together changing the shape of the enzyme so that catalysis can take place o Reaction Rate There is a max rate for any given enzyme which depends on substrate concentration Enzyme concentration usually significantly lower than concentration of substrate All enzyme bound to substrate maximum reaction rate Used to calculate enzyme efficiency molecules of substrate converted to product per unit time turnover Ranges from 1 to 40 million molecules per second for different enzymes Enzymatic pathways are interconnected o Thousands of chemical reactions occurring in cells at the same time o Reactions organized in metabolic pathways which are all interconnected o Each reaction is catalyzed by a specific enzyme o The enzymatic pathways regulate enzymes with reactions ultimately helping maintain internal homeostasis Enzyme activity regulations o Inhibitor Naturally occurring and mad made molecules that bind to the enzyme and slow reaction rates Types of inhibitors Competitive o Compete with natural substrate for binding sites concentration dependent Noncompetitive o Bind to the enzyme at a different site not active site and alter active site often function as metabolic regulators Reversible o Bonds