February 26 2013 FREE ENRGIRE EQUILIBRUI CONSTANTS KINETICS AND ENZYMES How do living organisms transfer energy Free energies of spontaneous activities are negative Forms of Energy and Laws of Energy Conversion Potential energy that matter possesses bc of its position or structure Kinetic associated with motion Chemical potential energy available for release in chemical reactions First Law of Thermodynamics conservation of energy total energy of the universe is constant never created nor destroyed o Ex bear eats a fish at the cellular level when the food is eaten it becomes ATP chemical energy gives energy to bear Second Law of Thermodynamics every energy transfer increases the disorder entropy of the universe o Ex bear is running through water releases heat and breathes out CO2 and H2O sooo what the bear is breathing out contributes to the heterogeneity of the air around the bear which makes it more complex and more disordered How do Living Systems Increase their Order Increasing the order of living systems results in an increase in the disorder of their environments We use the energy around us to make us more organized but that increases the disorder of our surrounding environments Spontaneous Reaction Man diving off diving board gravitational motion Diffusion Oxidation of glucose chemical reaction all there accompanied by decreases in free energy G o delta G G products end G reactants Spontaneous reactions are exergonic release energy o Change in free energy is negative Non spontaneous reactions are endergonic require energy o Change in free energy is positive Chemical Equilibria and Equilibrium Constants Diagram 1 Keq B A 1 A Metabolic Pathway Starting molecule enzyme 1 reaction 1 enzyme 2 reaction 2 enzyme 3 reaction 3 Product Catabolic pathways break down complex molecules into simpler ones net free energy change is negative exergonic chemical energy released can be stored in part in ATP which will b used to make other things in cell do work Anabolic pathways build up complex molecules are produced from simpler molecules endergonic energy required for synthesis is from ATP Energy of ATP Hydrolysis can Drive Endergonic Reactions ATP negatively charged Oxygens on phosphate groups so breaking the bond by hydrolyzing it separates the negative charges of one phosphate to the other 2 phosphates ADP free phosphate 2 phosphate pentose AHHH Free Energy Changes during Chemical Reactions During the progress of reaction there is a point in the transition state when the free energy increases covalent bonds weaken AHHHH Reactants have to climb up energy barrier in order to become product Enzymes Reduce the Energies of Activation of Reactions HOW ENZYMES FUNCTION AND HOW THEY RE REGULATED 2 28 13 Ex ribonucleas enzyme catalyzes RNA bc its made of ribonucleotides Metabolic Pathways above Enzymes accelerate rates of metabolic reactions by lowering activation barrier the enzymes help the reactant get over barrier The action will be spontaneous the free energy change will be negative If the reactant has higher potentional energy than products it will eventually convert to product The speed depends on how high the activation barrier is The place wehere the enzyme is catalyzed is in the cleft groove where the Reactants are faster in t substrate goes in at the active site The Catalytic Cycle Enzyme substrate molecules enter enzyme substrate complex then they are converted to products when the products are relased and tthen the active site is available for two new substrate molecules How Does Active site Accelerate Reactions o Position the substrates optimally o Provides optimal environment polarity charge o Increases free energy of bound substrate by putting strain on its o Transfers protons between enzyme and substrate acid base catalyst o Decreased free energy of transition state by forming favorable structure ineractions with it o Sometimes enzyme forms covalent bond with substrate intermediate Reaction Rate Depends on Substance Concentrate to achieve maximum rate Vmax substrate must saturate active site Rate Also Depends on Environmental Conditions pH Temp Ionic Strength 3 5 13 Enzyme Cofactors Metal ions metalloenzymes Organic molecules coenzymes o Often derive from vitamins o Deficiencies lead to disease DO NOT NEED TO KNOW Vitamin A retinol color blindness low vision yellow fruits and veggies Vitamin B1 thiamine beriberi rice husks Vitamin B3 niacin pellagra grains not corn Vitamin C ascorbic acid scurvy citrus fruits Vitamin D sterols rickets sunlight calcium Enzyme Inhibitors look at FIGURE 3 used to make sure enzyme isn t producing too much product Competitive inhibitors bind at active sight penicillin inhibits lactamases enzymes enzymes that synthesis bacteria cell walls reduce total concentration of active site so substrate wont fit on perfectly Noncompetitive inhibitor bind remote from active site exert action at distance sarin inhibits acetylchlorlinesterase enzyme in nervous system it goes into the other side of the enzyme so that the substrate doesn t have to compete to go into the active site but you cant really reduce the inhibitor on enzyme so it would actually reduce the rate of a reaction Allosteric Regulation of Enzyme Activity FIGURE 4 binding at a site other than the active site Active form and inactive form are both allosteric reactions Binding of regulatory molecule at one site causes changes in affinity or activity of other sites Occurs in enzymes with subunits Involves changes in tertiary the way loops form between alpha helix and pleaeted sheets so the protein can form a compact 3D shape and then form an active site and quaternary structure Activation depends on increases in substrate affinity cooperativity how strong an enzyme and substrate are attracted to each other Inhibition depends on decreases in affinity Cooperative substrate binding inactive form add substrate changes shape into a stabilized active form Feedback Regulation by Allosteric Regulation regulation of a metabolic pathway by an end product Threonine to isoleucine end product is an allosteric inhibitor of the first enzyme in the pathway feedback inhibition the end product tells the initial enzyme whether or not it needs to work harder faster if not enough isoleucine was produced or slower if a lot of isoleucine was produced NEW POWERPOINT How Carbohydrates are Oxidized in the Cell Flow of energy and materials in ecosystem like when a chimpanzee eats a leaf Oxidation and reduction in redox systems
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