February 26, 2013FREE ENRGIRE, EQUILIBRUI, CONSTANTS, KINETICS, AND ENZYMES- How do living organisms transfer energy?- Free energies of spontaneous activities are negativeForms 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 disorderedHow 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 positiveChemical Equilibria and Equilibrium Constants- Diagram 1- Keq = [B]/[A] = 1A 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 ATPEnergy 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, AHHHFree Energy Changes during Chemical Reactions - During the progress of reaction, there is a point in the transition state when thefree energy increases (covalent bonds weaken) AHHHH- Reactants have to climb up energy barrier in order to become productEnzymes 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- Reactants are faster in t- The place wehere the enzyme is catalyzed is in the cleft/groove where the 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 isavailable 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 structureo Transfers protons between enzyme and substrate (acid-base catalyst)o Decreased free energy of transition state by forming favorable ineractions with ito 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)3/5/13Enzyme Cofactors- Metal ions (metalloenzymes)- Organic molecules (coenzymes)o Often derive from vitaminso 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 concentrationof 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 reactionAllosteric 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 ofother 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 formFeedback Regulation by Allosteric Regulation – regulation of a metabolic pathway by an end productThreonine to isoleucine – end product is an allosteric inhibitor of the first enzyme inthe pathway feedback inhibition – the end product tells the initial enzyme
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