Ch. 3 - Energy, Catalysis, and Biosynthesis(1).pdf

Energy, Catalysis, and Biosynthesis Key Concepts Energy and Chemical Reactions Define energy, potential vs. kinetic energy Laws of Thermodynamics Exergonic vs. endergonic reactions ATP Overview of Metabolism Explain metabolic pathways Redox reactions...

Energy, Catalysis, and Biosynthesis Key Concepts Energy and Chemical Reactions Define energy, potential vs. kinetic energy Laws of Thermodynamics Exergonic vs. endergonic reactions ATP Overview of Metabolism Explain metabolic pathways Redox reactions Catabolic vs. Anabolic reactions  Enzyme catalyzed reactions are usually connected in a series. The product of one reaction is the starting point for a new reaction The sum of catabolism and anabolism constitutes the cells metabolism  Thermodynamics First Law Law of conservation of energy – energy can Cells take energy from the environment neither be created or destroyed (food, inorganic molecules, sunlight) Second Law Any energy transfer or transformation from one form to another increases the degree of disorder in a system (CHAOS!!), called entropy. Both important to Biology! Return heat (entropy) to their surroundings Living organisms are highly ordered They are constantly building and re- building Most nonliving things are usually decaying  Energy and Chemical Reactions Energy – ability to promote change or do work Kinetic vs. Potential Chemical energy – energy in molecular bonds Glucose has A LOT! Bond with high potential energy Energy can be neither created nor destroyed, but… it can certainly change forms Two Major Processes Help Convert Energy Photosynthesis – transforms sunlight energy into stored chemical energy. ENERGY FROM SUNLIGHT IS THE BASIS FOR LIFE ON EARTH Two Parts: Capture light energy Make sugars Photosynthesis and cellular respiration are complements All life on Earth is intertwined Essential Cell Biology, Fifth Edition Copyright © 2019 W. W. Norton & Company Q: According to the Second Law of Thermodynamics, which of the following is true about energy in cellular reactions? A) Cellular reactions always increase the amount of usable energy. B) All energy from cellular reactions is stored for later use. C) Energy transformations increase the entropy (disorder) in the system. D) Cells decrease entropy by using ATP in chemical reactions. Q: Which of the following scenarios illustrates the Second Law of Thermodynamics in cellular processes? A) ATP synthesis in mitochondria results in no loss of energy. B) During metabolism, some energy is lost as heat, increasing the system's disorder. C) Cells create order from disorder by using chemical energy, violating the law of entropy. D) Cells can convert 100% of glucose energy into ATP without any loss.  Two Major Processes Help Convert Energy Cellular Respiration – oxidation reaction Energetically stable form Carbon – CO2 Hydrogen - H2O Carbon atoms are in continuous flux and circulate between sources  Oxidation Reduction Reactions AKA Redox reactions Electrons from one molecule moved to another molecule; e- transfers Oxidation – Electron donor, loss of e- Reduction – Electron acceptor; gain of e- Example: NADH is reduced version of NAD+ NADH – activated electron carrier Releases energy to help make ATP Donates electrons during synthesis reactions OIL RIG  Oxidation and reduction involve the transfer of electrons Oxidation Reduction Reactions AKA Redox reactions Electrons from one molecule moved to another molecule Oxidation – Electron donor Reduction – Electron acceptor Example: More C-H bonds, reduced Hydrogenated Less C-H bonds, oxidized Dehydrogenated  Activation Energy Initial input of energy to start a reaction Allows molecules to get close enough to cause bond rearrangement Energetically favorable reactions also require a Reactants can stretch and reach boost in activation energy transition state Enzymes lower activation energy increases the likelihood that a reaction will occur Straining bonds in reactants Positioning reactants together Changing local environment Anatomy of an Enzymatic reaction Active Site Substrate Enzyme-substrate complex – Non-covalent bonds Enzyme catalysis allows reactions to occur rapidly at the normal temperature inside cells Enzymes, like all catalyzing agents, remain unchanged after participating in a reaction Review of the anatomy of an enzyme Catalase is an enzyme found in liver that breaks down the Hydrogen peroxide (H2O2) into water and oxygen. Q: In the chemical reaction between hydrogen peroxide (H₂O₂) and water, which of the following correctly identifies the enzyme, substrate, and products? A) Enzyme: Catalase; Substrate: Hydrogen Peroxide; Products: Water and Oxygen B) Enzyme: Amylase; Substrate: Water; Products: Hydrogen Peroxide and Oxygen C) Enzyme: Catalase; Substrate: Oxygen; Products: Hydrogen Peroxide and Water D) Enzyme: Peroxidase; Substrate: Water; Products: Hydrogen Peroxide and Oxygen Q. Enzymes lower activation energy increases the likelihood that a reaction will occur A) TRUE B) FALSE Free Energy and Catalysis: Factors Governing Chemical Reaction Direction of the chemical reaction Reversible? Not? A+ B ⇌ C + D Can be determined by free energy and reactants’ concentration Will only proceed if loss of free energy Rate of the reaction Enzymes! Energetically favorable reactions have a negative ΔG, whereas energetically unfavorable reactions have a positive ΔG. Reaction coupling can drive an energetically unfavorable reaction. Essential Cell Biology, Fifth Edition Copyright © 2019 W. W. Norton & Company Free Energy Determines Direction of Reaction Energy – important to many cell processes Reaction can only occur if increases disorder in the universe Total energy = Usable energy + Unusable energy Total Energy = Enthalpy (H) Usable Energy = Free Energy (G) i.e. Gibbs Free Energy Unusable Energy = System’s Entropy (S) Free Energy Determines Direction of Reaction So we can rewrite the process… H = G + TS Total Energy = Enthalpy (H) Usable Energy = Free Energy (G) i.e. Gibbs Free Energy Unusable Energy = System’s Entropy (S) Absolute temperature (Kelvin) = T