Metabolism Biol 1000 Winter 2025 PDF

Biology 1 – Cells, Molecular Biology and Genetics (Biol 1000) Professor: Dr. Michael Cardinal-Aucoin Winter 2025  Metabolism (Chapter 8) Overview Basic Thermodynamics Thermodynamics and Metabolism – ATP – Enzymes En...

Biology 1 – Cells, Molecular Biology and Genetics (Biol 1000) Professor: Dr. Michael Cardinal-Aucoin Winter 2025  Metabolism (Chapter 8) Overview Basic Thermodynamics Thermodynamics and Metabolism – ATP – Enzymes Enzyme action Biol1000 - Dr. M. Cardinal-Aucoin 2  Overview of Metabolism Metabolism is the totality of an organism’s chemical reactions. An organism’s metabolism transforms matter and energy. Metabolism is an emergent property of life that arises from interactions between molecules within the Remember cell theory: energy cell. flow occurs in cells. Biol1000 - Dr. M. Cardinal-Aucoin 3  Overview of Metabolism The chemistry of life is organized into Metabolic Pathways. A metabolic pathway begins with a specific reactant molecule and ends with a product. Each step is catalyzed by a specific enzyme. Another way to say this is that metabolism is enzyme mediated. The regulation of these metabolic (biochemical) pathways is very important and usually controlled at the level of one of the enzymes. Enzyme 1 Enzyme 2 Enzyme 3 A B C D Reaction 1 Reaction 2 Reaction 3 Starting Product molecule Biol1000 - Dr. M. Cardinal-Aucoin 4  Overview of Metabolism There are 2 broad categories of metabolic process: – Catabolism: breaking down of substances (i.e. digestion). – Anabolism: building up of substances (i.e. protein synthesis in muscle). Biol1000 - Dr. M. Cardinal-Aucoin 5  Overview of Metabolism Catabolic pathways release energy by breaking down complex molecules into simpler compounds. Example: Cellular respiration involves the breakdown of glucose in the presence of oxygen to form CO2, water, and ATP. Biol1000 - Dr. M. Cardinal-Aucoin 6  Overview of Metabolism Anabolic pathways consume energy to build complex molecules from simpler ones. Example: The synthesis of glucose from CO2 and water (i.e. photosynthesis). In healthy cells the two processes are balanced (tightly regulated). Biol1000 - Dr. M. Cardinal-Aucoin 7  Overview of Metabolism Cells get energy from catabolic reactions. But how much energy is available to do work? Biol1000 - Dr. M. Cardinal-Aucoin 8 Speaking of energy, let’s do a little physics! Biol1000 - Dr. M. Cardinal-Aucoin 9  What is energy? “Energy is the capacity to cause change.” The capacity to do work or the ability to move or elicit change in matter. Cells use energy to move, transport molecules and ions, reproduce, respond to stimuli, replicate DNA, synthesize molecules, etc., etc. Biol1000 - Dr. M. Cardinal-Aucoin 10  Basic Thermodynamics All chemical systems (collection of physical objects, e.g. an organism, a cell) contain energy. – Internal energy = enthalpy = H How do cells get access to this energy to do work? Biol1000 - Dr. M. Cardinal-Aucoin 11  Basic Thermodynamics The First Law of Thermodynamics According to the first law of thermodynamics, the energy of the universe is constant: – Energy can be transferred and transformed, but it cannot be created or destroyed. The first law is also called the principle of conservation of energy. Biol1000 - Dr. M. Cardinal-Aucoin 12  Basic Thermodynamics The First Law of Thermodynamics Cells convert energy from one form to another. – Kinetic energy (movement) – Chemical energy (in chemical bonds) – Light energy – Electrochemical potential energy (potential energy of concentration gradient) And use that energy to do work. But how much of that energy is available to the cell to do work!? Biol1000 - Dr. M. Cardinal-Aucoin 13  Basic Thermodynamics Gibbs Free Energy Gibbs energy (∆G) is the proportion of a system’s energy that can perform work! Note: ΔG depends on temperature, pressure, and the concentration of reactants and products, but in living systems we can assume temperature and pressure are constant. **In living systems there is generally an inverse relationship between ∆G & ∆S.** Biol1000 - Dr. M. Cardinal-Aucoin 14  USABLE ENERGY (available to do work ENERGY = ΔG!) TRANSFER ENERGY NOT available to do work Energy is more spread out; entropy increases (e.g. heat - endothermy) Biol1000 - Dr. M. Cardinal-Aucoin 15  Basic Thermodynamics The Second Law of Thermodynamics During every energy transfer or transformation, some energy is unusable, and is often lost as heat. According to the second law of thermodynamics: – Every energy transfer or transformation increases the entropy (disorder) of the universe. Entropy is a measure of disorder. Biol1000 - Dr. M. Cardinal-Aucoin 16  Basic Thermodynamics The Second Law of Thermodynamics There is a tendency toward disorder. Energy input is required to do work to maintain order in living systems. Biol1000 - Dr. M. Cardinal-Aucoin 17 In a biological system (cell)… Enthalpy (H) Increases Entropy (S) Decreases Enthalpy (H) Decreases Entropy (S) Increases Biol1000 - Dr. M. Cardinal-Aucoin 18  Basic Thermodynamics Gibbs Free Energy So ΔG is the energy of the system (ΔH) that remains after we’ve accounted for the energy contributed by the environment (-TΔS). Biol1000 - Dr. M. Cardinal-Aucoin 19  Basic Thermodynamics Gibbs Free Energy The driving force of a chemical reaction has two components: 1. ΔH is the drive toward stability (enthalpy) 2. ΔS is the drive toward disorder (entropy) ΔG is the net driving force of the chemical reaction. Biol1000 - Dr. M. Cardinal-Aucoin 20  Basic Thermodynamics Gibbs Free Energy ΔG is the energy input required so that the reaction will proceed: 1. If ΔG < 0 – the reaction is spontaneous (‘favors products’) 2. If ΔG = 0 – the reaction is at equilibrium 3. If ΔG > 0 – the reaction is non-spontaneous (‘favors reactants’) Biol1000 - Dr. M. Cardinal-Aucoin 21  Basic Thermodynamics Gibbs Free Energy Graphing Gibbs free energy of a reaction: Energy contained in the molecules. Energy in reactants Gibbs free energy of the reaction Energy in (ΔG). products Also sometimes Time or Reaction Coordinate Biol1000 - Dr. M. Cardinal-Aucoin 22  Basic Thermodynamics Gibbs Free Energy An exergonic reaction (a) Exergonic reaction: energy released, spontaneous Reactants proceeds with a net Amount of release of free energy energy released Free energy (ΔG < 0) Energy (∆G < 0) and is Products spontaneous. Progress of the reaction Biol1000 - Dr. M. Cardinal-Aucoin 23  Basic Thermodynamics Gibbs Free Energy An endergonic (b) Endergonic reaction: energy required, nonspontaneous Products reaction absorbs free Amount of energy from its energy required Free energy (ΔG > 0) surroundings (∆G > 0) Reactants Energy and is non- Progress of the reaction spontaneous. Biol1000 - Dr. M. Cardinal-Aucoin 24 Biol 2230 - Dr. M. Cardinal-Aucoin 25 Biol1000 - Dr. M. Cardinal-Aucoin 26  Thermodynamics and Metabolism Gibbs Free Energy Reactions in a closed system eventually reach equilibrium and then do no work A defining feature of life is that metabolism is never at equilibrium. Why?? Cells are not in equilibrium; they are open systems experiencing a constant flow of matter and energy. ΔG < 0 ΔG = 0 ΔG < 0 (a) An isolated hydroelectric system (b) An open hydro- Biol1000 - Dr. M. Cardinal-Aucoin electric system 27  Thermodynamics and Metabolism Gibbs Free Energy A catabolic pathway in a cell releases free energy ΔG < 0 in a series of reactions. ΔG