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Biology 105 Chapter 7: Energy and Metabolism Pgs 154-171 Student Outcomes Define Energy and how it is related to work and heat Contrast potential, kinetic energy and the laws of thermodynamics Distinguish between exergonic and endergonic reactions Student Outcomes Discuss entropy and enthalpy and how free energy affects both processes. Discuss the role of ATP in energy metabolism of the cell. Explain how enzymes are regulated and their functions in reactions. Energy Energy - the capacity to do work Measured in Kilojoules (Kj) or Kilocalories, kcal Terms of Energy Potential Energy - capacity to do work Kinetic Energy - Energy of motion Chemical Energy - Potential energy stored in chemical bonds Mechanical Energy - Performing work by moving matter (muscles) Thermodynamics The study of energy Closed system - no energy exchange with its surroundings Open system - energy exchange with surroundings Laws of thermodynamics 1st Law Energy is neither created nor destroyed, it just changes form Organisms cannot create their own energy to do work, they must capture energy from the environment and transform it to a useable form Laws of Thermodynamics • • 2nd law As energy is converted from one form to another, some energy is lost as HEAT to the surroundings. Measured as Entropy Metabolism All the chemical Two Types Anabolism reactions in a cell - complex molecules are synthesized from simpler substances, Ex: organic compounds Catabolism - complex molecules are broken down into smaller substances. Energy to do work H=G+TS H=Enthalpy (potential energy) G=Free energy T=Temperature (absolute-Kelvin) S=Entropy (unuseable energy) ∆G = change in free energy Exergonic Reactions Release energy-less free energy in the products than in the reactants, downhill slope on a graph. ∆G= a negative number Usually spontaneous and catabolic Endergonic reaction Gain in free energy - More energy in the products than in the reactants. ∆G = a positive value For every Endergonic reaction - driven by an exergonic reaction Anabolic reactions ATP Adenosine Triphosphate - Chemical compound of energy in all living things. ATP has three parts: adenine (nitrogenous base), ribose (5 carbon sugar) and three phosphates ATP A cell continually spends its ATP and it must be continually replaced. The energy is stored in the phosphate bonds ∆G (free energy) is app. -32 kJ/mol or -7.6 kcal/mol (Energy released by the phosphate bond breaking) ATP synthesis ATP 10 - ADP - AMP times the amount of ATP vs ADP in a typical cell. ATP Fun Facts Estimated 10 million molecules of ATP are made from ADP every second in every cell Adult human at rest uses about 45 kg of ATP each day ATP present in the body is less than 1g Redox Reactions Oxidation - chemical process where a substance loses electrons Reduction - a substance gains electrons. When a substance is oxidized it gives up energy and the opposite is true NAD+ becomes NADH Enzymes Biological catalysts - increase the speed of a chemical reaction without being consumed by the reaction. Most Very are proteins specific to their job. Have a specific pH and temperature they function at. Will denature if too strong of pH or too high temperature. Enzymes Example Hydrogen Peroxide H2O2 is a poisonous substance to cells. It breaks down slowly One molecule of the enzyme Catalase will decompose 40 million molecules of hydrogen peroxide per second. Activation Energy Energy needed for a reaction to occur Needed to break the existing bonds and begin the reaction. Enzymes needed lower the Activation Energy Substrates Enzymes form a ‘complex’ with the substrate at an ‘active site’ (connect at a groove that matches enzyme to substrate) Enzyme examples Sucrase Pepsin Trypsin Catalase Enzyme Regulation Cells regulate enzymes Feedback inhibition A-----B-----C-----D As the concentration of Product D increases, it inhibits (stops) the Enzyme that acts on Reactant A. Reversible inhibition Competitive The inhibition inhibitor competes with the substrate for binding to the active site of the enzyme Noncompetitive The inhibition inhibitor competes with the substrate for binding at the non active site. Irreversible inhibition An inhibitor permanently inactivates or destroys the enzyme EX: cyanide affects cytochrome oxidase Sulfa drugs - prevent microorganisms from synthesizing folic acid. Penicillin inhibit the enzyme transpeptidase needed for cell wall construction.
