Bio Chapter 8 Energy, Enzymes, and Metabolism PDF

8 Energy, Enzymes, and Metabolism © Oxford University Press Chapter 8 Energy, Enzymes, and Metabolism Learning Objectives Define “energy” Explain the difference between kinetic potential energy, and chemical energy Discuss the con...

8 Energy, Enzymes, and Metabolism © Oxford University Press Chapter 8 Energy, Enzymes, and Metabolism Learning Objectives Define “energy” Explain the difference between kinetic potential energy, and chemical energy Discuss the concepts of activation energy Define exergonic and endergonic reactions and be able to distinguish between the two. Explain the First and Second Laws of Thermodynamics as well as the concept of entropy List the basic characteristics of enzymes Describe the terms active site and substrate in regard to enzymes Describe how factors such as inhibitors influence enzyme activity Define coenzyme and cofactors © Oxford University Press Energy - Is the capacity to do work - Without energy source ALL LIFE would stop - Energy CANNOT be created - Animals gain energy from food - Algae and plants get energy from the sun - Traps energy and stores it in molecules - Then eaten as food and broken down for use in cells by consumers. - Energy cannot be created only transferred. © Oxford University Press Energy ON EXAM What’s different? Come in different forms - Potential Energy: Stored in the chemical energy bonds - Chemical Energy: Energy stored in chemical bonds - Kinetic Energy: Energy of motion or movement © Oxford University Press Figure 8.1 Energy Conversions and Work  Potential and Kinetic energy Figure 6.1 6 Chemical Transformations Involve Energy and Energy Transfers Food has potential energy stored in chemical bonds. Energy has two forms: kinetic and potential. Energy Conversions and Work Potential and kinetic Water behind a dam Waterfall Laws of Thermodynamics ON EXAM 1st law – energy is neither created or destroyed 2nd law – When energy is converted from one form to another, some of that energy becomes unavailable to do work. No energy transformation is 100% efficient; some energy is lost. Laws of energy help us understand how cells harvest and transform energy to sustain life. © Oxford University Press Figure 8.2 The Laws of Thermodynamics © Macmillan Learning Concept 8.1 Chemical Transformations Involve Energy and Energy Transfers In biological systems: - Total energy is called enthalpy (H) Enthalpy the amount of energy contained in a compound of system Entropy is a measure of disorder - Free energy (G) is the unstable energy that can do work. - Unstable energy is represented by entropy (S) multiplied by the absolute temperature (T). - H = G + TS - Change in energy can be measured in calories or joules - Change in free energy (∆G) of a chemical reaction: © Oxford University Press Energy in the body ON EXAM Endergonic reactions consume free energy Anabolism makes a single product (a highly ordered substance) out of many similar reactants (less ordered) – complexity (order) increases Endergonic Anabolism is a biochemical process in metabolism where simple molecules combine to generate complex molecules and this requires energy. Exergonic reactions release free energy Catabolism breaks down an ordered reactant into smaller, more randomly distributed products – complexity decreases (generates disorder) Exergonic catabolism break down of large organic molecules into smaller molecules this process releases energy contained in the chemical bonds. © Oxford University Press Figure 8.6 Coupling of Reactions © Macmillan Learning ATP ATP (adenosine triphosphate) captures and transfers free energy. ATP can be hydrolyzed to ADP (Adenosine diphosphate) and P1 (Inorganic phosphate), releasing a lot of energy for endergonic reactions. ATP can also phosphorylate (donate a phosphate group to) other molecules, which gain some energy. © Oxford University Press  ON EXAM Concept 8.3 Enzymes Speed Up Biochemical Transformations Catalysts increases rates of chemical reactions. The catalyst is not altered by the reactions. Most biological catalyst are enzymes (proteins) that act as a framework in which reactions can take place Catalyst - substances that regulate and accelerate the rate of biochemical reactions Some reactions are slow because of an energy barrier – the amount of energy required to start the reaction, called activation energy (Ea) Activation energy - energy required to initiate a chemical reaction. Enzymes lower the activation energy of a reaction thereby greatly speeding up the rate of the reaction. © Macmillan Learning Enzymes Accelerate Chemical Reactions (a) Without enzyme lactose glucose + galactose activation energy without enzyme net energy released from splitting of lactose (b) With enzyme lactase lactose glucose + galactose activation energy with enzyme net energy released Figure 6.9 © 2011 Pearson Education, Inc. Enzymes Speed Up Biochemical Transformations Enzymes are highly specific to the kind of reactant with which they combine Reactants are called substrates Substrate the molecule (reactant) to which they enzyme attaches itself. Enzyme substrate complex the temporary molecule that forms when the enzyme and substrate link. Substrate molecules bind to the active site of the enzyme. Active site particular site on the enzyme where the substrate binds Enzyme releases the P (product) The 3D shape of the enzyme determines the specificity. The enzyme – substrate complex (ES) is held together by hydrogen bonds, electrical attraction, or covalent bonds. E + S → ES → E + P The enzyme may change while bound to the substrate but returns to its original form. © Oxford University Press Figure 8.9 Enzyme and Substrate © Macmillan Learning Concept 8.5 Enzyme Activities Can Be Regulated Inhibitor – substance that binds to enzyme and decreases its activity Enzyme inhibitors molecules that bind to the enzyme and slow down the reaction Competitive inhibitor -- completes with substrate for active site. Competitive inhibitor cancer drug methotrexate Noncompetitive inhibitor – binds to enzyme at a site other than active site - Causes shape change that makes enzyme unable to bind substrate. Pyruvate kinase © Oxford University Press 20 Enzyme Inhibition © Oxford University Press 21  Cofactors and Coenzymes Cofactors – Inorganic ion or vitamin derivative - Assist enzymes - Can be metal ions: Zinc, molybdenum, manganese. - Often found in the active site Coenzymes – Organic molecule changes, during reaction - Cofactors that are nonprotein organic molecules - Vitamins © Oxford University Press 22  https://www.youtube.com/watch?v=qgVFkRn8f10&app=de sktop https://www.youtube.com/watch?v=UVeoXYJlBtI https://www.youtube.com/watch?v=pVoytz_3H_s https://www.youtube.com/watch?v=ueup2PTkFW8 © Oxford University Press 23