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Download Energy Cells transform energy as they perform work Kinetic
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Energy • • • • • • Cells transform energy as they perform work Energy & Laws of Thermodynamics Chemical Reactions Enzymes How cells “make” and use Energy: ATP Cell Respiration Photosynthesis Energy is the capacity to do work & cause change – Work is accomplished when an object is moved against an opposing force, such as friction – There are two kinds of energy – Kinetic energy is the energy of motion – Potential energy is energy that an object possesses as a result of its location Copyright © 2009 Pearson Education, Inc. Kinetic & Potential Energy Kinetic Potential Kinetic to Potential Energy transformations Energy conversion Fuel Waste products Heat energy Carbon dioxide Gasoline Combustion Kinetic energy of movement Water Oxygen Energy conversion in a car Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 1 Energy transformations in a cell Fuel Waste products Energy conversion Heat Two laws govern energy transformations It is important to understand two laws that govern energy transformations in organisms – The first law of thermodynamics — energy in the universe is constant Glucose Cellular respiration Carbon dioxide – The second law of thermodynamics — energy conversions increase the disorder of the universe – Entropy is the measure of disorder, or randomness Oxygen Water Energy for cellular work Energy conversion in a cell Copyright © 2009 Pearson Education, Inc. Endergonic reactions require energy Reactants Amount of energy released Energy released Products Potential energy of molecules Potential energy of molecules Exergonic reactions release energy Products Energy required Amount of energy required Reactants 2 Chemical reactions either release or store energy A living organism produces thousands of endergonic and exergonic chemical reactions – All of these combined is called metabolism – A metabolic pathway is a series of chemical reactions that either break down a complex molecule or build up a complex molecule Copyright © 2009 Pearson Education, Inc. Cellular work is coupled to exergonic reactions A cell does three main types of cellular work – Chemical work — driving endergonic reactions – Transport work — pumping ions across membranes – Mechanical work — beating of cilia To accomplish work, a cell must manage its energy resources, and it does so by energy coupling — the use of exergonic processes to drive an endergonic one Copyright © 2009 Pearson Education, Inc. ATP – Energy Currency of the Cell Adenosine ATP – Energy Currency of the Cell Triphosphate (ATP) Adenosine Triphosphate (ATP) Phosphate group Adenine Adenine Ribose Phosphate group Ribose Hydrolysis + Adenosine Diphosphate (ADP) 3 The ATP cycle Chemical work Mechanical work Transport work Solute ATP Motor protein Membrane protein Reactants Phosphorylation Energy from exergonic reactions Hydrolysis ADP+ P Energy for endergonic reactions Product Protein moved Molecule formed Solute transported Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings ATP Powers Cellular Work ATP Synthesis ATP Chemical work Mechanical work Transport work Membrane protein P + Motor protein 2. Mechanisms of ATP synthesis ¾ Chemiosmosis ¾ Substrate Level Phosphorylation P Reactants 1. ADP + Phosphate Æ ATP Solute P P P Product Molecule formed P Protein moved Solute transported ADP + P Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 4 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fig. 9.3 (TEArt) ATP synthesis: Chemiosmosis H+ H+ ATP Synthesis Substrate-Level Phosphorylation H+ H+ H+ + H+ H H+ PEP a te ru v Py Substrate P ATP Synthase ADP + P ATP Enzyme P H+ P P P AT P P ADP eno Ad Adenosine sin e Enzymes lower activation energy HOW ENZYMES FUNCTION Activation Energy Barrier Enzyme Catalyst Reactants Products Copyright © 2009 Pearson Education, Inc. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 5 Enzymes lower activation energy Activation Energy • Activation energy Reaction without enzyme EA without enzyme Energy EA with enzyme Reactants Net change in energy (the same) Reaction with enzyme – extra energy required – destabilizes existing chemical bonds – initiates a chemical reaction • Enyzme – Catalyst – lowers activation energy Products Progress of the reaction Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The catalytic cycle of an enzyme 1 Enzyme available with empty active site Active site 1 Enzyme available with empty active site Active site Substrate (sucrose) 2 Substrate binds to enzyme with induced fit Enzyme (sucrase) Enzyme (sucrase) 6 1 Enzyme available with empty active site Active site Substrate (sucrose) 2 Substrate binds to enzyme with induced fit Enzyme (sucrase) 1 Enzyme available with empty active site Active site Glucose Substrate (sucrose) 2 Substrate binds to enzyme with induced fit Enzyme (sucrase) Fructose 3 Substrate is converted to products 4 Products are released 3 Substrate is converted to products The catalytic cycle of an enzyme 1 Enzyme with Active site Active site 2 Glucose END Substrate (sucrose) Substrate binds to enzyme Part I: Energy Enzyme Fructose H2O 4 Products released 3 Substrate converted to products Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 7
