Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 5 Introduction to Energy Transfer

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Energy The ability to perform work Emerges only when a change takes place Bioenergetics –The flow and exchange of energy within a living system First law of thermodynamics –Energy cannot be created or destroyed but transforms from one form to another without being depleted

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Potential and Kinetic Energy Total energy of a system = Potential energy + kinetic energy –Potential energy: Energy associated with a substance’s structure or position Ex: Macronutrients before releasing stored energy in metabolism –Kinetic energy: Energy of motion

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Potential and kinetic energy example

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Biosynthesis Bound energy in one substance directly transfers to other substances to increase their potential energy –Specific building-block atoms of carbon, hydrogen, oxygen, and nitrogen become activated and join other atoms and molecules to synthesize important biologic compounds and tissues

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Energy-Releasing and Energy-Conserving Processes Exergonic –Any physical or chemical process that releases energy to its surroundings –Represent “downhill” processes because of a decline in free energy Endergonic –Chemical reactions that store or absorb energy –Represent “uphill” processes and proceed with an increase in free energy

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Energy flow in chemical reactions

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Interconversions of Energy Transfer of potential energy in any spontaneous process always proceeds in a direction that decreases the capacity to perform work Second Law of Thermodynamics –Tendency of potential energy to degrade to kinetic energy of motion with a lower capacity for energy All of the potential energy in a system degrades to the unusable form of kinetic or heat energy Total energy in an isolated system remains constant; a decrease in one form matches an equivalent increase in another

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Forms of Energy Each energy form can convert or transform to another –Chemical –Mechanical –Heat –Light –Electrical –Nuclear

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Interconversions of forms of energy

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Examples of Energy Conversion Photosynthesis –Endergonic process where plants transfer the energy of sunlight to the potential energy bound within carbohydrates, lipids, and proteins Respiration –Exergonic process that releases stored energy in plants for coupling to other chemical compounds for biologic work

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Photosynthesis

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Review What constitutes the total energy of a system? a.Chemical and electrical energy b.Potential and biochemical energy c.Potential and kinetic energy d.Kinetic energy and heat

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Answer What constitutes the total energy of a system? a.Chemical and electrical energy b.Potential and biochemical energy c.Potential and kinetic energy d.Kinetic energy and heat

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Biologic Work in Humans Three forms of biologic work –Chemical: Biosynthesis of cellular molecules –Mechanical: Muscle contraction –Transport: Transfer of substances among cells

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Cellular respiration

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Factors That Affect Rate of Bioenergetics Enzymes –Protein catalysts that accelerate chemical reaction rates without being consumed or changed in the reaction Coenzymes –Nonprotein organic substances that facilitate enzyme action by binding a substrate to its specific enzyme

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Classifications of Enzymes Oxidoreductases Transferases Hydrolases Lyases Isomerases Ligases

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Turnover Number Enzymes do not all operate at the same rate –Turnover number Number of moles of substrate that react to form product per mole of enzyme per unit time pH and temperature alter enzyme activity

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Effects of temperature and pH on enzyme action turnover rate

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Lock and Key Mechanism Enzyme-substrate interaction –Enzyme turns on when its active site joins in a “perfect fit” with the substrate’s active site –Ensures that the correct enzyme matches with its specific substrate to perform a particular function

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Steps in the “lock and key” mechanism of an enzyme and substrate

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Enzyme Inhibition Substances inhibit enzyme activity to slow the rate of a reaction –Bind to enzyme’s active site but enzyme cannot change them –Noncompetitive inhibitors Don’t resemble enzyme’s substrate or bind to its active site Bind to enzyme at a site other than active site to change enzyme’s structure and ability to catalyze the reaction

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Review What is the unique property that enzymes possess? a.They an interchange themselves with one another b.They can be in chemical reactions without being consumed or changed in them c.They can “learn” to perform another function d.They can remain active continually if necessary

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Answer What is the unique property that enzymes possess? a.They an interchange themselves with one another b.They can be in chemical reactions without being consumed or changed in them c.They can “learn” to perform another function d.They can remain active continually if necessary

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Hydrolysis Catabolizes carbohydrates, lipids, and proteins into simpler forms the body easily absorbs and assimilates Splits chemical bonds by adding H + and OH  to the reaction byproducts Condensation –Structural components of the nutrients bind together to form more complex molecules and compounds

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Hydrolysis and condensation of carbohydrates

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Oxidation and Reduction Oxidation –Reactions that transfer oxygen or hydrogen atoms, or electrons –A loss of electrons always occurs with a net increase in valence Reduction –Ay process in which atoms in an element gain electrons, with a corresponding net decrease in valence

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Oxidation and Reduction cont’d Reducing agent –Substance that donates or loses electrons as it oxidizes Oxidizing agent –Substance being reduced or gaining electrons

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Respiratory Chain and Electron Transport Respiratory chain: Transport of electrons by specific carrier molecules constitutes the respiratory chain Electron transport: Represents the final common pathway in aerobic metabolism –For each pair of hydrogen atoms, two electrons flow down the chain and reduce one oxygen atom –Process ends when oxygen accepts two hydrogens and forms water

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Review What is photosynthesis an example of? a.Potential energy b.Kinetic energy c.An exergonic reaction d.Energy conversion

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins What is photosynthesis an example of? a.Potential energy b.Kinetic energy c.An exergonic reaction d.Energy conversion Answer