Chapter 5

1. Chapter 5 Introduction to Energy Transfer

2. 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

3. 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

4. Potential and kinetic energy example

5. 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

6. 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

7. Energy flow in chemical reactions

8. 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

9. Forms of Energy • Each energy form can convert or transform to another • Chemical • Mechanical • Heat • Light • Electrical • Nuclear

10. Interconversions of forms of energy

11. 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

12. Photosynthesis

13. Review • What constitutes the total energy of a system? • Chemical and electrical energy • Potential and biochemical energy • Potential and kinetic energy • Kinetic energy and heat

14. Answer • What constitutes the total energy of a system? • Chemical and electrical energy • Potential and biochemical energy • Potential and kinetic energy • Kinetic energy and heat

15. Biologic Work in Humans • Three forms of biologic work • Chemical: Biosynthesis of cellular molecules • Mechanical: Muscle contraction • Transport: Transfer of substances among cells

16. Cellular respiration

17. 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

18. Classifications of Enzymes • Oxidoreductases • Transferases • Hydrolases • Lyases • Isomerases • Ligases

19. 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

20. Effects of temperature and pH on enzyme action turnover rate

21. 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

22. Steps in the “lock and key” mechanism of an enzyme and substrate

23. 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

24. Review •  What is the unique property that enzymes possess? • They an interchange themselves with one another • They can be in chemical reactions without being consumed or changed in them • They can “learn” to perform another function • They can remain active continually if necessary

25. Answer •  What is the unique property that enzymes possess? • They an interchange themselves with one another • They can be in chemical reactions without being consumed or changed in them • They can “learn” to perform another function • They can remain active continually if necessary

26. 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

27. Hydrolysis and condensation of carbohydrates

28. 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

29. Oxidation and Reduction cont’d • Reducing agent • Substance that donates or loses electrons as it oxidizes • Oxidizing agent • Substance being reduced or gaining electrons

30. 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

31. Review • What is photosynthesis an example of? • Potential energy • Kinetic energy • An exergonic reaction • Energy conversion

32. Answer • What is photosynthesis an example of? • Potential energy • Kinetic energy • An exergonic reaction • Energy conversion