lecture slides on the topic Bioenergetics 1.ppt
- 1. Department of Biochemistry Baba Ahmed University, Kano. Dr. Dayyab Shehu
- 2. INTRODUCTION • The ultimate source of energy for life in our solar system is the sun. • Because of its size, it has a gravitational force that pulls all its mass inwards, creating an intense amount of pressure at its core. • This pressure is capable of forcing atoms of hydrogen (H) to fused into atoms of helium (He) accompanied with the release of large amount of energy called solar energy. • It is this solar energy that reaches our planet and living organism used it to sustain their existence through a series of reactions.
- 3. An Overview • Autotrophic organisms (organisms capable of synthesizing their own food e.g. photosynthetic organism) uses the sun's solar energy and an electron (e- ) from water (H2O) to reduce carbon dioxide (CO2) into a more complex glucose unit (C6H12O6). • From this sugars, the organism obtained the carbon skeleton for the synthesis of all that it needs, including adenosine triphosphate (ATP).
- 4. Heterotrophic organism • Heterotrophic organism (e.g humans) consume these components synthesized by autotrophs and extracts the necessary electrons they need from them via series of chemical reactions to ultimately synthesize ATP and releases CO2 andH2O. • ATP plays a vital role in synthesis of macromolecules, in transport of solutes across membranes, and in mechanical motion (e.g. muscle contraction and flagella movement).
- 5. • In this note we are going look at the principle behind these energy transformation in cell using thermodynamics and have a look at the synthesis of ATP by substrate level phosphorylation and oxidative phosphorylation.
- 6. BIOENERGETICS • Living cells and organisms must perform work to stay alive, to grow, and to reproduce. • They need a constant supply of energy to maintain homeostasis (to adjust internal environment to achieve a steady state) and to put off death as long as possible. • The ability to harness energy and to channel it into biological work is a fundamental property of all living organisms and this is what bioenergetics looks into. • Thus, Bioenergetics is the quantitative study of the energy transductions that occur in living cells and of the nature and function of the chemical processes underlying these transductions.
- 7. • These energy conversions are required for three main types of work that maintains homeostasis, viz: • chemical work in a form of macromolecule synthesis of organic molecules. • osmotic work to maintain a concentration of intracellular salts and organic compounds that are different than the extracellular milieu, and • mechanical work in the form of flagella rotation and muscle contraction.
- 8. Constant Supply of energy Maintain Homeostasis The ability to harness energy and to channel it into biological work is a fundamental property of all living organisms and this is what bioenergetics looks into Bioenergetics is the quantitative study of the energy transductions that occur in living cells and of the nature and function of the chemical processes underlying these transductions Chemical Work Osmotic Work Mechanical Work These energy transformation are better explained by the knowledge of Thermodynamics
- 9. THERMODYNAMICS • Thermodynamic is the branch of physical science dealing with the study of energy changes. • The principle of thermodynamics talked about the system - collection of matter in a defined space; • surrounding - the encasement of the system; universe - which consist of a system with its surrounding and the interaction between them.
- 10. Interaction between a system and its surrounding • isolated system or (adiabatic system): there are no exchange of energy nor matter between the system and its surrounding; • closed system: there is an exchange of energy only between the system and its surrounding but not matter and; • open system where both energy and matter are exchanged between the system and its surrounding.
- 11. • Biological systems are open systems as both matter (nutrients and waste products) and energy (primarily in a form heat) are exchanged with their surroundings. • These exchanges are driven by the need to achieve equilibrium between the system and the surrounding. • Once achieved, then there is no net change in the universe. • For living organism its means they need to maintain a steady state far from equilibrium (homeostasis) in order to survive and prevent reaching equilibrium with their surrounding as long as possible by obtaining energy from the surroundings.
- 12. Laws of Thermodynamics • Many quantitative observations made by physicists and chemists on the inter- conversion of different forms of energy led, in the nineteenth century, to the formulation of two fundamental laws of thermodynamics:
- 13. • The first law is the principle of the conservation of energy that states: for any physical or chemical change, the total amount of energy in the universe remains constant; energy may change forms or it may be transported from one region to another, but it cannot be created or destroyed.
- 14. • This transformation of energy is not 100% efficient as certain amount energy is lost as other forms of energy. • In biology, for example, energy transformation proceeds usually with the change of energy in form of heat calculated as enthalpy change (ΔH). • Enthalpy, H, is the heat content of the reacting system. • It reflects the number and kinds of chemical bonds in the reactants and products. • When a chemical reaction releases heat, it is said to be exothermic; the heat content of the products is less than that of the reactants and ΔH has, by convention, a negative value. • Reacting systems that take up heat from their surroundings are endothermic and have positive values of ΔH. • The units of ΔH is joules/mole or calories/mole
- 15. The First Law of Thermodynamics In biologically energy transformation proceeds usually with the change of energy in form of heat calculated as enthalpy change (ΔH) Enthalpy, H, is the heat content of the reacting system It reflects the number and kinds of chemical bonds in the reactants and products When a chemical reaction releases heat, it is said to be exothermic (ΔH=-ve) When a chemical reaction gains heat, it is said to be endothermic (ΔH=+ve)
- 16. • The second law of thermodynamics says that the universe always tends toward increasing disorder: • in all natural processes, the change in entropy (ΔS) of the universe increases (without an input of energy). • Entropy, S, is a quantitative expression for the randomness or disorder in a system. When the products of a reaction are less complex and more disordered than the reactants, the reaction is said to proceed with a gain in entropy and ΔS is positive e.g. the melting of ice at room temperature. • Units of entropy are joules/mole/Kelvin (J/mol/K) • This law is useful in determining the directionality of a reaction i.e. its spontaneity.
- 17. Natural Process Energy Input SECOND LAW OF THERMODYNAMICS Ordered Disordered Entropy, S, is a quantitative expression for the randomness or disorder in a system Metabolic energy is required to sustain life and restrain the natural tendency of the molecules within the organism to become disordered (reach equilibrium with its surrounding) as dictated by the second law of thermodynamics This law is useful in determining the directionality of a reaction i.e. its spontaneity
- 18. Gibbs Free Energy • Cells are isothermal systems—they function at essentially constant temperature (they also function at constant pressure). • Heat flow is not a source of energy for cells, because heat can do work only as it passes to a zone or object at a lower temperature. • The energy that cells can and must use is free energy, described by the Gibbs free-energy function G. This is the amount of energy capable of doing work during a reaction at constant temperature and pressure.
- 19. • When a reaction proceeds with the release of free energy (that is, when the system changes so as to possess less free energy), the free-energy change, ΔG, has a negative value and the reaction is said to be exergonic (favorable). • In endergonic reactions (unfavorable), the system gains free energy and ΔG is positive. • At equilibrium ΔG is zero meaning that no net product and reactant formation. • Gibbs free-energy allows for the prediction of the direction of chemical reactions their exact equilibrium position, and the amount of work they can, in theory, perform at constant temperature and pressure. The units of ΔG is joules/mole or calories/mole.