Bioenergetics
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The document discusses bioenergetics, which explores energy changes in biochemical reactions in living organisms, categorizing reactions as exergonic (energy-releasing) or endergonic (energy-consuming). Key concepts include the role of adenosine triphosphate (ATP) as the primary energy currency, the laws of thermodynamics, and the significance of energy-rich compounds. Additional topics covered include redox potential, the classification of carbohydrates, amino acids, proteins, and fatty acids, and specific biochemical reactions.
Bioenergetics
- 1. Bioenergetics Mr. S Maheen Abdul Rahman, M. Pharm. Assistant Professor Department of Pharmaceutical Chemistry PA College of Pharmacy (PACP) Mangalore, Karnataka.
- 2. Bioenergetics The term bioenergetics is made up of two words Bio means life of living Energetics means study of energy So, basically Bioenergetics or biochemical thermodynamics deals with the study of energy changes (transfer and utilization) in biochemical reactions in living body. The reactions are broadly classified as exergonic (energy releasing) and endergonic (energy consuming)
- 3. The concept of free energy (ΔG) The energy actually available to do work (utilizable) known as free energy. Changes in the free energy (ΔG) are valuable in predicting the feasibility of chemical reactions. Adenosine triphosphate (ATP) is the main "energy currency" for organisms; the goal of metabolic and catabolic processes are to synthesize ATP from available starting materials (from the environment), and to break- down ATP (into adenosine diphosphate (ADP) and inorganic phosphate) by utilizing it in biological processes.
- 4. In a cell, the ratio of ATP to ADP concentrations is known as the "energy charge" of the cell. A cell can use this energy charge to relay information about cellular needs; if there is more ATP than ADP available, the cell can use ATP to do work, but if there is more ADP than ATP available, the cell must synthesize ATP via oxidative phosphorylation.
- 5. Types of Bioenergetics Reactions 1. Exergonic Reaction Exergonic implies the release of energy from a spontaneous chemical reaction without any concomitant utilization (use) of energy. Most of these reactions involve the breaking of bonds during the formation of reaction intermediates as is evidently observed during respiratory pathways. The bonds that are created during the formation of metabolites are stronger than the cleaved bonds of the substrate.
- 6. The release of free energy, G, in an exergonic reaction (at constant pressure and temperature) is denoted as The hydrolysis of ATP is a classical example of exergonic reaction If free energy change (ΔG) is represented by a negative sign, there is a loss of free energy. The reaction is said to be exergonic reaction.
- 7. On the other hand, a positive ΔG indicates that energy must be supplied to the reactants. The reaction cannot proceed spontaneously and is endergonic in character. 2. Endergonic Reactions The reversal of the reaction (ADP + Pi -+ ATP) is endergonic and occurs only when there is a supply of energy of at least 7.3 Cal/mol (ΔG is positive).
- 8. Bioenergetics is concerned with the changes in energy during biochemical processes. It does not deal with the mechanism or speed of the process. Thermodynamics is the branch of physical chemistry that deals with the energy changes. There are two fundamental laws of thermodynamics which explain interconversions of various forms of energy. The laws of thermodynamics
- 9. The first law of thermodynamics The first law of thermodynamics states that ‘energy can neither be created nor destroyed, but can be converted into other forms of energy’. It means, the total amount of energy in the universe (system + surroundings) remains constant. According to this equation, change in the energy of a system depends only on the initial and the final stages, and not the path of the transformation.
- 10. The second law of thermodynamics The first law of thermodynamics cannot be used to predict the spontaneity or non-spontaneity of the reaction. On the other hand, the second law introduces a term ‘entropy’, which is denoted by symbol ‘S’ Entropy is degree of randomness or disorder of a system and explains whether a reaction takes place spontaneously. Entropy measures the amount of heat dispersed or transferred during a chemical process.
- 11. The Enthalpy (H) which is the heat content of the system. Enthalpy is the amount of heat energy transferred (heat absorbed or emitted) in a chemical process under constant pressure.
- 12. Redox potential (Oxidation-Reduction potential) The oxidation-reduction potential or, simply, redox potential, is a quantitative measure of the tendency of a redox pair to lose or gain electrons On the other hand, a more positive redox potential indicates a greater tendency (of oxidant) to accept electrons The redox potential (Eo) is directly related to the change in the free energy (ΔGo ).
- 13. Energy Rich Compounds Certain compounds are encountered in the biological system which, on hydrolysis, yield energy. The term high-energy compounds or energy rich compounds is usually applied to substances which possess sufficient free energy to liberate at least 7 Cal/mol at pH 7.0 Certain other compounds which liberate less than 7 Cal/mol (lower than ATP hydrolysis to ADP + Pi) are referred to as low energy compounds.
- 14. All the high-energy compounds-when hydrolysed-liberate more energy than that of ATP. These include phosphoenol pyruvate, 1,3- bisphosphoglycerate, phosphocreatine etc. Most of the high-energy compounds contain phosphate group (exception acetyl CoA) hence they are called high-energy phosphate compounds.
- 15. ATP: the universal currency of free energy The living organisms derive free energy from the environment. The photosynthetic organisms take this energy from sunlight whereas, chemotrophs (non photosynthetic organisms) obtain it by oxidation of food stuff. Before being utilized in the above-mentioned process the free energy (derived from light or from the oxidation of food stuff) is partly converted into a special form, adenosine triphosphate (ATP).
- 16. ATP is also known as universal currency of free energy. It plays a central role in the transfer of free energy from exergonic (energy releasing) processes to endergonic (energy consuming) processes in the cells. During the breakdown of the energy rich food stuff, some of the free energy is consumed in synthesis of ATP from adenosine diphosphate (ADP) and inorganic phosphate (Pi). Also, it can convert into AMP
- 18. cyclic AMP Cyclic AMP (cAMP, cyclic adenosine 3',5'-monophosphate) is a ubiquitous nucleotide. It consists of adenine, ribose and a phosphate (linked by 3',5' linkage). cAMP acts as a second messenger for a majority of polypeptide hormones. The membrane-bound enzyme adenylate cyclase converts ATP to cyclic AMP. cAMP is hydrolysed by phosphodiesterase to 5-AMP
- 19. Assignment for the Unit-I 10 Marks: 1. Define and classify carbohydrates with suitable examples. Add a note on the functions of carbohydrates 2. Describe the classification of amino acids along with their structures 5 Marks 3. Describe the classification of proteins with suitable example 4. Discuss the saturated and unsaturated fatty acids of biological importance, along with their structure 5. Write an account of Essential amino acids 6. What is bioenergetics . Write a different types of Bioenergetics Reactions 2 Marks 7. Saponification number 8. Essential fatty acids 9. What is Glycosidic bond with examples. 10.Peptide bond with structure 11.Sanger’s reagent and Edman's reagent 12.Zwitterion 13.Structure of ATP 14.Energy Rich Compounds Important Questions too…
- 20. REFERENCE BOOK: Text book of biochemistry by Satyanarayana and chakrapani