Biological oxidation Bioenergetics and general concepts (part - I)
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The document discusses biochemical thermodynamics and energy transformations that occur in living systems. It explains that biochemical thermodynamics deals with the energy changes in biochemical reactions and predicts whether processes are possible, while kinetics measures reaction rates. The first and second laws of thermodynamics are described, with the first law stating that energy cannot be created or destroyed, only converted between forms, and the second law stating that spontaneous reactions result in increased disorder. ATP is discussed as the major carrier of chemical energy in cells, with its hydrolysis being an exergonic reaction and synthesis being endergonic. Substrate-level phosphorylation and electron transport chain are described as mechanisms for generating ATP.
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Biological oxidation Bioenergetics and general concepts (part - I)
- 1. ( Part –I )
- 3. biochemical thermodynamics Its deals with the study of energy changes in biochemical reactions. It is concerned with the initial & final states of energy component of the reactants and not the mechanism of chemical reactions. In short, bioenergetics predicts if a process is possible, whereas kinetics measures how fast the reaction occurs.
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- 5. Energy • Capacity to perform work
- 6. • The study of energy transformations that occur in a collection of matter. • Two Laws: 1. First Law of Thermodynamics 2. Second Law of Thermodynamics
- 7. First Law of Thermodynamics • Energy cannot be created or destroyed, but only converted to other forms. • This means that the amount of energy in the universe is constant.
- 8. The First Law is not much help... What prevents a melting ice cube from spontaneously refreezing? Why doesn’t water flow uphill? Will L-alanine convert into D-alanine? The energy of the system and its surrounds won’t change. If it does not occur, what is driving force?
- 9. The Second Law helps resolve problem Only those events that result in a net increase in disorder will occur spontaneously
- 10. Second Law of Thermodynamics • All energy transformations are inefficient because every reaction results in an increase in entropy and the loss of usable energy as heat. • Entropy: the amount of disorder in a system.
- 11. Stage 1 Stage of hydrolysis Polysaccharides, are broken down to glucose, Lipids (TG) is hydrolysed to FFA & glycerol. Proteins are hydrolysed to amino acids.
- 12. Foods GLYCOLYSIS CarbohydratesProteins Lipids Amino acids Fatty acid & glycerol NADH + H+ NADH + H+ FADH2 O2 H2O Glucose Pyruvate Acetyl CoA CO2 CO2 PDH COMPLEX Waste products NH3 Stage 1 Stage of hydrolysis Preparatory stage Oxidative stage Stage 3 CO2 NADH + H+ KREBS CYCLE e- e- e- ETC
- 13. Energy containing nutrients Carbohydrates Fats Proteins Energy Depleted End products CO2 H2O NH3 Cell macromolecules Proteins Polysaccharides Lipids Nucleic acids Precursor molecules Amino acids Sugars Fatty acids Nitrogenous bases Catabolism Anabolism ATP + Pi NADH+H+ NADPH+H+ FADH2 ADP + Pi NAD+ NADP+ FAD
- 14. Free Energy Change • Free energy (∆G) – The energy actually available to do work (utilizable). • Enthalpy (∆H) – is a measure of the change in heat content of the reactants, compared to products. • Entropy (∆S) – a change in the randomness or disorder of reactants and products. • The relation between these three… ∆G = ∆H - T∆S
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- 16. There is a loss of free energy. These are spontaneous reactions. The free energy change (∆G) is represented by a negative sign. E.g. Hydrolysis of ATP. ATP + H2O → ADP + P (∆G°= –7.3 Cal/mol)
- 17. Hydrolysis of ATP Hydrolysis (add water) P P P Adenosine triphosphate (ATP) P P P+ Adenosine diphosphate (ADP) (∆G°= –7.3 Cal/mol)
- 18. Endergonic Reactions Energy must be supplied to the reactants. These are non-spontaneous reactions. The free energy change (∆G) is represented by a positive sign. E.g. Synthesis of ATP. ADP + P → ATP + H2O (∆G°= +7.3 Cal/mol)
- 19. Dehydration of ADP Dehydration synthesis (remove water) P P P Adenosine triphosphate (ATP) P P P+ Adenosine diphosphate (ADP) (∆G°= +7.3 Cal/mol)
- 20. But at equilibrium, it is zero (∆G = 0) The energy coupling occurs by coupling of exergonic and endergonic reactions and liberation of heat.
- 21. What Can Cells Do with Energy? Cells use energy for: –Chemical work –Mechanical work –Electrochemical work
- 23. ❖Substances which possess sufficient free energy to liberate at least 7.3 kcal/mol at pH 7.0 are termed as high-energy compounds or energy rich compounds. ❖All the high-energy compounds, when hydrolyzed liberate more energy than that of ATP. 24
- 24. Standard free energy of hydrolysis of some phosphorylated compounds
- 25. ATP Major activities promoted by ATP: -locomotion -membrane transport -signal transduction -keeping materials in the cell -nucleotide synthesis • ATP is the principal carrier of chemical energy in the cell! • High Energy compounds. • Go’ = -7.3 kcal/mol 26
- 26. THE GENERATION OF ATP ATP is generated by the phosphorylation of ADP
- 28. - Substrate-level phosphorylation is the transfer of a high-energy PO4- to ADP at the expense of the energy of the substrate without involving the electron transport chain. The substrate has higher energy level than the product, the surplus energy is used up for ATP formation.
- 29. Substrate-level phosphorylation – transferring a phosphate directly to ADP from another molecule Example – PEP + ADP → Pyruvate + ATP
- 30. Redox potential of a system is the electron transfer potential E0 Oxidation being termed for the removal of electrons. Reduction for gain of electrons, When a substance exists both in the reduced state and in the oxidized state, the pair is called a redox couple.
- 31. When a substance has lower affinity for electrons than hydrogen, it has a negative redox potential. NADH, has a negative redox potential (–0.32 V ) If the substance has a positive redox potential, it has a higher affinity for electrons than hydrogen. oxygen has a positive redox potential (+0.82 V) In electron transport chain, the electrons flow from electronegative potential (-0.32) to electropositive potential (+ 0.82).
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