Endergonic vs Exergonic Reactions PDF

Endergonic vs Exergonic Reactions SIJ1003 The laws of thermodynamics The Laws of Thermodynamics describe what is known about energy transformations in our universe. The First Law of Thermodynamics According to the first law of thermodynamics, the energy of the universe is constant:...

Endergonic vs Exergonic Reactions SIJ1003 The laws of thermodynamics The Laws of Thermodynamics describe what is known about energy transformations in our universe. The First Law of Thermodynamics According to the first law of thermodynamics, the energy of the universe is constant: Energy can be transferred and transformed, but it cannot be created or destroyed. The first law is also called the principle of conservation of energy. ENTROPY : a thermodynamic quantity representing the unavailability of a system's thermal energy for conversion into mechanical work, often interpreted as the degree of disorder or randomness in the system ENTHALPY: a thermodynamic quantity equivalent to the total heat content of a system. It is equal to the internal energy of the system plus the product of pressure and volume. The Second Law of Thermodynamics During every energy transfer or transformation, some energy is unusable, and is often lost as heat. - 100% efficiency of energy transfer is impossible. - In many life important process such as photosynthesis and oxidation of glucose, the efficiency is only about 42%. According to the second law of thermodynamics: – Every energy transfer or transformation increases the entropy (disorder) of the universe. Entropy: a measure of disorder and randomness in the system (or the surroundings).  Systems tend to proceed from ordered (low- entropy) states to disordered (high-entropy) states. The entropy of the system plus surroundings is unchanged by reversible processes; the entropy of the system plus surroundings increases for irreversible processes. ENTHALPY a thermodynamic quantity equivalent to the total heat content of a system. It is equal to the internal energy of the system plus the product of pressure and volume.  We can spend hours cleaning our room, but we can undo it all in seconds. Similarly, cells use a lot of energy to fight the natural tendency toward dispersion into many different arrangements and to keep the cell structure intact. Exergonic and endergonic reactions in metabolism An exergonic reaction proceeds with a net release of free energy and is spontaneous. ∆G is negative. An endergonic reaction absorbs free energy from its surroundings and is non-spontaneous. ∆G is positive. Δ G = 0, the process is at equilibrium, no net flow either in forward or reverse direction. A quick review of the videos Gibbs free energy – measure of amount of usable energy in that system ΔG - change in Gibbs free energy = Gfinal – Ginitial  Reactants Amount of energy released (∆G < 0) Free energy Energy Products Progress of the reaction (a) Exergonic reaction: energy released Products Amount of energy required Free energy (∆G > 0) Energy Reactants Free energy changes (ΔG) in exergonic and Progress of the reaction endergonic reactions (b) Endergonic reaction: energy required  Endergonic reactions are coupled with exergonic reactions E.g. Glucose → glucose-6- ΔG = +3.2 phosphate ATP → ADP + Pi kcal/mol ΔG = - 7.3 kcal/mol Glucose + ATP → glucose-6-phosphate + ADP ΔG = -4.1 + Pi kcal/mol  If a reaction is endergonic in one direction then it must be exergonic in the other, and vice versa. Under standard biochemical conditions : 25°C, 1M concentrations, 1 atm pressure, pH 7. ATP Energy currency Transfer of chemical energy Stored energy ATP and coupling reactions ATP hydrolyzed must be coupled with something that needs it  P P P Adenosine triphosphate (ATP) H2O Pi + P P + Energy Use to drive a Inorganic phosphate Adenosine diphosphate (ADP) variety of endergonic reactions The hydrolysis of ATP ATP: Energy currency of the cell The role of ATP as energy currency in process that release energy and process that use energy. ATP cannot be stored. ATP is constantly being formed and decomposed. Its turnover is very high. 1 7