When ATP donates a phosphate group, it is converted to a group with low energy, forming phosphoric esters of alcohols. This reaction is catalysed by kinases. Among them is hexokinase, which catalyses the transfer of phosphate group from ATP to D-glucose. This reaction is proceeded by an orthophosphate cleavage of ATP, in which, ATP loses…
The processes that feed ~P into ATP/ADP cycle fall mainly within four groups:
ATP has a position midway down the list of standard free energies of organophosphates. So ATP acts as a donor of high-energy phosphates to the compounds which have free energy less than the ATP. ADP can accept high-energy phosphate in the presence of enzyme to form ATP from the compounds whose free energy is greater…
When ATP is hydrolysed, it loses its terminal γ-phosphate group to form ADP and orthophosphate or inorganic phosphate (Pi). ATP + H2O ADP + Pi The standard free energy change ΔG° for this reaction is −7.3 Kcal/mol. Standard free energy changes have also been determined for the hydrolysis of other phosphorylated compounds or organophosphates. Under…
Adenosine Triphosphate (ATP) is the universal currency of free energy in biological systems; living objects require a continuous supply of free energy mainly for the following four purposes: The free energy in these processes is derived from the environment. Autotrophs obtain this energy by trapping light energy from the sun. On the other hand, heterotrophs…
Consider the reaction A → B A mathematical relation for the free energy change can be derived. ΔG = ΔG° + RT ln Where ΔG° = Standard free energy changeR = Gas constantT = Absolute temperatureln = Natural logarithmB = Concentration of productA = Concentration of reactantΔG° is related to equilibrium constant (Keq) When a reaction A ↔ B is at equilibrium (eq), the free energy…
If a reacting system is not in equilibrium, the force used to attain the equilibrium is defined as free energy change, ΔG. Standard free energy ΔG is defined as the force required to attain equilibrium at standard condition (298K = 25°C) and when the reactants and products are present at 1M concentration at 1 atm. At constant…
It represents a change in the randomness or disorder of the reactants and products. Entropy attains maximum as the reaction approaches equilibrium. The relation connecting the changes of free energy, enthalpy and entropy is expressed as ΔG = ΔH – T ΔS T = Absolute temperature in Kelvin (K = 273 + °C)
Enthalpy refers to the heat content of the reducing system. It indicates the number and kinds of chemical bonds in the reactants and products. A chemical reaction that releases heat is known as an exothermic reaction. The heat content of the product is less than that of reactants, and ΔH is negative. When a chemical reaction…
The energy actually available to do work during a reaction at constant temperature and pressure is called free energy, ΔG. When a reaction proceeds with the release of free energy, the free energy change, ΔG, is negative, and the reaction is said to be exergonic. In endergonic reaction, the system gains free energy, and ΔG is positive.