Bioenergetics And Metabolism in a cell.
It takes energy to break the chemical bonds that hold the atoms in a molecule together. Heat energy, because it increases atomic motion, makes it easier for the atoms to pull apart. Both chemical bonding and heat have a significant influence on a molecule, the former reducing disorder and the latter increasing it. The net effect, the amount of energy actually available to break and subsequently form other chemical bonds, is called the free energy of that molecule. In a more general sense, free energy is defined as the energy available to do work in any system. In a molecule within a cell, where pressure and volume usually do not change, the free energy is denoted by the symbol G (for “Gibbs’ free energy,” which limits the system being considered to the cell). G is equal to the energy contained in a molecule’s chemical bonds (called enthalpy and designated H) minus the energy unavailable because of disorder (called entropy and given the symbol S) times the absolute temperature, T, in degrees Kelvin (K = °C + 273): G = H – TS reactions break some bonds in the reactants and form new bonds in the products. Consequently, reactions can produce changes in free energy. When a chemical reaction occurs under conditions of constant temperature, pressure, and volume—as do most biological reactions— the change in free energy (ΔG) is simply:
ΔG = ΔH – T ΔS <0 for any spontaneous reaction
Driving factor behind any Biological reaction is to make overall del(G)<0.In the previous paper i defined why del(G) is required to be negative.Mathematically it is related to Thermodynamics and second law of thermodynamics which says about the direction of chemical reaction which depends upon both Enthalpy change for a chemical reaction and Entropy change of a chemical reaction. I will mathematically
talk about these factor in Bio-chemistry as i am a mathematician but today i wanted to give you its overall
picture. Lets depict it in terms of graph
Energy in chemical reactions. (a) In an endergonic reaction, the products of the reaction contain more energy than the reactants, and the
extra energy must be supplied for the reaction to proceed. (b) In an exergonic reaction, the products contain less energy than the reactants,
and the excess energy is released.
Free energy is the energy available to do work. Within cells, the change in free energy (ΔG) is the difference in bond energies between reactants and products (ΔH), minus any change in the degree of disorder of the system (T ΔS). Any reaction whose products contain less free energy than the reactants (ΔG is negative) will tend to proceed spontaneously.
Activation Energy:
The rate of an exergonic reaction depends on the activation energy required for the reaction to begin. Reactions with larger activation energies tend to proceed more slowly because fewer molecules succeed in overcoming the initial energy hurdle. Activation energies are not constant, however. Stressing particular chemical bonds can make them easier to break. The process of influencing
chemical bonds in a way that lowers the activation energy needed to initiate a reaction is called catalysis, and substances that accomplish this are known as catalysts.
The rate of a reaction depends on the activation energy necessary to initiate it. Catalysts reduce the activation energy and so increase the rates of reactions, although they do not change the final proportions of reactants and products.\\
Activation energy and catalysis. (a) Exergonic reactions do not necessarily proceed rapidly because energy must be supplied to destabilize existing chemical bonds. This extra energy is the activation energy for the reaction. (b) Catalysts accelerate particular reactions by lowering the amount of activation energy required to initiate the reaction.
ATP : Adenosine TriPhosphate.
Each ATP molecule is a nucleotide composed of three smaller components as given below The first component is a five-carbon sugar, ribose, which serves as the backbone to which the other two subunits are attached. The second component is adenine, an organic molecule composed of two carbon-nitrogen rings. Each of the nitrogen atoms in the ring has an unshared pair of electrons and weakly attracts hydrogen ions. Adenine, therefore, acts chemically as a base and is usually referred to as a nitrogenous base (it is one of the four nitrogenous bases found in DNA and RNA). The third component of ATP is a triphosphate group (a chain of three phosphates).
How ATP Stores Energy The key to how ATP stores energy lies in its triphosphate
group. Phosphate groups are highly negatively charged, somthey repel one another strongly. Because of the electrostatic repulsion between the charged phosphate groups, the
two covalent bonds joining the phosphates are unstable. The ATP molecule is often referred to as a “coiled spring,” the phosphates straining away from one another. The unstable bonds holding the phosphates together in the ATP molecule have a low activation energy and are easily broken. When they break, they can transfer a considerable amount of energy. In most reactions involving ATP,
only the outermost high-energy phosphate bond is hydrolyzed, cleaving off the phosphate group on the end. When this happens, ATP becomes adenosine diphosphate (ADP), and energy equal to 7.3 kcal/mole is released under standard conditions. The liberated phosphate group usually attaches temporarily to some intermediate molecule. When that molecule is dephosphorylated, the phosphate
group is released as inorganic phosphate (Pi).
It takes energy to break the chemical bonds that hold the atoms in a molecule together. Heat energy, because it increases atomic motion, makes it easier for the atoms to pull apart. Both chemical bonding and heat have a significant influence on a molecule, the former reducing disorder and the latter increasing it. The net effect, the amount of energy actually available to break and subsequently form other chemical bonds, is called the free energy of that molecule. In a more general sense, free energy is defined as the energy available to do work in any system. In a molecule within a cell, where pressure and volume usually do not change, the free energy is denoted by the symbol G (for “Gibbs’ free energy,” which limits the system being considered to the cell). G is equal to the energy contained in a molecule’s chemical bonds (called enthalpy and designated H) minus the energy unavailable because of disorder (called entropy and given the symbol S) times the absolute temperature, T, in degrees Kelvin (K = °C + 273): G = H – TS reactions break some bonds in the reactants and form new bonds in the products. Consequently, reactions can produce changes in free energy. When a chemical reaction occurs under conditions of constant temperature, pressure, and volume—as do most biological reactions— the change in free energy (ΔG) is simply:
ΔG = ΔH – T ΔS <0 for any spontaneous reaction
Driving factor behind any Biological reaction is to make overall del(G)<0.In the previous paper i defined why del(G) is required to be negative.Mathematically it is related to Thermodynamics and second law of thermodynamics which says about the direction of chemical reaction which depends upon both Enthalpy change for a chemical reaction and Entropy change of a chemical reaction. I will mathematically
talk about these factor in Bio-chemistry as i am a mathematician but today i wanted to give you its overall
picture. Lets depict it in terms of graph
Energy in chemical reactions. (a) In an endergonic reaction, the products of the reaction contain more energy than the reactants, and the
extra energy must be supplied for the reaction to proceed. (b) In an exergonic reaction, the products contain less energy than the reactants,
and the excess energy is released.
Free energy is the energy available to do work. Within cells, the change in free energy (ΔG) is the difference in bond energies between reactants and products (ΔH), minus any change in the degree of disorder of the system (T ΔS). Any reaction whose products contain less free energy than the reactants (ΔG is negative) will tend to proceed spontaneously.
Activation Energy:
The rate of an exergonic reaction depends on the activation energy required for the reaction to begin. Reactions with larger activation energies tend to proceed more slowly because fewer molecules succeed in overcoming the initial energy hurdle. Activation energies are not constant, however. Stressing particular chemical bonds can make them easier to break. The process of influencing
chemical bonds in a way that lowers the activation energy needed to initiate a reaction is called catalysis, and substances that accomplish this are known as catalysts.
The rate of a reaction depends on the activation energy necessary to initiate it. Catalysts reduce the activation energy and so increase the rates of reactions, although they do not change the final proportions of reactants and products.\\
Activation energy and catalysis. (a) Exergonic reactions do not necessarily proceed rapidly because energy must be supplied to destabilize existing chemical bonds. This extra energy is the activation energy for the reaction. (b) Catalysts accelerate particular reactions by lowering the amount of activation energy required to initiate the reaction.
ATP : Adenosine TriPhosphate.
Each ATP molecule is a nucleotide composed of three smaller components as given below The first component is a five-carbon sugar, ribose, which serves as the backbone to which the other two subunits are attached. The second component is adenine, an organic molecule composed of two carbon-nitrogen rings. Each of the nitrogen atoms in the ring has an unshared pair of electrons and weakly attracts hydrogen ions. Adenine, therefore, acts chemically as a base and is usually referred to as a nitrogenous base (it is one of the four nitrogenous bases found in DNA and RNA). The third component of ATP is a triphosphate group (a chain of three phosphates).
The ATP molecule. (a) The model and (b) structural diagram both show that like NAD+, ATP has a core of AMP. In ATP the reactive group added to the end of the AMP phosphate group is not another nucleotide but rather a chain of two additional phosphate groups. The bonds connecting these two phosphate groups to each other and to AMP are energy-storing bonds.
How ATP Stores Energy The key to how ATP stores energy lies in its triphosphate
group. Phosphate groups are highly negatively charged, somthey repel one another strongly. Because of the electrostatic repulsion between the charged phosphate groups, the
two covalent bonds joining the phosphates are unstable. The ATP molecule is often referred to as a “coiled spring,” the phosphates straining away from one another. The unstable bonds holding the phosphates together in the ATP molecule have a low activation energy and are easily broken. When they break, they can transfer a considerable amount of energy. In most reactions involving ATP,
only the outermost high-energy phosphate bond is hydrolyzed, cleaving off the phosphate group on the end. When this happens, ATP becomes adenosine diphosphate (ADP), and energy equal to 7.3 kcal/mole is released under standard conditions. The liberated phosphate group usually attaches temporarily to some intermediate molecule. When that molecule is dephosphorylated, the phosphate
group is released as inorganic phosphate (Pi).
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