Chapter 6: Energy and Metabolism Free energy is defined as the energy available to do work in any system. The free energy is denoted by the symbol G. G = H – TS* H: the energy contained in a m olecule’s chemical bonds,
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Chapter 6: Energy and Metabolism Free energy is defined as the energy available to do work in any system. The free energy is denoted by the symbol G. G = H – TS* H: the energy contained in a m olecule’s chemical bonds, called enthalpy.* TS: the energy term related to the degree of disorder in the system. T is the absolute temperature (K), and S is the entropy.We can use the change in free energy to predict whether a chemical reaction is spontaneous or not:- G positive: the products contain more free energy than the reactants. The bond energy (H) is higher, or the disorder (S) is lower First -- energy cannot be created or destroyed, but can be transformed from a more useful form to a less useful form, such as from wood to smoke and ashes Second -- Energy moves towards entropy -- the potential energy of a system will be less than the initial energy, if there are no inputs of energy. 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. ATPs are used as the main energy source for metabolic functions. They are consumed by energy-requiring (endothermic) processes and produced by energy-releasing (exothermic) processes in the cell. It does this by giving either losing or gaining a phosphate group. ATP (high energy) ⇔ ADP (low energy) Most enzymes are proteins, which are complicated structures that include primary, secondary, tertiary, and sometimes quaternary interactions. These interactions define the shape of a protein, including the active and allosteric sites. The shape of these sites is specific for the substrates. One of the factors that affects enzyme activity is the pH. If there are small changes in the pH, the enzyme will denature and catalytic activity will be lost. Another factor is the temperature. Enzyme-catalyzed reactions will have the rate increased as the temperature increases. Because the enzymes are proteins, they will become denatured and turn inactive at the higher temperatures. The concentration of the enzyme also affects the activity. If the concentration of the enzyme is increased while the concentration of the substrate is kept constant, the rate of the reaction will double as the enzyme concentration doubles. This is due to the fact that the molar concentration of the enzyme being used almost always will be lower than the molar concentration of the substrate Chapter 7: How Cells Harvest Energy Energy is given off during ATP breakdown. When electrons move closer to the nucleus, energy is released. Electron carriers, such as NADH and FADH can donate their hydrogen to other molecules. These two electron carriers will ultimately produce ATP. Without oxygen, cellular respiration could not occur because oxygen serves as the final electron acceptor in the electron transport system. The electron transport system would therefore not be available. Glycolysis can occur without oxygen. Although glycolysis does not require oxygen, it does require NAD+. Cells without oxygen available need to regenerate
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