MBB222-lecture4 %5bCompatibility Mode%5d

MBB222-lecture4 %5bCompatibility Mode%5d - Energy the...

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Energy • the ability to do work • production, storage, and use are at the centre of the cellular economy • 2 principle forms: kinetic and potential
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Kinetic Energy: the energy of movement • e.g., thermal energy (heat) of the motion of molecules radiant energy of photons (waves of light) mechanical energy of shortening cytoskeletal filaments electric energy of moving electrons/charged particles Potential Energy: the energy of position / location • e.g., chemical potential energy stored in covalent bonds concentration gradients across cellular membranes electric potential energy across cellular membranes
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First Law of Thermodynamics: • energy is neither created nor destroyed, but rather is converted from one form to another • because of this, all energy forms can be expressed in the same units of measurement – standard unit = joule, but biochemists have traditionally used an alternate unit: the calorie (1 cal = 4.184 J)
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Free Energy: • all systems change in such a way that free energy (G) is minimized • consider the simple chemical reaction: reactants products • the change in free energy, Δ G, is given by Δ G = G products - G reactants • if Δ G < 0, the forward reaction will occur spontaneously • if Δ G > 0, the reverse reaction will occur spontaneously • if Δ G = 0, both forward and reverse reactions will occur at equal rates (i.e., the reaction is at equilibrium)
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Δ G o is the change in free energy under standard conditions (25°C = 298 K, 1 atm pressure, pH = 7.0, and initial
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MBB222-lecture4 %5bCompatibility Mode%5d - Energy the...

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