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gen bio Chapter 7

gen bio Chapter 7 - Chapter 7 Energy and Metabolism I...

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Chapter 7 – Energy and Metabolism I. Biological work a. Energy i. Defined as capacity to do work – any change in state or motion of matter ii. Energy expressed in units of work – kilojoules (kJ) iii. Also expressed in units of heat energy – kilocalories (kcal) iv. 1 kcal = 4.184 kJ b. Organisms carry out conversions between PE and KE c. The total energy in the universe does not change i. First law of thermodynamics – energy cannot be created/destroyed, only transferred/converted from one form to another ii. Organisms cannot create energy required to live, must capture energy from environment and transform it to form used for biological work d. The entropy of the universe is increasing i. Second law of thermodynamics – when energy converted from one form to another, some usable energy is converted into heat that disperses into surroundings ii. Heat = KE of randomly moving particles 1. Cannot perform work unlike heat energy iii. Total amount of energy available to do work increasing over time iv. Entropy (S) – measure of this disorder or randomness of less-usable energy 1. Continuously increasing in all natural processes v. No process requiring energy conversion is ever 100% efficient vi. Organisms maintain high level of order, don’t appear to become disorganized, but maintain their degree of order over time only with constant input of E from surroundings vii. Although order within organisms may tend to increase temporarily, total entropy of universe always increases II. Energy and metabolism a. Metabolism – sum of all chemical activities taking place in organism i. anabolism – various pathways in which complex molecules synthesized from simpler substances ii. catabolism – pathways in which larger molecules broken down into smaller ones b. enthalpy is the total PE of a system i. every specific type of chemical bond has certain amount of bond energy = energy required to break bond ii. total bond energy equivalent to total PE of system iii. enthalpy (H) = total PE of system c. free energy is available to do cell work i. free energy (G) = amount of E available to do work under conditions of biochemical reaction ii. free energy and entropy related by following equation 1. H = G + TS 2. H = enthalpy; G = free energy; T = abs. temp; S = entropy
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3. Enthalpy = free (usable) energy + entropy (usable E) iii. As entropy increases, amount of free energy decreases 1. G = H – TS iv. If entropy = 0, free E = to total PE (enthalpy), increase in entropy reduces amount of free E v. As temp increases, increase in random molecular motion which multiplies effect of entropy d. Chemical reactions involve changes in free energy i. Equation G = H – TS can be extended to predict whether chemical reaction will release energy or require input of energy 1. Change in free E can be measured ii. To express what happens WRT energy in chemical reaction 1. ΔG = ΔH – TΔS 2. Δ in free E = Δenthalpy minus (abs. temp)(Δentropy) e. Free energy decreases during exergonic reaction i. Exergonic reaction – release energy, said to be spontaneous or “downhill” reaction ii. From higher to lower free E
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gen bio Chapter 7 - Chapter 7 Energy and Metabolism I...

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