Slide 1 / 64 Chapter 8 Metabolism Slide 2 / 64 Metabolic Pathways Metabolism is the totality of an organism’s chemical reactions. Metabolism is a property of all life. Slide 3 / 64 Metabolic Pathways There are two types of metabolic pathways: Catabolic pathways release energy by breaking down complex molecules into simpler compounds. Anabolic pathways consume energy to build complex molecules from simpler ones.
Slide 4 / 64 Metabolic Pathways A metabolic pathway begins with a specific molecule and ends with a product Each step is catalyzed by a specific enzyme No enzyme, no reaction enzyme 3 enzyme 1 enzyme 2 C B A D Reaction 1 Reaction 3 Reaction 2 Starting Product Molecule Slide 5 / 64 Biological Energy Flow Living things use anabolic pathways to synthesize more complex organic molecules using the energy derived from catabolic pathways. Molecules from the environment are broken down. Their energy and matter are used to: · build structures · drive processes But living things still obey the Laws of Thermodynamics. Slide 6 / 64 The First Law of Thermodynamics ΔE = w + q Energy is neither created nor destroyed. The total energy of the universe is a constant; if a system loses energy, it must be gained by the surroundings, and vice versa. Initial Final state E Initial state E final Internal energy, E Internal energy, E E Final < E initial E final > E initial ∆E < 0 ( negative) # E > 0 (positive) Energy lost to Energy gained surroundings from surroundings Final Initial state E Final state E initial E of system decreases E of system increases
Slide 7 / 64 System and Surroundings The system includes whatever we want to study, living or non-living. The surroundings are everything else. Surroundings System I System II Slide 8 / 64 Exchange of Heat between System and Surroundings When heat is absorbed by When heat is released by the system, the process is the system, the process endothermic. is exothermic . System System Surroundings Heat Heat Endothermic Exothermic Remember that a change in heat is a change of enthalpy. Slide 9 / 64 1 If a hot rock is placed in cold water, and your system is the rock, the process is _____. A endothermic B exothermic C neither, there is no change in energy D it depends on the temperature
Slide 10 / 64 2 If a hot rock is placed in cold water, and your system is the water, the process is _____. A endothermic B exothermic C neither, there is no change in energy D it depends on the temperature Slide 11 / 64 3 If an ice cube is placed in warm water, and your system is the ice cube, the process is _____. A endothermic B exothermic C neither, there is no change in energy D it depends on the temperature Slide 12 / 64 4 If an ice cube is placed in warm water, and your system is the warm water, the process is _____. A endothermic B exothermic C neither, there is no change in energy D it depends on the temperature
Slide 13 / 64 5 Water droplets evaporating from the skin surface will make you feel cold. For your skin, this process is _____. A endothermic B expothermic C neither, there is no change in energy D it depends on the temperature Slide 14 / 64 Biological Order and Disorder Life creates ordered structures from less ordered materials in anabolic reactions. Life also consumes ordered forms of matter and breaks them down, releasing energy, with catabolic reactions. Living things are highly ordered. Slide 15 / 64 Biological Order and Disorder Organisms increase the disorder of the universe in order to increase their own order. Entropy may decrease in an organism, but the universe’s total entropy increases. Life obeys the Second Law of Thermodynamics.
Slide 16 / 64 The Second Law of Thermodynamics The First Law tells us that energy cannot be created nor destroyed; the total energy of the universe is a constant. The First Law allows any process in which the total energy is conserved, including those where energy changes forms. However, the First Law alone cannot explain what we see around us every day. Slide 17 / 64 The Second Law of Thermodynamics For instance, the First Law would allow the broken cup shown below to reassemble itself, but it never will. The absence of processes like this shows that the conservation of energy is not the whole story. If it were, movies run backwards would look perfectly normal to us! Slide 18 / 64 The Second Law of Thermodynamics The Second Law is a statement about which processes occur and which do not. · Heat can flow spontaneously from a hot object to a cold object; but not from a cold object to a hot object. · It is impossible to build a perpetual motion machine. · The universe always gets more disordered with time. · Your bedroom will get increasingly messy unless you keep cleaning it up.
Slide 19 / 64 Order to Disorder Natural processes tend to move toward a state of greater disorder. · Stir sugar into coffee and you get coffee that is uniformly sweet. No amount of stirring will get the sugar back out. · When a tornado hits a building, there is major damage. You never see a tornado pass through a pile of rubble and leave a building behind. · You never walk past a lake on a summer day and see a puff of steam rise up, leaving a frozen lake behind. The First Law says all these could happen, the Second Law says they won't. Slide 20 / 64 Spontaneous Processes and the Second Law The Second Law tell us what will happen spontaneously, without outside intervention. Spontaneous doesn't mean fast, it just means that it will naturally occur if a system is left on its own. Slide 21 / 64 Spontaneous Processes · Spontaneous processes are those that can proceed without any outside intervention. · The gas in vessel B will spontaneously effuse into vessel A , but once the gas is in both vessels, it will not spontaneously return to vessel B .
Slide 22 / 64 Spontaneous Processes Processes that are spontaneous in one direction are nonspontaneous in the reverse direction. Slide 23 / 64 Spontaneous Processes · Processes that are spontaneous at one temperature may be nonspontaneous at other temperatures. · Above 0 °C it is spontaneous for ice to melt. · Below 0 °C the reverse process is spontaneous. Slide 24 / 64 6 A reaction that is spontaneous _____. A is very rapid B will proceed without outsode intervention C is also spontaneous in the reverse direction D has an equilibrium position that lies far to the left E is very slow
Slide 25 / 64 7 Which of the following statements is true? Processes that are spontaneous in one direction are A spontaneous in the opposite direction. Processes are spontaneous because they occur at an B observable rate. C Spontaneity can depend on the temperature. D All of the above statements are true. Slide 26 / 64 Entropy Entropy is a measure of the randomness or disorder of a system. The second law of thermodynamics states that the entropy of the universe increases for spontaneous processes. Slide 27 / 64 8 The thermodynamic quantity that expresses the degree of disorder in a system is ______. A enthalpy B internal energy C bond energy D entropy E heat flow
Slide 28 / 64 9 The entropy of the universe is __________. A constant B continually decreasing C continually increasing D zero E the same as the energy, E Slide 29 / 64 Entropy and Life Growth of an individual, and evolution of a species, are both processes of increasing order. Do they violate the second law of thermodynamics? Slide 30 / 64 Entropy and Life Do they violate the second law of thermodynamics? No! Life is not an isolated system. Even though life itself shows increasing order, it creates an increasing amount of disorder in its surroundings: the total disorder of the universe is increased by life.
Slide 31 / 64 10 If the entropy of a living organism is decreasing, which of the following is most likely to be occurring simultaneously? The entropy of the organism's environment must also be A decreasing. B Heat is being used by the organism as a source of energy. Energy input into the organism must be occuring in order to C drive the decrease in entropy. In this situation, the second law of thermodynamics must not D apply. Slide 32 / 64 11 According to the second law of thermodynamics, which of the following is true? A Energy conversions increase the order in the universe. B The total amount of energy in the universe is constant. The decrease in entropy in life must be offset by an increase C in entropy in the environment. D The entropy of the universe is constantly decreasing. Slide 33 / 64 Spontaneous Reactions Biologists want to know which reactions occur spontaneously and which require the input of energy. To do so, they need to determine the energy and entropy changes that must occur. As you learned last year, this determines the change in the Gibbs Free Energy: ΔG.
Slide 34 / 64 Spontaneous Processes A process will occur spontaneously if the result is a reduction of the Gibbs Free Energy (G) of the system. G takes into account the resulting change in the energy of a system and the change in its entropy . If the effect of a reaction is to reduce G, the process will proceed spontaneously. If ∆G is negative , the reaction will occur spontaneously. If ∆G is zero or positive , it will not occur spontaneously. Slide 35 / 64 Free-Energy Change: Δ G Exergonic reactions have a negative ∆G and occur spontaneously Endergonic reactions have a positive ∆G and do not occur spontaneously Slide 36 / 64 Spontaneous (Exergonic) Processes
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