Biology 1201 EXAM2

Biology 1201 EXAM2 - Biology 1201 Exam 2 How do cells...

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Biology 1201 Exam 2 How do cells regulate metabolism? Metabolism=Biological chemical reactions True How do cells organize and control the chemical reactions that support life? Metabolic transformations Chemical reactions Small steps Controlled processes Each step controlled by a protein catalyst o Enzyme Biological Chemical Reactions Regulated by protein catalyst- enzymes Synthesis of energy carrier molecules to store energy, transport it from place to place, and regulate its flow Couple reactions together so that unfavorable reactions can occur at the expense of reactions that release energy Enzymes Protein catalyst Not used up Specific reactions require specific enzymes Enzymes lower activation energy barrier Enzymes speed up reaction 10 8 -10 20 times faster
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Biology 1201 Exam 2 Do not reverse an energetically unfavorable reaction Thermodynamics Study of the energy relationships of a system Energy=The capacity to do work True Energy Potential Kinetic First Law of Thermodynamics Within any closed system the total amount of energy remains constant Second Law of Thermodynamics All spontaneous processes result in an increase in randomness and disorder in the universe And consequently in a loss of localized concentrations of energy Entropy is increasing You must define “the system” A closed system The earth is not a closed system o Input of energy from the sun Fig. 8.7 Spontaneous chemical reactions: Release energy
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Biology 1201 Exam 2 Chemical Reactions Endergonic (Endothermic) – require net input of energy (heat) to proceed Exergonic (Exothermic)—energy (heat) is released from the reaction: Spontaneous, delta-G is negative Fig 8.6 Chemical Reactions Only proceed spontaneously in the “downhill” reaction Downhill=exergonic direction o Negative delta g(-∆G) o Energy is released Burning of Coal “B”=∆G Delta G Determines whether the reaction proceeds to the right Exergonic (exothermic)- energy is being released Coal and oxygen o Reactants H 2 O and CO 2 o Products Heat is released Lump of coal on the table
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Biology 1201 Exam 2 o Wouldn’t burn all semester. Why? - You would have to add energy! The activation energy barrier- energy required making the reaction occur! Transition state ∆G≠ - Delta G double-dagger “A” represents the activation energy barrier The height of this barrier determines the rate of the reaction ∆G≠ Energy required for the favorable positioning of the reactants so the reaction can occur Transition state Fig 8.14/13? Enzymes- accelerate chemical reactions Reaction rates are increased because enzymes lower the activation energy barrier Enzymes cannot reverse energetically unfavorable reactions o They do not make the reaction go uphill (cannot reverse the reaction) The activation energy barrier is lowered because the enzyme positions
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