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Lecture 4

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Department
Biology
Course
Biology 1002B
Professor
Denis Maxwell
Semester
Winter

Description
Lecture 4: Energy and Enzymes 1. Isolated, closed and open systems.  Isolated system – Does not exchange matter or energy with its surroundings E.g. thermos  Closed system – Does not exchange energy but not with its surroundings E.g. green house, earth  Open system – Energy and matter can move freely between system and surroundings E.g. ocean 2. First law of thermodynamics  Energy transformed into another form or transferred to another place but not created or destroyed 3. Second law of thermodynamics  Energy transformations increase disorder 4. What is meant by the phrase "it takes energy to maintain low entropy" (section 4.1e)  The universe favours higher entropy  Life obeys the second law o Molecules, structures and living cells created order from less order structures o Cells are an open system o Uses energy (food) to maintain order and give off heat (increase disorder) o Entropy of a system is allowed to decrease as long as entropy of universe as a whole increases 5. Potential, kinetic, chemical energy  Potential energy – energy possessed by virtue of its position relative to others  Kinetic Energy – mechanical energy that a body has by virtue of its motion  Chemical Energy – part of energy in a substance that can be released by a chemical reaction 6. Entropy, enthalpy (H), DH, exothermic, endothermic  Entropy o + ∆S = more disorder o - ∆S = less disorder  Enthalpy (potential energy) o + ∆H = endothermic (energy gained from surrounding, potential energy of products > reactants) o - ∆H = exothermic (potential energy of products < reactants – see graph) 7. Gibbs Free Energy, exergonic, endergonic, spontaneous reaction  + ∆G = endergonic o Not spontaneous  - ∆G = exergonic = spontaenous o Spontaneous reaction  Potential energy of products < reactants (exothermic) *tends to be spontaneous  Products are more disordered (increase in entropy) o Phase change from solid  liquid  gas  Endothermic process but positive entropy is large enough to make - ∆G  Entropy driven since more disorder of molecules 8. Catalyst, rate of reaction, energy of activation (EA), transition state, kinetic stability  Catalyst – substance that increases rate of chemical reaction without permanently changing itself  activation energy o amount of energy needed to overcome the barrier to get totransition state o where bonds start t
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