Biology 1002B Lecture Notes - Lecture 4: Ionic Bonding, Extremophile, Isolated System

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3 Feb 2013

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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
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 to break
e.g. propane
o thermodynamically unstable but kinetically very stable
o it you throw it, it won’t explode
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