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Chapter 4

# Biology 1202B Chapter Notes - Chapter 4: Vacuum Flask, Family Of Sets, Thermodynamics

Department
Biology
Course Code
BIOL 1202B
Professor
Patrick Mc Donald
Chapter
4

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Biology 1202B: Chapter 4 – Energy and Enzymes
Why it Matters
Life relies on biological catalysts called enzymes to speed up the rate of chemical
reactions without an increase in temperature
The reversible addition and removal of a phosphate group from a particular protein is a
central mechanism of intracellular communication
Enzymes typically make reactions 106 times faster than the uncatalyzed rate
4.1 Energy and Laws of Thermodynamics
Energy is defined as the capacity to do work
4.1a Energy Exists in Different Forms
Energy can change from one form to another, this usually isn’t an efficient process
Kinetic energy is possessed by objects in motion
oE.g. waterfall
Potential energy is stored energy due to position or cell structure
oBoulder sitting at the top of a hill has the potential to fall down, changing to
kinetic energy (some energy is lost to sound and/or heat during this transition)
oElectron far from nucleus has the potential to fall down energy levels giving off
energy in the form of light
4.1b The Laws of Thermodynamics Describe Energy and Its Transformation
Thermodynamics: study of energy flow during chemical and physical transformations
System could be anything, anything outside the set system is the surroundings
oSurroundings + system = universe
3 types of systems
1. Isolated does not exchange matter or energy with surroundings
E.g. Thermos bottle, universe
2. Closed can exchange energy but not matter with surroundings
E.g. earth, pot of boiling water with lid on
3. Open both energy and matter can move freely between the system and
surroundings
E.g. ocean
4.1c The First Law of Thermodynamics
Energy cannot be created or destroyed, only change forms
oBoulder at top of hill has potential energy, when it falls down the hill it is
converted into kinetic energy, and some energy is lost to heat and sound
The sum of all the energy in the universe is constant
4.1d The Second Law of Thermodynamics
The energy in a system tends to disperse due to entropy (tendency towards
randomness)
Entropy is abbreviated by S

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Entropy is the measure of how much energy has flowed from local position to more
widely dispersed
Energy that is being transformed from one state to another will always lose some to its
4.2 Free Energy and Spontaneous Processes
Spontaneous processes can occur without energy input
oDoes not refer to the speed of the reaction
4.2a Energy Content and Entropy Contribute to Making a Reaction Spontaneous
Enthalpy (H) = the total potential energy of a system
Endothermic reactions absorb energy from surroundings (+ΔH)
Exothermic reactions release energy into the surroundings (-ΔH)
Reactions tend to be spontaneous if:
oThey are exothermic – the products have less potential energy than the reactants
oThe entropy of the products is greater than that of the reactants
E.g. glucose breaking down into smaller, simpler molecule
Entropy increases when the reaction results in an increase in molecules
Entropy also increases when a solid transforms to a liquid or a liquid
transforms into a gas
4.2b The Change in Free Energy Indicates Whether a Process is Spontaneous
The change in Gibbs Free Energy (G) is a measure of whether or not a reaction is
spontaneous
oFormula: ΔG = ΔH – TΔS
G = free energy
H = enthalpy
T = temperature in Kelvin
S = entropy
A spontaneous process will have less free energy in products than the reactants
Spontaneous reactions are also referred to as exergonic processes
oThe opposite is a non-spontaneous reaction referred to as endergonic
2 main factors influencing free energy:
oEnthalpy
oEntropy
Entropy drives diffusion across a cell membrane from areas of high
concentration to low concentration (energy is spread out)
4.2c Exergonic Processes Reach Equilibrium Rather than Going to Completion
Chemical equilibrium = the point where there is no overall change in the concentration of
reactants to products
oThe molecules continue to react, just equally in both directions
Free energy drops as a reaction reaches equilibrium
The more –ΔG the farther toward completion the reaction will go before equilibrium
oΔG at 0 means the reaction is easily reversible with slight changes to the
concentration of reactants/products

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