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Lecture 2

BIOL 1201 Lecture Notes - Lecture 2: Lipid Bilayer, Enzyme Inhibitor, Spontaneous Process


Department
Biological Sciences
Course Code
BIOL 1201
Professor
Bill Wischusen
Lecture
2

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EXAM 2
Chemical Reactions
Occur anytime two or more atoms, ions, or molecules collide in such a way
that they produce a new substance
Must physically run into each other with sufficient force and in the right
orientation
Reactions go faster with heat
Molecules move faster when hit with heat, thus speeding reactions up
Laws of Thermodynamics
First Law:
Energy can neither be created nor destroyed, only converted from one
form to another
If the reactors have greater energy than the products, then energy must
be released
Second Law:
When converting energy from one form to another the amount of useful
energy decreases
Well never be able to do these energetic conversions 100%
efficiently, well always lose some amount of energy in the form of
heat normally
Types of Chemical Reactions
Spontaneous
Can occur without outside help (energy)
Spontaneous (-G)
Non-spontaneous
Can occur only with outside help (energy)
Non Spontaneous (+G)
As enthalpy decreases, entropy increases (spontaneous)
Free Energy
Energy that is free and available to do work
Amount of energy when/for reactions/processes to occur
Diver on top of the dock has more free energy, less stable, and greater work
capacity
When diving: less free energy, more stable, less work capacity
Figure 8.5
Change of physical location changes free energy
Free Energy and Chemical Reactions
Spontaneous
Release free energy (Negative Delta G - exergonic)
Non-spontaneous
Require free energy or else it cannot occur (positive delta G -
endergonic)
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G=H-TS
G = Free Energy
If G is positive, its non spontaneous
G is negative if its a spontaneous process
H = Enthalpy (heat energy not the temperature)
How much heat COULD be released not how hot it is
Positive if it took up heat energy
Negative if it released heat
T = Temperature (K)
Are no negatives
S = Entropy (measure of disorder)
How complex a molecule is
LOWER DISORDER MEANS GREATER FREE ENERGY
(Match lighting demonstration) What happened during this reaction?
Heat energy was released and it was spontaneous
Free energy decreases because heat increases
DECREASE G = H - TS
DECREASE G = H DECREASE
DECREASED G= -TS INCREASED
(Cold pack and water demonstration) What happened during this reaction?
Took up heat energy which is what made it cold, it was spontaneous
(which means it cant have an increase in free energy)
DECREASE G = H - TS
INCREASED G = H INCREASED
DECREASED G= -TS INCREASED
Which of the following reactions will always be spontaneous?
Enthalpy decreases, entropy increases
Heat energy decreases, disorder increases
Which of the following reactions will always be non-spontaneous?
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Enthalpy increases, entropy decreases
A spontaneous reaction occurring at 100K and with a 250Kcal increase in
enthalpy must have the following change in entropy?
G has to be negative, because problem said it was spontaneous
Fill in known information
S has to make G negative chose from choices that will make it
negative
-100 = 250 - 350
3.5 Kcal
A non-spontaneous reaction occurring at 200K with a 150Kcal decrease in
enthalpy has which of the following changes in entropy?
G has to be positive since its non-spontaneous
Fill in known information
S has to make G positive chose from choices that will make it
positive
G=H-TS
+G =-150Kcal-200KS
A) -1.0 Kcal because you need to have something to make your delta G
positive
So, +G =-150Kcal-200K(-1.0 Kcal) = a positive G
A spontaneous reaction occurring at 200K with a 1.5 Kcal decrease in
entropy has which of the following changes in enthalpy?
G=H-TS
-G = H 200K (-1.5)
A) -400 to get -G = (-400) 200K (-1.5)
On which side do the molecules have greater entropy?
Side with less molecules (more disorder to go anywhere they want to go)
On which side do the molecules have greater free energy?
Side with more molecules (less disorder makes a negative times a
negative making G a positive)
The net movement of molecules will be towards what side?
Side with the least amount of molecules
Molecules move towards less concentration (greater free energy to
lower free energy) down hill energetically
What happens to the energy of the molecules as they move from side A
(more molecules) to side B (less molecules)
The amount of energy decreases
Have to give energy off
Living vs. Non-Living Systems
Non-Living:
Less organized
Lower energy
Very slow
Example: Rust
Living:
Highly organized
High energy
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