Biochemistry 212 Winter 2006

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Biochemistry 212Winter 2006
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Dr. Elizabeth L. Gross
742A Biosciences 292-9480 gross.3_at_osu.edu
Office hours T-R 1-3 PM
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Important Information

• You are responsible for the parts of the
• textbook discussed in class.

2. Two exams (Midterm Final) 45 each The
final is not cumulative Pop quizzes 5
Writing assignment 5
3. Short answer-essay no multiple choice
3 x 5 inch cheat sheet
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Theme for the quarter
1. Energy storage utilization
2. Synthesis and breakdown of biomolecules.
Carbohydrates Fats Proteins (amino acids) Nucleic
acids (nucleotides)

• Integration of metabolism

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Energy
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Why do we need energy?

• Synthesis of macromolecules

2. Activities e.g. Motion
3. Maintaining life (order).
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Types of Energy
Chemical
Mechanical
Light
Kinetic
Potential
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Energy Changes
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High energy
Low energy
Potential Energy energy of position
Kinetic energy energy of motion
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Spontaneous Reactions
Will take place
at constant T and P
Without the input of energy
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• The most useful criterion for predicting
  spontaneity is the change in free energy, DG, for
  a process constant temperature pressure.
• ?G lt 0 exergonic, spontaneous, energy
  released
• ?G 0 the system is at equilibrium
• ?G gt 0 endergonic, nonspontaneous, energy
  required

Get energy
Require energy
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A Spontaneous Reaction
Glucose 6O2 6CO2 6 H2O
DG lt 0
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A Nonspontaneous Reaction
ADP Pi
ATP H2O
DG gt 0
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ADP Pi ATP H2O DG gt 0 ATP H2O
ADP Pi DG lt 0
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DG depends on concentrations and pH. For
convenience, however, we talk about standard
states. What is a standard state?
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• Standard states - ?G
• for pure solids and liquids, the pure substance
• for gases, the gas at a pressure of 1 atm
• for solutions, a concentration of 1 mol/L
• pH 7

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How do we calculate DGo? A. From equilibrium
constants B. From entropy and enthalpy
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keq Cc Dd Aa Bb
A. From equilibrium constants.
What is an equilibrium constant? keq
Consider the reactioon aA bB ?? cC dD
Products Reactants
DGo -RT ln keq 2.303 RT log keq
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If I give you an equilibrium constant, you
should be able to calculate the free energy.
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B. From enthalpy and entropy. What are enthalpy
and entropy? To understand these, we need to
understand the laws of thermodynamics.
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Free Energy, Enthalpy Entropy
Enthalpy
DH is the heat of reaction at constant pressure
Entropy
DS measures the disorder of a system
DS gt 0 means an increase in disorder.
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Laws of ThermodynamicsFirst Law
Conservation of energy. Energy can not be created
or destroyed
You cant win.
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Second Law of Thermodynamics. You cant win.
Every time you change forms of energy, you pay a
penalty. The amount of useful energy decreases.
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But the total amount of energy stays the same.
First law.
What happens to it? The universe becomes more
disordered. Entropy
High entropy disorder Low entropy order.
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Low Entropy High Entropy
Living Things
Dead
Live
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Low Entropy High Entropy
Molecules
Protein or Nucleic acid
Amino acids or nucleotides
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Things spontaneously become more
disordered. Entropy naturally increases.
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Living things are highly ordered. How can this
be in view of the second law of thermodynamics?.
The second law of thermodynamics applies to the
entire universe.
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How is life possible?
System
DSlt0
DSgt0
Universe
Requires energy
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Why do we need energy?

• Synthesis of macromolecules

2. Activities e.g. Motion
3. Maintaining life (order).
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Sun
Respiration
ATP
Proteins Cells
Glucose
H
Photosynthesis
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Take home lessions

• Free energies changes (D Go)
• determines whether a reaction is
• spontaneous.
• 2. Entropy changes (DS) determine
• whether the system is becoming
• more or less ordered.

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• The second law of thermodynamics
• says that the entropy of the universie is
• increasing but the entropy of living
• systems is low.
• Living systems require energy to
• maintain a low entropy.