Intro to biochemistry
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Transcript of Intro to biochemistry
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Biochemistry 461 Fall, 2015 Lecture 1
Introduc<ons & Review of some chemistry
Reading & Problems: Please see the syllabus
Helpful site for review: hHp://www.biology.arizona.edu/
biochemistry/
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Hyponatremia in Athletes
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The Goal of Biochemistry: Understanding biology at the chemical
level.
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Biochemistry in the Grand Scheme Anatomy & Physiology
Cell Biology
Biochemistry
Next slide
Organism
Organ
Cell
Organelle
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Biochemistry: Structure & Func<on of Macromolecular Complexes and
Macromolecules
Transfer RNA Glucokinase Lipid Cellulose
Nucleosome Ribosome
Chemistry
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Chemistry
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General Structure Specific Example
STRUCTURE & NONCOVALENT BONDS
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THERMODYNAMICS:What is possible?
The power of thermodynamics lies in its ability to provide informa<on about
what is possible. ΔG provides informa<on about
spontaneity ΔG<0-‐Favorable Process, exergonic
ΔG>0-‐Unfavorable Process, endergonic
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Energy Flow in Organisms
Energy
Enthalpy
Entropy
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Gibbs free energy comes in two forms
• ΔG=ΔH-‐TΔS
• ΔH-‐enthalpy: heat transferred at constant pressure
For our purposes this means the energy of bond breakage and forma<on
• ΔS-‐entropy: a measure of disorder
• Temperature is also important
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Example:Why does NaCl readily dissolve in Water?
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Halobacteria: Can live in 5M salt
hHp://www.brasdelport.com/wp-‐content/gallery/halobac1/halobact1.jpg
Likes 4M salt!
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Why does sodium chloride dissolve so readily in water?
• Salt crystals are very stable with strong inter-‐ionic interac<ons:
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Bond Exchange in Dissolving a Salt
For NaCl the ΔHsoln=+3.87 kJoule/mol in water at 25oC
SO WHY DOES NaCl DISSOLVE SO EASILY IN WATER?
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Entropy Rules!
The sodium and chloride ions have more disorder when dissolved.
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Spontaneity is determined by both enthalpy and entropy
ΔG=ΔH-‐TΔS
Mul<ple possible combina<ons of enthalpy and entropy can result in a spontaneous reac<on. Measurements of the enthalpy and entropy can provide clues about the structural origins of the favorable free energy.
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Units of Energy typically used in Biochemical Thermodynamics
• Energy unit: 1 cal = 4.184 J: so 1 kcal/mol = 4.184 kJoule/mole
• Enthalpy: kcal/mol or kJ/mole • Entropy: cal/mol-‐K or J/mole-‐K
• Cal: calorie • J:Joule (named for James PrescoH Joule) • K-‐Temperature in Kelvin
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Energy and Chemistry Standard Free Energy Changes for
Chemical Reac<ons, ΔGo, at equilibrium
• Gibbs: ΔGo = -‐RT ln Keq • Rewrite: Keq = exp(-‐ΔGo/RT)
• Keq is equilibrium constant; formula depends on reac<on type
• For aA + bB → cC + dD, Keq = ([C]c[D]d)/([A]a[B]b)
• For Biochemical reac<ons the standard state ΔG’o and K’eq refer to pH7.0 and [H2O]=55.5M, 25oC, and ini<al concentra<ons of each component at 1M.
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Example
• ATP + H2O ADP + Pi ΔG’o=-‐7.3 kcal/mol -‐30.5 kJ/mol
• What is the equilibrium constant?
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Role of Reactant Concentra<ons
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ΔG = ΔG'o +RT ln [C]c[D]d
[A]a[B]b
How does the reac<on proceed if the quo<ent of the reactant and product concentra<ons are far from equilibrium?
What happens when equilibrium is reached?
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• Dependence of ΔG on Concentra<ons
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ΔG = ΔG'o +RT ln [C ]c[D]d
[A]a[B]b
Q =[C ]c[D]d
[A]a[B]b
[Reactants]>>[Products], ΔG<ΔG’o
[Reactants]<<[Products], ΔG>ΔG’o
Think about how in the cell the Gibbs Free Energy for a reac<on can be made more favorable.
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Coupled reac<ons ;An unfavorable reac<on can be driven by a favorable
reac<on.
The favorable or exergonic movement of the large weight pays for raising the smaller weight.
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Chemical Example
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A Brief Word about Kine<cs: Thermodynamics may indicate that a process is possible. However, it mat be very slow-‐or have a very large
barrier associated with it.
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Enzymes Speed up Reac<ons by Lowering the Energe<c Barrier that separates reactant Reactant from Product