fig. 1-7 chapter 3 energy, catalysis, and biosynthesis by maintaining highly ordered states, cells...
TRANSCRIPT
Fig. 1-7
Chapter 3 Energy, Catalysis, and Biosynthesis
By maintaining highly ordered states, cells seemingly defy the laws of thermodynamics: 1) There is a finite amount of energy in the universe. It can neither be created nor destroyed, onlychanged from oneform to another. 2) A change will alwaysbe accompanied byan increase in disorder.
The same principle applies to our everyday lives.A housewife’s work is never done….Neither is the cell’s.
Fig. 3-4
Thermodynamics: Study of Energy Transformations
Fig. 3-6
Fig. 3-6
Photosynthesis Makes Sugars for Cellular Respiration
All energy required to maintain life is derived from the sun.
Fig. 3-7 Vincent van Gogh
Chemical Energy from Glucose Used by Cells to Synthesize Macromolecules
energy releasing
Fig. 3-2
energy consuming
Cells Do Not Defy the Laws of Thermodynamics in the Context of the Whole Universe
Fig. 3-5 macromoleculesorganelles, etc.-anabolism
CO2 and H2O-catabolism
DH = DG + TDS
Gibbs Free Energy Equation:
Potential Energy
WorkEnergy
Energy Lostto Disorder
DG = DH - TDS
Rearranged:
Study of Energy Transformations: Thermodynamics
began w/ invention of steam engine
earlySteam Engine
DG = DH - TDS
Exergonic: DG < 0- will occur w/o external energy Endergonic: DG > 0- will NOT occur w/o external energy
& Products more disordered than Reactants (DS>0)Products have lower bond energies than Reactants (DH<0)
DH<0 and DS > 0DG < 0 (will occur w/o external energy) when:
OR DH<<<<0 and DS < 0OR DH>0 and DS >>>> 0
∆G measures likelihood a reaction will occur
Chemical Bond Energy
< Cell
.
Respiration
Fig. 3-4
Cell Respiration: DH <<< 0 allows DS < 0
DG = DH - TDS
Chemical Energy from Glucose Used to Synthesize Macromolecules
energy releasing
Fig. 3-2
energy consuming
DG < 0 DG > 0DH < 0, DS > 0 DH > 0, DS < 0
How Can Endergonic Reactions (DG >0) Occur in Cells?
Fig. 3-17
One mechanism is to couple it to a highly exergonic reaction.
Chemical Energy from Glucose Used to Synthesize Macromolecules
energy releasing
Fig. 3-2
energy consuming
Activated Energy Carriers
ATP, NAD(P)H2
hydrolysissynthesis
Fig. 3-31
Energy from Glucose Oxidation Storedin Activated Energy Carrier, ATP
Examples:
Panel 3-1g
NADH and NADPH are Activated Carriers of Electrons
Fig. 3-34
Electrons are transferred from glucose to these portable electron carriers.
.
DG under non-standard conditions (in cells) depends on true concentrations of molecules
Rxn 1DG>0
Rxn 2DG<<0
Coupled RxnDG<0
Rxn 2 keeps [Prod]/[React] of Rxn 1 low
DG = DGo + RT ln [Product] [Reactant]
Fig. 3-21
.
will occur without external energy, but not on useful timescale
without enzyme
with enzyme
Fig. 3-27b (modified)
Enzymes Increase the Velocity of a Reaction (Not the Thermodynamics)
Enzymes Lower Activation Energy
Fig. 3-12
Enzymes Lower Activation Energy
Fig. 3-14
By Lowering Activation Energyat Discrete Steps, Enzymes Direct Reaction Pathways
Fig. 3-14
Enzymes are not altered by the reactions they catalyze.They used over and over again.
Fig. 3-15
Enzymes allow the cell to extract energy from glucosein small steps, instead of all at once in the form of heat.Some energy can be harnessed for useful work.
Fig. 3-30
How Do Enzymes Lower the Activation Energy?
Fig. 4-36
Example: Lysozyme
Amino acid side chains at active site alter chemical properties of substrate to ease it into activated transition state.
bond bent, then broken by enzyme
Fig. 4-35
Measuring Enzyme Performance
Fig. 3-27v = Vmax [S] KM + [S]
Fig. 3-28
A stopped-flow apparatus is needed to catch the initial velocity.
We do the best we can with what we have.
Double Reciprocal Plot Allows for Easier Determination of Vmax and KM
Fig. 3-27c 1/v = KM (1/[S]) + 1/Vmax
Vmax straight line formula: y = a(x) + b
Enzyme Kinetic Assays Can be Used to Evaluate Drugs
Fig. 3-29
+ competitiveinhibitor
+ competitiveinhibitor
+ noncompetitiveinhibitor
+ noncompetitiveinhibitor