ap biology chapter 8: metabolism and enzymes. kinetic energy vs. potential energy
TRANSCRIPT
AP Biology
Chapter 8:Metabolism and Enzymes
Kinetic Energy vs. Potential Energy
Potential Energy vs. Kinetic Energy
Potential Energy vs. Kinetic Energy
Thermodynamics
LE 8-3
Chemical energy
Heat CO2
First law of thermodynamics Second law of thermodynamics
H2O
LE 8-7a
G = 0
A closed hydroelectric system
G < 0
LE 8-7b
An open hydroelectric system
G < 0
LE 8-7c
A multistep open hydroelectric system
G < 0G < 0
G < 0
LE 8-6a
Reactants
EnergyProducts
Progress of the reaction
Amount ofenergyreleased(G < 0)
Fre
e en
erg
y
Exergonic reaction: energy released
LE 8-6b
ReactantsEnergy
Products
Progress of the reaction
Amount ofenergyrequired(G > 0)
Fre
e en
erg
y
Endergonic reaction: energy required
Fig: 8.8
Phosphorylation
LE 8-11
NH2
Glu
P i
P i
P i
P i
Glu NH3
P
P
P
ATPADP
Motor protein
Mechanical work: ATP phosphorylates motor proteins
Protein moved
Membraneprotein
Solute
Transport work: ATP phosphorylates transport proteins
Solute transported
Chemical work: ATP phosphorylates key reactants
Reactants: Glutamic acidand ammonia
Product (glutamine)made
+ +
+
LE 8-15
Course ofreactionwithoutenzyme
EA
without enzyme
G is unaffectedby enzyme
Progress of the reaction
Fre
e en
erg
y
EA withenzymeis lower
Course ofreactionwith enzyme
Reactants
Products
LE 8-16
Substrate
Active site
Enzyme Enzyme-substratecomplex
LE 8-17
Enzyme-substratecomplex
Substrates
Enzyme
Products
Substrates enter active site; enzymechanges shape so its active siteembraces the substrates (induced fit).
Substrates held inactive site by weakinteractions, such ashydrogen bonds andionic bonds.
Active site (and R groups ofits amino acids) can lower EA
and speed up a reaction by• acting as a template for substrate orientation,• stressing the substrates and stabilizing the transition state,• providing a favorable microenvironment,• participating directly in the catalytic reaction.
Substrates areconverted intoproducts.
Products arereleased.
Activesite is
availablefor two new
substratemolecules.
R groups of Amino Acids
Optimal Performance
LE 8-19Substrate
Active site
Enzyme
Competitiveinhibitor
Normal binding
Competitive inhibition
Noncompetitive inhibitor
Noncompetitive inhibition
A substrate canbind normally to the
active site of anenzyme.
A competitiveinhibitor mimics the
substrate, competingfor the active site.
A noncompetitiveinhibitor binds to the
enzyme away from theactive site, altering the
conformation of theenzyme so that its
active site no longerfunctions.
LE 8-20a
Allosteric enzymewith four subunits
Regulatorysite (oneof four) Active form
Activator
Stabilized active form
Active site(one of four)
Allosteric activatorstabilizes active form.
Non-functionalactive site
Inactive formInhibitor
Stabilized inactive form
Allosteric inhibitorstabilizes inactive form.
Oscillation
Allosteric activators and inhibitors
LE 8-21
Active siteavailable
Initial substrate(threonine)
Threoninein active site
Enzyme 1(threoninedeaminase)
Enzyme 2
Intermediate A
Isoleucineused up bycell
Feedbackinhibition Active site of
enzyme 1 can’tbindtheoninepathway off
Isoleucinebinds toallostericsite
Enzyme 3
Intermediate B
Enzyme 4
Intermediate C
Enzyme 5
Intermediate D
End product(isoleucine)
LE 8-20b
Substrate
Binding of one substrate molecule toactive site of one subunit locks allsubunits in active conformation.
Cooperativity another type of allosteric activation
Stabilized active formInactive form
LE 5-20e
Chains
ChainsHemoglobin
IronHeme
CollagenPolypeptide chain
Polypeptidechain