an introduction to metabolism chapter 8. metabolism i. introduction all of an organism’s chemical...
TRANSCRIPT
![Page 1: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/1.jpg)
An Introduction to Metabolism
Chapter 8
![Page 2: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/2.jpg)
METABOLISM• I. Introduction• All of an organism’s chemical reactions• Thousands of reactions in a cell
• Example: digest starch use sugar for energy and to build new molecules
![Page 3: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/3.jpg)
II. Metabolic Pathways
• starting molecule chemical reactions product(s)
• Each step catalyzed by specific enzyme
Enzyme 1 Enzyme 2 Enzyme 3
DCBAReaction 1 Reaction 3Reaction 2
Startingmolecule
Product
![Page 4: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/4.jpg)
• Catabolic pathways - – break down complex molecules into simpler
compounds– release energy for cells to use
• Ex. Glucose metabolism yeilds ATP
![Page 5: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/5.jpg)
• Anabolic pathways use energy to build complex molecules from simpler ones
• Ex. Protein synthesis from amino acids
![Page 6: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/6.jpg)
III. Energy
• Energy – capacity of a system to do work– can be converted from one form to another
– 1. Kinetic energy = energy of motion
– Due to vibration of atoms /molecules
![Page 7: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/7.jpg)
• Kinetic energy examples:– LIGHT Energy -electromagnetic energy includes visible light, x-rays, gamma
rays and radio waves. – MOTION energy in the movement of objects. The faster they move, the
more energy. Wind is motion energy. When a car comes to a total stop, releases all motion energy in uncontrolled instant.
– SOUND -movement of energy through substances in longitudinal waves. Sound produced when force causes object or substance to vibrate —energy is transferred through the substance in a wave. Far less than other forms of
energy.– HEAT – average total kinetic energy of molecules
![Page 8: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/8.jpg)
2. Potential energy = energy stored within systemEx. rubberband
Chemical energy = PE available for release in chemical reaction
Ex. Glucose has high CE
![Page 9: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/9.jpg)
![Page 10: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/10.jpg)
IV. The Laws of Energy Transformation
• Thermodynamics – study of energy transformation
• In open system energy and matter can be transferred between system and surroundings
• Why are organisms/cells open systems?
![Page 11: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/11.jpg)
First Law of Thermodynamics
• The energy of universe is constant: • Energy can be transferred and transformed, but
it cannot be created or destroyed.
• This is the principle of conservation of energy
![Page 12: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/12.jpg)
Second Law of Thermodynamics
• Every energy transfer or transformation increases entropy (disorder) of the universe
• Living systems (open) increase entropy in environment
• During E transfer some E is released as heat (unusable)
![Page 13: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/13.jpg)
(a) First law of thermodynamics (b) Second law of thermodynamics
Chemicalenergy
Heat CO2
H2O
+
First Law: chemical E infood converted to kinetic E
Second Law: disorder is entered intoenvironment as heat, CO2
Kinetic, potential energy Campbell
![Page 14: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/14.jpg)
V. Biological Order
Cells create ordered structures from less ordered materialsEx. proteins built from amino acids
Amino acids in cell -----------------------------------------------Growth hormone
![Page 15: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/15.jpg)
Organisms replace ordered forms of matter and energy with less ordered
break down molecules, releases heat
• Energy flows into ecosystem as ___ and leaves as _____
![Page 16: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/16.jpg)
VI. Free-energy (G)
• G = amt. of energy available to do work in biochemical reaction
• Δ G = change in free energy• unstable systems move towards stable
(equilibrium)• System at equilibrium does no work
![Page 17: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/17.jpg)
Equilibrium and Metabolism
• Reactions in closed system eventually reach equilibrium and then do no work
(a) An isolated hydroelectric system
∆G < 0 ∆G = 0
It’s a positive free energy change for the surroundings, negative for the system
![Page 18: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/18.jpg)
Equilibrium and Metabolism
• Cells are open systems – constant flow of materials
– not in equilibrium
(b) An open hydroelectric system
∆G < 0
![Page 19: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/19.jpg)
Equilibrium and Metabolism• catabolic pathway releases free energy in series of
reactions
(c) A multistep open hydroelectric system
∆G < 0
∆G < 0
∆G < 0
![Page 20: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/20.jpg)
Spontaneous processes 1. occur without (additional) energy input
– explosion, rusting (slow!)
2. release energy, usually heat3. Gives up energy -Δ G4. Exergonic
The Gibbs free energy equation does depend on T, increasing T may increase reaction rate
![Page 21: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/21.jpg)
Exergonic reaction
-Δ G = exergonic reaction •releases energy •Spontaneous•“downhill”•Products have less G than reactants
Energy
(a)Exergonic reaction: energy released
Progress of the reaction
Fre
e en
erg
yProducts
Amount ofenergyreleased(∆G < 0)
Reactants
![Page 22: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/22.jpg)
Exergonic reaction
• Cellular respiration
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O
ΔG = -686kcal/mol available for work
• ATP + H2O → ADP + Pi (hydrolysis)
ΔG = -7.3 kcal/mol
![Page 23: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/23.jpg)
• +Δ G = endergonic rxn– Absorbs free energy from surroundings – Non-spontaneous
![Page 24: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/24.jpg)
• Many exergonic reaction are also exothermic (release heat)• The bombardier beetle has two sets of chemicals stored separately in
paired glands. • The larger of the pair contains hydroquinones and H2O2.
• The the smaller gland contains catalases and peroxidases.
![Page 25: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/25.jpg)
Endergonic• Photosynthesis
6CO2 + 6H2O (+ light energy) C6H12O6 + 6O2
686kcal/mol
![Page 26: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/26.jpg)
Energy
(b) Endergonic reaction: energy required
Progress of the reaction
Fre
e en
erg
y
Products
Amount ofenergyrequired(∆G > 0)
Reactants
![Page 27: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/27.jpg)
VI. ATP powers cellular work
ATP
– High stored chemical potential energy – drives cell activities
![Page 28: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/28.jpg)
ATP
• ATP =adenosine triphosphate
Energy released when terminal phosphate bond broken by hydrolysis
![Page 29: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/29.jpg)
Energy
Adenosine triphosphate (ATP)
P P
P P P
P ++
H2O
i
ATP --- ADP + PΔ G = -7.3kcal/mol
![Page 30: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/30.jpg)
• Phosphorylation • Transfer P from ATP to other molecule to
phosphorylate it.
• The phosphorylated molecule is less stable
Phosphorylation opens an aquaporin(spinach)
http://www.sciencedaily.com/releases/2005/12/051222085140.htm
![Page 31: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/31.jpg)
The Nobel Prize in Physiology or Medicine 1992
• Edmond H. Fischer and Edwin G. Krebs
for their discoveries concerning "reversible protein phosphorylation as a biological regulatory mechanism".
![Page 32: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/32.jpg)
• Coupling = Use exergonic reactions to drive endergonic rxns (overall exergonic)
![Page 33: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/33.jpg)
• Regeneration of ATP– Add phosphate group to ADP– Muscle cell uses 10 million ATP per second
ADP + P ATP is this + or - Δ G ?
Δ G = 7.3kcal/mol
![Page 34: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/34.jpg)
P iADP +
Energy fromcatabolism (exergonic,energy-releasingprocesses)
Energy for cellularwork (endergonic,energy-consumingprocesses)
ATP + H2O
Coupled reactions
![Page 35: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/35.jpg)
VIII. ENZYMES
![Page 36: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/36.jpg)
A. Enzymes speed up metabolic reactions
• catalyst =chemical agent that speeds up a reaction– Unchanged by reaction
• enzyme = catalytic protein (organic)• Ex. Hydrolysis of sucrose by sucrase
![Page 37: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/37.jpg)
B. Enzymes lower activation energy barrier
• chemical reaction = bonds broken/formed
• free energy of activation = activation energy (Ea) = energy to start chemical reaction
• Ea contorts molecule makes bonds unstable
• No change in Δ G (doesn’t affect reactants or product energy)
![Page 38: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/38.jpg)
Progress of the reaction
Products
Reactants
∆G is unaffectedby enzyme
Course ofreactionwithoutenzyme
Fre
e en
erg
y
EA
withoutenzyme EA with
enzymeis lower
Course ofreactionwith enzyme
![Page 39: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/39.jpg)
C. How Enzymes Lower the EA
• 37oC reactants do not reach EA (transition state)
• Enzymes speed rate to transition state• Reactants most unstable• Does not affect Δ G of rxn. Why?
![Page 40: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/40.jpg)
D. Substrate Specificity of enzymes
• S= Substrate = reactant• ES = Enzyme-substrate complex• P = Product(s)
Sucrose + Sucrase E-S complex Fructose + Glucose + ? substrate enzyme products
McGraw Hill Enzymes
![Page 41: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/41.jpg)
• Active site region on enzyme where substrate binds
• Induced fit - enzyme shape changes to fit to substrate
Substrate
Active site
Enzyme Enzyme-substratecomplex
(b)(a)
![Page 42: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/42.jpg)
E. Catalysis in Active Site1000 – 1,000,000 rxns/sec•Induced fit by:
– Hydrogen bonds– Ionic bonds– Hydrophobic interactions
•Enzyme can catalyze forward or reverse rxn– Always in direction of equilibrium
•Active site can lower Ea
– Orient substrates– Contort bonds– Provide microenvironment– Covalently bond to substrate
![Page 43: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/43.jpg)
Substrates
Enzyme
Products arereleased.
Products
Substrates areconverted toproducts.
Active site can lower EA and speed up a reaction.
Substrates held in active site by weakinteractions, such as hydrogen bonds andionic bonds.
Substrates enter active site; enzyme changes shape such that its active siteenfolds the substrates (induced fit).
Activesite is
availablefor two new
substratemolecules.
Enzyme-substratecomplex
![Page 44: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/44.jpg)
F. Local Conditions
• activity affected by– temperature , pH (each has optimal)– chemicals
![Page 45: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/45.jpg)
![Page 46: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/46.jpg)
Ra
te o
f re
ac
tio
n
Optimal temperature forenzyme of thermophilic
(heat-tolerant) bacteria
Optimal temperature fortypical human enzyme
(a) Optimal temperature for two enzymes
(b) Optimal pH for two enzymes
Ra
te o
f re
ac
tio
n
Optimal pH for pepsin(stomach enzyme)
Optimal pHfor trypsin(intestinalenzyme)
Temperature (ºC)
pH543210 6 7 8 9 10
0 20 40 80 60 100
![Page 47: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/47.jpg)
G. Cofactor assists enzyme
• Non-protein• inorganic cofactor
Metal ion (trace elements Zn2+ (cofactor for carbonic anhydrase), Cu2+, Mn2+, K+, Na+.)
• organic cofactor is a coenzymeVitamins (B, C, K)
Bind to active site
![Page 48: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/48.jpg)
H. Enzyme Inhibitors
• Competitive inhibitors – bind to active site of enzyme– compete with substrate at active site
Alcohol dehydrogenase enzyme
![Page 49: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/49.jpg)
• Noncompetitive inhibitors
– bind to another part of enzyme– change shape of active site– May not be reversible
• toxins, poisons, pesticides, antibiotics
![Page 50: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/50.jpg)
(a) Normal binding (c) Noncompetitive inhibition(b) Competitive inhibition
Noncompetitive inhibitor
Active siteCompetitive inhibitor
Substrate
Enzyme
![Page 51: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/51.jpg)
9. Regulation of enzyme activity helps control metabolism
• metabolic pathways are tightly regulated
![Page 52: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/52.jpg)
Allosteric Regulation (normal in cells)
• Regulatory molecule binds to enzyme but not at the active sites! (note: each subunit has its own active site)
• Most enzymes have inactive and active forms – shape changers!
Non-functionalactivesite
Inactive form
Oscillation
Active form
Regulatorysite (oneof four)
Allosteric enzymewith four subunits
Active site(one of four)
![Page 53: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/53.jpg)
A. Allosteric inhibition molecule binds to stabilize inactive state blocks substrate
• Binding is reversible
Allosteric Regulation
InhibitorNon-functionalactivesite
Stabilized inactiveform
Inactive form
![Page 54: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/54.jpg)
B. Allosteric cooperativity boosts enzyme activity
• Regulatory molecule binds to one site • stabilizes favorable shape changes at other
subunits
ActivatorActive form
Stabilized active form
Regulatorysite (oneof four)
Active site(one of four)
![Page 55: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/55.jpg)
IX. Feedback Inhibition
• End product of metabolic pathway turns off pathway
• No wasting chemical resources by synthesizing more product than is needed
![Page 56: An Introduction to Metabolism Chapter 8. METABOLISM I. Introduction All of an organism’s chemical reactions Thousands of reactions in a cell Example:](https://reader036.vdocument.in/reader036/viewer/2022062717/56649e415503460f94b33f6a/html5/thumbnails/56.jpg)
Intermediate C
Feedbackinhibition
Isoleucineused up bycell
Enzyme 1(threoninedeaminase)
End product(isoleucine)
Enzyme 5
Intermediate D
Intermediate B
Intermediate A
Enzyme 4
Enzyme 2
Enzyme 3
Initial substrate(threonine)
Threoninein active site
Active siteavailable
Active site ofenzyme 1 nolonger bindsthreonine;pathway isswitched off.
Isoleucinebinds toallostericsite