an introduction to metabolism a.p. biology. the living cell is a miniature factory where thousands...
TRANSCRIPT
![Page 1: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/1.jpg)
An Introduction to Metabolism
A.P. Biology
![Page 2: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/2.jpg)
![Page 3: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/3.jpg)
![Page 4: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/4.jpg)
The living cell
Is a miniature factory where thousands of reactions occur
– Converts energy in many ways
Figure 8.1
Bioluminescence
![Page 5: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/5.jpg)
Metabolism
– Is the totality of an organism’s chemical reactions
– Arises from interactions between molecules
– An organism’s metabolism transforms matter and energy, subject to the laws of thermodynamics
![Page 6: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/6.jpg)
Thermodynamics
– Is the study of energy transformations
• The first law of thermodynamics– Energy can be transferred and transformed– Energy cannot be created or destroyed
• The second law of thermodynamics– Spontaneous changes that do not require outside energy
increase the entropy, or disorder, of the universe
![Page 7: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/7.jpg)
1st Law of Thermodynamics
Figure 8.3
First law of thermodynamics: Energy can be transferred or transformed but Neither created nor destroyed. For example, the chemical (potential) energy in food will be converted to the kinetic energy of the cheetah’s movement in (b).
(a)
Chemicalenergy
![Page 8: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/8.jpg)
2nd Law of Thermodynamics
Figure 8.3
Second law of thermodynamics: Every energy transfer or transformation increasesthe disorder (entropy) of the universe. For example, disorder is added to the cheetah’ssurroundings in the form of heat and the small molecules that are the by-productsof metabolism.
(b)
Heat co2
H2O+
![Page 9: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/9.jpg)
![Page 10: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/10.jpg)
Living systems
– Increase the entropy of the universe
– Use energy to maintain order
![Page 11: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/11.jpg)
Metabolic Pathways
•A metabolic pathway has many steps
–That begin with a specific molecule and end with a product
–That are each catalyzed by a specific enzyme
Enzyme 1 Enzyme 2 Enzyme 3
A B C DReaction 1 Reaction 2 Reaction 3
Startingmolecule
Product
![Page 12: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/12.jpg)
Types of Metabolic Pathways
• Catabolic pathways– Break down complex molecules into simpler
compounds– Release energy
• Anabolic pathways– Build complicated molecules from simpler
ones– Consume energy
![Page 13: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/13.jpg)
![Page 14: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/14.jpg)
Energy can be convertedfrom one form to another
On the platform, a diverhas more potential energy.
Diving converts potentialenergy to kinetic energy.
Climbing up converts kinetic
energy of muscle movement
to potential energy.
In the water, a diver has less potential energy.
Figure 8.2
![Page 15: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/15.jpg)
Free Energy
• The free-energy change of a reaction tells us whether the reaction occurs spontaneously
• A living system’s free energy– Is energy that can do work under
cellular conditions
![Page 17: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/17.jpg)
![Page 18: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/18.jpg)
![Page 19: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/19.jpg)
∆G
• The value of ∆ G for a reaction at any moment in time tells us two things.
• The sign of ∆ G tells us in what direction the reaction has to shift to reach equilibrium.
• The magnitude of ∆ G tells us how far the reaction is from equilibrium at that moment.
![Page 20: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/20.jpg)
![Page 21: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/21.jpg)
Chemical reaction. In a cell, a sugar molecule is broken down into simpler molecules.
.
Diffusion. Molecules in a drop of dye diffuse until they are randomly dispersed.
Gravitational motion. Objectsmove spontaneously from ahigher altitude to a lower one.
• More free energy (higher G)• Less stable• Greater work capacity
• Less free energy (lower G)• More stable• Less work capacity
In a spontaneously change • The free energy of the system decreases (∆G <0) • The system becomes more stable• The released free energy can be harnessed to do work
(a) (b) (c)
Figure 8.5
At maximum stability
–The system is at equilibrium
![Page 22: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/22.jpg)
Higher G means…
0%
0% 1. More free energy
2. Less free energy
![Page 23: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/23.jpg)
If ∆G is negative that means…
0%
0%
0%
0% 1. The reaction is spontaneous
2. The reaction takes in energy
3. The reaction is not spontaneous
4. The reaction is less stable as products
![Page 24: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/24.jpg)
Exergonic and Endergonic Reactions in Metabolism
• An exergonic reaction– Proceeds with a net release of free energy
and is spontaneous
Figure 8.6
Reactants
Products
Energy
Progress of the reaction
Amount ofenergyreleased (∆G <0)
Fre
e e
ne
rgy
(a) Exergonic reaction: energy released
![Page 25: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/25.jpg)
Endergonic reaction
–Is one that absorbs free energy from its surroundings and is non-spontaneous
Figure 8.6
Energy
Products
Amount ofenergyreleased (∆G>0)
Reactants
Progress of the reaction
Fre
e e
ne
rgy
(b) Endergonic reaction: energy required
![Page 26: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/26.jpg)
An exergonic reaction…
1. Takes in energy
2. Gives off energy
3. Has a positive ΔG
![Page 27: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/27.jpg)
![Page 28: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/28.jpg)
![Page 29: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/29.jpg)
Reactions in a closed system
– Eventually reach equilibrium
Figure 8.7 A
(a) A closed hydroelectric system. Water flowing downhill turns a turbine that drives a generator providing electricity to a light bulb, but only until the system reaches equilibrium.
∆G < 0 ∆G = 0
![Page 30: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/30.jpg)
Reactions in an open system
• Cells in our body– Experience a constant flow of
materials in and out, preventing metabolic pathways from reaching equilibrium
Figure 8.7
(b) An open hydroelectric system. Flowing water keeps driving the generator because intake and outflow of water keep the system from reaching equilibrium.
∆G < 0
![Page 31: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/31.jpg)
An analogy for cellular respiration
Figure 8.7 (c) A multi-step open hydroelectric system. Cellular respiration is analogous to this system: Glucose is broken down in a series of exergonic reactions that power the work of the cell. The product of each reaction becomes the reactant for the next, so no reaction reaches equilibrium.
∆G < 0
∆G < 0
∆G < 0
![Page 32: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/32.jpg)
ATP – Adenosine Tri-phosphate
• ATP powers cellular work by coupling exergonic reactions to endergonic reactions
• A cell does three main kinds of work– Mechanical– Transport– Chemical
![Page 33: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/33.jpg)
The Structure and Hydrolysis of ATP
– Provides energy for cellular functions
Figure 8.8
O O O O CH2
H
OH OH
H
N
H H
O
NC
HC
N CC
N
NH2Adenine
RibosePhosphate groups
O
O O
O
O
O
-- - -
CH
![Page 34: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/34.jpg)
Energy is released from ATPWhen the terminal phosphate bond is broken
and the negative charge on the PO4 groups repel
Figure 8.9
P
Adenosine triphosphate (ATP)
H2O
+ Energy
Inorganic phosphate Adenosine diphosphate (ADP)
PP
P PP i
![Page 35: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/35.jpg)
![Page 36: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/36.jpg)
ATP hydrolysiscan be coupled to other
reactionsEndergonic reaction: ∆G is positive, reaction is not spontaneous
∆G = +3.4 kcal/molGlu Glu
∆G = - 7.3 kcal/molATP H2O+
+ NH3
ADP +
NH2
Glutamicacid
Ammonia Glutamine
Exergonic reaction: ∆ G is negative, reaction is spontaneous
P
Coupled reactions: Overall ∆G is negative; together, reactions are spontaneous ∆G = –3.9 kcal/molFigure 8.10
ATP hydrolysis
![Page 37: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/37.jpg)
ATP drives endergonic reactionsBy phosphorylation, transferring a phosphate to other molecules
(c) Chemical work: ATP phosphorylates key reactants
P
Membraneprotein
Motor protein
P i
Protein moved(a) Mechanical work: ATP phosphorylates motor proteins
ATP
(b) Transport work: ATP phosphorylates transport proteins
Solute
P P i
transportedSolute
GluGlu
NH3
NH2
P i
P i
+ +
Reactants: Glutamic acid and ammonia
Product (glutamine)made
ADP+
P
Figure 8.11
Three types of cellular work are powered by the hydrolysis of ATP
![Page 38: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/38.jpg)
ATP is used for energy in the cell, catabolic pathways are responsible
for which of the following?
0%
6%
11%
83% 1. Regeneration of ATP
2. Using energy from ATP
3. Are endergonic processes
4. Build complex molecules from simple ones
![Page 39: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/39.jpg)
The Regeneration of ATP• Catabolic pathways
– Drive the regeneration of ATP from ADP and phosphate
ATP synthesis from ADP + P i requires energy
ATP
ADP + P i
Energy for cellular work(endergonic, energy-consuming processes)
Energy from catabolism(exergonic, energy yieldingprocesses)
ATP hydrolysis to ADP + P i yields energy
Figure 8.12
![Page 40: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/40.jpg)
∆ G = -7.3 kcal/mol
∆ G = +7.3 kcal/mol
![Page 41: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/41.jpg)
Enzymes• Enzymes speed up metabolic reactions by lowering
energy barriers
• A catalyst– Is a chemical agent that speeds up a reaction without being
consumed by the reaction
• An enzyme– Is a catalytic protein
E + S ES E + P
![Page 42: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/42.jpg)
![Page 43: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/43.jpg)
Every chemical reaction between moleculesinvolves both bond breaking and bond
forming
18%
82% 1. True
2. False
![Page 44: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/44.jpg)
Every chemical reaction between molecules
Involves both bond breaking and bond forming
•Hydrolysis is an example of a chemical reaction
Figure 8.13
H2O
H
H
H
H
HO
OH
OH
OH
O
O OO OHH H H
H
H
H
CH2OH CH2OH
OHCH2OH
Sucrase
HOHO
OH OHCH2OH
H
CH2OH
H
CH2OH
H
O
Sucrose Glucose Fructose
C12H22O11 C6H12O6 C6H12O6
+HOH H
![Page 45: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/45.jpg)
Activation Energy (EA)
• The activation energy, EA
– Is the initial amount of energy needed to start a chemical reaction
– Is often supplied in the form of heat from the surroundings in a system
• An enzyme catalyzes reactions– By lowering the EA barrier
![Page 46: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/46.jpg)
![Page 47: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/47.jpg)
Exergonic Reactions
Fre
e en
ergy
Progress of the reaction
∆G < O
EA
Figure 8.14
A B
C D
Reactants
A
C D
B
Transition state
A B
C D
Products
![Page 48: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/48.jpg)
Progress of the reaction
Products
Course of reaction without enzyme
Reactants
Course of reaction with enzyme
EA
withoutenzyme
EA with enzymeis lower
∆G is unaffected by enzymeF
ree
ener
gy
Figure 8.15
![Page 49: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/49.jpg)
Substrate Specificity of Enzymes
• The substrate– Is the reactant an enzyme acts on
• The enzyme– Binds to its substrate, forming an
enzyme-substrate complex
• The active site– Is the region on the enzyme
where the substrate binds
Figure 8.16
Substrate
Active site
Enzyme
(a)
![Page 50: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/50.jpg)
Induced fit of a substrate
– Brings chemical groups of the active site into positions that enhance their ability to catalyze the chemical reaction
Figure 8.16 (b)
Enzyme- substratecomplex
![Page 51: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/51.jpg)
Enzyme & Substrate fit like a lock & key (Shape specific)
pH or temperature can change the active site shape on any enzyme
Active site is where the Active site is where the reactants bind to the reactants bind to the enzymeenzyme
![Page 52: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/52.jpg)
Substrates
Products
Enzyme
Enzyme-substratecomplex
1 Substrates enter active site; enzymechanges shape so its active siteembraces the substrates (induced fit).
2 Substrates held inactive site by weakinteractions, such ashydrogen bonds andionic bonds.
3 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.
4 Substrates are Converted intoProducts.
5 Products areReleased.
6 Active siteIs available fortwo new substrateMole.
Figure 8.17
![Page 53: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/53.jpg)
The active site can lower an EA barrier by:
– Orienting substrates correctly– Straining substrate bonds– Providing a favorable
microenvironment– Covalently bonding to the substrate
![Page 54: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/54.jpg)
The activity of an enzyme
– Is affected by general environmental factors– Temperature– pH
Figure 8.18
Optimal temperature for enzyme of thermophilic
Rat
e o
f re
actio
n
0 20 40 80 100Temperature (Cº)
(a) Optimal temperature for two enzymes
Optimal temperature fortypical human enzyme
(heat-tolerant) bacteria
![Page 55: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/55.jpg)
Figure 8.18
Rat
e o
f re
actio
n
(b) Optimal pH for two enzymes
Optimal pH for pepsin (stomach enzyme)
Optimal pHfor trypsin(intestinalenzyme)
10 2 3 4 5 6 7 8 9
![Page 56: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/56.jpg)
Enzyme cofactors
• Cofactors– Are non-protein enzyme helpers e.g.
zinc, iron, copper atoms
• Coenzymes– Are organic cofactors e.g. vitamins
• Ex Vitamin C is used in at least 8 enzymatic reactions (to make collagen)
![Page 57: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/57.jpg)
Enzyme Inhibition
![Page 58: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/58.jpg)
![Page 59: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/59.jpg)
Enzyme Inhibitors
• Competitive inhibitors
– Bind to the active site of an enzyme, competing with the substrate
Figure 8.19 (b) Competitive inhibition
A competitiveinhibitor mimics the
substrate, competingfor the active site.
Competitiveinhibitor
A substrate canbind normally to the
active site of anenzyme.
Substrate
Active site
Enzyme
(a) Normal binding
![Page 60: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/60.jpg)
![Page 61: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/61.jpg)
Michaelis-Menten Equation-V = Vmax [S] / Km + [S]
V = velocity (rate of reaction)Vmax = when all of the enzyme molecules contain bound
substrate (saturated), maximal velocity [S] = concentration of the substrate Km = concentration of the substrate needed to give half
maximal velocity (1/2 Vmax), a measure of affinity, enzyme
for substrate
![Page 62: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/62.jpg)
![Page 63: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/63.jpg)
Enzyme Inhibitors
• Noncompetitive inhibitors– Bind to another part of an enzyme,
changing the function
Figure 8.19
A noncompetitiveinhibitor binds to the
enzyme away fromthe active site, altering
the conformation ofthe enzyme so that its
active site no longerfunctions.
Noncompetitive inhibitor
(c) Noncompetitive inhibition
![Page 64: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/64.jpg)
Enzyme Regulation
• Regulation of enzyme activity helps control metabolism
• A cell’s metabolic pathways– Must be tightly regulated
![Page 65: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/65.jpg)
Allosteric regulation– Is the term used to describe any case in
which a protein’s function at one site is affected by binding of a regulatory molecule at another
Activator Inhibitor
![Page 66: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/66.jpg)
![Page 67: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/67.jpg)
Stabilized inactiveform
Allosteric activaterstabilizes active fromAllosteric enyzme
with four subunitsActive site
(one of four)
Regulatorysite (oneof four)
Active formActivator
Stabilized active form
Allosteric inhibitorsstabilizes inactive form
InhibitorInactive formNon-functionalactivesite
(a) Allosteric activators and inhibitors. In the cell, activators and inhibitors dissociate when at low concentrations. The enzyme can then oscillate again.
Oscillation
Figure 8.20
![Page 68: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/68.jpg)
Cooperativity– Is a form of allosteric regulation that
can amplify enzyme activity
Figure 8.20
Binding of one substrate molecule toactive site of one subunit locks all subunits in active conformation.
Substrate
Inactive form Stabilized active form
(b) Cooperativity: another type of allosteric activation. Note that the inactive form shown on the left oscillates back and forth with the active form when the active form is not stabilized by substrate.
![Page 69: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/69.jpg)
Feedback inhibition
– The end product of a metabolic pathway shuts down the pathway
Active siteavailable
Isoleucineused up bycell
Feedbackinhibition
Isoleucine binds to allosteric site
Active site of enzyme 1 no longer binds threonine;pathway is switched off
Initial substrate(threonine)
Threoninein active site
Enzyme 1(threoninedeaminase)
Intermediate A
Intermediate B
Intermediate C
Intermediate D
Enzyme 2
Enzyme 3
Enzyme 4
Enzyme 5
End product(isoleucine)
Figure 8.21
![Page 70: An Introduction to Metabolism A.P. Biology. The living cell Is a miniature factory where thousands of reactions occur –Converts energy in many ways](https://reader030.vdocument.in/reader030/viewer/2022032708/56649e605503460f94b5b11a/html5/thumbnails/70.jpg)
How to Name Enzymes
• Change the ending on the name of the substrate to –ase
• Sucrose (substrate) – Sucrase (enzyme)
• Lipid – Lipase• Protein – Protease• DNA - DNAse