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Cap 3 –
Energía,
Catálisis y
Biosíntesis
JA Carde, PhD
Universidad Adventista
Alberts et al.
Enzimas
03_01_A series of enzyme.jpg
03_02_metabolic pathways.jpg
03_03_Catabolic anabolic.jpg
Estructuras biológicas: orden
03_04_Biological structur.jpg
Entropía espontánea diaria
03_05_Toward disorder.jpg
03_06_Second law of thermo.jpg
03_07_forms of energy.jpg
Oxidacion: perdida de e-; que se traduce en
03_12_Oxidation reduction.jpg
Disminucion en los enlaces C-H
Enzimas: ayudan en la célula a empujar las reacciones por
sobre la E de activacion
03_13_activation energy.jpg
Mientras mas E por molecula  menos moleculas tienen esa
energia!!!
03_14_Lowering activation.jpg
La presencia de una Enzima hace que un Numero mayor de
moleculas tengan la energia para que la reaccion proceda!!!
Selectivas: catalizan
03_15_Enzymes catalyze.jpg
una reaccion especifica
Hay una enzima
presente PLT…
Rutas especificas: una
serie de enzimas
presentes determina la
ruta metabolica que una
molecula X seguira;
esto implica:
CONTROL
Sitio Activo: region en la enzima con caracteristicas unicas para
una molecula unica o sea su sutrato.
03_16_Enzymes convert.jpg
Participan en la reaccion PERO no son alteradas o afectadas.
03_17_Negative positiveDG.jpg
03_18_Reaction coupling.jpg
Reacciones E favorables:
crean desorden pq disminuyen la E
libre del sistema PLT tienen ΔG
negativo
Reacciones E desfavorables:
crean orden pq aumentan la E libre
del sistema PLT tienen AG positivo
Entonces una reacción
YX va de
YX ; si tiene ΔGo va de
YX; si tiene ΔG+
Que factores afectan ΔG de una
reacción?
- la energía almacenada en cada molécula
(potencial químico)
- las concentraciones de las moléculas en la
mezcla
Ej: un exceso de Y sobre X favorece la
YX, pq habrá mas moléculas haciendo esa
transición PLT el ΔG será mas negativo también
Como yo puedo determinar cuanta
diferencia en [ ] se necesita para
compensar una disminución en energía
química?
Con un análisis termodinámico, donde se
separa la parte del cambio de energía
libre que es dependiente de [ ] de la parte
que es independiente de [ ] .
*ΔG=
o
AG +
0.616 ln [X]/[Y]
- Δgo - depende de las característica intrínsecas de
las moléculas (en condiciones ideales)
- +… dependiente de las concentraciones
- * para una reacción YX , 37oC
- ΔG – Kcal/mol
- [Y] y [X] – concentraciones de estos
- RT = 0.616 constante y ln log natural
*ΔG=
o
AG +
0.616 ln [X]/[Y]
-Si las concentraciones de X y Y son 1M; Que pasa con la relación
entre ΔG y AGo ?
-Si la razón X:Y disminuye, ΔG sera mas negativo, PQ?
-Cuando la velocidad de ambas reacciones es igual se llega al
equilibrio qumico: estado en el que la razon de X y Y se mantiene
constante;
K = [X]/[Y]; donde K es la constante de equilibrio;
punto donde el efecto de las concentraciones balancea el empuje
dado a la reaccion por el ΔG,
PLT no hay cambio en energia libre que empuje la reacción hacia
ningun lado asi que AG = 0
03_19_Chemical equilibrium.jpg
Relacion entre K y G
03_20_binding interactions.jpg
03_25_enzyme’s performance.jpg
03_26_equilibrium point.jpg
03_30_Activated carriers.jpg
03_31_Mechanical model.jpg
03_32_ATP and ADP cycle.jpg
03_33_terminal phosphate.jpg
03_34_ATP hydrolysis.jpg
03_35_NADPH.jpg
03_36_NADPH to cholesterol.jpg
03_37_Acetyl coenzyme A.jpg
03_38_activated carrier.jpg
03_39_Condensation hydrolysis.jpg
03_40_2_Synthesis polymer.jpg
03_40_3_Synthesis polymer.jpg
03_40_Synthesis polymer.jpg
03_42_Synthesis RNA or DNA.jpg
03_27_Reaction rate data.jpg
03_28_A stopped_flow appar.jpg
Inhibidores
• Inhibitors are compounds which interact with an enzyme to
slow down its rate of reaction
• Many toxic compounds are enzyme inhibitors, being toxic
because they inhibit enzymes responsible for vital reactions.
• Inhibitors can interact with an enzyme in different ways and
enzyme kinetics is a major tool in distinguishing between these
mechanisms.
Inhibicion Competitiva
• In the presence of a competitive inhibitor the enzyme
can bind
• to the substrate: to form an enzyme-substrate complex,
• or the inhibitor: to form an enzyme-inhibitor complex.
Inhibicion Competitiva
•
•
•
•
•
Competitive inhibitors prevent the substrate from binding to the enzyme and thereby
prevent the enzyme from converting it to product.
They are mutually exclusive with the substrate so prior binding of the substrate prevents
the inhibitor from binding.
Consequently competitive inhibitors are inactive at very high substrate
concentrations and do not therefore alter the maximal velocity.
They are active at low substrate concentrations which is seen as an increase in the
slope of the Lineweaver-Burk plot.
They reduce the affinity of the enzyme for its substrate; seen as an increase in the
Michaelis constant.
Inhibicion Competitiva
•
•
•
•
•
Effects on Km
Km is an indication of enzyme-substrate
affinity.
In the presence of a competitive inhibitor
some enzyme molecules will exist as free
enzymes, others as enzyme-inhibitor
complexes. So a competitive inhibitor
reduces enzyme-substrate affinity, or
increases Km.
• Effects on Vmax
Vmax is the velocity at very high substrate
concentration.
Under these conditions the inhibitor is
competed out by the substrate and does not
inhibit the enzyme at all. So competitive
inhibitors do not slow the reaction at
high substrate concentrations and then
is no change in Vmax.
03_29_competitive inhibitor.jpg
Inhibicion NO-Competitiva
•
•
•
A noncompetitive inhibitor binds to an inhibitor site on the enzyme which
is remote from the active site and brings about a conformational change
in the active site.
In this sense it's very similar to one of the competitive inhibitor types.
The difference is that this time the change in the active site is such that it
does not prevent substrate binding but, rather, prevents the enzyme from
converting the bound substrate to product.
Inhibicion NO-Competitiva
Effects on Km
A classical noncompetitive inhibitor
has no effect whatsoever on substrate
binding so the enzyme-substrate
affinity, and hence the Km, are
unchanged.
Effects on Vmax
Noncompetitive, of both the classical
and mixed varieties, inhibit at high
substrate concentrations so the Vmax
is decreased.
Inhibicion DE-Competitiva
Probably the main claim to fame of uncompetitive
inhibitors is the frequent confusion of names between
them and noncompetitive inhibitors!
The key feature of these inhibitors is they are
incapable of binding to free enzyme.
Inhibicion DE-Competitiva
•They can only bind to the enzyme-substrate complex.
•This could be because the substrate is itself directly
involved in binding the inhibitor or because it brings about a
conformational change in an inhibitor binding site which was
previously incapable of binding the inhibitor.
•Once the inhibitor has bound it prevents the enzyme from
turning the substrate into product. Again this could be some
kind of direct interaction, or due to a change in conformation
of the active site.
Inhibicion DE-Competitiva
•Uncompetitive inhibitors can bind only to enzyme substrate
complex, not to free enzyme.
•As a result they do not inhibit at very low enzyme
concentrations.
•They show an apparent increase in affinity for the substrate
as more substrate binds to the enzyme but only in the
formation of an abortive ternary complex.
Inhibicion DE-Competitiva
Efecto en Km:
Disminuye
Efecto en Vmax:
Disminuye
Inhibición
Modelo Michaelis-Menten
Lineweaver Burke