Reacción de acoplamiento para crear glucosa 6 fosfato | Biología | Khan Academy en Español
Summary
TLDRThe provided transcript discusses the significance of phosphorylating glucose in biological systems. Phosphorylation of glucose is crucial as it prevents the molecule from leaving the cell, allowing the cell to retain as much glucose as possible. The process begins with glucose-6-phosphate, a key molecule that initiates various cellular processes. However, phosphorylation is an endergonic reaction, requiring energy, which is provided by ATP. The coupling of ATP hydrolysis, an exergonic process, with the phosphorylation of glucose allows the reaction to proceed spontaneously under appropriate conditions. The transcript also highlights the role of enzymes, particularly hexokinase, in facilitating this reaction by reducing activation energy and managing electron repulsion. The presence of a magnesium ion within the enzyme structure aids in this process, enabling the nucleophilic attack necessary for the reaction. This overview underscores the importance of ATP as an energy currency and the vital role of enzymes in making energetically unfavorable reactions possible within biological systems.
Takeaways
- 🍬 **Phosphorylation of Glucose**: The process of adding a phosphate group to a glucose molecule is crucial in biological systems as it helps retain glucose within the cell.
- 🔒 **Negative Charge Retention**: Once glucose is phosphorylated, its negative charge makes it more difficult for the molecule to exit the cell, thus the cell retains more glucose molecules.
- ⚙️ **Energy Requirement**: The phosphorylation of glucose is an endergonic reaction, meaning it requires energy input and does not occur spontaneously.
- 💰 **ATP as Energy Currency**: The cell uses ATP (adenosine triphosphate) as its energy currency to facilitate the phosphorylation of glucose.
- 💥 **Coupling Reactions**: The phosphorylation reaction is coupled with the hydrolysis of ATP, making the overall process energetically favorable and spontaneous under the right conditions.
- 📉 **Energy Activation**: Even though the net reaction is exergonic, some activation energy is needed to initiate the reaction, which can be provided by enzymes.
- 🔬 **Role of Enzymes**: Enzymes, specifically referred to as exocin Asas in the script, play a vital role in reducing the activation energy and facilitating the reaction.
- 🧲 **Magnesium Ions**: The enzyme uses magnesium ions to help stabilize and manage the negative charges, allowing the nucleophilic attack to occur more readily.
- ⚡ **Nucleophilic Attack**: The mechanism involves a nucleophilic attack by the hydroxyl group on the phosphate, which is facilitated by the enzyme's ability to manage electron repulsion.
- 🔄 **Product Formation**: The end products of the coupled reaction are glucose-6-phosphate and ADP (adenosine diphosphate), which is energetically favorable.
- 🔗 **Importance of Enzymes**: Enzymes are essential in biological systems to lower activation energy and allow reactions that are not energetically favorable to proceed efficiently.
Q & A
Why is phosphorylation of glucose important in biological systems?
-Phosphorylation of glucose is important because it adds a phosphate group, which gives the glucose molecule a negative charge. This makes it more difficult for the glucose molecule to leave the cell, allowing the cell to retain as many glucose molecules as possible for energy and metabolic processes.
What is the role of glucose-6-phosphate in cellular processes?
-Glucose-6-phosphate is a crucial molecule that initiates a series of metabolic processes within the cell. It is a key intermediate in glycolysis and the pentose phosphate pathway, among other pathways.
Why does the phosphorylation of glucose require energy?
-The phosphorylation of glucose is an endergonic reaction, meaning it has a positive ΔG (Gibbs free energy) and does not occur spontaneously. It requires energy to proceed, which is provided by the hydrolysis of ATP.
How does ATP act as the cellular energy currency in the phosphorylation of glucose?
-ATP provides the necessary energy for the endergonic phosphorylation reaction by undergoing hydrolysis to ADP and an inorganic phosphate. This process is exergonic (releases energy) and makes the phosphorylation of glucose energetically favorable.
What is the role of an enzyme in facilitating the phosphorylation of glucose?
-An enzyme, specifically an exocin (such as hexokinase), facilitates the phosphorylation reaction by reducing the activation energy required for the reaction to occur. It does this by stabilizing the transition state and bringing the reactants closer together.
How does the presence of a magnesium ion assist in the phosphorylation process?
-The magnesium ion acts as a cofactor in the enzyme-catalyzed reaction, helping to stabilize the negative charges on the phosphate group and the glucose molecule. This reduces the activation energy and facilitates the nucleophilic attack by the glucose molecule on the phosphate.
What is the overall ΔG for the coupled reaction of ATP hydrolysis and glucose phosphorylation?
-The overall ΔG for the coupled reaction is calculated by summing the individual ΔG values of the ATP hydrolysis (negative) and glucose phosphorylation (positive). The result is -1.7 kJ/mol, indicating that the reaction is exergonic and can proceed spontaneously under the right conditions.
Why is it necessary to lower the activation energy for the phosphorylation reaction to occur?
-Lowering the activation energy allows the reaction to proceed more readily. Without the enzyme to facilitate the reaction and reduce the activation energy, the reaction would have a high activation energy barrier, making it less likely to occur.
How does the enzyme hexokinase help in the phosphorylation of glucose?
-Hexokinase, as an exocin, helps by providing a magnesium ion that interacts with the phosphate group of ATP and the glucose molecule. This interaction helps to stabilize the transition state and reduce the activation energy, allowing the reaction to proceed more efficiently.
What is the significance of the nucleophilic attack in the phosphorylation of glucose?
-The nucleophilic attack is the key step in the phosphorylation of glucose, where the glucose molecule attacks the phosphate group of ATP. This step is facilitated by the enzyme and the presence of the magnesium ion, leading to the formation of glucose-6-phosphate and ADP.
How does the hydrolysis of ATP relate to its role in providing energy for cellular processes?
-The hydrolysis of ATP to ADP and an inorganic phosphate releases energy, which is harnessed by the cell to perform various endergonic reactions, such as the phosphorylation of glucose. This process effectively couples the exergonic hydrolysis of ATP with other energy-requiring reactions.
What is the significance of the three-dimensional structure of enzymes in facilitating reactions?
-The three-dimensional structure of enzymes is crucial as it allows them to create a specific active site that can accommodate and interact with the substrate molecules in a precise manner. This spatial arrangement helps in stabilizing the transition state and reducing the activation energy, making the reaction more likely to occur.
Outlines
🔬 Phosphorylation of Glucose in Cellular Systems
This paragraph discusses the importance of phosphorylating glucose in biological systems. It explains that once glucose is phosphorylated, it becomes more difficult for the molecule to exit the cell, which is beneficial as cells aim to retain as many glucose molecules as possible. The process initiates a series of reactions within the cell. However, phosphorylation of glucose is an endergonic reaction, meaning it requires energy and will not occur spontaneously. To facilitate this, the cell uses ATP, the cellular energy currency, through a process analogous to ATP hydrolysis, which is energetically favorable and spontaneous under the right conditions. An enzyme, referred to as exocin Asa, is necessary to lower the activation energy and catalyze the reaction, resulting in the formation of glucose-6-phosphate and ADP. The net reaction is exergonic, meaning it releases energy, and can occur spontaneously, especially if the activation energy is reduced.
🌟 The Role of Enzymes in Facilitating Reactions
The second paragraph delves into the mechanism of the reaction without an enzyme, highlighting the difficulty due to the high activation energy and repulsion between the negative charges of oxygen atoms. It emphasizes the role of enzymes, specifically exocin Asa, which contains magnesium ions to help stabilize and occupy electrons, facilitating the nucleophilic attack necessary for the reaction to proceed. The paragraph uses an example to illustrate how enzymes, with their complex protein structures, can help in the reaction by shielding electrons with positive charges, thus reducing the activation energy and allowing the reaction to occur. It concludes by stressing the energetic favorability of the process, assuming the presence of an enzyme to distract the electrons, and provides insight into how ATP is useful in carrying out reactions that might not be energetically favorable on their own.
Mindmap
Keywords
💡Phosphorylation
💡Glucose
💡Glucose 6-phosphate
💡ATP (Adenosine Triphosphate)
💡Hydrolysis
💡Endergonic Reaction
💡Exergonic Reaction
💡Coupling Reactions
💡Energy of Activation
💡Enzymes
💡Nucleophilic Attack
Highlights
Phosphorylating a glucose molecule is very valuable in biological systems as it helps the cell retain more glucose molecules.
Once glucose is phosphorylated, it becomes negatively charged and harder for the molecule to exit the cell.
Glucose 6-phosphate is an important molecule that initiates a series of processes inside cells.
The glucose phosphorylation reaction is endergonic, meaning it requires energy and will not occur spontaneously.
The reaction has a positive ΔG, indicating it is not energetically favorable on its own.
To make the reaction occur, the cell uses ATP, the energy currency, through a process similar to ATP hydrolysis.
The hydrolysis of ATP to ADP and a phosphate group is energetically favorable and spontaneous under the right conditions.
An enzyme is needed to reduce the activation energy and facilitate the reaction by keeping the negatively charged oxygens occupied with ions.
The enzyme uses a magnesium ion to help in the nucleophilic attack of the oxygen on the phosphate.
The overall coupled reaction has a negative ΔG, making it exergonic and spontaneous with the enzyme's help.
The enzyme, specifically an exocin like ASA, plays a crucial role in facilitating the reaction by reducing the activation energy.
The coupled reaction produces glucose 6-phosphate, ADP, and inorganic phosphate, with the release of a phosphate group from ATP being energetically favorable.
The enzyme's 3D structure allows it to surround and interact with the substrates, facilitating the necessary nucleophilic attack.
ATP's release of a phosphate group is energetically favorable, but it can also drive reactions in the system that are not inherently energetically favorable.
The importance of enzymes in biology is highlighted, as they help lower activation energy and facilitate essential reactions.
The example of how ATP can be used to drive the phosphorylation of glucose, even though it is an endergonic reaction, demonstrates the versatility of ATP in cellular processes.
The reaction mechanism is discussed in detail, providing insight into the role of enzymes and the energetics of biochemical reactions.
Transcripts
es muy valioso en los sistemas
biológicos el poder fosforilar una
molécula de glucosa Así que vamos a
empezar con una molécula de glucosa y
fosforilar la y la razón por la que es
tan importante es que una vez que tiene
este grupo fosfato o una vez que tenga
esta carga negativa en esta glucosa se
fosfato se vuelve mucho más difícil para
la molécula salir de la célula la célula
quiere quedarse con el mayor número de
moléculas de glucosa que pueda cuando la
glucosa no está cargada le es posible
pasar a través de la membrana celular
pero una vez que está fosforilada va a
permanecer en la célula y la glucosa 6
fosfato es una molécula muy importante
que da inicio a toda una serie de
procesos en el interior de las células
desgraciadamente esta reacción de la
fosforilación de la glucosa requiere de
energía es
endergónica no va a suceder de forma
espontánea tiene una Delta G
positiva y así te puedes imaginar lo que
vamos a necesitar para que esto ocurra
vamos a tener que usar la moneda
energética de la célula nuestro buen
amigo
ATP y la forma en que vamos a hacer que
esta reacción suceda es que vamos a
llevar a cabo lo que podríamos Llamar la
hidrólisis del ATP aunque no vamos a
tener exactamente una molécula de agua
en el mecanismo pero lo que es
funcionalmente la hidrólisis de ATP en
adp y un grupo fosfato lo cual es
energéticamente favorable es
exergónica va a suceder de forma
espontánea bajo las condiciones
adecuadas esto no quiere decir que va a
suceder siempre dentro de una solución
se necesita un poco de energía de
activación o una enzima para reducir la
energía de activación pero la reacción
neta es
exergónica así que lo que podemos hacer
es acoplar estas dos reacciones y así
cuando acoplamos las dos reacciones
tenemos
ATP
ATP más
glucosa en los reactivos y usamos la
enzima el término general para ella es
exocin Asa para facilitar esta reacción
para reducir la energía de activación y
se va a producir glucosa seis
fosfato
glucosa
seis
fosfato y
adp y
adp ahora bien Cuál es el Delta G para
esta reacción bueno es una reacción de
acoplamiento Así que podemos
visualizarla como una combinación de
estas dos reacciones y así en términos
generales se puede decir que vamos a
sumar El delta G Así que sumamos los
Delta G aquí vamos a obtener si sumamos
este Delta G negativo y este Delta G
positivo vamos a obtener
-3.5 +
13.8 eso va a ser
-1.7 kj por
mol por lo que esta reacción de
acoplamiento va a ser exergónica no es
tan exergónica como la hidrólisis porque
ahora vamos a utilizar parte de esa
energía Pero esto puede ocurrir de forma
espontánea especialmente si se logra
bajar la energía de activación para que
esto
ocurra ahora vamos a ver el mecanismo de
la reacción si no tuviéramos un enzima
la forma en que esta reacción necesita
ocurrir es la siguiente tenemos un par
de electrones libres aquí en este grupo
hidróxilo
y tiene que hacer lo que llamamos un
ataque nucleofílico a este fósforo por
aquí pero sin una enzima va a ser muy
difícil que este ataque ocurra va a
tener una energía de activación alta
porque va a ser afectada por todas estas
cargas negativas de estos oxígenos a los
electrones no les gusta pasar cerca de
otras cargas negativas las cargas
negativas Se repelen entre sí así que
vamos a tener una enzima para ayudar a
facilitar esta reacción para ayudar a
reducir la energía de activación y
esencialmente va alejar a estos
electrones y la enzima o el término
general para las enzimas que hacen esto
es exocin Asa déjame escribir esto
exocin
Asa y la forma en que lo hace es
proporcionando iones para mantener a
estos electrones ocupados y en
particular tiene un ion de
Magnesio un ion de Magnesio justo aquí y
esto se encuentra Unido al resto de la
exin Asa recuerda todo esto está
sucediendo en tres dimensiones Así que
la exocin Asa está alrededor de todo
esto por lo que estos pueden mantener a
los electrones ocupados hay otros iones
en la exin Asa que pueden mantener a
estos electrones
ocupados y así estos electrones pueden
colarse y hacer el ataque
nucleofílico Recuerda que cuando
hablamos de enzimas son estas proteínas
son estas estructuras plejas de
proteínas algo como esto y aquí podría
ir el I
magnesio y luego tal vez la molécula de
glucosa se une
aquí y luego el ATP se une justo aquí y
esto es solo un ejemplo Esto no es
exactamente lo que está sucediendo pero
esencialmente gracias a que es envuelto
con estas cargas positivas es capaz de
alejar a los electrones para ayudar a
facilitar este ataque nucleofílico que
tiene que suceder para que la reacción
proceda entonces este enlace de aquí
entre este oxígeno y este fósforo ese va
a ser este enlace justo aquí y mientras
esto sucede estos dos electrones pueden
ser tomados por este oxígeno por lo que
este oxígeno es este oxígeno de aquí y
ahora tiene una carga negativa entonces
lo que acabamos de obtener es glucosa
seis fosfato y adp y adp y Es
energéticamente favorable es exergónico
Esto va a suceder asumiendo que tienes
la enzima para ayudar a distraer a estos
electrones reduciendo la energía de
activación y sé lo que estás pensando
teníamos este hidrógeno por aquí por lo
que este hidrógeno debería estar por
aquí todavía y luego otra molécula de
agua podría venir y atrapar el protón el
protón de
hidrógeno y así una vez más nos quedamos
solo con la glucosa seis
fosfato Espero que esto te dé una idea
acerca de cómo se produce la reacción de
acoplamiento y también una idea de cómo
el ATP Es realmente útil cuando me
enteré por primera vez del ATP entendí
que lo que el ATP realmente quiere es
soltar a este grupo fosfato y que eso es
energéticamente favorable Pero cómo es
que eso se utiliza para poder llevar a
cabo reacciones en el sistema que
podrían no ser energéticamente
favorables y espero que esto te dé una
idea de cómo eso sucede y también de la
importancia de un enzima en la
facilitación de estas
reacciones
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