(b) How ATP increases the apparent KM for substrate fructose-6-phosphate, inhibiting PFK.
(b) How ATP increases the apparent KM for substrate fructose-6-phosphate, inhibiting PFK.
Biochemistry
9th Edition
ISBN:9781319114671
Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Chapter1: Biochemistry: An Evolving Science
Section: Chapter Questions
Problem 1P
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Question
![### Transcription and Explanation for Educational Website
**Text:**
3) Briefly explain the relationships between [ATP] and [F-6-P] in the following graph (b).
*Fructose – 6 – phosphate (F6P) → Fructose 1,6 – bisphosphate (FBP)*
\[ \Delta G = -22.2 \, \text{kJ/mol} \]
**Graph Explanation:**
The graph depicts the relationship between fructose-6-phosphate (F6P) concentration and phosphofructokinase (PFK) activity at different ATP concentrations.
- **Axes:**
- The x-axis shows the concentration of [Fructose-6-phosphate].
- The y-axis displays PFK activity as a percentage of V_max (maximum reaction rate).
- **Curves:**
- The black curve represents PFK activity at low ATP concentration.
- The red curve indicates PFK activity at high ATP concentration.
**Analysis:**
- At low ATP concentrations, the PFK activity increases sharply with increasing [F6P], approaching V_max quickly. This suggests that ATP does not significantly inhibit PFK activity.
- At high ATP concentrations, the curve rises more gradually, indicating an increased apparent K_m for F6P. This suggests that ATP acts as an inhibitor, reducing PFK activity by requiring a higher F6P concentration to achieve similar reaction rates compared to low ATP levels.
**Conclusion:**
This graph illustrates how ATP serves as a negative regulator of PFK activity by increasing the apparent K_m for its substrate, fructose-6-phosphate, thereby decreasing the enzyme’s affinity for this substrate and inhibiting its activity at higher ATP levels. This is a classic example of feedback inhibition in glycolysis.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fa01d43e9-d5a5-45d6-84e7-84e66a881f35%2F264f91e0-3ce1-4b43-b2df-4c81d5e58d70%2Fm5rt8fm_processed.png&w=3840&q=75)
Transcribed Image Text:### Transcription and Explanation for Educational Website
**Text:**
3) Briefly explain the relationships between [ATP] and [F-6-P] in the following graph (b).
*Fructose – 6 – phosphate (F6P) → Fructose 1,6 – bisphosphate (FBP)*
\[ \Delta G = -22.2 \, \text{kJ/mol} \]
**Graph Explanation:**
The graph depicts the relationship between fructose-6-phosphate (F6P) concentration and phosphofructokinase (PFK) activity at different ATP concentrations.
- **Axes:**
- The x-axis shows the concentration of [Fructose-6-phosphate].
- The y-axis displays PFK activity as a percentage of V_max (maximum reaction rate).
- **Curves:**
- The black curve represents PFK activity at low ATP concentration.
- The red curve indicates PFK activity at high ATP concentration.
**Analysis:**
- At low ATP concentrations, the PFK activity increases sharply with increasing [F6P], approaching V_max quickly. This suggests that ATP does not significantly inhibit PFK activity.
- At high ATP concentrations, the curve rises more gradually, indicating an increased apparent K_m for F6P. This suggests that ATP acts as an inhibitor, reducing PFK activity by requiring a higher F6P concentration to achieve similar reaction rates compared to low ATP levels.
**Conclusion:**
This graph illustrates how ATP serves as a negative regulator of PFK activity by increasing the apparent K_m for its substrate, fructose-6-phosphate, thereby decreasing the enzyme’s affinity for this substrate and inhibiting its activity at higher ATP levels. This is a classic example of feedback inhibition in glycolysis.
![2) Briefly explain the relationships between [AMP], [ADP], and [F 2,6-BP] and [F-6-P] in the following graph (a).
**Fructose-6-phosphate (F6P) → Fructose 1,6-bisphosphate (FBP)**
ΔG = -22.2 kJ/mol
**Graph (a) Description:**
The graph illustrates the activation of phosphofructokinase (PFK) by fructose-2,6-bisphosphate. It plots PFK activity as a percentage of maximum reaction rate (% Vmax) against the concentration of fructose-6-phosphate.
- **Red Curve:** Represents the presence of 0.13 mM fructose-2,6-bisphosphate. The curve shows a steep increase in enzyme activity, indicating enhanced PFK activity.
- **Black Curve:** Represents the absence of fructose-2,6-bisphosphate. This curve is less steep, indicating a lower rate of PFK activity compared to the presence of an activator.
Overall, the graph shows that fructose-2,6-bisphosphate significantly activates PFK, enhancing the conversion of fructose-6-phosphate to fructose 1,6-bisphosphate.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fa01d43e9-d5a5-45d6-84e7-84e66a881f35%2F264f91e0-3ce1-4b43-b2df-4c81d5e58d70%2F3o9shma_processed.png&w=3840&q=75)
Transcribed Image Text:2) Briefly explain the relationships between [AMP], [ADP], and [F 2,6-BP] and [F-6-P] in the following graph (a).
**Fructose-6-phosphate (F6P) → Fructose 1,6-bisphosphate (FBP)**
ΔG = -22.2 kJ/mol
**Graph (a) Description:**
The graph illustrates the activation of phosphofructokinase (PFK) by fructose-2,6-bisphosphate. It plots PFK activity as a percentage of maximum reaction rate (% Vmax) against the concentration of fructose-6-phosphate.
- **Red Curve:** Represents the presence of 0.13 mM fructose-2,6-bisphosphate. The curve shows a steep increase in enzyme activity, indicating enhanced PFK activity.
- **Black Curve:** Represents the absence of fructose-2,6-bisphosphate. This curve is less steep, indicating a lower rate of PFK activity compared to the presence of an activator.
Overall, the graph shows that fructose-2,6-bisphosphate significantly activates PFK, enhancing the conversion of fructose-6-phosphate to fructose 1,6-bisphosphate.
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