12 3. To explore the consequences of coupling ATP hydrolysis under physiological conditions to a thermodynamically unfavorable biochemical reaction, consider the hypothetical transformation X - Y, for which AG° = 20 kJ/mol. (a) What is the ratio [Y]/[X] at equilibrium? (b) Suppose X and Y participate in a sequence of reactions during which ATP is hydrolyzed to ADP and Pi. The overall reaction is →Y+ ADP + P X + ATP + H2O Calculate [Y]/[X] for this reaction at equilibrium. Assume that the temperature is 25 C and the equilibrium concentrations of ATP, ADP, and Piare all 1 M. (c) We know that [ATP], [ADP], and [Pi] are not 1 M under physiological conditions. Calculate [Y]/[X] for the ATP-coupled reaction when the values of [ATP], [ADP], and [Pi] are those found in rat myocytes (look at the Table 13-5). TABLE 13-5 Total Concentrations of Adenine Nucleotides, Inorganic Phosphate, and Phosphocreatine in Some Cells Concentration (MM) ATP ADP AMP PCr Rat hepatocyte 3.38 1.32 0.29 4.8 0. Rat myocyte 8.05 0.04 8.05 28 0.93 2.72 0.06 4.7 Rat neuron 2.59 0.7 0.25 0. 2.25 0.02 1.65 Human erythrocyte E. coli cell 0.82 7.9 1.04 7.90 For erythrocytes the concentrations are those of the cytosol (human erythrocytes lack a nucleus and mitochondria). In the other types of cells the data are for the entire cell contents, although the cytosol and the mitochondria have very different concentrations of ADP. PCr is phosphocreatine, discussed on p. 516. BThis value reflects total concentration; the true value for free ADP may be much lower (p. 509). Cellular ATP concentration is usually far above the equilibrium concentration, making ATPA very potent source of chemical energy.
12 3. To explore the consequences of coupling ATP hydrolysis under physiological conditions to a thermodynamically unfavorable biochemical reaction, consider the hypothetical transformation X - Y, for which AG° = 20 kJ/mol. (a) What is the ratio [Y]/[X] at equilibrium? (b) Suppose X and Y participate in a sequence of reactions during which ATP is hydrolyzed to ADP and Pi. The overall reaction is →Y+ ADP + P X + ATP + H2O Calculate [Y]/[X] for this reaction at equilibrium. Assume that the temperature is 25 C and the equilibrium concentrations of ATP, ADP, and Piare all 1 M. (c) We know that [ATP], [ADP], and [Pi] are not 1 M under physiological conditions. Calculate [Y]/[X] for the ATP-coupled reaction when the values of [ATP], [ADP], and [Pi] are those found in rat myocytes (look at the Table 13-5). TABLE 13-5 Total Concentrations of Adenine Nucleotides, Inorganic Phosphate, and Phosphocreatine in Some Cells Concentration (MM) ATP ADP AMP PCr Rat hepatocyte 3.38 1.32 0.29 4.8 0. Rat myocyte 8.05 0.04 8.05 28 0.93 2.72 0.06 4.7 Rat neuron 2.59 0.7 0.25 0. 2.25 0.02 1.65 Human erythrocyte E. coli cell 0.82 7.9 1.04 7.90 For erythrocytes the concentrations are those of the cytosol (human erythrocytes lack a nucleus and mitochondria). In the other types of cells the data are for the entire cell contents, although the cytosol and the mitochondria have very different concentrations of ADP. PCr is phosphocreatine, discussed on p. 516. BThis value reflects total concentration; the true value for free ADP may be much lower (p. 509). Cellular ATP concentration is usually far above the equilibrium concentration, making ATPA very potent source of chemical energy.
Chemistry
10th Edition
ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter1: Chemical Foundations
Section: Chapter Questions
Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...
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Part c
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3. To explore the consequences of coupling ATP hydrolysis under physiological conditions to a
thermodynamically unfavorable biochemical reaction, consider the hypothetical transformation X
- Y, for which AG° = 20 kJ/mol.
(a) What is the ratio [Y]/[X] at equilibrium?
(b) Suppose X and Y participate in a sequence of reactions during which ATP is hydrolyzed to ADP
and Pi. The overall reaction is
→Y+ ADP + P
X + ATP + H2O
Calculate [Y]/[X] for this reaction at equilibrium. Assume that the temperature is 25 C and the
equilibrium concentrations of ATP, ADP, and Piare all 1 M.
(c) We know that [ATP], [ADP], and [Pi] are not 1 M under physiological conditions. Calculate [Y]/[X]
for the ATP-coupled reaction when the values of [ATP], [ADP], and [Pi] are those found in rat
myocytes (look at the Table 13-5).](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F079cba43-566f-4c95-9de9-a2e279b041b7%2F671f8e0d-9ab0-47c4-a6ec-cdf264eee5a9%2Fmtvy918.jpeg&w=3840&q=75)
Transcribed Image Text:12
3. To explore the consequences of coupling ATP hydrolysis under physiological conditions to a
thermodynamically unfavorable biochemical reaction, consider the hypothetical transformation X
- Y, for which AG° = 20 kJ/mol.
(a) What is the ratio [Y]/[X] at equilibrium?
(b) Suppose X and Y participate in a sequence of reactions during which ATP is hydrolyzed to ADP
and Pi. The overall reaction is
→Y+ ADP + P
X + ATP + H2O
Calculate [Y]/[X] for this reaction at equilibrium. Assume that the temperature is 25 C and the
equilibrium concentrations of ATP, ADP, and Piare all 1 M.
(c) We know that [ATP], [ADP], and [Pi] are not 1 M under physiological conditions. Calculate [Y]/[X]
for the ATP-coupled reaction when the values of [ATP], [ADP], and [Pi] are those found in rat
myocytes (look at the Table 13-5).
Transcribed Image Text:TABLE 13-5 Total Concentrations of Adenine Nucleotides, Inorganic
Phosphate, and Phosphocreatine in Some Cells
Concentration (MM)
ATP
ADP
AMP
PCr
Rat hepatocyte
3.38
1.32
0.29
4.8
0.
Rat myocyte
8.05
0.04
8.05
28
0.93
2.72
0.06
4.7
Rat neuron
2.59
0.7
0.25
0.
2.25
0.02
1.65
Human erythrocyte
E. coli cell
0.82
7.9
1.04
7.90
For erythrocytes the concentrations are those of the cytosol (human erythrocytes lack a nucleus and
mitochondria). In the other types of cells the data are for the entire cell contents, although the cytosol and
the mitochondria have very different concentrations of ADP. PCr is phosphocreatine, discussed on p. 516.
BThis value reflects total concentration; the true value for free ADP may be much lower (p. 509).
Cellular ATP concentration is usually far above the equilibrium
concentration, making ATPA very potent source of chemical energy.
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