Biochemistry: Concepts and Connections (2nd Edition)
2nd Edition
ISBN: 9780134641621
Author: Dean R. Appling, Spencer J. Anthony-Cahill, Christopher K. Mathews
Publisher: PEARSON
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Chapter 2, Problem 12P
Describe the preparation of 2.00 L of 100 glycine buffer, pH 9.0, from glycine and 1.00 M NaOH. What mass of glycine is required, what volume of 1.00 NaOH is required? The appropriate pKa of glycine is 9.6.
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Macmillan Learning
The phosphorylation of glucose to glucose 6-phosphate is the initial step in the catabolism of glucose. The direct
phosphorylation of glucose by P, is described by the equation
Glucose + P
←
glucose 6-phosphate + H₂O
AG = 13.8 kJ/mol
Coupling ATP hydrolysis to glucose phosphorylation makes thermodynamic sense, but consider how the coupling might
take place.
Given that coupling requires a common intermediate, one conceivable mechanism is to use ATP hydrolysis to raise the
intracellular concentration of Pi. The increase in P; concentration would drive the unfavorable phosphorylation of glucose by Pi-
Is increasing the P; concentration a reasonable way to couple ATP hydrolysis and glucose phosphorylation?
No. The phosphate salts of divalent cations would be present in excess and precipitate out.
Yes. Increasing the concentration of P; would decrease K'eq and shift equilibrium to the right.
Yes. The extra ATP hydrolysis would provide enough free energy to drive the…
The phosphorylation of glucose to glucose 6-phosphate is the initial step in the catabolism of glucose. The direct
phosphorylation of glucose by P, is described by the equation
Glucose + P → glucose 6-phosphate + H₂O AG' = 13.8 kJ/mol
In principle, at least, one way to increase the concentration of glucose 6-phosphate (G6P) is to drive the equilibrium reaction to
the right by increasing the intracellular concentrations of glucose and Pj.
The maximum solubility of glucose is less than 1 M, and the normal physiological concentration of G6P is 250 μM. Assume a
fixed concentration of P, at 4.8 mM. The calculated value of K'cq is 4.74 × 10-³ M-¹.
Calculate the intracellular concentration of glucose when the equilibrium concentration of glucose 6-phosphate is 250 μM, the
normal physiological concentration.
[glucose] =
10.99
Correct Answer
Would increasing the concentration of glucose be a physiologically reasonable way to increase the concentration
of G6P?
No. Because the concentration of P,…
Calculate the equilibrium constant for the phosphorylation of glucose to glucose 6-phosphate at 37.0 °C.
K'eq =
M-'
In the rat hepatocyte, the physiological concentrations of glucose and P, are maintained at approximately 4.8 mM. What is the
equilibrium concentration of glucose 6-phosphate (G6P) obtained by the direct phosphorylation of glucose by P.?
[G6P] =
Does this reaction represent a reasonable metabolic step for the catabolism of glucose? Why or why not?
Yes, because the value of AG" is positive.
No, because the K'eq is too large for the reaction to proceed in the forward direction.
Yes, because AG is negative at the calculated value of K'eq
No, because [G6P] is likely to be higher than the calculated value.
M
Chapter 2 Solutions
Biochemistry: Concepts and Connections (2nd Edition)
Ch. 2 - Suppose a chloride ion and a sodium ion are...Ch. 2 - Draw two different possible hydrogen-bonding...Ch. 2 - Prob. 3PCh. 2 - 4. What is the pH of each of the following...Ch. 2 - Prob. 5PCh. 2 - The weak acid HA is 2% ionized (dissociated) in a...Ch. 2 - 7. Calculate the pH values and draw the titration...Ch. 2 - What is the pH of the following buffer mixtures?...Ch. 2 - a. Suppose you wanted to make a buffer of exactly...Ch. 2 - Prob. 10P
Ch. 2 - You need to make a buffer whose pH is 7.0, and you...Ch. 2 - Describe the preparation of 2.00 L of 100 glycine...Ch. 2 - Carbon dioxide is dissolved in blood (pH 7.4) to...Ch. 2 - What is the molecular basis for the observation...Ch. 2 - The anno acid arginine ionizes according to the...Ch. 2 - It is possible to make a buffer that functions...Ch. 2 - A student is carrying out a biological preparation...Ch. 2 - Histidine is an amino acid with three titratable...Ch. 2 - Prob. 19PCh. 2 - A biochemical reaction takes place in a 1.00 ml...Ch. 2 - Is RNA-binding enzyme RNase A more likely to have...Ch. 2 - Consider a protein in which a negatively charged...Ch. 2 - Prob. 23PCh. 2 - Prob. 24P
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- 2) Consider the following reaction: A + 2B 3C + D At equilibrium the concentration of the reactants and products are: [A] = 20.0 mM [C] = 3.0 mM [B] = 4.0 mM [D] = 50.0 mM Calculate (a) the equilibrium constant and (b) AG". Comment on which side of this reaction is more likely to occur.arrow_forwardGlycine is a diprotic acid, which can potentially undergo two dissociation reactions, one for the a-amino group (NH), and the other for the carboxyl (-COOH) group. Therefore, it has two pK₁ values. The carboxyl group has a pK₁ of 2.34 and the α-amino group has a pK2 of 9.60. Glycine can exist in fully deprotonated (NH2-CH2-COO¯), fully protonated (NH3-CH2-COOH), or zwitterionic form (NH3-CH2-COO¯). Match the pH values with the corresponding form of glycine that would be present in the highest concentration in a solution of that pH. fully deprotonated form NH2-CH2-COO- fully protonated form NH–CH,–COOH zwitterionic form NH–CH,−COO Answer Bank pH 7.0 pH 11.9 pH 6.0 pH 8.0 pH 1.0arrow_forwardThe AG of hydrolysis of a sugar phosphate (S-O-P) to the free sugar (S-OH) is -26.6 kJ/mol in a hypothetical cell in which the steady-state concentrations of sugar phosphate, free sugar, and inorganic phosphate are 1.0 mM, 0.20 mM, and 50.0 mM, respectively. S-O-P + H2O S-OH + Pi (a) What is the AG°' for this reaction? (b) In the cell, S-O-P is formed by the transfer of a phosphate group from ATP. What would the AG be for the transfer of the g-phosphate from ATP to this sugar (S-OH)? [AG for ATP hydrolysis is -31 kJ/mol.]arrow_forward
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