The reaction catalyzed by aldolase splits fructose-1,6-bisphosphate (F16BP) into glyceraldehyde-3-phosphate (G3P) and dihydroxyacetone phosphate (DHAP). The AGº' for the 1. reaction is 23.8 kJ/mole. If the concentrations of G3P and DHAP are 2.5 mM and 1 mM, respectively, what concentration of F16BP is needed for the reaction to be at equilibrium in a human cell?

1. A. phosphoenolpyruvate (PEP) is one of the two phosphoryl group donors in the synthesis of ATP during glycolysis. In human erythrocytes, the steady state concentration of ATP is 2.24 mM, that of ADP is 0.25 mM, and that of pyruvate is 0.051 mM. Calculate the concentration of PEP at 25° C, assuming that the pyruvate kinase reaction (see figure 13-13) is at equilibrium in the cell. B. The physiological concentration of PEP in human erythrocytes is 0.023 mM. Compare this with the value obtained in A. Explain the significance of this difference.

The hydrolysis of pyrophosphate to orthophosphate drives biosynthetic reactions such as DNA synthesis. In Escherichia coli, a pyrophosphatase catalyzes this hydrolytic reaction. The pyrophosphatase has a mass of 120 kDa and consists of six identical subunits. A unit of activity for this enzyme, U, is the amount of enzyme that hydrolyzes 10 umol of pyrophosphate in 15 minutes. The purified enzyme has a Vnax of 2800 U per milligram of enzyme. When (S] >> KM, how many micromoles of substrate can 1 mg of enzyme hydrolyze per second? Vnax = umol -s. mg- If cach enzyme subunit has one active site, how many micromoles of active sites, or (E]r, are there in 1 mg of enzyme? (Er = umol - mg-

Consider the given interconversion, which occurs in glycolysis. fructose 6-phosphate = glucose 6-phosphate K = 1.97 What is AG" for the reaction (K, measured at 25 °C)? AG" = kJ/mol If the concentration of fructose 6-phosphate is adjusted to 1.3 M and that of glucose 6-phosphate is adjusted to 0.60 M, what is AG? AG = kJ/mol Which statements are consistent with the conditions at which AG'• is measured? | The pressure is 101.3 kPa (1 atm). The pH is 7. The initial concentrations of reactant and product are 1 M. The temperature is 273 K. O O

The AG" of the dephosphorylation of phosphocreatine is -43.0 kJ/mol. Phosphocreatine → creatine +Pi; -43.0kJ/mol When coupled to the phosphorylation of ADP to ATP (+30.5kJ/mol) ADP +Pi → ATP; +30.5 kJ/mol calculate the actual, physiological AG for the following reaction in kJ/mol: Phosphocreatine + ADP creatine + ATP at 37°C, with concentrations as follows: Phosphocreatine = 0.715 mM creatine = 0.566 mM ADP = 0.431 mM ATP = 2.382 mM

3. Enolase catalyzes the conversion of 2-phosphoglycerate to phosphoenolpyruvate all water. The biochemical standard free energy change (AG") for this reaction is 1.8kJ/mol. If the concentration of 2-phosphoglycerate is 0.045mM and the concentration of phosphoenolpyruvate is 0.034mM, what is the free energy for the enolase reaction under these non-standard conditions? is 98.6°F. change (AG) Assume the temperature

Determine the direction that each of the reactions will progress. Assume that the reactants and products are present in equimolar amounts. The standard free energy of hydrolysis of ATP is –30.5 kJ/mol.   fructose+ATP ____fructose 6‑phosphate+ADP The standard free energy of hydrolysis for fructose 6‑phosphate is −15.9 kJ/mol.   3‑phosphoglycerate+ATP___1,3‑bisphosphoglycerate+ADP The standard free energy of hydrolysis for 1,3‑bisphosphoglycerate is −49.3 kJ/mol.   creatine+ATP___creatine phosphate+ADP The standard free energy of hydrolysis for creatine phosphate is –43.0 kJ/mol.

2. Experimental Determination of Keq' and AG If a 0.1 M solution of glucose 1-phosphate at 25 °C is incubated with a catalytic amount of phosphoglucomutase, the glucose 1-phosphate is transformed to glucose 6-phosphate. At equilibrium, the concentrations of the reaction components are Glucose1-phosphate glucose6-phosphate 9.6 x 10-2 M 4.5 x 10-3 M Calculate Keg' and AG for this reaction.

6. What class do the enzymes that catalyze the following reaction belong? (oxidoreductases, transferases, hydrolases, lyases, isomerases, ligases) H H H. C=C H-----H Hi H. H H ↑

3. Hexokinase catalyzes the first reaction in glycolysis and phosphorylates D-glucose to D-glucose 6-phosphate using ATP as the source of the phosphate. Under conditions of pH 7, 25°C and a Hexokinase concentration of 3.0 nmol/mL, the KM for Hexokinase for the substrate glucose was determined to be 3.0 x 10 M. a. When the glucose concentration was set to 160 μM, the initial rate of the reaction was found to be 65.0 μmol/(mL s). What is Vmax for Hexokinase under these conditions? b. What is the turnover number for Hexokinase under these conditions? c. What is the catalytic efficiency for Hexokinase under these conditions?