Water is present in the cell at a concentration of 55.5 M, whereas P, is present at a concentration of 10-3M. So it is remarkable that an enzyme can catalyze phosphorolysis in preference to hydrolysis. What product would result if glyceraldehyde-3-phosphate dehydrogenase mistakenly used water instead of phosphate to complete its enzyme-catalyzed reaction.

For an enzyme catalyzed reaction of the form: S + E → P + E, the rate of product formation, [P], is given by: d[P]/dt = k2[E}total [S] /(Km + [S]) = For the enzymatically catalyzed hydrolysis of ATP at 25 °C and pH 7.0, the Michaelis Menten constant, Km was found to be equal to 16.8 μmol L 1 and the value of k2[E]total was found to be 0.220 μmol L-¹s¹. Find the initial rate at an initial ATP concentration of 30.0 μmol L-1

The protein catalase catalyzes the reaction 2H,O,(aq) — 2H,O(l) + O,(g) and has a Michaelis-Menten constant of KM = 25 mM and a turnover number of 4.0 × 107 s¯¹. The total enzyme concentration is 0.010 µM and the initial substrate concentration is 4.83 µM. Catalase has a single active site. Calculate the value of Rmax (often written as Vmax) for this enzyme. Rmax Calculate the initial rate, R (often written as V), of this reaction. R = ×10 mM.s-1 mM-s-1

The isoelectric point (pI) of 6-phosphogluconate dehydrogenase is 6.0.  Explain why the buffer used in DEAE cellulose chromatography must have a pH greater than 6 but less than 9 in order for the enzyme to bind to the DEAE resin.

When grown anaerobically on glucose, yeast (S. cerevisiae) converts pyruvate to acetaldehyde, then reduces acetaldehyde to Pethanol using electrons from NADH. Write the chemical equation for the reaction that reduces acetaldehyde (CH3CHO) to ethanol (CH3CH2OH). The table provides the standard reduction potential, E', of the relevant half-reactions. Half-reaction Acetaldehyde + 2 H+ + 2e¯ → ethanol NAD+ + 2H+ + 2e¯ → NADH + H+ E'° (V) -.197 -.320 Calculate the equilibrium constant, K'eq, at 25.0 °C for the reaction that reduces acetaldehyde to ethanol. K'e ×10 = eq

The standard free energy change for the reaction catalyzed by phosphoglucomutase is -7.1 kJ/mol. Calculate the equilibrium constant for the reaction. Calculate AG at 37°C when the concentration of glucose-1-phosphate is 1-mM and the concentration of glucose-6-phosphate is 25-mM. Is the reaction spontaneous under these conditions? HOCH, -20;POCH, H H H H H H ОН Н НО ОН Н H НО ОН H ОН H. ОН Glucose-l-phosphate Glucose-6-phosphate

In humans, the biosynthesis of L-glutamine is catalyzed by the L-glutamine synthetase. The global reaction can be written as follows: ATP + glutamate + NH3 ADP + phosphate + glutamine The A,Gº' value for this reaction is -16.3 kJ.mol-1 (from left to right). 1- Explain the significance this information. 2- This reaction can be considered as the sum of two component reactions which are exergonic and endergonic, respectively, under standard conditions. Write these two component reactions and evaluate A,Gº of the endergonic reaction. Data: A,Gº of ATP hydrolysis = -30.4 kJ mol-¹

Phosphocreatine (G0ʹ = -43.1 kJ/mol) has a higher phosphoryl group transfer potential than ATP (G0ʹ = -30.5 kJ/mol). However, under certain physiological conditions, phosphoryl group is transferred from ATP to creatine. Explain this discrepancy. Many biochemical conversions are carried out via multi-step pathways although similar conversions can be done in an organic chemistry lab in fewer steps. Explain why energetically it is reasonable to use multiple steps in biochemical conversions.  What are isozymes? Humans contain several isozymes of hexokinase. Why does the body need several isozymes of hexokinase? 1,3-bisphosphoglycerate is used to produce ATP. Which of the two phosphates of 1,3- bisphosphoglycerate is transferred to ADP to make ATP. Explain why it is this specific phosphate and not the other one. Triose phosphate isomerase is a diffusion-controlled enzyme. What reaction is catalyzed by this enzyme (structures of molecules not needed)? Explain why…

The mechanism of chymotrypsin can be viewed as a two-step process, acylation of the enzyme active site followed by a deacylation reaction. What accounts for the observed "burst" in rapid kinetic studies of the hydrolysis of N-acetyl-L-phenylalanine p-nitrophenyl ester by chymotrypsin? The rate of hydrolysis of the acyl-enzyme intermediate is faster than the rate of forming the acyl-enzyme intermediate. The rates of the acylation and deacylation reactions are equal. The rate of the acylation reaction is slower than the rate of the deacylation reaction. The rate of the acylation reaction is faster than the rate of the deacylation reaction.

Enolase catalyzes the reversible reaction shown below.  Draw the detailed mechanism for the reaction that occurs in gluconeogenesis, namely the reaction of phosphoenolpyruvate to form 2-phosphoglycerate (the reverse direction in the reaction below).