Problem 15
Protection. Suggest why the enzyme lysozyme, which degrades cell walls of some bacteria, is present in tears.
Problem 16
Stability matters. Transition-state analogs, which can be used as enzyme inhibitors and to generate catalytic antibodies, are often difficult to synthesize. Suggest a reason.
Problem 18
Free energy! Consider the following reaction: Glucose 1-phosphate \(\rightleftharpoons\) glucose 6 -phosphate After the reactants and products were mixed and allowed to reach equilibrium at \(25^{\circ} \mathrm{C},\) the concentration of each compound was measured: $$\begin{array}{l} \text { [Glucose 1-phosphate] }_{\mathrm{eq}}=0.01 \mathrm{M} \\ \text { [Glucose }6 \text { -phosphate }]_{\mathrm{eq}}=0.19 \mathrm{M} \end{array}$$ Calculate \(K_{\mathrm{eq}}\) and \(\Delta G^{\circ \prime}.\)
Problem 19
More free energy! The isomerization of dihydroxyacetone phosphate (DHAP) to glyceroldehyde 3-phosphate (GAP) has an equilibrium constant of 0.0475 under standard conditions \((298 \mathrm{K}, \mathrm{pH} 7) .\) Calculate \(\Delta G^{0 \prime}\) for the isomerization. Next, calculate \(\Delta G\) for this reaction when the initial concentration of DHAP is \(2 \times 10^{-4} \mathrm{M}\) and the initial concentration of GAP is \(3 \times 10^{-6} \mathrm{M} .\) What do these values tell you about the importance of \(\Delta G\) compared with that of \(\Delta G^{0 \prime}\) in understanding the thermodynamics of intracellular reactions?
Problem 20
A tenacious mutant. Suppose that a mutant enzyme binds a substrate 100 times as tightly as does the native enzyme. What is the effect of this mutation on catalytic rate if the binding of the transition state is unaffected?
Problem 23
Potential donors and acceptors. The hormone progesterone contains two ketone groups. At pH \(7,\) which side chains of a protein might form hydrogen bonds with progesterone? (EQUATION CAN'T COPY)
