In the starved state, the liver synthesizes ketone bodies which are utilized as fuel molecules in the peripheral tissues. Ketone bodies enter the cells of the brain via the monocarboxylate transporters. In the mitochondria of neurons, b-hydroxybutyrate dehydrogenase catalyzes the oxidation of b- hydroxybutyrate to acetoacetate as shown in the reaction below. NAD+ NADH + H+ OH H3C i Hola H3C B-hydroxybutyrate dehydrogenase CO coo 1. Determine the change in the standard reduction potential (Dec) and the standard free energy change (DG) of the above reaction. 2. The ratio of NAD*/NADH is an indicator of mitochondrial health. In aging and with neurodegenerative diseases this ratio decreases, and total levels of the nicotinamide adenine dinucleotides decline. Determine the NAD*/NADH ratio utilized in the exergonic b- hydroxybutyrate dehydrogenase reaction (DG = -2.11 kJ/mol) in the neuron (at 37C), when the [acetoacetate] =245 M and [b-hydroxybutyrate] = 18.9 M.