Answer to Question #22820 in Biochemistry for IV

Question

The kidney functions to eliminate ammonia from the blood. Based on ammonia's pK value, what is the molecular form that predominates in the blood? Could this molecule easily diffuse through the hydrophobic lipid membrane of a kidney cell? Explain

Answer 1

Ammoniais neurotoxic. Marked brain damage is seen in cases of failure to to eliminateurea through the kidneys. The result of either of this event is a buildup of circulating levels of ammonium ion. Aside from its effect on blood pH, ammonia readily traverses the brain blood barrier and in the brain is converted to glutamate via glutamate dehydrogenase, depleting the brain of a -ketoglutarate. As the a -ketoglutarate is depleted,oxaloacetate falls correspondingly, and ultimately TCA cycle activity comes to a halt. In the absence of aerobic oxidative phosphorylation and TCA cycle activity, irreparable cell damage and neural cell death ensue. In addition, the increased glutamate leads to glutamine formation. This depletes glutamate stores which are needed in neural tissue since glutamate is both a neurotransmitter and a precursor for the synthesis of g- aminobutyrate, GABA, anotherneurotransmitter. Therefore, reductions in brain glutamate affect energy production as well as neurotransmission.