Question

4. List two properties of ammonia that cause problems for cells trying to acquiring nitrogen. (Don’t just say ammonia is too scarce in the environment) (1) _______________________________ (2) ______________________________ Describe in general terms how the cell solves this nitrogen acquisition problem (no enzyme names): ____________________________________________

Answer 1

4) Ammonia is a nitrogen containing substance obtained as a product of protein cataboism. It may cause problems to cell trying to acquring nitrogen. Ammonia occurs in hydrated form.

i) High level of ammonia in our blood cells changes the consciousness and thus affect the function of liver, diagonising a liver disease called hepatic encephalopathy. It results in coma in the advanced stages. It is a regular metabolite in the Central Nervous System of our brain. But when it enters in excess quantities in brain through blood, it is toxic to CNS cell. excessive amount of ammonia has detrimental effect on central nervous system. Hence high level of ammonia causes neurological disorder. It mostly affects astrocytes of CNS cell as it is a site where ammonia is metabolized. Due to bioenergetic failure, and interfefence of ammonia with different stages of glutamin- glutamate cycle, will leads to cerebral- edema and the alteration of amino acidergic neurotransmission respectively. Ammonia has direct effect on neurons as changes the nitric oxide / cGMP / NMDA pathway. Overactivation of NMDA receptors causes oxidative and nitrosative type of stress in neurons.

ii) It also disturbes intra as well as extra cellular acid base concentation in a cell. - ketoglutrate can be degraded after the formation of ammonium from glutamine and produce 2 bicarbonate molecules. This bicarbonate molecule act as buffer for dietary acids. when ammonium is excreted in urine, it results in net acid loss. Sometimes it may diffuse itself across the renal tubules and combines with a hydrogen ion and thus causes further acid excretion.

cells can solve the nitrogen acquisition problem in many ways:

i) It depends on suspects and the presence and absence of underlying causes. If hepatic encephalopathy is acute we can go for liver transplant

ii) High level of protein in our diet or malnourished also leads to increased risk of hepatic encephalopathy. so adequate aountof protein in our diet is recomended to maintain stable body weight. our diet should be supplemented with branched chain amino acids to show more imporvement.

iii) Lactulose and lacitol are some diasaccharides which is not absorbed from digestive tract and thought to decrease the ammonia generation by bacteria. This renders ammonia anabsorbable by convetint this ammonia in ammonium ion and thus increase bowel transit through gut. These two diasaccharides are recommended as first-line treatment.

iv) Some antibiotics like rifaximin, neomycine and metronidazole can be used as these ammonia are generated and converted by intestinal bacteria. So by killing these bacteria would reduce the generation of thse wasteproducts like ammonia.

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