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NEET Preparation: Important Notes on Uricotelism All living beings perform several physiological and biological processes for their existence. Metabolism is one of the most important processes that provide the required nutrients and energy to cells. However, due to this process, all living organisms produce newly created chemicals called nitrogenous waste in the form of uric acid, urea, and ammonia. These nitrogenous wastes build up in the organs and body fluids like blood, and can damage the natural systems of the body. Thus, it is important to remove these wastes. Majorly, there are four types of waste removal process- ammonotelism, ureotelism, aminotelism, and uricotelism. The following content is about uricotelism in physiology with detailed discussion. For your NEET preparation, this content can be highly helpful. Types of Excretion Process As said earlier, most of the organisms use four types of waste removal or excretion process to eliminate bodily waste. Here is the list in a tabular form- The Process of Nitrogenous Waste Production Proteins are known as polymers of different amino acids. In the metabolism process, deaminase, an enzyme removes the amino group from these amino acids. This process is called deamination. After deamination, based on the organism and availability of water, the released amino groups convert themselves into either uric acid, urea, or ammonia. The other part of amino acids can be reserved as carbohydrates or used to release energy through oxidation. Mostly in the liver, and sometimes in kidneys, purines produce uric acid (C5H4N4O3) via degradation. In uricotelic animals, purines are synthesised by excess nitrogen in the body. In this process, the purines convert into xanthine and then into uric acid by oxidation. Conversion of uric acid as nitrogenous waste requires the least amount of water among all excretion processes. Thus, it is seen in terrestrial animals like reptiles that have restricted access to water. Here is the chemical equation of the deamination process where amino acids deaminase to nitrogenous waste R-CH(NH2)-COOH (amino acid) ------ NH2 + H+ ----- (deaminase) ----NH3 (nitrogen that changes to uric acid, urea, or ammonia) Uricotelics The definition for uricotelism is a nitrogenous waste removal process that excretes nitrogenous wastes as uric acid or urates (a salt of uric acid) from the organism’s body. The organisms that remove uric acid are known as uricotelic organisms. As you know, uric acid is not readily soluble in water. Hence, the process of uricotelism needs a lesser amount of water. So, this process is seen in animals that live in dry places or can not access water constantly. Uricotelism examples are observed in reptiles, insects, birds, kangaroo rats, and land snails. However, other mammals and humans also remove uric acids in a small amount. Also, there are some common uric acid disorders found in them as well. Uric Acid Metabolism Disorder Gout The metabolic disorder sometimes accumulates excess uric acids and deposits in bone joints. This can lead to painful arthritis called gout. Kidney Stone Due to the precipitation of uric acid crystals into kidney tubules, blockage occurs inside the organ. In this case, animals can experience excruciating back and thigh pain. If this blockage occurs in the urinary bladder, patients may experience painful urination or bleed while urinating. Why Certain Organisms Prefer Uricotelism? Mostly, terrestrial animals with limited water access prefer uricotelism. Following are some reasons- Nitrogenous waste can be of three types – ammonia, urea, and uric acid. Among these three wastes, ammonia is highly water-soluble, and urea is fairly water-soluble. However, uric acid is hardly soluble in water. For example, to remove 1 gm of uric acid, only 10 ml of water is needed. But, 1 gm ammonia needs 300-500 ml water, and 1 gm urea needs 50 ml water for excretion. Ammonia has the highest toxic intensity as a nitrogenous waste. Urea has near about 1 lakh times lesser toxicity than ammonia. Moreover, uric acid is nearly non-toxic. Uric acid can stay inside organs for a longer time as primarily it is non-toxic and also almost insoluble in water. As uric acids do not require much water, it can be removed in solid pellet forms. The waste of bats and birds has white-coloured portion called guano. This guano is composed of crystals of uric acid. Questions and Answers Why are Most Terrestrial Animals Either Uricotelic or Urecotelic? Ans. Generally, most terrestrial animals are found to be either uricoletic or urecoletic. The reasons are listed below The nitrogenous body waste ammonia has a high water-soluble capacity. For instance, more or less 300-500 ml of water can remove only 1 gm ammonia. Thus, aquatic animals that have abundant access to water can utilise the source to remove ammonia. But terrestrial organisms do not have unlimited and constant access to water. Thus, these animals adopt another mode of excretion that does not require a large amount of water. In urecotelism and uricotelism, the removable wastes are respectively urea and uric acids that are not highly water-soluble. Due to the high toxicity of ammonia, ammonotelics can not store the waste inside the body for a long time. Thus, aquatic animals use the water source to diffuse ammonia waste and remove rapidly from their body. However, uric acids and urea do not have high toxicity, and hence terrestrial animals can store these wastes inside the body for longer-term and remove with a limited amount of water. What are The Different Modes of Excretion? The three major excretion modes are uricotelism, ureotelism, and ammonotelism. However, another mode of the waste removal process common in animals called aminotelism. What is The Main Application of Guano? Guano, the white coloured uric acid crystals, present in the faecal matter of bats and birds, are composed of high amounts of phosphorus, potassium, and nitrogen compound. So, guano can be utilised as fertiliser. What is The Primary Nitrogenous Waste in Humans? Humans mainly excrete urea as nitrogenous waste. Also, humans eliminate a little amount of uric acid as waste.
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काठमाडौँ । युरिक एसिड रगतमा नभई नहुने महत्वपूर्ण तत्व हो। यसले शरीरमा ‘एन्टी अक्सिडेन्ट’को काम गर्छ। तर, युरिक एसिडको मात्रा चाहिनेभन्दा बढी भएमा यसले जोर्नीहरुमा समस्या ल्याउँछ र ‘गाउट’ भन्ने रोग लाग्छ। युरिक एसिडलाई एक प्रकारको बाथरोगका रुपमा बुझ्न सकिन्छ। यसले जोर्नीहरुमा अत्याधिक दुखाइ गराउँछ। रगतमा युरिक एसिड बन्ने र युरिक एसिड पिसाबबाट बाहिर निस्किने प्रक्रियामा गडबडी भयो भने रगतमा पर्याप्त मात्रामा युरिक एसिड घुल्न पाउँदैन र विस्तारै गाउटको रुप लिन्छ। एउटा स्वस्थ मानिसमा युरिक एसिडको मात्रा ६ दशमलब ८ एमजीरडिएल हुनुपर्छ। जसलाई गाउट वा युरिक एसिडको समस्या छ त्यस्ता व्यक्तिमा युरिक एसिडको मात्रा ५ एमजीरडिएलभन्दा कम राख्नुपर्ने हुन्छ। कुनै व्यक्तिमा युरिक एसिड बढी देखिए पनि जोर्नीको दुखाइ नहुन सक्छ। यस्ता व्यक्तिलाई गाउट नभएर ‘हाइपरयुरेसिमिया’ भएको हुन सक्छ। त्यसले जोर्नीमा असर गर्दैन। जसलाई युरिक एसिड भएकै कारण जोर्नी (खुट्टाको बुढी औँला र आसपास) मा दुख्छ, त्यो गाउट हो भनेर बुझ्नुपर्छ। युरिक एसिडबाट हुने बाथरोग नै गाउट हो। यो वंशाणुगत समस्या पनि हुन्छ। यसलाई दुई तरिकाले हेर्न सकिन्छ। कसरी हुन्छ ? शरीरमा प्रोटिनको मेटाबोलिज्म भएर निस्कने तत्वलाई युरिक एसिड भनिन्छ । न्युक्लिक एसिड र प्युरिन ग्रुपको प्रोटिनबाट युरिक एसिड बन्छ । यो सामान्यतः पिसाबबाट बाहिर निस्कन्छ । जब मिर्गौलाको छान्ने क्षमता कम हुन्छ र युरिक एसिड रहन्छ, तब त्यो हड्डीको जोर्नीमा गएर जम्मा हुन्छ । मिर्गौलाले युरिक एसिड कम उत्सर्जन गर्दा पनि त्यो रगतमा जम्मा हुन पुग्छ । उपवास वा अत्याधिक रूपमा तौल घटाउने प्रयास गर्दा पनि अस्थायी रूपमा युरिक एसिडको स्तर बढ्न सक्छ । साथै युरिक एसिड बढाउन मधुमेहको औषधिले पनि उत्तिकै भूमिका खेल्ने गर्छ । असर शरीरका सानासाना जोर्नीमा दुख्ने समस्या उत्पन्न हुन्छ । यदि २५ वर्ष बढीे उमेरका युवाहरू छन् र धेरै खाना खाने गर्छन् भने यो रोगको जोखिममा पर्न सक्ने सम्भावना अत्यधिक रहन सक्छ। राति सुतेको बेला हातको औंला र खुट्टाको औंलाका जोर्नीमा दुखाइ महसुस हुन्छ भने त्यो युरिक एसिडको लक्षण हुन सक्छ। युरिक एसिड खासगरी हड्डीको जोर्नीमा गएर जम्मा हुन्छ र जोर्नीमा पीडा महसुस हुन्छ। युुरिक एसिड एक्कासी बढ्न पनि सक्छ । यदि यो अचानक बढेमा खुट्टाको पिडौला, जोर्नी, मिर्गौला तथा शरीरका अन्य भागमा जमेर बस्न सक्छ र यसले भविष्यमा जोर्नीको दुखाइ बाथरोग लाग्न सक्छ। यो रोग लागेका १० देखि २५ प्रतिशत व्यक्तिलाई मिर्गौलाको पत्थरी, मुत्रनलीको संक्रमण, अनिद्रा, चिन्ता तनाव र नैराश्यताजस्ता मनोरोग पनि लाग्न सक्छन्।