UREA: Decomposition by UreaseUrea is the end product of nitrogen metabolism in h
ID: 257116 • Letter: U
Question
UREA: Decomposition by UreaseUrea is the end product of nitrogen metabolism in humans and is normally excreted by the kidneysUrease was the first enzyme to be prepared in the crystalline state. It catalyzes the decomposition of urea, according to the following equation:H20 + CO(NH2)2? CO2 + 2 NH3To 3 mL of 0.1 M urea add 4 drops of 0.04% phenol red solution. Add 0.1 M acetic acid, drop by drop, until the pink color is just discharged (pH 7). The solution will turn yellow. Add 0.5 g of soy bean (or 5 drops Jack bean solution, Biochemika) meal, and shake. Observe the solution for several minutes. Note the color of the solution. Explain the final change from colorless to colored. Phenol red Yellow --- Red6.8 --- 8.4
SO Why must the pH be carefully adjusted?
Explanation / Answer
Decomposition of urea by urease is a very pH sensitive reaction.There is a pH shift from acidic to basic, and the color therefore changes.The ammonia that forms as a product of the reaction serves to alkalinze the reaction medium.
Urease reaction test is used to identify various microorganisms, for example Helicobacter pylori and various diagnostic tests, where color change is a key indicator.
Thus, pH should be very carefully adjusted so as not to interfere the reaction color change.
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