Why dung?
Who hasn't gone out for some fresh air and been incommoded by the pungent smell of manure? Why have farmers been flinging dung on their ploughed fields for thousands of years? The answer is nitrogen. Though our ancestors were unaware of the chemistry involved in their actions, they did realise that what livestock excreted - urine and faeces - was good for their crops. This is because animal urine is full of urea, which is full of nitrogen. When livestock faeces and urine is mixed, the faecal enzyme urease breaks down the urea to release carbon dioxide and the nitric compound ammonia, which is volatile. That's the stench. Ammonia is fixed by plants, which then use it to form compounds as fundamental as DNA, RNA, ATP and amino acids. In animals, or humans for that matter, ammonia is actually a waste product and can be toxic at high levels. Our liver deals with this toxicity by transforming ammonia into urea. But it is not the only way to deal with this compound. Scientists discovered that the enzyme glutamine synthetase can also render ammonia harmless by transforming it into glutamine.
