Nitrogenous Wastes

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Background Information Question 1: (Produce a table that compares and contrasts the three types of nitrogenous wastes, examples of organisms that produce the waste, their relative toxicity and water requirements for excretion) Question 2: (Describe the role the liver has in the production of the nitrogenous waste most commonly produced in humans) In humans and other vertebrate animals, the major excretory product of ammonia is urea, which means they are classified as uricotelic animals (Rayat, 2009). As the ammonia is toxic to cells it must be excreted from the body. Aquatic creatures are able to expel the ammonia directly into the water, but land-based animals, need another disposal method. Hence the liver converts the ammonia to urea, which is a less toxic compound, which can be safely transported to the kidneys via the blood, where it exits the body in urine. Urea synthesis (the process which means that the synthesised urea is released into the blood and cleared by kidneys in the urine) in the liver is a process which involves five enzymes. Urea is made from ammonia and carbon dioxide. Question 3: (Thoroughly explain how water balance is maintained in the human body. Include references to the relevant systems, organs and hormones involved) When you drink a glass of water, the water gets absorbed into the blood. We know when to drink water because nerve centres deep within the brain are stimulated, resulting in the feeling of thirst. As the body’s requirement for water increases, as does the feeling of thirst. This prompts you to drink the water you need. Likewise, when the body has a lack of water, the pituitary gland (in the brain) excretes vasopressin (an anti-diuretic hormone (ADH), meaning it causes urine to be sup... ... middle of paper ... ...t not excrete faeces. At 12:00 pm, each participant was fed a sandwich incorporating 2 x slices of white bread, 1 tsp of margarine, 30 g of cheese, and 1 x leaf of lettuce. All participants were able to drink 250mL water every hour, except for the hours between 7:00 am and 10:00 am, where they may only drink their prescribed beverages. At 6:00 pm, each participant was fed 100g spaghetti with 80g bolognese sauce, sprinkled with cheese. At 8:00 pm, each participant was weighed. The difference in weight gain/loss between the coffee drinking and water drinking groups was recorded and studied. Results These results show that the water drinkers retained more urine than the coffee drinkers. Put another way, this shows the diuretic actions of caffeine, as the coffee drinkers gained less weight throughout the day, showing that they excreted more fluid due to the caffeine.
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