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  • one year ago

Discuss the three kinds of waste that humans must remove from their bodies, and explain why waste removal is important to living organisms.

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  1. anonymous
    • one year ago
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    Urine is the by product or fluid secreted by the kidneys, transported by the ureters to the urinary bladder where it is stored until it is voided through the urethra. It is a transparent solution that is clear to amber in color, and usually is light yellow. Urine is made up of a watery solution of metabolic wastes (such as urea), dissolved salts and organic materials. Fluid and materials being filtered by the kidneys, destined to become urine, come from the blood or interstitial fluid. The composition of urine is adjusted in the process of reabsorption when essential molecules needed by the body, such as glucose, are reabsorbed back into the blood stream via carrier molecules. The remaining fluid contains high concentrations of urea and other excess or potentially toxic substances that will be released from the body via urination. Urine flows through these structures: the kidney, ureter, bladder, and finally the urethra. Urine is produced by a process of filtration, reabsorption, and tubular secretion. Urine contains large amounts of urea, an excellent source of nitrogen for plants. As such it is a useful accelerator for compost. Urea is 10,000 times less toxic than ammonia and is formed by the combination of the byproducts of deamination (2 NH3 molecules) and cellular respiration (1 CO2 molecule). Other components include various inorganic salts such as sodium chloride (the discharge of sodium through human urine is known as natriuresis). Urination is the primary method for excreting toxins, chemicals and drugs from the body. These chemicals can be detected and analysed by urinalysis. Cellular metabolism results in a buildup of toxic nitrogen compounds, or nitrogenous waste. Since this waste is toxic, most animals have excretory systems (in humans this is known as the Urinary system, which consists of the Kidneys, Urinary Bladder, Ureter, and Urethra) to rid themselves of this waste. The kidneys extract the nitrogenous wastes from the bloodstream, as well as excess water, sugars, and a variety of other chemicals. In cases of kidney or urinary tract infection (UTI), the urine will contain bacteria, but otherwise urine is virtually sterile and nearly odorless when it leaves the body. However, after that, bacteria that contaminate the urine will convert chemicals in the urine into smelly chemicals that are responsible for the distinctive odor of stale urine; in particular, ammonia is produced from urea. Some diseases alter the quantity and consistency of the urine, (e.g., sugar in the urine is a sign of diabetes). Carbon dioxide is an end product in organisms that obtain energy from breaking down sugars, fats and amino acids with oxygen as part of their metabolism, in a process known as cellular respiration. This includes all plants, animals, many fungi and some bacteria. In higher animals, the carbon dioxide travels in the blood from the body's tissues to the lungs where it is exhaled. In plants using photosynthesis, carbon dioxide is absorbed from the atmosphere. CO2 is carried in blood in three different ways. (The exact percentages vary depending whether it is arterial or venous blood.) Most of it (about 80%–90%) is converted to bicarbonate ions HCO3− by the enzyme carbonic anhydrase in the red blood cells. 5%–10% is dissolved in the plasma 5%–10% is bound to hemoglobin as carbamino compounds. The CO2 bound to hemoglobin does not bind to the same site as oxygen; rather it combines with the N-terminal groups on the four globin chains. However, because of allosteric effects on the hemoglobin molecule, the binding of CO2 does decrease the amount of oxygen that is bound for a given partial pressure of oxygen. Hemoglobin, the main oxygen-carrying molecule in red blood cells, can carry both oxygen and carbon dioxide, although in quite different ways. The decreased binding to oxygen in the blood due to increased carbon dioxide levels is known as the Haldane Effect, and is important in the transport of carbon dioxide from the tissues to the lungs. Conversely, a rise in the partial pressure of CO2 or a lower pH will cause offloading of oxygen from hemoglobin. This is known as the Bohr Effect. Carbon dioxide may be one of the mediators of local autoregulation of blood supply. If it is high, the capillaries expand to allow a greater blood flow to that tissue.[citation needed] Bicarbonate ions are crucial for regulating blood pH. As breathing rate influences the level of CO2 in blood, too slow or shallow breathing causes respiratory acidosis, while too rapid breathing, hyperventilation, leads to respiratory alkalosis. It is interesting to note that although it is oxygen that the body requires for metabolism, it is not low oxygen levels that stimulate breathing, but is instead higher carbon dioxide levels. As a result, breathing low-pressure air or a gas mixture with no oxygen at all (e.g., pure nitrogen) leads to loss of consciousness without subjective breathing problems. This is especially perilous for high-altitude fighter pilots, and is also the reason why the instructions in commercial airplanes for case of loss of cabin pressure stress that one should apply the oxygen mask to oneself before helping others—otherwise one risks going unconscious without being aware of the imminent peril. According to a study by the USDA, an average person's respiration generates approximately 450 liters (roughly 900 grams) of carbon dioxide per day. Sweat or perspiration, fluid secreted by the sweat glands of mammalian skin and containing water, salts, and waste products of body metabolism such as urea. The dissolved solid content of sweat is only one eighth that of an equal volume of urine, the body's main vehicle of salt excretion; however, excessive sweating may produce severe salt loss (see heat exhaustion). Human sweat glands are of two types, eccrine and apocrine. The eccrine glands, found everywhere on the body surface, are vital to the regulation of body temperature. Evaporation of the sweat secreted by the eccrines cools the body, dissipating the heat generated by metabolic processes The liver breaks down toxic substances and most medicinal products in a process called drug metabolism. This sometimes results in toxication, when the metabolite is more toxic than its precursor. The liver converts ammonia to urea also.

  2. anonymous
    • one year ago
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    shes completely right ^

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