Tag: excretion in living organisms

Ammonia is more water soluble and more toxic than Urea or uric acid. Ammonia is extremely toxic and its accumulation in the body can be lethal. So the liver converts toxic ammonia into less toxic urea through the urea cycle.

Ketone bodies are byproducts in the metabolism of fat. During starvation or fasting conditions the liver synthesizes glucose through a process called gluconeogenesis. Gluconeogenesis is a metabolic pathway that results in the generation of glucose from fat. During gluconeogenesis, the ketone bodies are formed as byproducts where the product is glucose. The Kerone bodies consist of acetoacetic acid, acetone and beta-hydroxybutyric acid.

• Birds, reptiles, and fishes produce uric acid waste and they are called Uricothelic organisms.
  
• They tend to excrete uric acid as its waste which is in the form of a white paste or powder.
• Producing uric acid over urea is advantageous because it is less toxic and reduces water loss and the subsequent need for water.  in these organisms.
• The correct answer is OPTION A.

When muscles work continuously enough, oxygen is not reached to muscles to burn glucose aerobically in such conditions glucose is converted into lactic acid i.e anaerobic glycolysis. The lactic acid produced in muscles is moved to the liver and converted to glucose. In ureotelic organisms, lactic acid is converted into Glucose through the Cori cycle. This metabolic cycle was discovered by Carl Ferdinand Cori and  Gerty Cori, hence named Cori cycle.

Aquatic plants respire and dispose of wastes by diffusion. Diffusion is a process by which oxygen and nutrients dissolve in water and reach aquatic plants. The waste materials diffuse out of the plants as diffusion takes place from higher concentration to lower concentration. Shedding of leaves occurs in deciduous trees. The process of getting rid of excess water in form of water vapour is called transpiration. 

The plants secrete many materials as the by-products of reactions and metabolic processes.

Plant roots excrete a variety of organic compounds to the soil such as sugars, amino acids, organic acids and phenols. Organic acids are usually present in root exudates and they seem to be part of a nutrient mobilization strategy. For example, oxalic acid is most efficient for phosphorus mobilization, while citric and malic acids are more efficient with iron. Water, oxygen and calcium carbonate are not excreted by plant roots.