nitrogenous waste

Question 1

explain how plants get rid of their nitrogenous waste

Answer 1

• they uptake nitrogen and ammonium ions from the soil via facilitated diffusion and active transport
• Fabaceae plants have nitrogen fixing bacteria

Question 2

explain how animals get rid of their nitrogenous waste

Answer 2

• eat proteins and use amino acids to create proteins
• excess amino acids are deaminated in the liver and converted into other molecules which are then excreted

Question 3

what is deamination

Answer 3

• surplus amino acids cannot be stored in the body
• removal of the amine group to leave ammonia and pyruvic acid

Question 4

what is nitrogenous waste

Answer 4

• the type of organism produces depends on the environment they live in
• some animals excrete ammonia directly
• other animals convert it into urea of uric acid

Question 5

explain how some organism get rid of ammonia

Answer 5

• most aquatic animals excrete ammonia
• ammonia = very toxic, small and soluble
• soft bodied invertebrates = the ammonia diffuses directly across their whole surface area into the surrounding water
• freshwater fish = most ammonia lost is excreted as ammonium ions over the epithelium of the gills

Question 6

explain how some organisms get rid of ammonia as uric acid

Answer 6

• land snails, birds, insects and some reptiles
• almost insoluble in water
• excreted as precipitate once almost all of the water has been reabsorbed by the kidneys
• in reptiles and birds = paste like urine is eliminated from intestine via the cloaca

Question 7

explain how some organisms excrete ammonia as urea

Answer 7

• most terrestrial animals convert ammonia to urea
• 100,000x less toxic than ammonia
• urea can be transported in a more concentrated form
• sacrifice less water to discard of the nitrogenous waste