Homeostasis - Nitrogenous Waste

Question 1

What are the three forms of nitrogenous waste?

Answer 1

Ammonia, Urea and Uric Acid.

Question 2

What factors impact the proportion of nitrogenous waste excreted from organisms?

Answer 2

Availability of water, the toxicity of N waste, the energy cost for producing the N waste, the pattern of species development (where the embryo develops).

Question 3

Outline the method for Ammonia excretion.

Answer 3

First product of breakdown of proteins:
Protein - Amino Acids - Ammonia.
This is highly toxic and can’t be stored in the body; immediately excreted in water to dilute toxicity.
Produced with very minimal energy.
- Freshwater/Marine fish, invertebrates, crocodile, etc.

Question 4

Outline the method for Urea excretion.

Answer 4

Second product of breakdown of proteins:
Protein - Amino Acids - Ammonia - Urea.
This is moderately toxic and can be stored in the bladder; diluted with water.
Produced with moderate energy input.
- Mammals, turtles, adult amphibians, etc.

Question 5

Outline the method for Uric Acid excretion.

Answer 5

Final product of protein breakdown:
Protein - Amino Acids - Ammonia - Urea - Uric Acid.
This is non-toxic and can be stored in the cloaca (rectal like chamber) or egg of a developing embryo.
Produced with high energy input yet doesnt require water input for dilution.
- Birds, reptiles, insects, etc.

Question 6

Outline the function of the kidney in this process.

Answer 6

Fluid/salt balance, removal of wastes (urea & ammonia), pH balance.
Water reabsorption:
60-70% - proximal convulate tubule.
30-40% - Henle loop, distile convulate tubule and collecting duct.

Question 7

What is the Nephron and how does it contribute to kidney function?

Answer 7

Responsible for reabsorption of water - maintaing fluid balance in bloodstream.
The waste removed from the bloodstream can be turned into urine for excretion.