7.3 The importance of Excreting Wastes

Metabolic Reactions - Breakdown complex organic molecules into simpler, but "Toxic" compounds. to maintain life, waste products must be removed.

Lungs - remove CO2
Large Intestines - Remove toxins during digestion
Liver - Toxins from Protein digestion (amines)
Kidneys - Excrete metabolites, balance PH and water

Deamination:

• Removes amino Group From protein (NH2)
• occurs in the liver, produces amonia
• Toxic to humans at <0.005mg>
• Water soluble
  

Land animals must store their wastes. 2 molecules of ammonia combine with CO2 to form urea.

Urea:

• Nitrogen waste, ammonia combined with CO2.
• 100 000 times less toxic than ammonia
  
• Blood can dissolve 33mg/mL of Urea

Kidneys:

• Maintain Water balance
• Humans cant survive without water (only a few days)
• 2L per day is lost (urine, perspiration, air)
• Humans must consume water to account for this
• 1%loss=thirsty, 5%loss=pain, 10%loss=Death

Excretion: simple to complex organisms

• Unicellular - Maintain everything through direct diffusion with the environment.
• Multicellular (simple) - Must have fluid regulation (i.e = earthworms, hydra)
• Multicellular (complex) - 3 layers, cells not in direct contact with environment. Specialised cells needed to remove wastes. (i.e = nephrons in kidneys)

-Brandon