BIO1022 Lecture Notes - Lecture 22: Collecting Duct System, Flatworm, Distal Convoluted Tubule
30 May 2018
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BIO1022 – Lecture – Salt and Water Balance
- kidneys have about four times the blood flow of the liver and about eight times
the blood flow of the brain
- water balance and waste disposal
-osmolarity and diffusion
• osmosis - diffusion of water down its concentration gradient
•
o water movement across a selectively permeable membrane
• osmorality
•
o sum of osmotically alive particles in solution
o water moves from hypo-osmotic - lower sodium concentration - to
hyper-osmotic - above - more osmotically active particles - binding
water
- osmoregulation
• balancing the uptake of water and solutes
• osmoconformers
•
o do not adjust internal concentration
• osmoregulatory
•
o use energy to adjust internal concentration
o against environment
- if you don’t regulate
• living organisms are an aqueous solution within a membrane
- osmotic challenges depend on envrionemt
• ocean is iso-osmotic or hypo-osmotic
• freshwater is hypo osmotic
• land lacks water - drying environment
- water balance and waste disposal
• osmoregulation
• controlled movement of solutes and water between internal fluid and
environment
• metabolic wastes may be harmful
• special organs may be used
• transport epithelia involved
• net balance between gain and loss
• must be controlled
• animals vary in ability and tolerance
• water loss
•
o evaporation
o
▪ from body surface
▪ drom respiraroty surface
o faeces
o urine
o other secretions e.g. milk
• water gain
find more resources at oneclass.com
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•
o drinking uptake via body surface
o
▪ from water
▪ from ai
o water in food
o metabolic water
o
▪ when processing glucose for energy
- nitrogenous wasters
• ammonia
•
o only animals that live in water
o highly soluble in water
o very toxic
o rapid diffusion in contact with h2o
• urea
•
o mammals
o some frogs and turtles
o sharks and rays - elasmobranchs keep urea in tissues
o solute in h2o
o can be concentrated
o starting point of ammonia and co2 - takes 3 atp to turn into urea
o low toxicity
o energetically expensive to produce
• uric acid
•
o relatively non toxic
o birds
o crocodiles
o turtles
o caterpillars
o all amniotes
o used in amniotic eggs
o insoluble in h2o
o little water required for excretion
o most expensive to produce
o mammals also produce uric acid
o most don’t convert to dry waste in faeces
o usually converted to allantoin
o excreted in urine
o monkeys and apes - including humans cant convert uric acid to
allantoin
o primates excrete uric acid in urine
o some desert dwelling mammals do excrete dry uric acid in faeces
• type of waste related to environment and life history go animal
• carbohydrates and fats
• protections = nitrous
find more resources at oneclass.com
find more resources at oneclass.com
