Unit 4- water balance Flashcards
water balance
the bodys internal envionment of extracellula fluid must maintain a constant volume, solute content, and often temp. it is importand for human and other terrestrial vertebrates to maintain stable aq environmnet
Osmosis
The movement of water molecules from a region of high concentration to a region of lower concentration through a selectively permeable membrane.
Selective permeability
- Only a few specific solute molecules can move through
- Maintains difference in solute conc. on the two sides of a biological membrane (ie. cell membrane)
Osmotic pressure:
the pressure that results from a difference in solute concentration between the two sides of a selectively permeable membrane.
* ↑ [water] gradient, the ↑ the osmotic pressure difference
hyperosmotic (hypertonic)
the solution on one side of a permeable membrane that has the lower concentration of water
* Water tends to move to the hyperosmotic side
hypoosmotic (hypotonic)
the solution on one side of a permeable membrane that has the higher concentration of water
* Water tends to move from the hypoosmotic solution.
Isosmotic (isotonic)
two solutions that have equal water concentrations
Water Balance – Aquatic organisms
Living in the Ocean
- Seawater is 96.5% H2O
- Fish cells are 98.6% H2O
- Marine fish cells are hypo-osmotic (more H2O)
problem in Water Balance – Aquatic organisms
Living in the Ocean
- Lose H2O
- Gain too much salt
solution in Water Balance – Aquatic organisms
Living in the Ocean
- Drink lots of water
- Secrete salt through gills
- Excrete small amount of concentrated salty urine
Water Balance – Aquatic organisms Living in freshwater
- Freshwater is 100% H2O
- Fish cells are 98.6% H2O
- Freshwater fish are hyperosmotic (less water)
problem in Water Balance – Aquatic organisms Living in freshwater
- Lose salt
- Gain too much H2O by osmosis
solution in Water Balance – Aquatic organisms Living in freshwater
- Does not drink
- Salt absorbed by gills
- Large volume of dilute urine
Osmoregulation
Osmoregulation = biological processes involved in controlling the levels of water and salt in the body fluids and cells.
concentration of water and solutes
both inside and outside the cells must be kept in a constant balance. this requires continues movement of water by osmosis and movement of solutes by diffusion and active processes into and out of the cell (intracellular and extracellular fluid must be ISOMOTIC)
Intercellular Waste
made during digestion
protein = C,H,O,N
=co2 +h2o + n
nucleic acids = C,H,O,N,P
=co2 + h2o + p + n
Nitrogenous waste disposal
- Animals secrete nitrogen waste in different forms: ammonia, urea, uric acid
- These vary in toxicity and the energy costs of producing them
ammonia (NH3)
- Very toxic
- Carcinogenic
- Very soluble
- Therefore easily crosses membranes
- Access a lot of water
- Must dilute it & get ride of it… fast!
how u get rid of waste depends on
- Who you are (evolutionary relationship)
- Where you live (habitat)
3 types of nitrogenous waste
Ammonia
* Most toxic
* Freshwater organisms
Urea
* Less Toxic
* Terrestrial
Uric acid
* Least toxic
* Egg layers
* Most water conservative
Freshwater Organisms
= Nitrogen waste disposal in water
- if you have a lot of water you can dilute ammonia then excrete
- Ex. Freshwater fish pass ammonia continuously through gills
- Need to excrete a lot of water anyway so excrete very dilute urine
- Ex. freshwater invertebrates pass ammonia through their whole-body surface
Side note abt urine
- If you have a lot of water you can urinate out a lot of dilute urine.
- Predators track fish by sensing ammonia gradients in water.
- Transport epithelia in the gills of freshwater fishes actively pump salts from the dilute water passing
Land Animals
Nitrogen waste disposal on land
- evolved less toxic waste product
- need to conserve water
- Must process ammonia so less toxic
- urea = larger molecule = less soluble = less toxic
kidney
- filter wastes out of blood
- reabsorb H2O (+any useful solutes)
- excrete waste
- urine = urea, salts, excess sugar & H2O
- urine is very concentrated
- concentrated NH3 would be too toxic
What is Urea?
- 2NH2 + CO2 = urea
- Combined in the liver
- Requires energy to produce
- Worth the investment of energy
- 100,000 less toxic than ammonia
- Carried to kidneys by circulatory system
Story time - birds
The salt secreting glands of some marine birds, such as an albatross, secrete an excretory fluid that is much more salty than the ocean.
The salt-excreting glands of the albatross remove excess sodium chloride from the blood, so they can drink sea water during their months at sea.
The counter-current system in these glands removes salt from the blood, allowing these organisms to drink sea water during their months at sea.
Egg-laying land animals
Nitrogen waste disposal occurs in egg
* no place to get rid of waste in egg
* Doesn’t harm the embryo
* White dust in egg
* need even less soluble molecule
* uric acid = Bigger = less soluble = less toxic
* birds, reptiles, insects
What is Uric Acid
Insects, land snails, and many reptiles, including birds, mainly excrete uric acid.
* Uric acid is relatively nontoxic, large molecule and does not dissolve readily in water
* It can be secreted as a white paste in adults with little water loss
* Uric acid is more energetically expensive to produce than urea
