Animal osmoregulation Flashcards
What is an osmole
An Osmole= number of moles of solutes in a solvent.
What is osmolality?
What is osmolarity?
Osmolality= A measure of osmoles of solute per kilogram of solvent (Osm/kg).
Osmolarity=The measure of osmoles of solute per liter of solution (Osm/L).
[Osmolarity is also called ‘osmotic concentration’]
Another term is ‘Water potential’.
What is water potential?
which measures the concentration of free water molecules. It is a measure of the tendency of these molecules to diffuse to
another area.
What is osmosis?
Water moves from a high to a low water concentration (low to high solute concentration) across a semi-permeable membrane until equilibrium.
Explain hyperosmotic and hypo-osmotic solution in terms of water?
Water will move into a hyperosmotic solution (lot of solutes) and out of a hypo-osmotic solution.
If organism is hyperosmotic, it is saltier than its environment
What gives a measure of osmotic pressure?
Osmotic pressure is the pressure developed by diffusion of a solvent through a membrane. This can change the volume of either side
What is osmoregulation and what does it affect?
Osmoregulation controls the amount of water in the body fluids relative to the amount of solutes.
- Maintains osmotic concentration (amount of water) and osmotic pressure
effects ion conc, Cell/tissue volume and hydrostatic pressure
What is ionic regulation and what does it affect?
The maintenance of the concentrations of the various inorganic ions in the body fluids relative to one another (e.g. Na+, Cl-, Mg2+)
It affects protein structure/enzyme co-factors, pH, electrical gradients an chemical gradients as stores of potential
energy
What are osmoconformers?
What are osmoregulators?
- Osmoconformers= Match cellular osmolarity to environment, i.e. “isoosmotic” e.g jelly fish
- Osmoregulators= Maintain a different solute concentration to the environment e.g mammal
What is a stenohaline?
What is a euryhaline?
If animal can tolerate only a narrow range of salinity concentrations = Stenohaline e.g deep sea crab (strong osmoconformer)
if animal can tolerate a wide range of salinity concentrations OC = Euryhaline e.g shore crab
What are the factors involved in osmotic exchanges?
- Permeability of the body wall
- Surface area of the exchange surfaces
- The osmolarity of the body fluids in relation to the osmolarity of the medium
Characteristics of a unicellular marine stenohaline in relation to osmosis
*No net driving force for osmosis: iso-osmotic.
*Negatively charged proteins induce osmotic effect in cells, which is offset by pumps for Na+ & K + and Mg 2+ & Ca 2+
*Proteins will be synthesised throughout life of plankton, so there will always be some ionic regulation due to lectrochemical gradients.
characteristics in multicellular marine stenohaline in relation to osmosis
*3 compartment system
*Osmotic concentrations: identical
*But osmotic concentrations broken down by separate solutes, seawater & ECF similar but intracellular differs: organic molecules (proteins etc), active transport
characteristics in marine elasmobranchs in relation to osmosis
*Blood can be iso-osmotic or slightly hyperosmotic to surroundings
-Ion concentration about 500mOSm, so ions diffuse in through gills and skin
*To increase osmotic concentration: 2 organic solutes, urea and Trimethylamine oxide
(TMAO; counteracts urea) = osmosis in, no need to drink!
*Kidney & rectal gland regulate ions, salt and retain urea (expensive, lost passively)
what do osmoregulatory organisms do?
- Maintain a constant solute concentration
- Marine vertebrates in the sea: excrete salt
*Freshwater fish: excrete hypotonic urine - On land: salt & water conservation
What are the different adaptations of marine and fresh water teleost fish?
Freshwater teleost:
Marine (1100mOsm) FW (5mOsm) = 500 mOsm
Hyperosmotic to surroundings (lose salt, gain water)
*Pavement cells in gills for active uptake of ions
*Do not drink
Marine teleost:
*Hypo-osmotic to surroundings (gain salt, lose water)
*Kidneys reduced (aglomerula)
*Chloride cells in gills for active excretion of ions
*Drink constantly
How much do we lose through urine
We have roughly 1800l and lose 1.5l urine (99% reabsorbed)
Vertebrate kidney form/function
- Regulation of water content of body (osmoregulation)
- Regulation of salt balance (Na+, K+, Cl-, Ca2 , Mg2+ etc; ionic regulation)
- Removal of nitrogenous waste (product of protein /nucleic acid metabolism)
-Ammonia/Ammonium (e.g. fish gills)
- Urea (e.g. mammals)
- Uric acid (e.g. bird guano)
What are the two kinds of nephrons?
Cortical & Juxta-medullary (longer goes down to middle e.g loop of Henle)
(~78% versus ~98% water reabsorbed)
How many Km of nephrons do humans have?
Humans = 60km of nephron
What is ultrafiltration?
Ultrafiltration is passive: hydrostatic pressure (blood pressure) ↑ by ↓ vessel diameter
* Forces fluid & solutes through glomerular capillaries, out of plasma, into the capsule
* Pore size between podocytes determines what can enter Bowman’s space
* Glomerular filtration rate is a balance with hydrostatic AND osmotic pressures
(glucose, amino acids etc in plasma too big to pass through) opposing filtration
Explain the properties of the ascending and descending loop in the loop of Henley (kidneys)?
Descending loop= Permeable to water, moves out by osmosis
Ascending loop= Impermeable to water and active transport OUT of NaCL
Explain kidneys function in reptiles & amphibians
- Reptiles & amphibians: cortical nephrons
*produce only iso-osmotic urine - Epithelium of cloaca (urogenital opening) reabsorbs
water (due to salt reabsorption at the cloaca), so that a
semi-solid uric acid paste is excreted. - And marine teleosts had reduced (aglomerular) kidneys
Kidneys are not the only organ of osmoregulation
What is our body water content (fractions).
Intracellular fluids (2/3)
Extracellular fluids (1/3)
Plasma
Interstitial
Transcellular, e.g. ocular,
gastrointestinal, cerebrospinal
What can organisms do when salinity varies?
*Short term behavioural measures, but quickly swell…
*Physiological responses: iso-osmotic urine production; altered amino acid synthesis (osmolytes); ion pumps expression.
Osmoregulators: who are they?
Maintain a constant solute concentration
Marine vertebrates in the sea: excrete salt
Freshwater fish: excrete hypotonic urine
On land: salt & water conservation
