Lecture Twenty Four - Salt and water balance I Flashcards
Define hypotonic and hypertonic solution and explain what happens to animal and plant cells in these conditions.
Hypotonic solutions:
Hypo = low, tonic = concentration of salts.
Therefore high concentration of water.
Bursting of animal cell = lyses.
This occurs in a hypotonic solution, as there is low concentration of salt outside the cell, and therefore water moves from the outside solution into the cell, where there is a higher concentration of solutes.
Plant cells in hypotonic solutions are not changed (turgid).
Hypertonic solutions:
Hyper = high, tonic = concentration of salts.
Therefore low concentration of water.
Animal cells in hypertonic solutions shrivel, as all the water in the cell leaves and goes into surrounding fluid.
Plant cells in hypertonic solutions undergo plasmolyzes, which involves plasma membrane separating from the membrane.
Isotonic solutions:
In isotonic solutions, animal cells are normal, and plant cells are flaccid.
Describe osmosis.
Diffusion and osmosis:
Semi-permeable membrane - not all things can pass through them equally.
E.g. sugar cannot pass through membrane, this sets up a concentration gradient.
The side with higher concentration of sugar causes water to enter this side of the membrane, in order to decrease the concentration (osmosis).
What is osmolatiry?
Osmolarity = The concentration of a solution expressed as the total number of solute particles per litre.
Osmotically active = something that wants to move through areas of different concentration.
Hypoosmotic = solute concentrations are lower outside the cell.
Hyperosmotic = solute concentrations are higher outside the cell.
The sum of osmotically active particles in solution is the osmolarity.
Water moves from hypoosmotic to hyperosmotic.
What are osmoconformers and osmoregulators?
Osmoconformers do not adjust internal concentration, and are just the same solute conc as the outside environment.
Osmoregulators use energy to change their internal solute concentration.
Controlled movement of solutes between internal fluid and envrionment.
Metabolic wastes may he harmful.
Special organs may be used.
Transport epithelia involced in this transport of metabolic wastes.
How can water be gained and lost in an organism?
Water loss:
Evapouration (body surface and resp surface).
Faeces.
Urine.
Other secretions (saliva, tears etc).
Water gain:
Drinking.
Uptake via body surface (from water and air).
Water in food.
Metbaolic water.
Describe life in the sea and how they regulate water.
Most invertebrates are osmoconformers, but ionoregulate.
Do not need to cop ewith movement of water.
Must regulate ion.
Most marine vertebrates are osmoregulators and ionoregulators.
Tend to lost water and gain salt by osmosis.
Seawater is Ma+ 450mmol/L.
Body Na+ 150-250 mmol/L.
Elasmobranchs unusual (a cartilaginous fish of a group that comprises the sharks, rays, and skates.Compare with selachian).
Vertebrates who do not osmoregulate store urea to keep osmotic conc high.
Water loss is a problem for marine vertebrates.
Fish cane produce concentrated urine (not well enough developed kidneys).
Chloride cells on gills.
Animals without gills have less water loss, as they don’t have gills, which is a large surface for water loss.
Air breathing marine animals:
Reptiles, birds and mammals.
Need specialised structures or efficient kidney.
Body osmolarity about 400mmol/L.
Can be considered terrestrial in water balance.
Mammals use kidney to excrete salt.
Reptiles and birds use salt glands.
Explain salt glands in reptiles (birds).
Salt glands can be found in reptiles and birds.
Very salt secretions.
More efficient than kidneys for getting rid of salt.
Describe osmoregulation in fresh water.
Invertebrates and vertrebrates similar.
Low envrionmental osmolarity (not a massive difference in solute content of envrionment and animal).
Tendency to gain water and lose salts.
Reducing permiability helps.
Active transport required.
Usually respiratory surfaces uptake ions.
Water gain is a problem.
Passive loss of ions to envrionmnet.
Active uptake.
Copious dilute urine produced.
Describe water balence on land.
Water loss to envrionment a constant problem.
Economical water use required.
Vapour limited systems e.g. frogs.
Membrane limited systems e.g. insects.
Terrestrial invertebrates:
Moist skinned must avoid dessication in warm dry environments, e.g. worms and snails.
Absorption of water through body.
Cuticular more resistant to drying.
Habitat and behaviour often specilaised.
Reptiles have low skin and resp water loss.
Excrete urate to conserve water.
Birds and mammals use water to keep cool.
Often high evapouration from skin and resp surfaces.
Cooling of air on exhalation saves us water.
Kidney major specialised ormoregulatory organ.
What are the various nitrogenous wastes produced by animals?
Proteins are broken down in to carbon dioxide, water and nitrogenous wastes.
Ammonia:
Highly soluble in water.
very toxic.
Repid diffusion in contact with water.
Fish.
Urea:
Soluble in water.
Low toxisity.
Can be concentrated.
Energetically expensive to produce.
Amphibians swich with ammonia when they metamorphose.
Elasmobranchs keep urea in tissues.
Uric acid:
Relatively non-toxic.
Insoluble in water.
Little water required for excretion.
Most expensive to produce.
Used in amniotic egg.
