Osmoregulation Flashcards

Question

Osmoconformer

Answer 1

Blood osmotic pressure is the same as the ambient osmotic pressure

Answer 2

Maintain 300 mOsm irrespective of how much water is consumed

Answer 3

Body is hyperosmotic to water around it Water moves into the body via osmosis Salts lost to the water Decreases osmotic pressure of the blood plasma (a challenge to osmotic regulation) Dilutes ions in the blood plasma (a challenge to ionic regulation) Increases volume of water in the blood plasma (a challenge to volume regulation)

Answer 4

Body is hyposmotic to water around it Water moves from the body to the sea water via osmosis Salt moves into body via gills and food Increases osmotic pressure of the blood plasma (a challenge to osmotic regulation) Concentrates ions in the blood plasma (a challenge to ionic regulation) Decreases volume of water in the blood plasma (a challenge to volume regulation)

Answer 5

Body is hyperosmotic but hypoionic to water around it Water moves from the seawater to the blood via osmosis via the gills Salt also moves into body via gills and food Decreases osmotic pressure of the blood plasma Concentrates ions in the blood plasma (a challenge to ionic regulation) Increases volume of water in the blood plasma (a challenge to volume regulation)

Answer 6

34-36 g NaCl per kg H2O Osmotic pressure = 1000 mOsm

Answer 7

< 0.5 g NaCl per kg H2O (often 0.1-0.2 g/kg) Osmotic pressure = 0.5-15 mOsm Calcium ion (Ca2+) concentration depends on geology and can have impact of water-salt physiology of freshwater animals

Answer 8

in estuaries varies in salinity both geographically and in time 0.5 - 30 g NaCl per kg H2O Osmotic pressure = 15 – 850 mOsm

Answer 9

Water as liquid has high partial pressure Water vapour has a partial pressure = proportion of water vapour per unit volume of air Evaporation takes place if partial pressure of water vapour in air is lower than that of liquid water Elevated temperature increases partial pressures at saturation water vapour pressure Rate of evaporation is increased as difference between liquid and air increases

Answer 10

Solute concentration

Answer 11

The difference between water vapour pressure of the solution and air, divided by the distance between the solution and air

Answer 12

Consumption of seawater by a hyposmotic whale will not gain water from the drink Excretion of the excess chloride ions (Cl-) requires more water than is ingested because kidneys cannot urine that is iso-ionic to seawater Bodily reserves of water are needed so drinking seawater leads to dehydration Halophytes have high levels of salt within their tissues that can be ingested by herbivores High sodium ion (Na+) concentrations mean that urine cannot concentrate enough ions to remove excess

Answer 13

Catabolism (breakdown) of sugars and lipids yields metabolically derived H2O (0.56 g g H2O per 1 g carbohydrate / 1.07 g H2O per 1 g lipid) Metabolically derived water can be crucial in those animals with limited access to water Protein diets generate more nitrogenous waste – ammonia, urea or uric acid – that needs to be excreted High protein diets for a urea-excreting mammal require more water for excretion than for a low protein diet

Answer 14

α-amino acid + α-ketoglutamate → glutamate + α-keto acid Glutamate taken up by mitochondria and oxidatively deaminated by glutamate dehydrogenase: glutamate → NH3 + α-ketoglutamate Ammonia (NH3) combines with water to form the weak base NH4OH, which disassociates into ammonium (NH4+) and hydroxide (OH-) ions

Answer 15

Glutamine synthetase reaction binds ammonium ions in an effective, non-toxic form for transport glutamate + MgATP + NH4+→ glutamine + MgADP + Pi This process consumes a lot of energy in the form of ATP. Protein catabolism also generates an excess of base as bicarbonate ions (HCO3-) relative to H+

Answer 16

Ammonia (NH3) and ammonium (NH4+) are highly toxic High levels lead to accumulation of glutamine and depletion of α-ketoglutamate and ATP Loss of α-ketoglutamate is problematic for the tricarboxylic acid cycle Glutamate is a neurotransmitter so disrupts the nervous system High levels of NH3 alkalanises and NH4+ acidifies the cytoplasmic pH NH3 diffuses into the mitochondria and binds with H+ to form NH4+ which reduces the pH gradient across the mitochondrial membrane and eliminates the electromotive force for ATP synthesis Biological imperative is to prevent increases in ammonia concentrations Excretion of ammonia at very low concentrations Formation of glutamine Formation of less toxic urea (CO(NH2)2) or uric acid (C5H4N4O3) [also liberates H+ that helps neutralise excess HCO3- released during protein catabolism]

Answer 17

Excretion of ammonia at very low concentrations Formation of glutamine Formation of less toxic urea (CO(NH2)2) or uric acid (C5H4N4O3) [also liberates H+ that helps neutralise excess HCO3- released during protein catabolism]

Answer 18

Urea is formed by the ornithine-urea cycle in the liver (and kidney) Urea is a neutral molecule with low toxicity Uric acid is a purine that metabolically produced from glutamine It is effectively insoluble in water as the urate salt

Answer 19

Ammonotelism - ammonia excretion with lots of water Ureotelism - urea excretion with some water Uricotelism - uric acid excretion with little water

Answer 20

Many reptile eggs vary in eggshell structure but can gain water with the nest environment Reptile embryos utilise protein for energy and generate little metabolic water Produce more urea than uric acid

Answer 21

Bird eggs have hard shells and only lose water vapour during incubation Bird embryos utilise lipid for energy and generate lots of metabolic water Produce uric acid to conserve water

Answer 22

Variety of kidney-like structures Malpighian tubules in insects

Answer 23

Kidney is a crucial organ Regulates composition of blood by removing water, salts and other solutes in a controlled manner Also gills in fish Rectal and salt glands in marine reptiles and birds

Answer 24

aridity - < 25 cm of precipitation per year

Answer 25

Sometimes conditions do allow for animals to be cooler than the ambient air which leads to condensation is water vapour pressure is high Some mammals can condense water vapour from exhaled breathe on turbinate bones, e.g. camels

Answer 26

Marine invertebrates- have a permeable integument and are isosmotic and iso-ionic to sea water

Answer 27

Hyperosmotic and hyperionic to the ambient water Impermeable cuticle Active uptake of Na+ and Cl- via the gills Production of copious dilute ammonotelic urine from antennas glands End sac (coelomosac) is supplied with arterial blood via lacunae - filtration of plasma Fluid then passes through labyrinth and nephridial tubule where molecules (eg glucose and NaCl) are reabsorbed from urine that is first stored in a bladder then exits the body via the nephropore Water reabsorbed along the length of the antennal gland Osmotic pressure is isosmotic in marine decapods Hypotonic in freshwater species and length of nephridial canal correlates with osmolality of urine

Answer 28

Waterproofed cuticle to minimise loss of water in insects Main excretory organ is Malpighian tubule which is engaged in active secretion of molecules across its wall (surrounded by haemolymph) to form primary urine in a blind-ended lumen that empties into the gut Solutes are actively transported from the haemolymph between or through cells Active recovery of water and ions in the hind gut Most insects consuming solid food produce frass that is a mix of nitrogenous waste molecules and faeces Insects feeding on liquid, blood or plant sap remove very little water from their urine and the excreta secreted is very liquid

Answer 29

Consider a tubule that has solution inside and the haemolymph outside, which are isotonic (1). ATP energy is used to move solute X molecules into the lumen, which increases the osmolality of the tubular fluid (2). Water then moves into the tubule from the haemolymph by osmosis which then dilutes solute Y (3). Solute Y then passively diffuses into the tubule down its concentration gradient (4). In this way the concentration of solutes X and Y are increased in the tubules.

Answer 30

With the exception of hagfish – marine fish that are isosmotic to seawater (1000 mOsm) – all vertebrates are effectively regulating bodily fluids at ~300 mOsm All modern fish (and vertebrates) arose from an ancestor adapted to freshwater Need to regulate water loss or gain in aquatic habitats and water loss in terrestrial habitats Need to regulate ion loss or gain in aquatic habitats Need to excrete nitrogenous waste products efficiently

Answer 31

gains water by ingestion of food and water Loses water mainly via osmosis via gills and in urine and faeces Gains solutes in food and diffusion across gills Loses solutes by urine and faeces

Answer 32

Gains water by ingestion and via osmosis by the gills Loses water in urine and faeces Gains solutes in food and by active transport across gills Loses solutes by diffusion from gills and in urine and faeces

Answer 33

Water is exchanged by osmosis across the semi-permeable epithelial membranes of the gills Large surface area and perfumed with blood Volume control is largely down to kidneys producing small (marine) or large (freshwater) amounts of urine

Answer 34

Sodium and chloride ions are key components of bodily tissues Freshwater fish lose ions in urine and faeces but also diffusion across the gills Ionic regulation by cells in the gill epithelium requires active exchange of H+ (out) for Na+ (in) and active exchange of HCO3- (out) and Cl- (in) Uses ATP and ions from the disassociation of carbonic acid produced by CO2 dissolving in water Mitochondrial-rich (chloride) cells are often associated with gill arch Pavement cells (pvc) thought to be site of oxygen exchange Active transport of NaCl into blood

Answer 35

Pavement cells

Answer 36

Mitochondrial-rich chloride cells

Answer 37

Same cells are seen as being able to actively transport chloride ions Na+, K+ and 2 Cl- move into cell via a cotransporter ATPase removes the Na+ Cells are packed with mitochondria Chloride ions move through a chloride channel to the sea water Sodium ions move between cells out into seawater to balance the ionic gradient Active loss of NaCl from blood

Answer 38

Body is hyperosmotic because retains urea within cells to increase osmolality of tissues Water moves from the seawater to the blood via osmosis via the gills Produces modest amounts of hyposmotic urine Sharks venturing into brackish water lower their osmolality by reducing urea production Hypoionic tissues relative to water around it Salt also moves into body via gills and food Excess salt ions are extracted from the blood by chloride cells in rectal glands and excreted with faeces

Answer 39

Marine turtles, lizards and birds are hyposmotic regulators Kidney is unable to produce hyperosmotic urine that would remove the excess salts consumed with food and water Salt glands are organs that allow for extra-renal salt excretion using chloride cells Salt gland tubules are lined with chloride cells and lie in a counter-current system with perfusing blood Salt is excreted down ducts on to the face as a hyperionic solution

Answer 40

Occupy terrestrial habitats that are humid and water-rich environments Annelids, gastropods, centipedes, terrestrial crabs and most amphibians

Answer 41

Adopted dry conditions Evolved a waterproof integument that minimises cutaneous water loss

Answer 42

Inverse relationship Very small birds lose relatively greater amounts of water compared with large birds

Answer 43

secretes lipids (waxy esters) from skin glands and spreads them over its skin with its legs Also is uricotelic rather than ureotelic - switching from urea to uric acid 70-fold saving of water

Answer 44

Osmotic pressure of urine/ osmotic pressure of blood plasma

Answer 45

Just like excreting blood plasma

Answer 46

Water preferentially excreted Solutes preferentially retained Osmotic pressure of plasma raised

Answer 47

Water preferentially retained Solutes preferentially excreted Osmotic pressure of plasma lowered

Answer 48

Primary urine produced by filtration or secretion from blood plasma is introduced into kidney tubules Modification by selective reabsorption leads to definitive urine that is excreted Urine crucial in removing nitrogenous waste whilst maintaining osmotic balance Energetically expensive process

Answer 49

The vertebrate kidney is centered around the Bowman’s capsule and the loop of Henle, which form part of the nephron. Blood vessels come into the kidney and there are capillary ‘balls’ called glomeruli that sit within the Bowman’s capsule. The reduction in blood vessel lumen in the glomerulus forces plasma out of the blood and this cross the ‘leaky’ wall of the Bowman capsule’s wall so that this primary urine accumulates within the lumen of the nephron.

Answer 50

Formation of copious urine

Answer 51

Volume of urine is controlled by changing the permeability of the kidney tubules to water Posterior pituitary gland produces anti-diuretic hormone (ADH) ADH renders the tubule wall more permeable to water and reduces glomerular filtration rate

Answer 52

nephron is not structurally organized in the kidney and the Bowman’s capsule lies within the entangled convoluted tubule. The proximal tubule if thicker than the distal tubule, which opens up into a collecting duct that collects urine from many tubules and delivers it to the ureter. the proximal part of the kidney tubule is freely permeable to water so the urine remains approximately isosmotic to the plasma but the walls of the distal tubule are poorly permeable to water so as Na+ and Cl- are selectively absorbed the water remains and the urine becomes progressively more dilute – a really useful trait if excreting ammonia.

Answer 53

Capillary beds extending into the kidney medulla

Answer 54

Arid environments = long loops of henle (thickness of medulla)

Answer 55

relies on the descending and ascending parts of the loop of Henle having different permeabilities to water and interstitial fluid composition Walls of the ascending part of the tubule are impermeable to water Single effect Sodium pumps transport NaCl out of the ascending tubule – water cannot follow – into the interstitial fluid, which becomes hyperosmotic Water is drawn out of the adjacent descending tubule and Na+ and Cl- can enter the descending tubule Descending and ascending tubules contain fluid of different osmolality

Answer 56

Sodium pumps transport NaCl out of the ascending tubule – water cannot follow – into the interstitial fluid, which becomes hyperosmotic Water is drawn out of the adjacent descending tubule and Na+ and Cl- can enter the descending tubule Descending and ascending tubules contain fluid of different osmolality

Answer 57

Combination of single effect and very long loops of Henle mean that very concentrated urine can be produced Countercurrent effect multiplies the osmotic differences between the descending and ascending tubules Urine and interstitial fluid get more concentrated as you go down the descending tubule but become more dilute as it comes back up the ascending tubule Urine then moves down collecting duct loses water through the wall (high ADH) and the urine is concentrated

Answer 58

Urea enters primary urine in filtrate Tubules and collecting ducts are relatively impermeable to urea More urea is filtered than excreted so it accumulates in the medullary interstitial fluid ADH controls amount of urea retained in tubules and collecting ducts