Water and Solute Balance 2
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Transcript of Water and Solute Balance 2
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Water and Solute Balance 2Water and Solute Balance 2
Ionic and Osmotic Regulation in Different Ionic and Osmotic Regulation in Different Organisms in Different EnvironmentsOrganisms in Different Environments
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OutlineLast time:
Ionic and osmotic regulation in and out of the cell
Ion uptake mechanisms
This Time:
(1) Ionic Regulation and Excretion
(3) Ionic and Osmotic Regulation in Different Organisms in Different Environments
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Water and Solute Balance 2Water and Solute Balance 2
Ion Uptake vs Ion ExcretionIon Uptake vs Ion Excretion
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Ion Uptake
The Ion Uptake enzymes are often conserved in amino acid sequence ( often no structural differences)
The following are often NOT conserved: Distribution and concentration of Ion Uptake
enzymes in a cell
The organization of the cells in an organ
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Ion UptakeIon Uptake vs Ion ExcretionIon Excretion
How can ionic regulation be accomplished through these methods?
And can the same organs be involved?
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UrineUrine
What is it?
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Varies
Amino (-NH2) groups unused from catabolism
Salts and Water
Osmotic concentration depends on Environment
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Osmoregulated urine is a convenient way to regulate ionic concentration (through excretion) and remove nitrogenous wastes
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UrineUrine concentrations relative to bloodblood
Marine invertebratesMarine invertebrates isosmoticisosmotic
Freshwater inverts + vertsFreshwater inverts + verts hyposmotic (dilute)hyposmotic (dilute)
Terrestrial AnimalsTerrestrial Animals hyperosmotichyperosmotic
Marine Verts Marine Verts
teleoststeleosts isosmotic isosmotic (use gills to remove salt)(use gills to remove salt)
elasmobranchselasmobranchs close to isosmoticclose to isosmotic mammalsmammals hyperosmotichyperosmotic
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Costs and Benefits of different nitrogenous waste products (Table 5.7)
Ammonia: Marine Animals, Inexpensive, water soluble, 1N/molec.(lose less C), permeable thru lipid bilayer, highly toxic
Urea: Expensive (2 ATP), water soluble, 2N/molec., moderately permeable thru lipid bilayer, moderately toxic
Uric Acid: Very Expensive, water insoluble, minimize water loss, not permeable thru lipid bilayer, 4N/molec., Low toxicity
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Water and Solute Balance 2Water and Solute Balance 2
Osmo/Ion-regulatory OrgansOsmo/Ion-regulatory Organs
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Question:
What do What do osmoregulatoryosmoregulatory organs of different organs of different animals have in common?animals have in common?
In what ways do they differ and why?In what ways do they differ and why?
What are some key differences between What are some key differences between osmoregulationosmoregulation in aquatic and terrestrial in aquatic and terrestrial environments?environments?
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Most animals have tubular osmoregulatory structures involving the same types of ion uptake and excretion mechanisms (see book)
In aquatic habitats nitrogenous excretion can occur across gills or integument (skin)…will be removed through simple diffusion
In terrestrial habitat osmoregulation and (nitrogenous) excretion is done together…use excess water to remove wastes
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Osmoregulatory Organs
Contractile vacuoles Protozoans, Sponges
None demonstrated Coelenterates (strictly marine) Echinoderms (strictly marine)
Nephridial organs Protonephridia (closed ends) Platyhelminthes, Aschelminthes Metanephridia (open ends) Annelids Nephridia Molluscs
Gut Many animalsAntennal glands CrustaceansMalpighian tubules InsectsKidneys VertebratesGills Crustaceans, Molluscs, FishesSkin AmphibiansSalt glands Birds, Reptiles
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Common Themes
Tubular structures
Remove or absorb ions
Remove or take up water
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Protonephridia of flatworms
Metanephridia of Annelids (segmented worms)
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Fish Gills
V-H+-ATPase Na+,K+-ATPase
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Salt glands of birds
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Vertebrate Kidney
Contains simple tubular structures
But which are compacted Around 1 million of these tubules (nephrons)
in humans
Filtration-Reabsorption System
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Evolutionary History of the kidney
First evolved in freshwater teleosts
Freshwater fish are hyperosmotic relative to environment
Face two problems: (1) Water rushing in thru osmosis
(2) loss of solutes
Solution: (1) Active uptake in gills
(2) Kidney to excrete dilute urine (hypotonic)
(3) Reabsorb ions across nephron tubules
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Vertebrate Kidney
Enormous osmo-iono-regulatory capacity Receives 20-25% of total cardiac output
Osmoregulation Excretion Regulate Blood Pressure pH Balance: produces about 1 liter of slightly acidic
urine daily (pH 6.0)
(blood maintained at pH 7.4)
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Human Kidney
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Figure 5.16The Functional Unit
The Nephron
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Mammalian Kidney
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Countercurrent Multiplier system
Na+ Cl- are pumped out
3Na+
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Countercurrent Multiplier system
Flow moving in opposite directions Flow moving in opposite directions (countercurrent)(countercurrent)
Where the concentration difference is not big Where the concentration difference is not big between the descending and ascending side of the between the descending and ascending side of the loop, BUT, along the whole length of the loop, the loop, BUT, along the whole length of the loop, the difference is additive and big (multiplicative)difference is additive and big (multiplicative)
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Countercurrent Multiplier system
A mechanism through which water is moved out of the tubule (to conserve water in the organism)
Na+
Cl-
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Countercurrent Multiplier system
A general method for exchange (heat, gas, liquid)A general method for exchange (heat, gas, liquid) (in this case water and ions)(in this case water and ions)
Creates a concentration gradient along the loopCreates a concentration gradient along the loop
Requires a loop structure Requires a loop structure
Common in animals, engineering, gills, lungsCommon in animals, engineering, gills, lungs
Relies on asymmetry and flow through the tubeRelies on asymmetry and flow through the tube
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Countercurrent Multiplier system
Na+ Cl- are pumped outAnd diffuses to the
Other side
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Countercurrent Multiplier system
Impermeable to waterImpermeable
to solutes
The interstitium becomeconcentrated
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Countercurrent Multiplier system
Impermeable to waterImpermeable to solutes
Water diffuses out ofThe descending loop
H20
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Countercurrent Multiplier system
Impermeable to waterImpermeable
to solutes
The fluid at the hairpinBecomes more concentrated
H20
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Countercurrent Multiplier system
Impermeable to solutes
The fluid at the hairpinBecomes more concentrated
Which gives the ascending loop
more ions to pump out
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Countercurrent Multiplier system
Impermeable to solutes
Which gives the ascending loop
more ions to pump out
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Countercurrent Multiplier system
The fluid at the hairpinBecomes more concentrated
H20
Which gives the ascending loop
more ions to pump out
Which causesMore water to
Diffuse out
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Countercurrent Multiplier system
H20 So with little energy,the fluid becomesIncreasingly concentrated
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Water and Solute Balance 2Water and Solute Balance 2
Ionic and Osmotic Regulation in Different Ionic and Osmotic Regulation in Different Organisms in Different EnvironmentsOrganisms in Different Environments
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(3) Ionic and Osmotic Regulation in Different Organisms in Different Environments
Last Time: Inside Cell vs Outside Cell
This Time: Inside the Organism (both
intracellular & extracellular fluids) vs The Environment
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K+
Na+
Cl-
HCO3-
Na+
K+
Mg++
Mg++
Ca++Ca++
Cl-
OrganicAnions
Extracellular Fluids Extracellular Fluids (blood)(blood)
The Cell
Last time we discussed strategies for regulation concentrations in and out of the cell
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K+
Na+
Mg++
Ca++
Cl-
OrganicAnions
The Cell
Cl-HCO3-
Na+
K+
Mg++
Ca++
Extracellular FluidsExtracellular Fluids
The EnvironmentThe EnvironmentNow, we want to discuss the interaction between the organism and the Environment
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Osmo/Iono-conformers: Osmotic pressure Osmo/Iono-conformers: Osmotic pressure (or ionic concentration) of extracellular fluid (or ionic concentration) of extracellular fluid (blood) matches that of the environment (blood) matches that of the environment
Osmo/Iono-regulators: Maintain relatively Osmo/Iono-regulators: Maintain relatively stable blood osmotic pressure (ionic stable blood osmotic pressure (ionic concentration) over a range of pressures concentration) over a range of pressures (ionic concentrations) in the environment(ionic concentrations) in the environment
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Hyperregulation
Hyporegulation
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Daphnia from Lake Mendota
Which is most likely to be Which is most likely to be an Osmo/Iono-conformer?an Osmo/Iono-conformer?
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Differences in Body Fluid Regulation in Different Environments
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Evolutionary patterns
Intracellular ionic concentrations are conserved (constraints of basic cell biochemistry)
Extracellular fluids and intra and extra cellular osmotic regulation varies much more
Osmotic Concentration (mOsm) Ionic Concentration (mM)
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E I E I E I E I E I
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Intracellular differences among species
Ionic composition is more conserved across species (differences related to evolutionary adaptations)
Osmotic concentration differs among species: Using osmolytes or urea to fill Solute Gap with Environment Depends on environment And on Evolutionary History
Osmotic Concentration (mOsm) Ionic Concentration (mM)
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E I E I E I E I E I
Relativelyconserved
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Osmotic differences among species
Ionic composition is more conserved across species
Osmotic concentration differs greatly among species: Need to maintain osmotic constancy in and out of the cell, and then try to
approach the osmotic concentration of the environment Using osmolytes or urea to fill Solute Gap with Environment Depends on Environment: Extracellular fluids provide a Buffer between the
cells and the Environment And on Evolutionary History
Osmotic Concentration (mOsm) Ionic Concentration (mM)
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TerrestrialVertebrate(Human)
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E I E I E I E I E I
OsmoticConcentrations vary
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Osmolytes Organic osmolytes: small solutes used by cells
to maintain cell volume
Compatible solutes: does not perturb macromolecules in the cell and are interchangeable (one functions as well as another)
However, not all osmolytes are compatible solutes and some have specific functions (read about in Yancey 2005)
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Osmotic RegulationExamples of Osmolytes: Carbohydrates, such as
trehalose, sucrose,
and polyhydric alcohols, such as glycerol and mannitol
Free amino acids and their derivatives, including glycine, proline, taurine, and beta-alanine
Urea and methyl amines such as trimethyl amine oxide (TMAO) and betaine
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Patterns of osmolyte composition in intracellular fluids
Yancey 2005
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Osmotic Concentration (mOsm) Ionic Concentration (mM)
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Teleost(Salmon)
TerrestrialVertebrate(Human)
FreshwaterInvertebrate
Freshwater
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E I E I E I E I E I
Extracellular Ionic & osmotic
concentrations vary among species in different habitats
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Osmotic Concentration (mOsm) Ionic Concentration (mM)
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E I E I E I E I E I
Match environment
Unusually low
Deal with low salinity
No longer an osmotic issue
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Metabolic Cost of Osmoregulation
The cost of iono- and osmoregulation varies greatly among animals
Depends on gradient between environment and Extracellular fluid
Permeability of the integument (skin) And particular evolutionary strategy
Examples:Low in Marine InvertebratesMarine Teleosts: 8-17% of resting metabolic rateFreshwater teleosts: 3-7% of resting metabolic rate
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Osmotic Concentration (mOsm) Ionic Concentration (mM)
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TerrestrialVertebrate(Human)
FreshwaterInvertebrate
Freshwater
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E I E I E I E I E I
Marine Invertebrates Extracellular ionic & osmotic concentrations close to sea water Some species do not regulate at all
Intracellular ionic concentration conserved (low) Intracellular osmotic concentration high
(Osmotic solute gap filled by osmolytes) High body permeability to water and ions
Isosmotic urine
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Extracellular ionic composition is close to seawater(intracellular is not)
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Adaptations to Fresh Water
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E I E I E I E I E I
Freshwater species are hyperosmotic relative to the environment
Energetic cost of osmotic-ionic regulation is 3-7% of resting metabolic rate
(1) Reduce ionic and osmotic gradient with the environment to reduce energetic cost
(2) Reduce body permeability to ions
(3) Excrete high volumes of dilute urine(4) Active Ion uptake
(5) Obtain ions from food
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Freshwater animals have reduced ionic and osmotic body fluid concentrations
Fresh
Marine
Composition of blood plasma and other fluids
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Freshwater animals excrete high volumes of dilute urine
Very dilute
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Did they evolve in Fresh Water?
VertebratesVertebrates
Low Extracellular ionic AND osmotic concentration They are osmoregulators, even when they return to marine
habitats.
Bones form more readily in Fresh Water (relative large availability of Calcium)
Greater degree of regulation
Osmotic Concentration (mOsm) Ionic Concentration (mM)
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Urea
Anions
K+
Na+
MarineInvertebrate(Horseshoe
Crab)
Seawater Elasmobranch(Ray)
Teleost(Salmon)
TerrestrialVertebrate(Human)
FreshwaterInvertebrate
Freshwater
OC
OC
E I E I E I E I E I
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Elasmobranchs, cartilaginous fishes
Low Extracellular ionic concentration!!!
(1/3 of seawater, evolution in fresh water?)
Solute gap for BOTH extra and intracellular fluids filled by ureaurea!!!
Some species slightly hyperosmotic
(limited osmoregulator, not osmoconformer)
Osmotic Concentration (mOsm) Ionic Concentration (mM)
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Urea
Anions
K+
Na+
MarineInvertebrate(Horseshoe
Crab)
Seawater Elasmobranch(Ray)
Teleost(Salmon)
TerrestrialVertebrate(Human)
FreshwaterInvertebrate
Freshwater
OC
OC
E I E I E I E I E I
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Elasmobranchs, cartilaginous fishes
Withers PC. 1998. Urea: diverse functions of a 'waste' product.Clin Exp Pharmacol Physiol. 25:722-7.
Urea is a waste product It destabilized proteins (but Trimethylamine N-oxide
TMAO stabilizes)
Close to isosmotic Don’t need to drink
Some are slightly hyperosmotic Water flows into gills (gains the water it needs this way)
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Osmotic Concentration (mOsm) Ionic Concentration (mM)
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Urea
Anions
K+
Na+
MarineInvertebrate(Horseshoe
Crab)
Seawater Elasmobranch(Ray)
Teleost(Salmon)
TerrestrialVertebrate(Human)
FreshwaterInvertebrate
Freshwater
OC
OC
E I E I E I E I E I
Extracellular fluid (blood) concentration 1/4 of marine animal More concentrated than freshwater animal
Not have to worry about loss of ions through osmosis
(so osmotic conc. can be higher than in fresh water) Instead, problem of evaporation (water loss through respiration) Mammals: another issue is water used for thermoregulation (sweat)
Terrestrial Vertebrates
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Terrestrial
Adaptations
Active behavioral uptake of water
Ion uptake from food
Skin and cuticle evolved to prevent water loss
Concentrated Urine (kidneys)
Some terrestrial animals can survive water loss (camel- survive 30% loss)
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Essentially a terrestrial vertebrate (cow) living in the seaExcrete Concentrated Urine (powerful kidneys)