Water and Solute Balance 2

1. Water and Solute Balance 2 • Ionic and Osmotic Regulation in Different Organisms in Different Environments

2. Outline Last 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

3. Water and Solute Balance 2 • Ion Uptake vs Ion Excretion

4. 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

5. Ion UptakevsIon Excretion How can ionic regulation be accomplished through these methods? And can the same organs be involved?

6. Urine What is it?

7. Varies Amino (-NH2) groups unused from catabolism Salts and Water Osmotic concentration depends on Environment

8. Osmoregulated urine is a convenient way to regulate ionic concentration (through excretion) and remove nitrogenous wastes

9. Urineconcentrations relative toblood Marine invertebrates isosmotic Freshwater inverts + verts hyposmotic (dilute) Terrestrial Animals hyperosmotic Marine Verts teleosts isosmotic (use gills to remove salt) elasmobranchsclose to isosmotic mammals hyperosmotic

10. 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

12. Water and Solute Balance 2 • Osmo/Ion-regulatory Organs

13. Question: • What do osmoregulatory organs of different animals have in common? • In what ways do they differ and why? • What are some key differences between osmoregulation in aquatic and terrestrial environments?

14. 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

15. 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 animals Antennal glands Crustaceans Malpighian tubules Insects Kidneys Vertebrates Gills Crustaceans, Molluscs, Fishes Skin Amphibians Salt glands Birds, Reptiles

16. Common Themes • Tubular structures • Remove or absorb ions • Remove or take up water

17. Protonephridia of flatworms Metanephridia of Annelids (segmented worms)

19. Fish Gills V-H+-ATPaseNa+,K+-ATPase

20. Salt glands of birds

21. Vertebrate Kidney • Contains simple tubular structures • But which are compacted • Around 1 million of these tubules (nephrons) in humans • Filtration-Reabsorption System

22. 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

23. 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)

24. Human Kidney

26. The Nephron Figure 5.16 The Functional Unit

27. Mammalian Kidney

28. 3Na+ Countercurrent Multiplier system Na+ Cl- are pumped out

29. Countercurrent Multiplier system • Flow moving in opposite directions (countercurrent) • Where the concentration difference is not big between the descending and ascending side of the loop, BUT, along the whole length of the loop, the difference is additive and big (multiplicative)

30. Countercurrent Multiplier system A mechanism through which water is moved out of the tubule (to conserve water in the organism) Na+ Cl-

31. Countercurrent Multiplier system • A general method for exchange (heat, gas, liquid) • (in this case water and ions) • Creates a concentration gradient along the loop • Requires a loop structure • Common in animals, engineering, gills, lungs • Relies on asymmetry and flow through the tube

32. Countercurrent Multiplier system Na+ Cl- are pumped out And diffuses to the Other side

33. Countercurrent Multiplier system Impermeable to water Impermeable to solutes The interstitium become concentrated

34. Countercurrent Multiplier system Impermeable to solutes Impermeable to water H20 Water diffuses out of The descending loop

35. Countercurrent Multiplier system Impermeable to water Impermeable to solutes H20 The fluid at the hairpin Becomes more concentrated

36. Countercurrent Multiplier system Which gives the ascending loop more ions to pump out Impermeable to solutes The fluid at the hairpin Becomes more concentrated

37. Countercurrent Multiplier system Which gives the ascending loop more ions to pump out Impermeable to solutes

38. Countercurrent Multiplier system Which gives the ascending loop more ions to pump out H20 Which causes More water to Diffuse out The fluid at the hairpin Becomes more concentrated

39. Countercurrent Multiplier system So with little energy, the fluid becomes Increasingly concentrated H20

40. Water and Solute Balance 2 • Ionic and Osmotic Regulation in Different Organisms in Different Environments

41. (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

42. Extracellular Fluids (blood) Na+ The Cell HCO3- K+ K+ Organic Anions Mg++ Cl- Mg++ Cl- Na+ Ca++ Ca++ Last time we discussed strategies for regulation concentrations in and out of the cell

43. The Environment Now, we want to discuss the interaction between the organism and the Environment Extracellular Fluids Na+ The Cell K+ K+ Organic Anions Mg++ Cl- Mg++ Na+ Ca++ Ca++ HCO3- Cl-

44. Osmo/Iono-conformers: Osmotic pressure (or ionic concentration) of extracellular fluid (blood) matches that of the environment Osmo/Iono-regulators: Maintain relatively stable blood osmotic pressure (ionic concentration) over a range of pressures (ionic concentrations) in the environment

45. Hyporegulation Hyperregulation

46. Daphnia from Lake Mendota Which is most likely to be an Osmo/Iono-conformer?

47. Differences in Body Fluid Regulation in Different Environments

48. Evolutionary patterns • Intracellular ionic concentrations are conserved (constraints of basic cell biochemistry) • Extracellular fluids and intra and extra cellular osmotic regulation varies much more

49. Intracellular differences among species Relatively conserved • Ionic compositionis 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

50. Osmotic Concentrations vary 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