Presentation on theme: "Controlling the Internal Environment II: Salt and water balance"— Presentation transcript:
1 Controlling the Internal Environment II: Salt and water balance
2 Keywords (reading p. 879-884) Ammonia toxicity Urea Uric acid OsmoconformerOsmoregulatorPassive transportFacilitated diffusionActive transportUniportAntiportsymportOsmoregulation by an aquatic invertebrateOsmoregulation in marine fishOsmoregulation in freshwater fishWater loss on landPermeable and impermeable body surfacesKangaroo rate water balanceanhydrobiosis
3 The internal environment In most animals, the majority of cells are bathed by internal fluids rather than the environmentThis is advantageous since there can be control of substrates needed for metabolism
4 Consider the origin of life: started out as enzymes in the primordial sea
5 Rates of reactions were determined by the concentrations of substrates in the environment
6 The first proto-organism enclosed it’s enzymes inside a membrane and became a cell
7 Control of substrate concentration Products do not diffuse away
8 Good because you can keep out molecules that you don’t want Good because reactions will work better and you don’t lose the productsGood because you can keep out molecules that you don’t wantBad because there can be osmotic problemsBad because hazardous by products can stay in the cellHazardous products
9 Therefore the internal chemical environment is controlled A. Avoiding buildup of toxic chemicalsDealing with ammoniaB. Osmoregulation - controlling internal solutes
11 Hazardous productsA major source of hazardous products is the production of nitrogenous wastesAmmonia (NH3) is a small and very toxic molecule that is normal product of protein and amino acid breakdownIf you are an aquatic organism, ammonia can readily diffuse out of the body and this is not a problem
13 Ammonia toxicity is a problem for terrestrial animals Ammonia does not readily diffuse away into the air.The strategy of terrestrial animals is to detoxify it then get rid of (excrete) it.
14 Ammonia can be converted to urea which is 100,000 times less toxic Mammals, most amphibians, sharks, some body fishes
15 The drawback of using urea Takes energy to synthesizeStill need to use water to “flush it out”
16 Some animals cannot afford to use water to excrete urea These animals use excrete uric acid instead
17 Since uric acid is not very soluble in water, it can be excreted as a paste. Less water is lostDisadvantages:Even more costly to synthesize.Loss of carbonUric acid
18 Who uses uric acid? Birds, insects, many reptiles, land snails Related to water use, but also reproductionEggs - N wastes from embryo would accumulate around it if ammonia or urea are used. Uric acid precipitates out.
19 B. Osmoregulation - controlling internal solutes
20 Osmolarity Osmolarity = # of solutes per volume solution Often expressed in moles (6.02 x 1023 atoms/molecules) per liter.1 mole of glucose = 1 mole of solute1 mole of NaCl = 2 moles of solute
21 Osmotic problemsHumans have internal solute concentration (osmolarity) of 300 milliosmoles per liter (mosm/L)The ocean is 1000 mosm/L
22 What would happen if your body surface is water permeable and you fall into the sea 1000 mosm/LKeep your internal concentrations the same as the environment (osmoconformer)Regulate your internal concentrations (osmoregulator)300 mosm/L
23 Jellyfish in the ocean 1000 mosm/L 1000 mosm/L Keep solutes at 1000 mosm/L no water loss or gain.A relatively simple solution1000 mosm/L1000 mosm/Ljellyfish
24 Life in freshwater - hydra living in a pond Can the same strategy of matching the environmental osmolarity be used?0 mosm/L0 mosm/LGreen hydra
25 Hydra living in a pondIf external osmolarity is very low like 0 mosm/L, hydra cannot maintain an internal osmolarity of 0 mosm/LWhy is this?Consequently freshwater animals will most likely have a higher osmolarity than the environment.
26 What happens to freshwater organisms? Water from the environment is continually entering tissues.The diffusion gradient favors loss of solutesTherefore there is a need to regulate solutes and water
27 Two ways to deal with osmotic problems Keep your internal concentrations the same as the environment (osmoconformer)Regulate your internal concentrations (osmoregulator)
28 Solute regulation Transport solutes across the body surface Note: even in the jellyfish example, there is ion regulation. Although the internal fluids have the same osmolarity as seawater, they do not have the same composition
30 Passive transport: Diffusion Works for lipid soluble molecules and gasesNo good for most water soluble molecules and ions
31 Passive transport: Facilitated diffusion Generally used for ions, larger molecules, non-lipid soluble molecules.Must be a gradient favoring diffusion
32 Active transportWorks for ions and molecules like glucose or amino acidsCan transport against a gradient.Costs energy, usually ATP
33 In this diagram, how might sodium get across the membrane? A) diffusionB) active transportC) facilitated diffusion or active transportNa+Na+Na+Na+
34 In this diagram, how might sodium get across the membrane? A) diffusionB) active transportC) facilitated diffusion or active transportNa+Na+Na+Na+Na+Na+Na+Na+Na+Na+Na+Na+
35 In this diagram, how might sodium get across the membrane? A) diffusionB) active transportC) facilitated diffusion or active transportNa+Na+Na+Na+Na+Na+
36 In this diagram, how might steroids get across the membrane? A) diffusionB) active transportC) facilitated diffusionD) all of the abovesteroidsteroidsteroidsteroidsteroid
37 In this diagram, how might steroids get across the membrane? A) diffusionB) active transportC) facilitated diffusionD) all of the abovesteroidsteroidsteroidsteroidsteroidsteroidsteroidsteroidsteroidsteroidsteroidsteroidsteroidsteroidsteroid
39 What type of active transport is this? A) uniportB) symportC) antiportK+
40 What type of active transport is this? A) uniportB) symportC) antiportK+Sodium potassium ATPaseNa+
41 What type of active transport is this? Cl-A) uniportB) symportC) antiportK+
42 Responses of soft-bodied invertebrates to changes in salinity Marine invertebrates can often be exposed to salinity changes (e.g., tidepool drying out, estuaries)If salts enter the body, pump them out using transportersIf salts are leaving body, take them up from the environment using transportersOr just let your internal concentrations follow changes in the environment
43 Dumping/pumping amino acids One way to respond while keeping internal ion concentrations the same is to pump amino acids out.Often used by bivalves living in estuariesClams, oysters, mussels
44 Estuary - high tide1000 mosm/L1000 mosm/Laaaaaaaaaaaaaaaa
47 Advantages of amino acid osmoregulation Changing amino acid concentrations is less disruptive on internal processes (enzyme function).Costs: pumping amino acids (can involve ATP), loss of amino acids (carbon and nitrogen)
48 Osmoregulation in other aquatic organisms Example: fishes maintain internal concentration of solutesBody volume does not changeInvolves energetic cost of active transportIn bony fishes this can be 5% of metabolic rate
50 Marine fishes Problem: lower internal osmolarity than seawater Water will leave body, sea salts will go inSolution: Fish drink large amounts of seawater, then transport out ions (Na+, Cl-) at their gill surface or in urine (Ca++, Mg++, SO4--).
52 Freshwater fishesThe opposite situation: tendency to lose solutes and gain waterSolutions: take up salts in food and by active transport across gillsEliminate water via copious dilute urine production
53 Water balance on landUnlike aquatic animals, terrestrial animals don’t lose or gain water by osmosisHowever, water loss or solute gain can be a major problemCells are maintained at around 300 mosm/LHumans die if they lose 12% of their body water
54 Why not just prohibit water loss? Impermeable surfaces: waxy exoskeleton (insects), shells of land snails, thick skin (vertebrates).Not all surfaces can be impermeable because gas exchange must also occur.Evaporation across respiratory surfaces is only one of the two main causes of water lossThe other is urine production
55 Drinking Replenishes water that is lost Water can also be gained by moist foodsWhat if there is no water to drink?
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