Zool 241 Lecture 2 - Water PDF

Zool 241 Lecture 2 - Water “The animal and its environment are one” Is this true? If we believe this, what happens when we change the environment? What must organisms have the ability to do? To regulate their internal conditions using… Homeostasis Standing in one position… B...

Zool 241 Lecture 2 - Water “The animal and its environment are one” Is this true? If we believe this, what happens when we change the environment? What must organisms have the ability to do? To regulate their internal conditions using… Homeostasis Standing in one position… But implicit in this is that change happens. So, what must systems have? Water Cornerstone of life on this planet Unique properties: Unique structure and polarity Liquid, frozen structures and hydrogen bonds… Ties all things together Is a great heat sink Incompressible and thick Viscous Dissolves many things Ions Gases Almost everything… at some concentration Water - structure Water – a binding agent for life Water – phase transition and surface tension Removing heat may increase structural order, i.e. form ice What if this did not occur??? Adding heat may enable the breaking of the hydrogen bonds and the formation of water vapor At a large range of temperatures, water will have a surface tension with respect to air above This tension is an invaluable interface for life to exist under and above Example animal, the mosquito https://www.youtube.com/watch?v=toWVK1LGNJQ  Water – surface tension A unique predator-prey interface The harder you push it, the harder it pushes back Example: the Jesus Christ Lizard, Basiliscus basiliscus https://www.youtube.com/watch?v=45yabrnryXk https://en.wikipedia.org/wiki/File:Basiliscus_basiliscus_running_on_water_-_pone.0037300.s001.ogv Water and heat Water and all of its bonds can absorb a great deal of heat There is a high ‘latent heat of vaporization’ (energy or ‘enthalpy’ to turn a liquid to a gas) One of the reasons we sweat Conversely, water can be used to store heat Life takes advantage of the water-heat relationship Most life Water – incompressible and thick There are no free ‘spaces’ in water… consequently, you can’t make room in it, you can only push it out of the way (Exception… gases and ions) What happens when you put water in a bottle and squeeze it then? Volume must change, right? What happens to animals that live under huge volumes of water? Huge pressures mean major adaptations, such as to gases Gas in water is under pressure The more pressure, the more gas in solution. Example, diving and ‘the bends’, i.e. decompression sickness (DCS) Water - viscosity What happens if an animal needs to move water? It will take energy Moving water or fluids from one place to another is called ‘bulk flow’ Example: https://en.wikipedia.org/wiki/Real-time_MRI  Water - Ions Water is typically full of ‘stuff’, even freshwater Some of the most important solutes are ions: Anion – charge unbalanced to the negative, i.e. more electrons than protons Cation – charge unbalanced to the positive, i.e. more protons than electrons Why do ions readily dissolve into water? Polarity Dipole Water Ammonia (NH3) Carbon dioxide (CO2) Water - ions Adding salt to water will increase fluid mass but strangely, not water volume… why? Believed to be due to the ordering of water around ions… ions are not sitting randomly in water. Example, the hydration shell of sodium: Consider, if a cell needs to move sodium, is it just moving sodium? What kind of bonds must be broken if just sodium were to be moved?  A mimic of Na+ and hydration shell: Tetrodotoxin (TTX) Found in pufferfish (Tetraodontiformes), toads, flatworms Derived from bacteria (Pseudomonas and Vibrio) Numbness of lips and tongue  paresthesia of extremities muscle fatigue bradycardia, hypotonic blood pressure respiratory failure and muscle paralysis By Jenny (JennyHuang) from Taipei - Flickr TTX Blocks voltage-gated Na+ channels Guanidinium moiety (blue) of TTX mimics the hydrated Na+, enters the Na+ channel, covalently binds to a glutamate side group inside channel Water - hydrophobicity Some compounds hate water, i.e. are not readily miscible Consider oil and water… what is behind this? Lack of polarity This saturated chain, i.e. no C=C only C-C with H, is not polar. Non-polar compounds may have hydrophobic interactions … without this, no cellular membranes… Water – the ‘gas’ CO2 Gases exist as gases in solution… but also many dissolve into solution Water hydrolyzes with CO2 to form a very valuable ion: bicarbonate CO2 + H2O H2CO3 HCO3− + H+ Non-polar Polar  Roughly, what is the difference in [ions]? *Exceptions Major vs minor ions? * What is special * about [CO2]? 5 g/kg Figure 27.4 Salinity trends in an estuary: An incredible gradient 25 g/kg some life copes with.  Water – ionic gradients in estuaries The ‘salt wedge’ or halocline Life moves and has moved across this gradient The challenge of estuaries: too much salt and too little salt Freshwater (FW) Life Seawater (SW) By C.Bergereau - Wiki Water – measuring ‘stuff’ in it Aside from measuring gas pressures, there really are just two ways to go to examine things in water: By their individual amounts, i.e. molarity (M) Or by the aggregate amount, i.e. osmolarity (Osm) Examples: 2 moles of urea are added to 1L of pure water What is the molarity? What is the osmolarity? 1 mole of NaCl is added to 1L of pure water What is the osmolarity? Water – movement across a barrier Guiding principle of everything: Things want to move down their gradient; everything wants to even itself out Nothing can move up a concentration gradient What does this mean for water movement with respect to ions? Osmolarity of a solution dictates where water will move In the below, where does water want to move? Freshwater (FW) Seawater (SW) Water – ion movement across a barrier Guiding principle of everything: Things want to move down their gradient; everything wants to even itself out Nothing can move up a concentration gradient What does this mean for ion movement with respect to water? Diffusion of ions dictates where they will move In the below, where do ions want to move? Freshwater (FW) Seawater (SW) Experiment: Change osmolarity Water – ions and cells around a cell Ions now at a higher concentration inside the cell, so water… (1) Cell volume therefore… (2) Over time, the cell returns to normal volume by: (3) Ions now at a higher concentration outside the cell, so water… (4) Cell volume therefore… (5) Over time, the cell returns to normal volume by: (6) In these examples, cell volume was held constant by the process of homeostasis. Implicit is that the cell is regulating internal ions. **Move ions and you move water Water – cell osmolarity *Takeaway: toxic solutes are held constant; non-toxic solutes are increased. Water – an estuary and a resident Questions: Where is homeostasis occurring? Where is homeostasis not occurring?