Osmolarity versus tonicity, and how we regulate water levels.
Osmolarity versus tonicity, and how we regulate water levels. ZO331
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This 3 page Class Notes was uploaded by Cody Brazel on Sunday September 13, 2015. The Class Notes belongs to ZO331 at Southeast Missouri State University taught by Dr. siegel in Spring 2015. Since its upload, it has received 46 views. For similar materials see animal physiology in Biology at Southeast Missouri State University.
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Date Created: 09/13/15
ANIMAL PHYSIOLOGY NOTES FOR WEEK 97911 2015 Osmolarity The concept behind osmolarity can be a difficult concept to get over in classes such as physiology One of the first confusing references in physiology is the difference between hypoosmotic and hypotonic as well as hyper o Hypotonic hypertonic and isotonic refer to the concentration of solutions on either side of a permeable membrane such as the lipid bilayer of our cells Cells that are hyperosmotic mean that they will begin to intake water and vice versa for hypotonicity This is caused by the natural tendency for water to flow towards areas of less water if a cell has more solutes hypertonic it has less water than it s surroundings sotonic cells are in equilibrium with their environment 0 Hyperosmotic hypoosmotic and isosmotic refer to how water will move across membrane In my understanding osmolarity is not concerned with measuring solute concentration it merely measures HOW WATER WILL FLOW Dr Siegel gives a multitude of examples of freshwater fish 0 Within the fish they have an osmolarity of 400mOsM with the water being around 3mOsM In this environment the fish is considered to be Hyperosmotic and the surrounding water hyposmotic Water will always move towards areas of lower osmolarity to higher osmolarity due to increased levels of water molecules in the hyposmotic environment Since there is more water in the surroundings the surrounding water molecules will continuously try to diffuse into the fish s cells Mechanisms of Osmoregulation In this section we will go over the different types of osmoregulation between freshwater fish saltwater fish and terrestrial organisms such as humans 0 Freshwater Fish 0 Since Freshwater Fish have a lower internal water potential than the outside water molecules are constantly attempting to diffuse into the fish and dilute its blood Fresh water fish regulate their water levels via three different methods Drinking very little water production of hyposmotic uring and active intake of salt through gills 1 The first method is very simple If you are trying to prevent water intake don t drink In terms of the second mechanism The urine that is produced by the fish is extremely diluted compared to the blood plasma meaning the urine is hyposmotic compared to the fish and this ensures that large amounts of water are expelled from the fish along with the urine makes the fish more hyperosmotic this makes sense because the fish is producing hyposmotic products which will in turn make it more hyperosmotic Lastly fish replace the loss of ions via constant diffusion via special gills that function with a unique mechanism The gills of the fish are excreting bicarb and hydrogen ions due to metabolic processes As the bicarb and hydrogen ions are pumped out necessary ions are absorbed into the blood plasma Since the absorption of ions happen indirectly via the primary excretion of bicarb this sort of ion transport is considered secondary active transport Salt water fish have the opposite problem than freshwater fish surprise Since they have a lower osmolarity than the surrounding environment water is constantly diffusing out the fish and into the environment To combat this saltwater fish do the exact opposite of freshwater fish 0 They drink large quantities of water 0 They produce very little urine that is isosmotic to the environment 0 Salt glands constantly excrete salts Terrestial organism have it rough in that the environment they are in land is arid and very hyperosmotic to the organism Because of this terrestrial organism had to develop complex processes and mechanisms to conserve water this takes a lot of energy Most of this conservative process takes place in the kidneys o Terrestial organism lose water via urination skin evaporation and respiratory evaporation breathing 1 Organisms have to urinate because cellular respiration and break down of proteins inevitably creates nitrogen waste This waste is nearly unusable by the body and is quite toxic Since nitrogen waste is water soluble ammonia is water soluble organisms must devote some quantity of water towards diluting it and excreting it Water is inevitably lost though the skin via simple evaporation Even organisms like humans that can control the rate of evaporative loss do not have perfect mechanisms to seal water Thus some water is lost at all times through evaporation While breathing water within the body can condense in the form of water vapor and be expelled from the body Ever seen your breath during a cold day It is the process of cold air reaching the warm air of your body that promotes condensation of water vapor and eventual exhalation Because of this water can be lost during breathing o Terrestial organisms mitigate water loss via drinking metabolism and the kindeys 1 Naturally the easiest to obtain water that has been lost is the drink it Water that we humans drink is called preformed water and it is vital to our survival 2 Cellular respiration creates water as a byproduct along with carbon dioxide ATP and heat So simple metabolic processes produce some amount of water 3 The kidneys of terrestrial organisms are capable of producing urine that is rich in solutes and is hyperosmotic to the blood plasma Since this type of urine is rich in solutes and low in water concentration water has been conserved by the organism Remember a hyperosmotic solution has less water potential therefore less water ie the urine than a hyposmotic solution therefore more water ie the blood plasma of human for example This will end the notes for this week Next week s notes will be in the form of a study guide Since the test is the 2239 In the study guide concepts over the first three weeks of school will be covered along with the intricacies of the nephrons within the kidneys