Biosc 0150 Foundations of Biology I Review 10 Chapter 42 Review Chapter 42 Water and electrolytes balance 1 Aquatic animals and osmoregulation a Are tissues of marine fish hypertonic or hypotonic to their environment Hypotonic b What would happen to the cells of a marine fish if it did not osmoregulate The cells would shrivel and die due to water loss c Are tissue cells of freshwater fish hypertonic or hypotonic to their environment Hypertonic d What would happen to the cells of a freshwater fish if it did not osmoregulate The cells would burst due to gain of water e What strategy do marine fish employ to regulate the osmolarity of their cells Explain your answer in terms of water solute intake or excretion Does this process require expenditure of energy Marine fish drink large quantities of water However this process brings in excess solutes The solutes are actively pumped out of the epithelial tissue of the gills Because active transport is used energy expenditure is required in terms of water solute f What strategy do freshwater fish employ to regulate the osmolarity of their cells Explain your answer intake excretion Does this process require expenditure of energy Freshwater fish excrete large amounts of water and do not drink However this process leads to the loss of solutes If the fish actively transports ions into its body through the epithelial gill tissue then energy expenditure is required The fish can also obtain solutes from its food 2 Land animals and osmoregulation a List three ways in which land animals may lose water to their environment Three possible answers are evaporation from the outside body evaporation from lung tissue and urination b Give one way in which an animal can gain water without the physical intake of liquid water or food Hint Recall cellular respiration Metabolic water can be gained when oxygen is reduced to water at the end of the electron transport chain 3 Explain why aquaporins are never phosphorylated by ATP Water is never actively transported so aquaporins never need to be phosphorylated The active transport of solutes by different membrane proteins is the driving force behind water movement 4 Explain why insects are more susceptible to water loss compared to other large organisms Insects have a large surface area to volume ratio so there is a larger area to lose water through the body by evaporation and a small volume to store water within the body a What advantages to spiracles have for insects Spiracles are adaptations for water loss control because when they are closed they can limit water loss Adel Anthony Megan Dr Swigonova Page 1 of 7 Biosc 0150 Foundations of Biology I Review 10 Chapter 42 b Suppose you were able to manipulate the amount of spiracles on an insect If you increased the amount by a lot would this be an advantage for the insect Why or why not Spiracles are advantageous for insects but increasing the amount of spiracles by too much can pose as a problem If there are a lot of spiracles water loss when the spiracles are open would be much greater when there are many spiracles which can make it harder to regulate water retention More is not always better in this case c Suppose there was an insect living in a tropical rain forest where water was plentiful and it was very humid What might the cuticle layer on this insect look like The cuticle layer would probably be thinner because the function of a cuticle is to prevent water loss due to the waxy layer that makes it impermeable to water In the rain forest water retention would not be as much of an issue so it might be advantageous to have a thinner cuticle that would decrease energy investment 5 Suppose there was a solution that was very acidic Would adding ammonia decrease or increase the pH and why Acidity is based on the number of dissolved H in solution the more H the more acidic and NH3 is a base so it will gain a proton and become NH4 This means there will be less H in solution which would increase the pH making the solution more basic a Why does too much ammonia pose as a problem for organisms Remember that enzymes have specific pH ranges in which they function best Ammonia can alter the pH of solutions to the point that an enzyme will not be able to function in that solution b List the different forms of nitrogenous waste excretions in the order of increasing water retention What is the trade off to being able to retain water Ammonia Urea Uric Acid Uric acid retains the most water of all the forms however it is energy demanding and requires specialized enzymes to make c Suppose you find an organism living in a dry desert Without knowing its evolutionary lineage what would you infer about its nitrogenous waste excretion It probably excretes a water retaining form of nitrogenous waste such as uric acid as water is rare in the desert d What about an organism living in a deciduous forest where it does rain It would be more difficult to decide without knowing its evolutionary lineage so it could probably be either ammonia or urea e Would you expect humans to ever excrete their nitrogenous wastes solely in the form of ammonia Probably not Humans are not constantly surrounded by water as fish are and it requires a lot of water to be able to excrete nitrogenous wastes as ammonia 6 Instead of blood what do insects contain and what does it consist of Insects possess hemolymph which contains oxygen nutrients waste and electrolytes a What is the function of an insect s Malpighian tubules and hindgut Both are forms of excretory organs where wastes are processed The Malpighian tubules function as a sort of pre urine creator where electrolytes and nitrogenous wastes are collected from the hemolymph which eventually empty into the hindgut for further processing for excretion b How do wastes and electrolytes diffuse into insect hindguts Insects possess two active transports a chloride pump and a sodium potassium pump As chloride and potassium accumulates inside the lumen of the Malpighian tubes a concentration gradient is created which allows water to diffuse in which allows wastes and electrolytes to follow down their concentration gradients as well Adel Anthony Megan Dr Swigonova Page 2 of 7 Biosc 0150 Foundations of Biology I Review 10 Chapter 42 c Why is it particularly advantageous for insects to have these two pumps When an insect is osmotically stressed for water or electrolytes these pumps can allow for reabsorption of water and electrolytes back into the hemolymph d Though