Bios 224 Final Exam - concentration to an area of high concentration ...

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Bios 224 Final Exam

• What is osmosis?

–Answer The passive diffusion of water through a semipermeable membrane from an area of low solute concentration to an area of high concentration

• the primary mechanism by which water is transported in and out of cells
• What is osmotic pressure?

–Answer

• Mechanical pressure required to prevent move- ment of water across a semipermeable

membrane

• Measure of the tendency of water to move into one solution from another by osmosis

The higher the osmotic pressure = the more water tends to move into it

3. T / F

–Answer All particles in a solution contribute to osmotic pressure on a membrane –Answer True

• What are osmoreceptors?

–Answer Sensory receptor primarily found in hypothalamus and in kidneys of most homeothermic organisms

• Detects change in osmotic pressure
• What is an osmol?

–Answer the unit of osmotic concentration

• What is osmolarity?

–Answer 1 / 4

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A measure of osmotic concentration in number of osmoles of solutes particles per litre of solution (Osm/L or "osmolar")

• Represents the pressure equivalent to the amount of solute that dissociates in a solution
• What are osmolytes?

–Answer Soluble compounds that affect osmosis maintaining cell volume and fluid balance

• natural non-electrolytes that affect osmosis

Ex –Answer when a cell swells due to external osmotic pressure, membrane channels open and allow influx of osmolytes which carry water with them, restoring normal cell volume

• What is Trimethylamine N-oxide (TMAO)?

–Answer organic compound in the class of amine oxides (found in natural osmolytes that can act as osmoprotectants)

• A protein stabilizer that may sere to counteract urea
• Trimethylamine N-oxide (TMAO) is found in what animals?

–Answer saltwater fish, sharks, rays, molluscs and crustaceans

• What is tonicity?

–Answer A measure of the effective osmotic pressure gradient (hyper- tonic, hypotonic, isotonic)

• What is tonicity influenced by?

–Answer Influenced by the solutes in which the cells are immersed

12. T / F

–Answer Solutes able to freely cross the membrane affect tonicity 2 / 4

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–Answer False, they do not affect tonicity

• What is molarity (molar mass/L)?

–Answer Measures the number of moles per solute

• What is molality (molar mass/kg)?

–Answer Measure the number of molals per solute

• What is osmoregulation?

–Answer An essential homeostatic mechanism

• the active regulation of the osmotic pressure of an organism's body fluids
• How do fish respond to the loss of water due to the hypertonicity of seawater?

–Answer Respond to the loss by drinking large amounts of saltwater and actively excreting excess salt Ex –Answer Marine teleosts

• Lose water by osmosis
• Gain salt by diffusion into the gill tissue
• Cl-, Na+ and K+ pumped out by chloride cells in gills
• What is an osmoregulator?

–Answer Tightly regulate body osmolarity, maintaining constant internal conditions despite changes in the environment

• energetically expensive
• What kinds of animals are osmoregulators?

–Answer 3 / 4

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Freshwater and terrestrial inver- tebrates?

• What is an osmoconformer?

–Answer Maintain an internal enviro osmotically equal to their external enviroronment

• What kind of animals are osmoconformers?

–Answer Marine organisms/invertebrates

• Starfish, mussels, marine crabs, lobsters, jellyfish, ascidians and scallops and some

insects

• How do muscles survive in a broad range of external salinities?

–Answer They close their shells to seclude from unfavourable external environments

• What are craniate osmoconformers?

–Answer Hagfish, skates and sharks

• Their body fluid is isosmotic w/ seawater but their high osmolarity is maintained by making

the concentration of organic solutes unnaturally high

• Sharks

–Answer adjust their internal osmolarity according to the seawater

• What is a stenohaline animal?

–Answer An animal that can only survive in a limited range of external osmolarities

• Echinoderms like starfish, sea urchin or sea cucumber
• What is a euryhaline animal?

–Answer An animal that can survive in a broad range of external osmolarities

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