Lecture 13: Osmoregulation on Land Part 1 Flashcards
What happens to a saltwater fish because it is hyposmotic to the ambient water?
a) Gains water by osmosis and retains salt
b) Loses water by osmosis and gains salt by diffusion
c) Loses salt and water through diffusion
d) Gains both salt and water through active transport
Answer: b) Loses water by osmosis and gains salt by diffusion
How do saltwater fish cope with high salt levels in their body?
a) By producing large volumes of dilute urine
b) By holding on to water and producing small amounts of urine rich in Mg and sulfate
c) By excreting large amounts of water with no salts
d) By storing salts in their gills
Answer: b) By holding on to water and producing small amounts of urine rich in Mg and sulfate
What process do saltwater fish use to handle monovalent ions like chloride?
a) Passive diffusion through their gills
b) Active transport, which requires energy
c) Filtration through their kidneys
d) Storage in specialized cells
Answer: b) Active transport, which requires energy
What is the primary function of gills in fish?
a) To regulate body temperature
b) To exchange oxygen (O₂) and carbon dioxide (CO₂) and regulate ions
c) To filter food from water
d) To store energy
Answer: b) To exchange oxygen (O₂) and carbon dioxide (CO₂) and regulate ions
What structure in the gills is used for oxygen and carbon dioxide exchange?
a) Gill arches
b) Secondary lamellae
c) Mitochondria-rich cells
d) NKCC1 transporters
Answer: b) Secondary lamellae
What are mitochondria-rich cells in gills also known as?
a) Lamellae cells
b) Chloride cells
c) ATPase cells
d) Filtration cells
Answer: b) Chloride cells
What is the role of Na⁺/K⁺ ATPase in gill cells?
a) To facilitate passive diffusion of gases
b) To actively transport sodium and potassium ions
c) To generate oxygen
d) To eliminate waste products
Answer: b) To actively transport sodium and potassium ions
What would happen if the sodium-potassium ATPase pump in chloride cells were inhibited?
a) Sodium would accumulate in the blood, reducing chloride excretion.
b) Chloride excretion would increase, causing a loss of ions.
c) The cell would switch to passive transport mechanisms.
d) Potassium levels in the cell would remain unaffected.
Answer: a) Sodium would accumulate in the blood, reducing chloride excretion.
If a fish experiences low environmental sodium levels, how might its chloride cells respond?
a) Increase ATPase activity to pump more ions
b) Reduce ATPase activity to conserve energy
c) Stop chloride excretion entirely
d) Begin absorbing chloride from the water
Answer: a) Increase ATPase activity to pump more ions
Which step is responsible for creating a favorable gradient for sodium to enter the cell?
a) Sodium-potassium ATPase activity
b) Passive diffusion of potassium out of the cell
c) Passive diffusion of chloride into the water
d) Increased mitochondrial activity
Answer: a) Sodium-potassium ATPase activity
In the Na⁺/K⁺ ATPase pump, for every ATP molecule used, how many sodium and potassium ions are exchanged?
a) 3 sodium out, 2 potassium in
b) 2 sodium out, 3 potassium in
c) 2 sodium in, 3 potassium out
d) 3 sodium in, 2 potassium out
Answer: a) 3 sodium out, 2 potassium in
What percentage of a marine teleost fish’s metabolic rate is used for ionoregulation?
a) 2-5%
b) 8-17%
c) 25-30%
d) 50-60%
Answer: b) 8-17%
What is the primary driver for the movement of sodium out of the blood during paracellular transport?
a) The buildup of negative charges in the gill cells
b) The direct use of ATP by sodium channels
c) The chloride gradient in the water
d) Mitochondrial production of ATP
Answer: a) The buildup of negative charges in the gill cells
How does transcellular chloride transport differ from paracellular sodium transport?
a) Chloride transport requires ATP, while sodium transport occurs between cells passively.
b) Sodium transport relies on ATPase, while chloride transport does not.
c) Chloride transport occurs between cells, while sodium transport is transcellular.
d) Both use the same electrochemical gradient but in opposite directions.
Answer: a) Chloride transport requires ATP, while sodium transport occurs between cells passively.
Why do fish migrating from freshwater to saltwater show an increase in NKCC1 and Na⁺/K⁺-ATPase abundance?
a) To absorb more oxygen for osmoregulation
b) To actively excrete excess salts in saltwater
c) To store more sodium in their cells
d) To increase water uptake through osmosis
Answer: b) To actively excrete excess salts in saltwater
What happens to the expression of NKCC1 and Na⁺/K⁺-ATPase when a saltwater fish is transferred back to freshwater?
a) Both are upregulated to retain salts
b) Both are downregulated to conserve energy
c) NKCC1 increases, while Na⁺/K⁺-ATPase remains unchanged
d) Na⁺/K⁺-ATPase increases, while NKCC1 decreases
Answer: b) Both are downregulated to conserve energy
If a trout were unable to upregulate Na⁺/K⁺-ATPase after transitioning to saltwater, what is the most likely outcome?
a) It would retain more sodium, leading to dehydration.
b) It would lose excess water, causing osmotic shock.
c) It would be unable to actively excrete sodium, leading to ion imbalance.
d) It would passively excrete chloride through paracellular transport.
Answer: c) It would be unable to actively excrete sodium, leading to ion imbalance.
A scientist keeps a trout in freshwater for 30 days and then transfers it to saltwater. What trend in gill protein expression is expected after the transfer?
a) Immediate and permanent decrease in NKCC1 and Na⁺/K⁺-ATPase
b) Gradual increase in NKCC1 and Na⁺/K⁺-ATPase over 60 days
c) Immediate increase in NKCC1 followed by a decrease in Na⁺/K⁺-ATPase
d) No change in protein expression
Answer: b) Gradual increase in NKCC1 and Na⁺/K⁺-ATPase over 60 days
If the NKCC1 co-transporter in a migratory fish were genetically inhibited, how would its osmoregulatory ability change in saltwater?
a) It would increase passive excretion of salts.
b) It would lose the ability to excrete chloride ions effectively.
c) It would compensate by upregulating paracellular sodium transport.
d) It would rely entirely on passive chloride diffusion.
Answer: b) It would lose the ability to excrete chloride ions effectively.
If a fish spends prolonged time in an environment with fluctuating salinity, what strategy might it use to conserve energy?
a) Downregulate proteins during transitions
b) Upregulate proteins regardless of environment
c) Maintain constant osmoregulatory protein levels
d) Rely solely on passive ion diffusion
Answer: a) Downregulate proteins during transitions
Why is the kangaroo rat more efficient at conserving water than laboratory rats?
a) It produces more metabolic water per gram of glucose oxidized.
b) It has lower obligatory water losses in urine and feces.
c) It breathes less frequently than laboratory rats.
d) It consumes more water-rich food.
Answer: b) It has lower obligatory water losses in urine and feces.
If a kangaroo rat loses 0.14 g of water through urine and a lab rat loses 0.24 g, what is the kangaroo rat’s primary adaptation for water conservation?
a) Greater fecal water loss to compensate
b) Reduced urea excretion in urine
c) Higher metabolic water production
d) Reduced kidney filtration
Answer: b) Reduced urea excretion in urine
What is a major problem for tetrapods living in aquatic environments?
a) Excess water absorption through the skin
b) Gaining salt while eating
c) Increased metabolic water production
d) Limited oxygen diffusion in water
Answer: b) Gaining salt while eating
How do air-breathing tetrapods reduce water loss via respiration?
a) Through specialized gills
b) By using blowholes and labyrinth nasal passages
c) By excreting salts through nasal glands
d) Through increased metabolic water production
Answer: b) By using blowholes and labyrinth nasal passages
