Ch. 28 Study Questions

List and briefly explain three factors that determine the rate of passive exchange of water and ions.

1) The magnitudes of the osmotic and ionic gradients between the blood and ambient water 2) the permeability of an animal's outer body covering to water and ions 3) the surface area across which exchange is occurring. Any change (increase or decrease) in these factors, will have an effect on the rate of passive exchange.

The integument of freshwater crayfish is no more than _______ as permeable to water and sodium as the integument of marine decapods of the same size.

10%

MRCs are abundant with Na+-K+-ATPases. In each cell, there are about _______ Na+-K+-ATPase molecules.

100,000,000

If the osmolarity of freshwater is 100 mOsm, the freshwater animals would regulate their blood to an osmolarity of about _______ mOsm.

120

Freshwater fish lose about _______ µmoles of sodium per day.

240

If an octopus has an osmolarity of 300 mOsm, the environment it lives in must have an osmolarity of ________ mOsm.

300

In freshwater teleosts, blood osmotic pressure is _______ mOsm _______ than the osmotic pressure of freshwater.

300; higher

If the potassium concentration in a squid's body fluid is 22 mmol/kg of H2O, the intracellular potassium concentration is _______ mmol/kg of H2O

400

If the sodium concentration in a squid's body fluid is 456 mmol/kg of H2O, the intracellular sodium concentration is _______ mmol/kg of H2O.

5

Marine teleosts that live in the ocean where the seawater has an osmotic pressure of 800 mOsm have an osmotic pressure of _______ mOsm.

500

The blood osmotic pressure of marine teleosts is about _____ mOsm _____ than the environmental osmotic pressure.

600; higher

If the blood osmolarity of a freshwater animal is 100 mOsm, the freshwater osmolarity is about _______ mOsm.

90

Which structure in crayfish is analogous to the kidney?

Antennal gland

Overall, which animal represented in the graph is the best osmotic regulator?

Brine shrimp

Taking into account both numerical scales and shape on both graphs, which line most closely represents that of a Pacific salmon?

Brine shrimp

Which organism has the highest concentration of potassium ions in their plasma?

Brown trout

The bicarbonate that is pumped out of the gills, from freshwater fish into the water, comes from

Carbon dioxide

If you were to apply an inhibitor that shuts down the mitochondria, what would occur in the gills of freshwater fish?

Chloride cells would cease to function

Which statement about chloride movement in frogs is false?

Chloride movement is directly associated with proton movement.

Which animal has the lowest osmotic U/P ratio?

Crayfish

Which organism has the highest concentration of sodium ions in its plasma?

Crayfish

What is the greatest contributor to total water loss in this animal?

Evaporation

Which animal has the highest weight-specific total rate of evaporative water loss?

House wren

Why is preformed water in food not a consistent value?

Humidity affects the amount of water in the food.

How would you categorize the blue crab?

Hyper-isosmotic regulator

Why is the permeability of a freshwater animal's integument to water and ions relatively low?

In freshwater animals, evolution selected for this low permeability because it reduces the rates of passive water and ion exchange and thus reduces the energy costs of maintaining a normal blood composition. Low permeability slows the processes that tend to bring the blood and ambient water to equilibrium.

If you take a freshwater animal and transfer it to seawater for 60 days, what do you expect to see when you perform immunocytochemistry?

Increased aquaporin expression in the intestinal epithelia, and increased NKCC expression in the gill lamellae

Which animal is not a hyposmotic regulator?

Marine echinoderm

Which organelle is the most important in moving sodium and chloride in freshwater animals?

Mitochondria

Based on the immunohistochemistry method used, the most common proteins found in the cells of gills in freshwater teleosts are

Na+-K+-ATPases and Na+/Cl-/K+ cotransporters

Which animal has the lowest weight-specific total rate of evaporative water loss?

Ostrich

Which animal has the highest osmotic U/P ratio?

Snail

Which statement best describes the movement of sodium in freshwater fish?

Sodium is lost by excretion in urine (2-3 µmole per day) and diffusion across the body (240 µmole per day).

Which statement about sodium movement in frogs is true?

Sodium moves across the skin by energy-requiring mechanisms, and its movement regulates acid-base levels.

Which statement regarding ionic movement across the gills of marine animals is true?

Sodium moves slower than chloride because of the overall positive charge inside the gill epithelium.

Which organism is most hyposmotic to seawater?

Teleost

Describe the structure of the gills and explain another role they serve, in addition to being respiratory organs.

The gills of teleost fish carry out two major functions that serve homeostasis. In both freshwater and seawater, the gills function both as ion-regulatory organs and as gas-exchange organs. The gills are the principle sites where Na+ and Cl- are taken up from freshwater. The microscopic structure of the filament consists of a thin, principal lamellar element bearing many folds called the secondary lamellae. The secondary lamellae are highly vascularized, increasing the surface area across which O2 and ions can move inward from the ambient water to the blood.

Which statement about chloride cells is false?

They are found in the gills of freshwater fish in greater quantities than pavement cells

In an experiment in which additional aquaporins are inserted onto the pelvic patch membrane of a frog, what is most likely to occur?

Water permeability will increase

Based on the figure, is there a point where this animal is out of water balance?

Yes, but only at very low humidity.

You conduct an experiment in which you make the environment of freshwater fish highly basic. You then isolate the ionocytes and conduct an immunocytochemistry technique. Under these conditions, you would be most likely to observe _______ in Cl-/HCO3- protein expression.

a drastic increase

Freshwater animals transport sodium into their body from the environment via

active transport

Gills in freshwater crayfish provide a(n)

advantage for oxygen intake but a disadvantage for water intake.

Animals that ascend rivers from the ocean to breed are

anadromous

Animals that leave a saltwater environment to breed in a freshwater environment are known as

anadromous and euryhaline.

The chloride channels in the mitochondria-rich cells of marine teleosts are located on the _______ membrane(s).

apical

Due to chloride active transport in the gills of freshwater fish, the epithelial cells of the gills

are neutral because each chloride ion is exchanged with a bicarbonate ion.

Due to sodium active transport in gills of freshwater fish, the epithelial cells of the gills

are neutral because each sodium ion is exchanged with a proton.

You perform an immunocytochemistry technique on fish MRCs and you observe that the Cl-/HCO3- countertransport protein is expressed in greater quantities than normal. The fish must have been living in a(n) _______ environment.

basic

In mitochondria-rich cells of marine teleosts, Cl- enters the cell through the

basolateral membrane by secondary active transport and exits via the apical membrane by simple diffusion

The excess protons that fish gills pump into the environment are the product of

carbon dioxide reacting with water

Animals that leave a fresh water environment to breed in a salt water environment are known as

catadromous

If a crayfish's antennal gland is damaged, which function is lost?

chemical consistency

If the chloride concentration in a frog's environment were to decrease to 0.01 mM, chloride intake from the environment would

continue to occur by active transport

If the sodium concentration in a frog's environment were to decrease to 0.01 mM, sodium intake from the environment would

continue to occur by active transport

In frogs, if the chloride concentration in the ambient environment increased, chloride intake from the environment would

continue to occur by active transport

In frogs, if the sodium concentration in the ambient environment increased, sodium intake from the environment would

continue to occur by primary active transport.

Species that are able to survive within a broad range of ambient salinity are called

euryhaline

Freshwater animals tend to

gain water and lose ions

In adult freshwater fish, the major site of sodium exchange is the

gill

In adult freshwater teleosts, ion exchange occurs in the

gill lamellae

In adult freshwater fish, chloride exchange with the environment occurs primarily in the

gills

All freshwater animals regulate their blood osmotic pressures at levels ________ to fresh water.

hyperosmotic

Freshwater animals are

hyperosmotic regulators

Squids' inner body fluid is

isosmotic to seawater

In adult freshwater teleosts, gas exchange occurs in the

lamelle

The line represented by II represents

metabolic water production

Which organelle is most abundant in chloride cells?

mitochondria

In terrestrial amphibians, the hormone ADH (antidiuretic hormone) is released from the

neurohypophysis

If a researcher applies BAPTA, a calcium chelator (binds calcium), to the environment of freshwater fish, the

number of chloride cells in the fish will increase.

NKCCs in the mitochondria-rich cells of marine teleost are located

on the basolateral membrane

In fish, movement of sodium across the gills depends on

permeability, concentration gradient, and electrical gradient

Which substance produces nitrogen waste when catabolized?

proteins

The antennal gland opens at the base of the

second antenna

In mitochondria-rich cells of marine teleosts, chloride moves by

secondary active transport, using ATP indirectly

In early freshwater fish larvae, the major site of chloride exchange is the

skin

Species that are able to survive only within a narrow range of ambient salinities are called

stenohaline

If you were to decrease the calcium concentration in a freshwater fish's environment,

the number of its chloride cells would increase

Fresh water animals' integuments have low permeability so that

the rate of water exchange is minimized without the expenditure of energy.

The line represented by I represents

total evaporative water loss

Animals that can live in dry, water poor environments are called

xeric