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BIOL 364 > Ion and Water Balance 3 > Flashcards

Ion and Water Balance 3 Flashcards

1
Q

what animals possess salt glands (2)

A
  • reptiles
  • birds
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2
Q

salt gland location (2)

A
  • near the eye
  • drain into ducts that empty near the nostril
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3
Q

what do salt glands do

A
  • excrete hyperosmotic solutions of Na+ and Cl- (large amounts of salt in small volume of water)
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4
Q

how do salt glands produce hyperosmotic solutions (2)

A
  • ion pumps
  • countercurrent multipliers
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5
Q

how do the ion pumps of salt glands work (2)

A
  • several ion pumps take ions from the blood and pump them into the lumen of the secretory tubule
  • water cannot passively follow the ions due to the high cholesterol content of the membrane, making it impermeable
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6
Q

how does the countercurrent flow of salt glands work

A
  • fluids flow down the secretory tubule in the opposing direction of blood flow
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7
Q

what organisms have a rectal gland

A
  • elasmobranchs
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8
Q

where is the rectal gland located

A
  • empties into the digestive tract
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9
Q

function of rectal gland

A
  • accessory excretory organ that transports Na+ and Cl- from the blood into lumen of the gland
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10
Q

rectal gland ion movement

A
  • ion transport similar to ionocytes and salt glands
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11
Q

rectal gland: rate of salt excretion (2)

A
  • regulated by hormones
  • specifically, vasoactive intestinal peptide (VIP)
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12
Q

terrestrial animals: water loss (2)

A
  • across skin and respiratory surface
  • in urine
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13
Q

terrestrial animals: water gain (3)

A
  • metabolic water
  • drinking
  • food
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14
Q

what is the rate of water loss associated with (2)

A
  • surface area to volume ratio
  • there is more water loss in smaller animals that have a larger SA:V ratio
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15
Q

mechanism of water conservation: breathing

A
  • nasal countercurrent heat exchanger operates to recycle and conserve water
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16
Q

nasal countercurrent heat exchanger: inspiration (2)

A
  • incoming air is warmed and humidified in nasal cavity before entering warm lung environment
  • nose is cooled as water evaporates into the air
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17
Q

nasal countercurrent heat exchanger: expiration (2)

A
  • outgoing air is cooled and loses water before exiting
  • nose is wetted from water condensing out of the air
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18
Q

what are mammal adaptations to desert life: water intake (2)

A
  • metabolic water derived from dry seeds
  • free water is consumed from seeds
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19
Q

what are mammal adaptations to desert life: water conservation (4)

A
  • animals remain in cool burrows during daytime
  • longer nose helps condense respiratory moisture in nasal passages
  • feces are dehydrated prior to defecation
  • urine concentrated by countercurrent exchange in extralong loop of Henle
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20
Q

what epithelia are typically involved in excretion of nitrogenous wastes

A
  • the epithelia that are involved in ion and water balance (gills, kidneys, etc)
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21
Q

why is nitrogen excretion (2)

A
  • ammonium produced during amino acid breakdown is toxic and must be excreted
  • ammonic is produced from consumed proteins
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22
Q

what forms are ammonia nitrogen excreted as (3)

A
  • ammonium
  • uric acid
  • urea
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23
Q

what is the term for the animals that excrete nitrogen in the form of ammonia

A
  • ammonioteles
24
Q

what is the term for the animals that excrete nitrogen in the form of uric acid

A
  • uricoteles
25
Q

what is the term for the animals that excrete nitrogen in the form of urea

A
  • ureoteles
26
Q

what animals are typically ammonioteles (2)

A
  • most aquatic animals, including most bony fishes
  • simple invertebrates
27
Q

what animals are typically ureoteles (4)

A
  • all mammals
  • most amphibians
  • sharks
  • some bony fishes
28
Q

what animals are typically uricoteles (3)

A
  • many reptiles, including birds
  • insects
  • land snails
29
Q

what are the “special” animals in the ureotele group (2)

A
  • some larval bony fish
  • estivating lungfish
30
Q

ureotele larval bony fish (2)

A
  • produce urea because ammonium cannot leave amniotic sac
  • built up ammonium would be toxic
31
Q

ureotele estivating lungfish (2)

A
  • lungfish go into hibernation during drought, lasting multiple years
  • produce urea to decrease toxicity levels during this phase
32
Q

aquatic animal nitrogen excretion

A
  • typically excrete ammonium
33
Q

terrestrial animal nitrogen excretion

A
  • typically excrete uric acid or urea
34
Q

how can animals respond to water availability in relation to nitrogen excretion

A
  • change mode of nitrogen excretion to match the availability of water
35
Q

ammonium excretion: advantages (2)

A
  • ammonium released by deamination of amino acids, requiring little energy to produce
  • more energy efficient in aquatic animals where water is abundant
36
Q

ammonium excretion: disadvantages (2)

A
  • highly toxic
  • requires large volumes of water to store and excrete (500mL H2O per gram)
37
Q

ammonia (2)

A
  • NH3
  • gas that moves rapidly across membranes down its partial pressure gradient
38
Q

ammonium (3)

A
  • NH4+
  • more toxic form of NH3 with similar composition to K+
  • can substitute for K+ in nervous tissue, resulting in convulsions at high levels
39
Q

what is the reaction between ammonia and ammonium

A

NH3 + H+ <–> NH4+

40
Q

what is the pK of the reaction between ammonia and ammonium

A
  • pK = 9
41
Q

at pH7, how much ammonia vs ammonium will exist

A
  • 99% ammonium, 1% ammonia
42
Q

at pH7, how much ammonia vs ammonium will exist

A
  • 50% ammonium, 50% ammonia
43
Q

fish: acid trapping (2)

A
  • H+ combines with NH3 to form NH4+ in the external environment
  • partial pressure of NH3 outside remains low, which encourages NH3 to continue diffusing out of the plasma and into the environment
44
Q

fish: how does NH3 leave the plasma

A
  • it travels transcellularly and paracellularly into the environment and down its partial pressure gradient
45
Q

fish: how does NH4+ leave the plasma (2)

A
  • it cannot leave the plasma in its form
  • must be converted into NH3 as NH3 is removed down its partial pressure gradient
46
Q

fish: where does the protons that combine with NH3 come from (2)

A
  • from CO2 after it is converted to bicarbonate and H+ by carbonic anhydrase
  • H+ ATPase transports it outside of the cell
47
Q

how will low pH water affect excretion of nitrogen in fish (2)

A
  • it will elevate nitrogen excretion
  • it will encourage NH3 to be converted into NH4+, which will continue to drive more NH3 out of the cell
48
Q

how will high pH affect excretion of nitrogen in fish (2)

A
  • it will slow nitrogen excretion
  • it will discourage NH3 to be converted into NH4+, which will halt the driving of NH3 out of the cell
49
Q

uric acid excretion: advantages (2)

A
  • few toxic effects
  • can be excreted in small volume of water (10mL per gram)
50
Q

uric acid excretion: disadvantages

A
  • ATP expensive to produce
51
Q

how is uric acid excreted

A
  • as anhydrous white crystals
52
Q

why did uric acid excretion evolve

A
  • to combat water loss in terrestrial environments
53
Q

urea excretion: advantages (3)

A
  • only slightly toxic
  • relatively inexpensive to produce
  • requires relatively less water (50mL per gram)
54
Q

urea excretion: disadvantages (2)

A
  • urea is a pertubing solute, it can cause issues with macromolecule folding in high concentrations
  • buildup of urea can result in gout, the crystallization of urea in joints
55
Q

where is urea synthesized and transported (2)

A
  • synthesized in the liver
  • transported by the blood to the kidney
56
Q

how do elasmobranchs use ureas (2)

A
  • as an osmolyte to increase plasma osmolarity to be similar to seawater while keeping ion concentrations low
  • helps to prevent water loss in marine environment
57
Q

how are ureas perturbing effects counteracted in elasmobranchs

A
  • counteracted by TMAO

BIOL 364 (44 decks)

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