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Biology of Cells and Organisms (sem 1) > Regulating Body Fluids > Flashcards

Regulating Body Fluids Flashcards

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1
Q

What do intracellular and extracellular fluids contain?

A
  • complex solutions consisting of solutes dissolved in a solvent (solvent being water)
  • these solutes include ions such as Na+ and K+, as well as organic molecules such as glucose, fatty acids and lipids
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2
Q

What is osmolarity and what is its unit?

A

Osmotic concentration, aka concentration of all osmotically active solutes known as osmolytes. (E.g na+ and cl- are osmolytes of nacl). Unit is Osm/L

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3
Q

Is osmolar concentration always equal to molar concentration?

A

No for solutes that dissociate. E.g 1M NaCl has molar concentration of 1 and osmolar concentration of 2 Osm/L. 2 because dissociates into two ions Na+ and Cl-

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4
Q

What is tonicity? What three terms describe it?

A

Concentration of non-permeable solutes (cannot cross semi-permeable membrane).
Hypertonic, hypotonic and isotonic.

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5
Q

What is a hypotonic solution?

A

Extracellular fluid has lower osmolarity than fluid inside the cell. Therefore net movement of water into the cell. (Hypo means less than)

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6
Q

What is a hypertonic solution?

A

Extracellular fluid has higher osmolarity than fluid inside the cell, therefore net movement of water out of cell

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7
Q

What is an isotonic solution?

A

Extracellular fluid and fluid inside cell are equal in osmolarity

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8
Q

What important aspects of the extracellular environment (surrounding animal’s cells) are regulated?

A

Major ions such as Na+ and Cl-, organic solutes, gases including O2 and CO2, pH and temperature

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9
Q

What is homeostasis?

A

Constancy of extracellular environment

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10
Q

Why is body water and solutes regulated?

A
  • in order to achieve homeostasis (constancy of extracellular environment)
  • exact and relative concentrations of solutes in body fluid are critical for proper chemical functioning
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11
Q

What is the way in which an animal regulates osmotic concentration determined by?

A

Surrounding environment.

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12
Q

What is an osmoconformer?

A

Animal allows the osmotic concentration of their extracellular fluids to equal that of their external environment. E.g iso-osmotic to seawater

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13
Q

What kinds of animals are osmoconformers?

A

Marine invertebrates.

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14
Q

What characteristics of the marine environment enables marine invertebrates to osmoconform?

A

The constancy of the seawater environment (e.g osmotic concentration, ion concentration, pH, temperature, gases) means that marine invertebrates do not require homeostatic mechanisms to regulate these variables.

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15
Q

Do osmoconformers live in environments where salinity changes very little or fluctuates a lot? Why or why not? Are they therefore stenohaline or euryhaline?

A
  • osmoconformers live in environments where salinity changes very little
  • this is because they cannot cope with large changes in body salinity
  • osmoconformers are therefore stenohaline
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16
Q

What type of homeostasis do osmoconformers use and how does it work? Is it active or passive?

A
  • Equilibrium homeostasis

- constancy of extracellular environment is achieved passively by simply being in equilibrium with their environment

17
Q

What does stenohaline mean and does it apply to osmoconformers or osmoregulators?

A
  • an animal that relies on passive homeostasis and has little tolerance to change in external environment
18
Q

What are the advantages and disadvantages of being an osmoconformer?

A

Benefit: conserve more energy to fuel other biochemical reactions or physiological processes as they do not need to use energy in regulating extracellular environment independently of external environment

Disadvantage: cannot easily control osmotic concentration if sudden extreme change occurs in environment

19
Q

What is an osmoregulator?

A

An animal that regulates extracellular osmotic concentration independently of external environment.

20
Q

What kinds of animals are osmoregulators?

A

Marine vertebrates, freshwater and terrestrial animals

21
Q

Do osmoregulators live in environments where salinity changes very little or fluctuates a lot? Why or why not? Are they therefore stenohaline or euryhaline?

A
  • live in environments where salinity changes a lot
  • this is because they can cope with a wide range of salinities
  • therefore euryhaline
22
Q

In terms of water and solute balance, what problems are faced by marine osmoregulators? How are these solved?

A
  • body fluid is HYPOTONIC to seawater (has lower tonicity and osmolarity than seawater)
  • high loss of water from body as water moves from region of high water potential to region of low water potential
  • LOSE water from body fluids to seawater via osmosis occurs across skin, gills if present, and in excretion of urea and faeces
  • water is replaced by animal drinking lots of seawater
  • problem is that seawater contains a lot of ions which enter the animal’s body passively via diffusion
  • not enough water, too much salt!
  • the influx of excess ions is counteracted by the animal releasing small amounts of concentrated urine and actively secreting ions either across gills, by kidneys or by salt glands
23
Q

In terms of water and solute balance, what problems are faced by freshwater osmoregulators? How are these solved?

A
  • body fluid is hypertonic to freshwater (body fluid has greater osmolarity and ion concentration than external environment)
  • therefore water will ENTER body via osmosis as it moves from region of high water potential to region of low water potential
  • lose solutes by passive diffusion
  • problem is too much water, not enough salt
  • this is counteracted by the animal producing lots of dilute urine to remove water
  • animal will not drink water
  • possess organs that actively retain salts (kidneys, gills)
24
Q

How do gill epithelial cells help freshwater osmoregulators?

A
  • pump Na+ and Cl- ions from water flowing over gills INTO blood
  • therefore increase solute concentration of blood
25
Q

How do gill epithelial cells help marine osmoregulators?

A
  • pump Na+ and Cl- ions from water flowing over gills OUT OF blood into water
  • therefore decrease solute concentration of blood
26
Q

How does the kidney function differ between marine and freshwater osmoregulators?

A

Marine: kidney tries to concentrate urine as much as possible, produces very small amount of urine to prevent loss of water

Freshwater: kidney produces lots of dilute urine

27
Q

How do salmon cope with life in both salt and freshwater?

A

Background: salmon are born in fresh water then migrate to ocean and spend years maturing at sea, then return to freshwater to breed
- kidneys as gills of salmon must therefore cope with both marine and freshwater conditions

  • this is achieved via acclimatisation. Salmon need to spend several days in brackish water at river mouth (water that has slightly more salinity than freshwater) to ACCLIMATISE
  • kidney function must change and Na+ and Cl- gill pumps must reverse direction.
28
Q

In terms of water and solute balance, what problems are faced by terrestrial osmoregulators? How are these solved?

A

Background: obligate osmoregulator, few problems with ion concentration

  • problem is not enough water in environment especially for desert animals
  • water is also lost from animal via evaporation and in urine and faeces

Solutions:

  • water is obtained from food including via metabolic water production (example: camels metabolise fat stored in humps, byproduct of this process is H2O)
  • respiratory surfaces kept inside to prevent them from drying out
  • some animals absorb water through skin and anus
  • insulate skin with hair which can change microenvironment to allow water in or out)
  • minimise water loss during waste excretion by concentrating urine
29
Q

How do thorny devils cope with life in the desert?

A

possess special adaptations:

  • specialised skin texture to capture dew and rainwater
  • scales surrounded by tiny interconnected channels that attract water
  • water is then funnelled into mouth
30
Q

What product of the metabolism of protein must be excreted?

A

Nitrogen

31
Q

What is the difference between excretion and elimination?

A

Excretion - via urine

Elimination - via faeces

32
Q

What is the FIRST product of protein metabolism and how do aquatic animals deal with it?

A
  • toxic ammonia NH3

Excreted by aquatic animals

33
Q

What do terrestrial organisms do with toxic NH3? How does this differ between terrestrial species?

A
  • convert toxic NH3 into non toxic form

Soluble urea in some invertebrates and mammals
Insoluble uric acid in reptiles and birds
Insoluble guanine in spiders and scorpions

34
Q

What is the kidney and what is its main function?

A
  • the kidney is the principle excretory organ of vertebrates

- its main function is to regulate the excretion of solutes and water

35
Q

What do juxtamedullary nephrons allow mammals to do?

A

Concentrate their urine

36
Q

What are the 4 key functions of a nephron?

A
  • filtration of all blood plasma except RBC and large proteins which occurs in renal tubule
  • reabsorption of ions (e.g sodium and chloride) and organic molecules(e.g glucose and vitamins) which re-enter blood
  • secretion of some ions (e.g K+, NH4+, H+) from blood into renal tubule
  • osmosis which controls amount of water in body (osmodilution and osmoconcentration)
37
Q

How does osmoconcentration in the mammalian kidney work?

A
  • juxtamedullary nephrons establish high osmotic concentration in the inner medulla
  • thick ascending limb of loop of Henle actively pumps ions out of filtrate
  • this causes water to move by osmosis out of the tubule which is then reabsorbed by the body
  • countercurrent multiplication establishes concentration gradient outside ducts
  • osmosis of H2O out of collecting duct and thin descending limb concentrates urine
38
Q

Why is the loop of Henle especially long in desert dwelling animals?

A
  • maintain as much water as possible before it gets converted into urine
39
Q

What will the loop of Henle’s length be when H2O upkeep isn’t as important?

A

Will be shorter in length

Biology of Cells and Organisms (sem 1) (17 decks)

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