Salinity and osmosis

Question 1

How is nitrogenous waste excreted in eukaryotes in aquatic organisms?

Answer 1

in the form of ammonia, which can be quickly carried away

Question 2

what salinity is salt water?

Answer 2

35

Question 3

What temperature does salt water freeze at?

Answer 3

-1.86 degreec C

Question 4

what is an osmoconformer?

Answer 4

an organism in which the internal osmostic concentration is approximately isoosmotic with the surrounding seawater

Question 5

what is an osmoregulator?

Answer 5

an organism which has to regulate the ionic and osmotic composition of their body fluids since they are often found in variable habitats, or migrate between habitats

Question 6

Name a species that regulates its salt content for improved buoyancy and explain how

Answer 6

Aurelia/common jellyfish exchnage sulphate ions for less dense ammonia and potassium ions

Question 7

Give a behavioural mechanism organisms may use to avoid exposure to extreme conditions

Answer 7

burrowing

Question 8

How do cells maintain an isosmotic intracellular composition?

Answer 8

regulate amino acids by breaking down or synthesising proteins.

Question 9

What is the main amino acid used in intracellular osmotic regulation?

Answer 9

glycine, and betaine or TMAO in higher organisms (e.g. cephalopods)

Question 10

What is a disadvantage of intracellular osmotic regulation?

Answer 10

it changes the electrochemical environment around proteins, including enzymes

Question 11

which amino acids are not used in osmotic regulation?

Answer 11

lysine and arginine, because they alter protein’s tertiary structure

Question 12

What is a hypotonic regulator?

Answer 12

organisms that maintain a low internal ionic concentration, i.e. marine vertebrates, that regulate ionic composition but not necessarily their total osmotic concentration

Question 13

How can organisms regulate their intracellular osmotic concentration without increasing their ionic levels?

Answer 13

by the accumulation of urea and TMAO

Question 14

Give a disadvantage of the accumulation of urea

Answer 14

it destabilises protein structure by lowering the denaturation temperature

Question 15

Give an advantage of using TMAO in addition to urea

Answer 15

the accumulation of TMAO may offset the negative effects of urea by stabilising proteins and increasing denature temperature

Question 16

How do marine vertebrates actively regulate their ionic concentration?

Answer 16

they remove ions that diffuse through gills and secrete them out through specialised removal mechanisms, e.g. cloacal gland extracts salts and deposits them into the cloaca

Question 17

What does it mean for a marine teleoist to be a true hypo-osmotic regulator

Answer 17

the composition of their body fluids are just a fraction of saltwater concentration

Question 18

How do marine teleosts counteract osmotic water loss?

Answer 18

they drink sea water, which is removed of chloride ions by large specialised chloride cells in active transport, and is followed by the passive removal of sodium ions.

Question 19

How do birds and reptile maintain an isosmotic internal concentration when they ingest a large amount of saltwater?

Answer 19

they have salt glands in their head which secrete hyperosmotic NaCl solution

Question 20

How does the chinese swamp turtle uniquely reduce urinary water loss?

Answer 20

it excretes urea through specialised glands in its mouth

Question 21

How can dolphins and whales ingest salt water without disrupting their isosmotic composition?

Answer 21

their kidneys form a concentrated urine of around 820mM Cl-.

Question 22

Name the 3 basic processes that make up a tubular filtration system of metabolically active organisms?

Answer 22

filtration, selective reabsorption/secretion, excretion.

Question 23

What is a protonephrial system?

Answer 23

tubules spread across the body. Beating cilia force interstitial fluid into the gut, where specialised cells with ionic channels and intermembrane pumps to reabsorb important ions in exchange for less useful CL- ions

Question 24

What is a metanephridial system?

Answer 24

has an internal opening (nephrostome) with funnel structure, allowing body fluids to pass along a convoluted tubule system, where lining cilia move to generate a unidirectional flow.

Question 25

What is the function of antennal/green glands in crustacea?

Answer 25

similar to kidneys - sac at top allows for diffusion of body fluids across wall of coelomosac, followed by labyrith to increase SA for selective reabsorption before nephridial canal.