lec 22

Question 1

in octopi, the pericardial fluid is protein free. what does this mean?

Answer 1

sac acts as the glomerulus, keeping out proteins from the ().

Question 2

1. scientists injected seawater into octopi.
2. they then withdrew some blood and injected more sea water.
3. finally, they added back the blood.
   at each step, what happened? what does this show?

Answer 2

1. urine was produced to balance out (what0
2. urine production was relatively stable. blood and SW can be inferred to be relatively similar osmolarity
3. urine prod incr once more

what we see is that urine production is largely a function of blood pressure

Question 3

in insects, the rectum is hyperosmotic but depending on the salt levels, the rectal pads may or may not absorb salts. what causes this hyperosmolarity?

Answer 3

prob nitrogenous wastes

Question 4

how exactly do rectal papillae work?

Answer 4

at resting state, intercell space is kept incredibly hyperosmotic (salts come from the gut)

water wants to get via osmosis

this hyperosmotic water will leave the lumen, but the salts will actually get resorbed, resulting in only water entering into blood

Question 5

define ammonotelic, ureotelic, and uricotelic. what are the advantages of being any type?

Answer 5

ammonotelic: secrete ammonia
- ammonia is toxic
+ in water its soluble so it dissolves readily

ureotelic: secrete urea
+ less toxic than ammonia
+ can be used as an osmolite, as seen in elasmobranchs
- req energy to convert ammonia to urea

uricotelic: secrete uric acid
- req even more energy
+ not soluble at all, which is actually really good for retaining water

Question 6

can u change your waste secretion type? why would you?

Answer 6

u can! bullfrogs do as they metamorphose from tadpoles to frogs

requires development of ornithine-urea pathway, including
1. arginase
2. arginine synthetase
3. ornithine transcarbamoylase
4. carbamoyl phosphate synthetase
[but what are the odds we’ll need to memorize this!]