L15 - Osmoregualtion

Question 1

How is the volume of fluid and the concentration of solutes maintained between narrow limits in an organism?

Answer 1

1) the ability to change membrane permeability
2) Decreasing the conc grad between body fluids and the environment
3) Active Transport of ions

Question 2

What is an Osmoconformer?

Answer 2

An organism that keeps it body fluid similar to the external environment

Most marine invertebrates have body fluids that are iso-osmotic with seawater, but many still have to regulate individual ion concentrations using pump mechanism in the gills and gut

Question 3

What is an osmoregulator?

Answer 3

An organism that can maintain a body fluid osmolality that is different from the external environment

Question 4

Give the problems facing, and solutions made by hypo-osmoregulating invertebrates

Answer 4

Problems:

• water loss
• salt gain

Solutions:

• reduce permeability (rare solution method)
• low urine output
• drinking
• active excretion of salts

Question 5

Give the problems facing, and solutions made by hyper-osmoregulating invertebrates

Answer 5

Problems:

• water gain
• salt loss

Solutions:

• reduce permeability
• excrete excess water
• dilute urine
• active absorption of ions

Question 6

Give 3 examples of vertebrates that are osmoconformers

Answer 6

1) Elasmobranchs (sharks and rays)
2) Coelacanth
3) Crab eating frog - their skin is very think which can lose/gain ions and water very quickly

Question 7

Some vertebrate osmoconformers use urea retention to achieve iso-osmotic ECF. What are the 3 adaptations do they have to be able to do this?

Answer 7

1) Low urine flow rate
2) A degree of tolerance to urea (high urea destabilises protein structure)
3) MAIN POINT - make counteracting solutes such as TMAO (Trimethylamineoxide) - this after urea destabilise proteins, with stabilise/reverse them back

Question 8

What is the [NaCl] of the blood of elasmobranchs and coelacanths in comparison to seawater?

Answer 8

[NaCl] of the blood is around 30% of that of seawater

Question 9

What 3 organs is Na+ excreted out in elasmobranchs and coelacanths?

Answer 9

1) Rectal gland
2) Kidney
3) Gills - chloride cells - contain many Na+/K+ ATPase’s

Question 10

In freshwater all vertebrates are ____________

Answer 10

Osmoregulators (all are hyperosmotic - their body fluids have a higher osmotic pressure than the external environment)

Question 11

What is a T.E.P and how is it created in a Chloride cell?

Answer 11

T.E.P = Trans epithelial potential

It is created by a symport on the apical membrane pumping Na+ and K+ into the cell. Cl- follows down an electrical gradient and then moves through the cell and out the other side through a CL- channel. This creates high [Na+] and [K+] at the apical side, and high [Cl-] at the basal side, which creates a difference in potential, around 20-30mV

Question 12

How do each excrete salt?

a) marine iguanas and seabirds
b) Terrapins
c) Sea snakes

Answer 12

a) Through nasal salt glands
b) lacrimal glands
c) Sublingual glands (salivary glands)