BIO 224 Lab 5 - Osmoregulation

Osmosis

Plays a crucial role in maintaining extracellular fluid composition and internal body conditions to minimize osmosis-induced changes in cell volume.

The only method by which water moves to and from cells.

Diffusion of water (water movement)

Dependant on a gradient in solute concentration across the plasma membrane. Always moves from an area of low solute concentration to high solute concentration. Governed during osmosis by thermodynamic considerations invovling the solutes and their interactions.

Plasma membrane

Aquaporin

Isotonic

Hypotonic

Hypertonic

Osmolality

Semipermeable membrane

Osmoregulation

Hemolysis

Crenation (as applied to cells)

Osmoregulators

Animals that maintain body solute concentrations different from the environment. (all fresh water animals, body weight dependant on the osmotic concentrations existing in their environment)

Osmoconformer

Animals that do not maintain their osmotic concentrations different from their environment. (some marine animals)

Freshwater blood concentration

250 to 400 mOsm

Seawater blood concentration

About 1000 mOsm

2 problems land invertebrates have associated with osmoregulation

• salts have to be consumed as they are not readily available on land

• water must be obtained and persevered within the animal since evaporation from the body will always occur

Function of external skin of terrestrial invertebrates

Let oxygen in and carbon dioxide out as well as preventing water and ion loss.

Metanephridia

A highly developed organ system in annelids that accomplishes excretion and osmoregulation.

Hydrophobic barrier

Restrict the movement of most solutes to and from cells.

Describe the function of aquaporins.

Where in the human body are ther membrane proteins found?

Why is it a bad idea for humans to drink sea water?

Describe how osmoregulatory challenges differ between the marine, freshwater and terrestrial environment for vertebrate animals.