Osmolarity, Tonicity, and Water Balance

Flashcards covering vocabulary and key concepts from a lecture on Osmolarity, Tonicity, and Water Balance in Living Organisms.

Osmolarity

The measure of the total concentration of solute particles in a solution.

Dissociation in Solution

When a salt dissociates in solution, each of the components contributes to the osmolarity.

Millimole to Milliosmole Conversion

One millimole of a substance contributes one milliosmole to the solution.

Solute Identity vs. Number

It's not the identity of the solute; it's just the number of solutes that determines the total osmolarity of the solution.

Semi-Permeable Membrane

A membrane that is permeable to some substances but not to others.

Iso-osmotic

Compartments with the same osmolarity, resulting in no net movement of water between them.

Hypo-osmotic

A compartment with lower osmolarity relative to another, leading to water movement towards the higher osmolarity compartment.

Hyperosmotic

A compartment with a higher osmolarity relative to another, attracting water from the lower osmolarity compartment.

Tonicity

The effect a solution has on a cell.

Hypotonic Solution

A solution that causes a cell to swell and potentially burst due to water moving into the cell.

Isotonic Solution

A solution in which a cell maintains a constant volume because there is a balance of water moving in and out of the cell.

Hypertonic Solution

A solution that causes a cell to shrink due to water moving out of the cell.

Ion and Water Balance

The concentration of ions and water balance.

Body Fluid Osmotic Concentration (BFOC)

The concentration of ions in body fluid.

Isosmotic

An organism has the same internal osmolarity as its environment.

Hyperosmotic Organism

An organism has a higher osmolarity inside than the environment.

Hypoosmotic Organism

An organism has an internal osmolarity that's lower than the environment

Euryhaline Animal

An animal that is able to live over a wide range of environmental conditions.

Stenohaline

Animals that have to live in a very narrow range of environmental osmotic concentrations.

Osmoconformer

An animal whose internal osmolarity is basically the same as seawater.

Osmoregulators

Animals that are able to have an internal osmolarity that's different than their environment are.

Ionoconformers

Animals that maintain the same total osmolarity and are also conforming in terms of relative contributions of different ions.

Osmoconformers

The distribution of ions within their body in such a way as to maintain their isosmotic status

Water and Ion Balance

For all the water and ions that come into the animal, they have to be equal to water and ions leaving the animal, right? You have to have a net change of zero.

Freshwater Fish

Fish that is a hyperosmotic living well above the isosmotic line, it's getting water passively all the time because it's living in an environment that has a much lower osmolarity than its internal solution

Saltwater Fish

Fish that is super hypoosmotic can have exactly the opposite problem. It's going to be losing water all the time because it's living in an environment that has much higher osmolarity than its internal concentrations