Topic 7: Tonicity and Osmoregulation

What is osmosis?

The movement of water across a semipermeable membrane (low solute concentration to high solute concentration)

What is tonicity?

The ability of an extracellular solution to cause a cell to gain or lose water

What are the 3 types of solutions?

1. Isotonic

2. Hypertonic

3. Hypotonic

What do cells do in isotonic solutions?

Cells have no net movement of water

In isotonic solutions, the concentration of non penetrating solutes inside the cell are..?

Equal to that outside the cell

What do cells do in hypertonic solutions?

Cells lose water to extracellular surroundings (The concentration of non penetrating solutes is HIGHER outside the cell)

Where will water move in hypertonic solutions?

To the extracellular fluid

(Cells shrivel and die)

What do cells do in hypotonic solutions?

Cells gain water (The concentration of non penetrating solutes is LOWER outside the cell)

What will animal cells do in in hypotonic solutions?

Swell and lyse

(Plant cells work optimally)

(Maintains turgor pressure)

What is osmoregulation?

Cells must be able to regulate their solute concentrations and maintain water balance

Animal cells will react differently than cells with what?

Cells Walls (plants, fungi, & some protists)

What is water potential?

A physical property that predicts the direction water will flow (Includes the effects of solute concentration & physical pressure)

Water will flow from areas of:

1. High water potential to areas of low water potential

2. Low solute to areas of high solute concentration

3. High pressure to areas of low pressure

Pressure potential can be positive or negative relative to:

Atmospheric pressure

An increase in solutes causes:

Binding to more free water (This reduces water potential/expressed as a negative number)