Tonicity

Tonicity

Passive transport are means by which

molecules move because of their own

Inherent energy. The movement is random.

This random movement eventually produces

an equal distribution of the molecules

throughout an environment.

Tonicity

Diffusion is one type of passive transport.

If an area has a higher concentration of

a substance, this substance tends to move

toward areas of lesser concentration of that

substance until an even distribution of the

substance is achieved.

Tonicity

A drop of food coloring diffuses from an area of high concentration (the drop)to the area of low concentration ( the rest of the container).

Examples in our bodies would include the movement of glucose, oxygen, and ions.

Original photograph

Tonicity

The tendency to move to an area of lesser

concentration is a pressure or concentration

gradient. This is true in all fluids; gases and

liquids.

No energy is required to be added in order

for this movement to occur.

Tonicity

Osmosis is a special type of diffusion.

Osmosis is the diffusion of water through asemi-permeable or selectively permeablemembrane. Water molecules are smallenough to pass through the pores of themembrane but other larger molecules cannot pass through the membrane.

Tonicity

Our cell membranes are selectivelypermeable membrane.

Osmosis follows the same pressure gradientas do molecules during diffusion; they movefrom an area of high water moleculeconcentration to an area of lower watermolecule concentration. This is referred to asosmotic pressure.

Tonicity

Solution Types:• Isotonic – A solution that has the same Amount of solute as the solution it is compared to.• Hypotonic – A solution that has a lesser concentration of solute than the solution it is compared to.• Hypertonic – A solution that has a greater concentration of solute than the solution it is compared to.

Tonicity - Isotonic

Public Domain image From WikiMedia Commons

Red Blood Cells in an isotonicsolution. The amount of solute in the cells is equal to the solution.

Osmosis is taking place.Water enters and exits the cells at an equal rate. There is no net gain in cell volume or mass.

Tonicity - Hypotonic

Red blood cells in a hypotonic solution. The amount of solute in the cells is more than the solution (less solvent).

The solution has more water than the cells, a pressure gradient exists. Water moves by osmosis into the cells. The cells swell and may burst.

Public Domain image From WikiMedia Commons

Tonicity - Hypertonic

Red blood cells in a hypertonic solution. The amount of solute in the cells is less than the solution (more solvent).

The solution has less water than the cells, a pressure gradient exists. Water moves by osmosis from the cells. The cells shrink and may get a scalloped looking border.

Public Domain image From WikiMedia Commons

Tonicity

Remember these are comparative strengthsbased upon the amount of solute. • ISO means the same • HYPO means below• HYPER means greater

Solutes “suck”. A greater amount of solute “sucks” the water to it.

Tonicity

Diffusion and osmosis are importantprocesses to cells and to our bodies. Theseprocesses are part of a group of processesthat help our bodies maintain homeostasis astable internal environment. The body hasmany homeostatic processes. Diffusion andosmosis form the foundation for many ofthem.

Tonicity

Diffusion can be used by our bodies to

deliver and remove molecule to and from

our cells.

Osmosis helps us maintain fluid and

electrolyte balances in our cells.

Tonicity

In a medical situation you might require a transfusion of saline solution because of sudden blood volume loss. A saline transfusion (0.9% NaCl) is isotonic.

If you are in medical care for an extended time and require many transfused medicinesan isotonic saline can be used to periodically flush and rinse the catheter that has been inserted into a blood vessel