Osmolarity and Tonicity

What is diffusion?

Process through which atoms or molecules intermingle because of their random thermal motion

What is net diffusion?

Directional movement due to a greater concentration in one location compared to another

What are the factors that affect the rate of net diffusion?

1. Area of contact: greater area = diffusion faster

2. Concentration gradient: larger concentration gradient = faster rate of diffusion

3. Size of molecules: smaller molecules move faster

4. Distance: diffusion is faster for short distances

What is osmolarity?

Number of particles in a solution

What are non-electrolytes?

• Molecules that do not dissociate when placed in solution

• Ex. sucrose or urea

• Molarity = osmolarity

What are electrolytes?

• Molecules that dissociate in solution

• Molarity (mM) x dissociated # = osmolarity (mOsm)

What is isosmotic?

• Two solutions have equal number of solute particles per unit volume

  • Generates same osmotic pressure

What is hyperosmotic?

One solution generates more osmolarity than another (A hyperosmotic to B)

What is hypoosmotic?

One solution generates less osmolarity than another (B hyposmotic to A)

What is osmosis?

Net movement of water molecules from the area of lesser concentration to the area of greater concentration

What is tonicity?

Tonicity describes the solution relative to the cell

What is isotonic?

• No net movement of water

  • No effect on cell

What is hypotonic?

• Water moves into cell because cell is concentrated

  • Lysis: cell swells and burst

What is hypertonic?

• Water leaves cell because outside cell is more concentrated

  • Crenation: cell shrinks