Osmosis & Tonicity This is going to show how cells transport substances in and out. 1

Osmosis through an Egg Membrane Check your results!

Diffusion across a membrane Semipermeable membrane The Plasma Membrane 12/4/2018 Osmosis Diffusion of water across a membrane Moves from HIGH water potential (low solute) to LOW water potential (high solute) Diffusion across a membrane Semipermeable membrane 3 G. Podgorski, Biol. 1010 3

Let’s take a closer look!

If the Solute can move through the membrane, it will diffuse until it reaches Equilibrium BUT WHAT IF the solute could not pass through the membrane? Can both sides reach equilibrium?

If the solute (purple) cannot get past the membrane, can the 2 sides of the tube reach equilibrium? What do you think will happen?

The solute cannot move, but the WATER can!!

Salt SUCKS! Sugar SUCKS! Solutes SUCK! Solutes will “suck” water to balance out the solute concentration Not Equal Equal concentration

We label solutions as hypertonic, hypotonic, or isotonic to help us understand the location of the highest solute concentration.

Hypotonic—Lower concentration of solute in solution (Sugar, Salt, etc Isotonic—Same concentration of solute in solution Hypertonic—Higher concentration of solute in solution

Hypotonic Solution “Hypo” = below or less Higher solute concentration inside the cell Water will move into the cell Cell will swell and burst (lyse) If the solution is HYPOtonic, then inside the cell is HYPERtonic

Hippo – Hypo: both are enlarged Hypotonic solution Hippopotamus Red Blood Cell in Hypotonic Solution Hippo – Hypo: both are enlarged

Isotonic Solution “Iso” = same Solute concentration is the same on both sides of the membrane Water will show no net movement Cell will show no change in size

Isotonic Solution Helpful Visual Red blood cell in Isotonic Solution isosceles triangle Both refer to something that is the same

Hypertonic Solution “Hyper” = more or greater than Solute concentration is higher OUTSIDE the cell Water will move OUT of the cell Cell will shrivel and die If the solution is HYPERtonic, then inside the cell is HYPOtonic

NO NET MOVEMENT OF H2O (equal amounts entering & leaving) The Plasma Membrane 12/4/2018 Isotonic Solution Hypotonic Solution Hypertonic Solution NO NET MOVEMENT OF H2O (equal amounts entering & leaving) CYTOLYSIS PLASMOLYSIS 17 G. Podgorski, Biol. 1010 17

Cytolysis & Plasmolysis The Plasma Membrane 12/4/2018 Cytolysis & Plasmolysis Cytolysis Plasmolysis G. Podgorski, Biol. 1010 18

What would happen to the animal cells in each beaker? 100% Distilled Water 80% H2O 70% Water 30% Dissolved Substances 80% H2O 80% Water 20% Dissolved Substances 80% H2O Ask the students to predict what would happen to the cells in the beaker. You may want to explain solutions first. Dissolved substances would be sugars, salts, ions, etc.

Which way did the water move? 100% Distilled Water 80% H2O Have the students predict – and then show the answer. You have to click to get the beaker and the question to show. Why did the cell get so big?

Which way did the water move? 80% Water 20% Dissolved Substances 80% H2O Predict and show answer. Why did the cell stay the same size?

Which way did the water move? 70% Water 30% Dissolved Substances 80% H2O Predict and show answer. Why did the cell get so small?