Lab Shedule
Lab 01
Lab 02
Lab 03
Lab 04
Lab 05
Lab 06
Lab 07

Cell cycle game

BIO 196 Official Website

Osmosis and Diffusion

Law of diffusion: molecules tend to move from areas of higher chemical potential to areas of lower chemical potential.

Higher Concentration >> Lower concentration

Chemical Potential :

A measure of free energy available to do the work of moving a mole of molecules from one location to another.

Water potential :

• Chemical potential per of water molecules.
• Affected by the amount of other substances (solutes) dissolved in the water
• Pure water = 0 water potential (at atmospheric pressure)
• More solutes added Negative water potential

Osmosis

Movement of water molecules from regions of higher water potential to regions of lower water potential across a semi-permeable or selectively permeable membrane.

Passive Transport: Move down energy gradient (Diffusion, Osmosis)

Active Transport: Against energy gradient

Brownian movement:

•  Molecules are in constant motion above zero temperature.

•  Motion is a form of energy.

•  Molecules are impossible to see but this movement is reveled by the jiggling called Brownian movement of minute particles suspended in water.

Place a drop of carmine suspension on a slide and cover with a cover slip. See under 40X

>> Click Here to See Video <<

Part 1 : Diffusion of Gas in a Gas

1. Wet a strip of paper with phenolphthalein
2. Add 10-20 ml of ammonium hydroxide to a 250 ml cylinder
3. Suspend the filter paper - (Should not touch ammonium hydroxide)
4. Close the cylinder

Observer...

Start	15 Mins Later

 

Part 2 : Diffusion of Liquid in a Liquid

1. Place a clear Petri dish on white paper.
2. Plastic ruler under the Petri dish
3. Pour 30 ml of distilled water
4. Allow to calm
5. Add a drop of ink of food coloring
6. Cover Petri dish
7. Find rate of discussion and record.

Part 3 : Effects of molecular weight on the rate of diffusion

NH4OH + HCL --------> NH4CL + H2O

1. Place cotton buds with NH4OH and HCL on either side and observe for white ring.
2. Check time and distance from each and calculate ratio
3. Compare with Molecular weigh

Cell membrane

•  selectively permeable

•  Dynamic - Changes and allow molecules to move.

•  Lipids and Protein

•  Water / Small polar, uncharged molecules move freely

•  Larger molecules and charged molecules move slowly or not at all

Dialysis membrane = Semi permeable

1. Dialysis tube - Add 15% Glucose + 1% starch and mix
2. Record color and rinse off the outside of bag
3. Fill beaker with water and add 4 drops of Lugol's reagent (I KI)
4. Put bag in beaker.
5. Observer
6. After color change Do benedicts test on the solution in the beaker.
7. Do benedicts test on the solution in the bag

Dialysis tube inside beaker	Dialysis Tube after 30 Mins	Benedicts Test Results A- Solution inside in beaker B- Solution in Dialysis Tube

Water Potential = Osmotic Potential + Pressure Potential

Adding of solute to water lower the osmotic potential

ISOTONIC = Identical osmotic potentials

HYPERTONIC = More negative osmotic potential

HYPOTONIC = Less negative osmotic potential

During OSMOSIS water moves from HYPOTONIC to HYPERTONIC

When Equilibrium - Net movement stops but water movement continues.

TURGOR PRESSURE : Osmotic pressure is exerted against the walls of a cell.

Part 1: Measuring Osmotic Potential

1. 6 Dialysis tubing Add Sucrose solutions and label.
2. Record weights of dialysis tubing
3. Fill 6 beakers with distilled water
4. Place each bag in a beaker - Make sure all parts of the bag is covered by water.
5. Let Stand for 1 Hr.
6. Take bags, blot and record weight

6 Dialysis tubing in 6 beakers

 

Calculate

% Change =((Final Mass - Initial Mass)/Initial Mass) X 100

Graph data.

Please note: This is not a replacement for the Lab Manual. Please refer your lab manuals for detailed information.