1. What is the best way to float a thin metal pin on water? How come it works, although the pin is much more dense / heavier than the water? 2. When are water drops larger – with or without soap? Why? Journal

Try it out: Observing water: 1) Drop on wax and on glass. 2) Floating a metal pin. 3) Pepper on water, with soap. 4) Ice on liquid water. For each trial, describe what happened. Explain why.

Consider the two beakers with grapes and soda: Green grapes – peeled off Purple grapes – not peeled. A.Describe what you see in words and a drawing. B. Try to explain why this happens. C. Suggest a way to confirm your explanation. J Journal

Membrane structure Membrane Structure Introduction Use Power notes handout

Properties of Water H2OH2OH2OH2O Water Molecules are Polar:

Electrons spend more time around the O than the H. The “O” side is more negative and “H” side more positive. The + and – sides attract one another  Water is Sticky! Water Molecules are Polar:Notes Animation of water behavior Animation: Closeups on WATER

- + Polar Solute Non- Polar

Polar substances – Mix well with water (Sugar, Salt, Water colors…) Notes Non-polar substances – Do not mix well with water (Oils, waxes, Fats) The same can be said In other terms..

WATER: Observations 1. Capillary climbing 2. Glass versus Wax 3. Paper chromatography 4. Drops on Penny 5. Pepper on water and… soap! 6. Phooo on wet towel! 7. Oil and water?! For each – describe what you see..

Water behaviorPolarity-based Explanation

Observe the two bottles. 1.Describe the behavior of the solvents (the liquids) and the solutes (materials that mix into the liquids). 2. Explain this behavior in terms of the hydrophobic – hydrophilic nature of the substances.

Hydrophilic – “loves” water Hydrophobic – “hates” water (or rather – hated by water) Totally hydrophobic: Oil Half hydrophobic, half hydrophilic: phospholipids Membrane structure Notes

Solvent: Fluid Substance that is present in large amount (water, oil) Solute: Substance that is in small amount and mixed into the solvent. (food coloring, paint, sugar..) Solution: Solute mixed into solvent Concentration: Amount of solute in unit volume of solvent.

Power notes: Membrane Structure

Membrane Fluidity Animation Stolaf edu/people/giann ini/flashanimat/li pids/membrane% 20fluidity.swf Formation of a bilayer (Click on Left Menu to choose) Membrane Structure (with cutting through a sphere..)

Purpose of biological membranes: * Constitute the border line of the cell and defines regions within the cell. * Membranes control what passes through, into and out of the cell.

tails

Phospholipids arrange themselves in a lipid bilayer: Water Hydro-phobic Hydrophilic

Membrane Structure (with cutting through a sphere..)

Fluid Mosaic Model for membrane Structure: Flexibility: The phospholipids in each layer can move from side to side, behaving like a fluid. Mosaic: Many proteins and other molecules are embedded in the bilayer. Membrane Fluidity Animation Stolaf

Membrane molecules that are not phospholipids: Proteins: Aid cell identification and movement across the membrane. Cholesterol: A small and rigid lipid. Solidifies the membrane. Carbohydrates: for cell identification.

BUBBLE LAB

1) Soap bubbles – why / how do they form? 2) What are similarities between a membrane and a soap bubble? Soap Bubbles explained water soap

Lipid bilayer, soap bubble: 1)Draw, label – polar and apolar areas. 2) What are similarities and differneces between a bilayer membrane and a soap bubble? Soap Bubbles explained

Membrane, Soap Bubble: Compare: How Similar? How different? water soap

Biological membranes are semi-permeable Pass easily: -Small molecules -Non-charged particles -WATER! Pass only with help: -Large particles -Ions ? Notes

We divide all the particles to four major groups: Uncharged Polar Charged (“super-polar”) +- Large (proteins) Non-polar (lipids) Pass freely: H2OH2O Ions Na + Cl - Need help to pass:

Phospholipid in 3D Triglyceride 3D Saturated and non-Saturated Fatty Acids Membrane Fluidity Animation Stolaf