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Diffusion = “high to low is the way to go!” Quote from Billy S. Osmosis = is the net movement of water from a region of high water concentration through.

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Presentation on theme: "Diffusion = “high to low is the way to go!” Quote from Billy S. Osmosis = is the net movement of water from a region of high water concentration through."— Presentation transcript:

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3 Diffusion = “high to low is the way to go!” Quote from Billy S. Osmosis = is the net movement of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration. This movement of water is driven by a difference in solute concentrations on the two sides of the membrane

4 A Hypertonic Solution has a higher solute concentration than the solution to which it is being compared. A hypertonic solution is the solution with the higher concentration of solutes. A Hypotonic Solution has a lower solute concentration than the solution to which it is being compared. A hypotonic solution is the solution with the lower concentration of solutes. Isotonic solutions have the same solute concentrations. The solutions being compared have equal concentration of solutes.

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6 Question: How do tap water and salt water solution surrounding a red onion cell influence osmosis?

7 Materials: red onion epidermis, forceps or fingernails, dropper, tap water, salt solution, paper towels, microscope, slide, and cover slip

8 Make a wet mount of the red onion epidermis. …The purple pigment is concentrated in the top layer. …It is not easy to peel off a THIN red onion skin. …Too thick and the osmostic action will not be observed because too many cells crowd the slide—layer upon layer. …A thin skin curls up on itself and must be placed flat against the slide— or again, too many cell layers will impede the osmotic observation. …Be careful flattening the skin so that you do not rupture the cells in the process and lose the purple pigment.

9 Step 1: Obtain a clean slide Step 3: Place a cover slip over the onion cells Step 2: Use forceps or fingernails to peel away a single cell layer (purple region) add a water drop covering the onion cells

10 Examine under low power. …Find few pockets of intact cells with purple inside. …Focus your work on these cells. …When you have a clear view switch to medium power. Cell membrane at the edge of the purple Cell Wall Yellowish area Make a labeled drawing, (SketchA) time viewed, title, name of cell, magnification viewed, and short description. This will give you a record of the original appearance of the onion cells.

11 Take a dropper and add several drops of salt solution to one side of your cover slip while placing a small piece of paper towel along the opposite edge of the cover slip. The paper should draw out the water and draw in the salt solution. Observe the effects of the sodium chloride (salt) solution on the onion cells. Salt water Slide Coverslip Paper towel Onion cells

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13 Once the salt solution (hypertonic) baths the red onion cells (hypotonic cytoplasm), the net movement of water is from the hypotonic cytoplasm of the red onion cells toward the hypertonic salt solution surrounding the red onion cells. The cells’ cell membrane pulls away from the cell wall as noted by the edge of the purple pigment. Make a properly labeled, careful drawing (SketchB) of the cells' appearance in a second sketch. Time viewed, title, name of cell, magnification viewed, and short description. This will give you a record of the appearance post-salt solution.

14 Question: What will occur when the red onion cells are bathed in tap water? TAP water Slide Coverslip Paper towel Onion cells Make a properly labeled drawing (SketchC) of the cells' appearance after replacement with the tap water. Time viewed, title, name of cell, magnification viewed, and short description. This will give you a record of the appearance post-salt solution.


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