Get Notes sheet from Table 1

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1 Get Notes sheet from Table 1

2 Elodea and red onion under normal conditions Cell wall Cell Membrane Cytoplasm Chloroplasts Plastids w/ anthocyanin

3 Elodea 1 Elodea 2 Onion cells in Salt water

4 Plant cells in distilled water Space between chloroplasts Chloroplasts spread out across cell Small space between adjacent cells.

5 Plant cells in salt solution Cell membranes pull away from the cell wall Chloroplasts Chloroplasts appear to cluster in the center of the cell.

6 What s happening?

7 Osmosis the movement of water across a cell membrane from high to low concentration. Plasmolysis - the shrinking of plant cells due to the loss of water by osmosis. - the cell membrane peels off of the cell wall as the vacuole collapses due to water loss.

8 Osmosis Water has DIFFUSED into some of these cells by OSMOSIS making them expand. Water has DIFFUSED out of some of these cells by OSMOSIS making them shrink.

9 TONICITY - Terms used to compare two areas of concentration Refers to concentration of solute in solution Hypotonic Hypertonic Lower solute [ ] Higher solute [ ] Isotonic Equal solute [ ]

10 Osmosis When placed in ISOTONIC, HYPERTONIC, or HYPOTONIC solution, water will diffuse across the cell membrane. When does diffusion or osmosis stop?

11 ISOTONIC SOLUTIONS ISO =SAME; TONIC = SOLUTION Occurs when the concentration of solute (solid) and solvent (liquid) inside and outside the cell are the same. Cells appear normal Solvent 80% Solute 20% Solution = Solvent 80% Solute 20% Cell

12 HYPERTONIC HYPER = ABOVE; TONIC = SOLUTION Occurs when the solute concentration in the surrounding solution is higher than the concentration in the cells. Cells appear to shrivel or shrink. Solvent 80% Solute 20% Solution > Solvent 90% Solute 10% Cell Cell

13 HYPOTONIC HYPO = LOW; TONIC = SOLUTION Occurs when the solute concentration in the surrounding solution is lower than the concentration in the cells. Cells appear to expand. Solvent 90% Solute 10% Solution < Solvent 80% Solute 20% Cell Cell

14 Osmosis in action

15 Osmosis When placed in a HYPERTONIC solution, water moves from inside the cell to the surrounding solution. It moves from HIGH concentration (inside the cell) to LOW concentration (outside the cell). low low same low high low same Equilibrium reached!

16 Osmosis When water moves out of a cell, water pressure decreases. The decrease in pressure allows the cell membrane to pull away from the cell wall. The organelles appear to cluster in the center of the cell. This is PLASMOLYSIS.

17 Write a definition for plasmolysis in your own words using the new terms.

18 Osmosis When placed in a HYPOTONIC solution, the water moves from the surrounding solution into the cell. It moves from HIGH concentration (outside the cell) to LOW concentration (inside the cell). high high same low same high high Equilibrium reached!

19 Osmosis What about ISOTONIC solutions? Molecules are always moving. Water moves in and out equally. same same Let s try some practice!

20 10% solute 5% solute Salt Sucks!

21 Knowing the tonicity of a solution allows you to predict what will happen to cells and organisms in certain environments. Tonicity is the comparison of concentrations of two areas

22 Higher WATER concentration Lower WATER concentration Beaker contains tap water and bag contains 20 % NaCl In the set up does the water in the narrow tube rise, fall down or shows no change? In which direction has the water moved?

23 Water moves from Is this a Hypertonic, Hypotonic, or Isotonic solution? beaker to bag!

24 Beaker and bag contain 20 % NaCl In this set up does the water in the narrow tube rise, fall down, or shows no change? In which direction has the water moved?

25 Is this a Hypertonic, Hypotonic, or Isotonic solution? Net movement of water is the same (going both IN and OUT, therefore overall no movement of water is seen.

26 Higher WATER concentration Lower WATER concentration Beaker contains25 % NaCl and bag contains 20 % NaCl In this set up does the water in the narrow tube rise, fall down or shows no change? In which direction has the water moved?

27 Water moves from bag into Is this a Hypertonic, Hypotonic, or Isotonic solution? beaker

28 On your lab illustrations: Label the HYPERTONIC solution HYPOTONIC solution ISOTONIC solution Draw arrows on each illustration to show which direction the water is moving Label the illustration that shows PLASMOLYSIS

29 Cells in an isotonic solution H 2 O H 2 O Water Molecule Dissolved Molecule Most cells use osmosis - surrounded by watery solutions. [ ] of dissolved substances outside the cell is the same as the [ ] of dissolved substances inside the cell. water molecules move into and out of the cell at the same rate, cells retain their normal shape.

30 Cells in a hypotonic solution Solute [ ] outside cell is lower than inside Solute [ ] inside cell is higher than outside water enters a cell by osmosis cell swells; enlarges H 2 O H 2 O Water Molecule Dissolved Molecule

31 Cells in a hypertonic solution Solute [ ] outside is higher than inside water leaves cell cell shrinks H 2 O H 2 O Water Molecule Dissolved Molecule

32 Plant Cells in an isotonic solution Cell wall vacuole A plant cell has its normal shape and pressure in an isotonic solution. flaccid state membrane

33 Plant Cells in a hypotonic solution Plant cells swell beyond their normal size as pressure increases. Increasing turgor pressure on cell walls Will become turgid What has happened to the vacuole? Notice the arrangement of the organelles compared to the isotonic?

34 Plant Cells in a hypertonic solution Plant cells lose pressure as the plasma membrane shrinks away from the cell wall. Plasmolysed What has happened to the membrane of the cell? Why? What happened to the vacuole? Why? Empty space Cell membrane

35 HYPOTONIC SOLUTION ISOTONIC SOLUTION HYPERTONIC SOLUTION

36 A B C

37 The control of water balance is extremely important for organisms ANIMAL CELL (1) Normal PLANT CELL ISOTONIC SOLUTION (4) Flaccid (5) Full = Turgid (2) Bursting = Lysing HYPOTONIC SOLUTION Plasma membra ne (6) Shriveled = plasmolyzed (3) Shriveled = crenulated isotonic hypotonic hypertonic Animal cells react to the watery environment around them. HYPERTONIC SOLUTION

38 ANIMAL CELLS --- red blood cells

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