Lab – Normal & Plasmolyzed Cells



Biology Hour_____ Name___________________________________

Wexler/Fennelly

MiniLab – Normal & Plasmolyzed Cells

Date:

Purpose –

To observe osmosis in Elodea plant cells. Elodea is a common water plant. In this lab you will look at normal Elodea plant cells and compare their insides to plasmolyzed plant cells. Plant cells lose water (plasmolysis) when the living cells are placed in an environment where the water concentration on the outside of the cell is less than the concentration on the inside of the cell. Because water moves from areas of high concentration to areas of lower concentration, the water moves out of the cell, causing its insides to shrink (plasmolysis).

Materials –

microscope coverslip water solution

microscope slide elodea plant salt solution

Procedures –

Part A- Normal Cells

• Prepare a wet mount slide of an elodea leaf in regular tap water

• Place slide on microscope and view at 4X objective, then 10X objective.

• Focus slide on medium power. Locate cells along the edge of the leaf and notice the location of the chloroplasts in relation to the cell wall.

• Focus slide at 40X objective and draw cells in left circle below

Part B – Plasmolyzed Cells

• Prepare a second wet mount slide using another elodea leaf in 10% salt solution (NaCl, 10g/100mL).

• Place slide on microscope and view at 4X objective, then 10X objective.

• Focus slide on medium power. Locate cells along the edge of the leaf and notice the location of the chloroplasts in relation to the cell wall.

• Focus slide at 40X objective and draw cells in left circle below

Normal Elodea Cell Plasmolyzed Elodea Cell

Part C – Label drawings

• When you have both drawings completed, look in your book or notes at structures of a plant cell.

• Go back to both drawings you made and label the following structures –

o Cell wall, cell membrane, chloroplasts

Analysis –

1) Describe the location of the chloroplasts in a normal Elodea cell.

2) Describe the location of the chloroplasts in a plasmolyzed Elodea cell.

Use these facts to answer the following questions

• Elodea cells have a normal concentration of 1% salt water and 99% water

• Tap water used in lab has a concentration of 1% salt water and 99% water

• Salt water used in lab has a concentration of 10% salt and 90% water

• Distilled water is 100% water

3) In Part A of the lab (water)

a) How did the concentration of water inside the cell compare to the concentration of water outside the cell? (same, more, less)

b) Did you expect the inside of the cell to gain water, lose water, or remain the same?

4) In Part B of the lab (salt water)

a) How did the concentration of water inside the cell compare to the concentration of water outside the cell? (same, more, less)

b) Did you expect the inside of the cell to gain water, lose water, or remain the same?

c) How was the cell affected by the salt water?

5) In the winter, roads are sometimes salted to melt ice and snow. This harms plants if too much salt is in the soil at springtime. Explain in terms of osmosis why the plants are harmed?

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