Teacher Section: Osmosis in Elodea Cells Answer Key

Observations

The student will receive one point for preparing any sketches and two points for completing all five sketches. Labels on the sketches will earn another point, and one point will be awarded for sketches that are neatly and carefully drawn. One point will also be given for written observations of the cells under each set of conditions.

Answers to Conclusion Questions

1. The shape of the typical Elodea cell is rectangular or boxlike.

2. The small green objects are the chloroplasts, which are responsible for photosynthesis (food production) in the plants.

3. The cells shrink although the shape of the cell wall stays the same. Thus, an open space appears between the cell membrane and the cell wall.

4. The cells swell until the cell membrane is pressed tightly against the cell wall.

5. The cell membranes would pull away from the cell wall as the cell lost water. This happens because water flows out of the cell faster than it flows back in.

Conclusions

Three points will be awarded for answering all five questions. Another point may be earned for answers that indicate accurate observation. Yet another point may be earned for a reasonable explanation of the changes based on the observations (question 5). A point will be deducted if answers are not in complete sentences.

Grading: Point totals will be recorded as part of the overall grade for the term.