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¶ … Eukaryotic Cell
Try to identify the following structures in an amoeba (Fig. 4.2):
Nucleus: A single, membrane-bounded oval structure.
Food vacuoles: Membrane-bounded spheres that contain engulfed food. Are these present? Yes.
Contractile vacuoles: Transparent, membrane-bounded spheres used to expel excess water. Are these present? Yes.
Animal Cell Structure
Animal cells contain all the structures in Table 4.1 except they do not have a cell wall and do not have chloroplasts. Can animal cells make their own organic food? No. Why or Why not?
Plants have chloroplasts which allows them to convert solar energy to carbohydrates. The carbohydrates are the organic food that plants then use for energy. Animals do not have chloroplasts and so are not capable of making their own organic food.
Observation: Elodea (Anacharis)
Can you locate the cell nucleus? Yes. It may be hidden by the chloroplasts, but when visible, it appears as a faint, gray lump on one side of the cell.
7. Can you detect movement of chloroplasts in this cell or any other cell? Yes. The chloroplasts are not moving under their own power but are being carried by a streaming of the nearly invisible cytoplasm.
Table 4.3 Diffusion Through a Differentially Permeable Membrane
At Start of Experiment At End of Experiment
Contents Color Benedict's Test Conclusion
Bag Glucose Clear Blue Brown
Starch and iodine
Starch present.
Beaker Water Amber Orange
No starch present,
Iodine glucose present.
Conclusions
Which solute did not diffuse across the dialysis membrane from the bag to the beaker?
Starch did not diffuse across the dialysis membrane from the bag to the beaker.
Explain. The liquid inside the dialysis bag is blue, indicating that starch is present. If starch had of diffused out of the bag, the liquid in the beaker would be blue, however it remains amber. This indicates that the starch has not diffused across the membrane.
Table 4.6 Effects of Tonicity on Elodea Cells
Solution Appearance on Cells Scientific Term
Hypotonic Cytoplasm even around the cell wall. N/A
Hypertonic Cytoplasm clumped together. Plasmolysis Plasma membrane pulled away from the cell wall.
Cell smaller.
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