Biology laboratory fundamentals and experimental methods

¶ … 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.