Biology (Holt)

PARTB:Plant Cells

3. Using forceps, carefully remove a
   small leaf from near the top of an
   Elodeasprig. Place the whole leaf in a drop
   of water on a slide, and add a cover slip.
   4.Observe the leaf under low power. Look
   for an area of the leaf in which you can
   see the cells clearly, and move the slide so
   that this area is in the center of the field
   of view. Switch to high power, and, if nec-
   essary, adjust the diaphragm. Identify as
   many cell parts as you can.
   5.Find an Elodeacell in which you can see
   the chloroplasts clearly. Draw this cell.
   Label the cell wall, a chloroplast, and any
   other cell parts that you can see.
   6.Notice if the chloroplasts are moving in
   any of the cells. If you do not see move-
   ment, warm the slide in your hand or
   under a bright lamp for a minute or two.
   Look for movement of the cell contents
   again under high power. Such movement
   is called cytoplasmic streaming.


4. Put on safety goggles and
   a lab apron. Make a wet
   mount of another Elodealeaf, using
   Lugol’s iodine solution instead of water.
   CAUTION: Lugol’s solution will stain
   your skin and clothing. Promptly wash
   off spills to minimize staining.Observe
   these cells under low and high power.
   8.Draw a stained Elodeacell. Label the cell
   wall and a chloroplast, as well as the cen-
   tral vacuole, the nucleus, and the cell
   membrane if they are visible.

PARTC:Cleanup and Disposal

9. Dispose of solutions, broken glass,
   and Elodealeaves in the waste con-
   tainers designated by your teacher. Do not
   pour chemicals down the drain or put lab
   materials in the trash unless your teacher
   tells you to do so.


10. Clean up your work area and all lab
    equipment. Return lab equipment to

its proper place. Wash your hands thor-

oughly before you leave the lab and after

you finish all work.

Analyze and Conclude

1. Recognizing PatternsIn what observ-
   able ways are animal and plant cells simi-
   lar in structure, and in what observable
   ways are they different?


2. Comparing StructuresCompare and
   contrast the cytoplasm of epithelial cells
   and Elodeacells.


3. Analyzing MethodsWhat is the reason
   for staining Elodeacells with iodine?


4. Inferring ConclusionsLugol’s iodine
   solution causes the movement of chloro-
   plasts to stop. Explain why.


5. Inferring ConclusionsIf some of the
   epithelial cells were folded over on them-
   selves but were still transparent, what
   could you conclude about their thickness?


6. Further InquiryWrite a new question
   about cell structure that could be explored
   with another investigation.

CHAPTER 3Cell Structure 71

On the Job

Microscopyis an important tool for biol-

ogists who study cell structure. Do

research to learn more about how biol-

ogists use specialized microscopes to

study cell structure. For more about

careers, visit go.hrw.comand type in the

keyword HX4 Careers.