Cells key

PART A - PLANT CELLS
1. Section 1 - Onion Epithelial Cells
  Stained on Low Power (100x), estimated size (see Microscope lab, p. 35): If field of view is 1.5 mm (1,500 µm) and see 5 cells lengthwise: Estimated cell length: 1500 µm/5 = 300 µm; width: 1500 µm/30 = 50 µm.
  Stained on High Power (400x), estimated size: If field of view is 0.4 mm (400 µm) and see 2 cells lengthwise: Estimated cell length is 400 µm/2 = 200 µm; width: 400 µm/10 = 40 µm.
2. Section 2 - Elodea
  1. Cellular Structure
    Low Power, estimated size: L = 50 µm W = 10 µm
    High Power with distilled water, estimated size: L = 50 µm W = 10 µm
  2. Water Balance in Plant Cells
    Hypothesis: If put plant cell in salt solution (hypertonic), then plasmolysis should occur: water should leave the cell and plasma membrane shrinks away from cell wall (p. 325).
    3% Salt: plasmolyzed. 10% Salt: plasmolyzed.
PART B - ANIMAL CELLS p. 328
1. Section 1 - Cheek Epithelial Cells
  Low Power, estimated size = 100 µm High Power, estimated size = 100 µm
2. Section 2 - Paramecium
  Low Power, estimated size = 150 µm High Power, estimated size = 150 µm

PART C - QUESTIONS

All nuclei and chloroplasts in onion and Elodea cells are located along the edges of the cells. However, when you viewed the onion cells, many of the nuclei appeared to be in the middle of the cells. And when you viewed the Elodea cells, many of the chloroplasts also appeared to be in the middle of the cells.
1. Why are these organelles not located in the middle of these cells? In other words, what about plant cell structure forces them to be along the edges?
  The central vacuole may push them aside.
2. Why do they sometimes look like they are in the middle of the cells?
  Cells are 3-dimensional, they may be on top of the central vacuole.
3. The nuclei of the cheek cells actually are in the middle of those cells. Why are these nuclei not along the edges like the onion and Elodea nuclei?
  Animal cells do not have a central vacuole.
What are the dimensions of the cells you viewed (in millimeters)?
1. Onion: Length .3 mm Width .03 mm.
2. Elodea: Length .05 mm Width .01 mm.
3. Cheek cell: Diameter .1 mm.
Carefully examine the high power drawings you made of Elodea in water, Elodea in 1% salt, and Elodea in 10% salt. You were instructed to make these drawings very carefully, and to meticulously look for how the appearance of the cells changed when the cells were placed in salt water.
1. Describe the most significant change in the appearance of the cells.
  The plasma membrane shrinks away from the cell wall.
2. What happened to the cells to cause them to change in this way?
  The cell has been plasmolyzed: water leaves the cell in hypertonic environments.
You observed the contractile vacuoles pumping when Paramecium was in an environment if fresh water (about 0.1% salt). What would happen to the rate at which the contractile vacuoles would pump if Paramecium were placed in a ________ solution?
1. 0% (distilled water): faster (hypotonic)
2. 5%: none (hypertonic)
3. 10%: none (hypertonic)

Use the results and observations of the cells that you have made in this lab to complete the chart below.

	Plant	Animal
Shape	rectangle	depends on tissue (squamous for cheek)
Arrangement	rows	depends on tissue
Size	10-100 µm	10-100 µm
Boundary	cell wall	plasma membrane
Nucleus	side	center
Vacuole	present	absent
Cytoplasm	present	present
Color	green(?) (onion cell is colorless, no chloroplast)	colorless

Indicate the characteristics of plant and animal cells so that you can recognize each type of cell.
Plant: geometrical, cell wall, central vacuole, possibly chloroplasts. Animal: none of above

Cells key p. 327

Cells key `p. 327`