Cells key

PART A - PLANT CELLS
- Onion Epidermal Cells
  Low Power (100x), Size (see Microscope lab, p. 45) If field of view is 1.5 mm and see 10 cells lengthwise: Length: 1.5 mm/10 = .15 mm = 150 µm Width: 1.5 mm/30 = .05 mm = 50 µm
  High Power (400x), Size: If field of view is 0.4 mm and see 3 cells lengthwise: Length: .4 mm/3 = .13 mm = 130 µm Width: .4 mm/10 = .04 mm = 40 µm
- Elodea (Cabomba)
  Low Power, if see 30 cells lengthwise: Size: L = 1.5 mm/30 = .05 mm = 50 µm W = .02 mm = 20 µm
  High Power, about 8 cells lengthwise: Size: L = .4 mm/8 = .05 mm = 50 µm W = .02 mm = 20 µm
PART B - ANIMAL CELLS p. 56
- Human Epithelial Cells
  Low Power, Diameter = .09 mm = 90 µm High Power, Diameter = .09 mm = 90 µm
PART C - PROTIST
- Paramecium
  Low Power, Diameter = .12 mm = 120 µm High Power, Diameter = .12 mm = 120 µm
PART D - QUESTIONS
1. The nuclei and chloroplasts in onion and Elodea (Cabomba) cells are usually located along the edges of the cells. However, when you viewed some onion cells, the nuclei appeared to be in the middle of the cells, and in some Elodea (Cabomba) cells, chloroplasts appeared to be in the middle of the cell.
  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 large, fluid filled central vacuole may push them aside.
  2. Why do they sometimes look like they are in the middle of the cells? p. 57
    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 (Cabomba) nuclei?
    Animal cells do not have a central vacuole.
2. What are the dimensions of the cells you viewed in millimeters?
  1. Onion: Length .15 mm; Width .05 mm.
  2. Elodea (Cabomba): Length .075 mm; Width .02 mm.
  3. Cheek cell: Diameter .09 mm.
3. Onion and Elodea (Cabomba) are both plants, yet chloroplasts are only visible in the Elodea cells. How do you explain this?
  The onion bulb is found underground, no light is available for photosynthesis.
4. Compare and contrast plant and animal cells including characteristics such as the type of cell boundary and organelles present in each cell type.
  Plant: boundary is cell wall (tend to be geometrical in shape and aligned in rows), central vacuole, possibly chloroplasts. Animal: boundary is plasma membrane (no cell wall), no central vacuole or chloroplasts.
5. Is Paramecium more like a plant cell or an animal cell? Explain your choice.
  It has organelles like plant and animal cells. It does not have a cell wall or chloroplasts; its contractile vacuoles are found in neither plant nor animal cells.

Cells key p. 55

Cells key `p. 55`