Dr. T logo BIO 100 General Biology I
Cell Structure Lab

The images seen here are micrographs of most of the material viewed during the cell structure lab meeting. Review these images to remember what you observed and pay particular attention to differences between prokaryotic and eukaryotic cells and between animal and plant cells.

Prokaryotic cells

•  Stained bacteria

Bacteria Cell Shapes
The three common shapes of bacterial cells. This is a light micrograph of stained cells.
Micrograph by John Tiftickjian

•  You may not have seen all three of these cell shapes in lab, but the cells seen here are similar to those you observed.

•  These cells have been stained with a dye to increase the contrast of the cells so that they are easier to see against the background.

•  Living cyanobacteria

•  Cyanobacteria contain chlorophyll and carry out photosynthesis. The green color seen here is natural. These cells have not been stained. Both of these organisms are filamentous-their cells are joined end to end in long chains. Cyanobacteria such as these are very common in freshwater ponds and lakes.

•  Oscillatoria

Oscillatoria, a filamentous cyanobacterium, get its name from its characteristic gliding motion. As a filament glides slowly along, its tip often waves back and forth in an oscillating manner.
Micrograph by John Tiftickjian

•  Anabaena

Anabaena, a common filamentous cyanobacterium with heterocysts.
Micrograph by John Tiftickjian

Eukaryotic cells

•  Protists

•  Physarum (a slime mold)

Physarium plasmodium
Living plasmodium of the slime mold Physarum. growing on agar and feeding on oatmeal.
Micrograph by John Tiftickjian

•  Slime molds are essentially huge single cells. Each "cell" has many nuclei. Slime molds are heterotrophic and feed by engulfing bacteria by endocytosis. Like animal cells, they do not have cell walls.

•  Animals

•  Human epithelial cells ("cheek" cells)

Human cheek cells
Human cheek epithelial cell, clockwise from top left: bright field unstained, methylene blue stained, phase contrast, DIC.
Micrographs by John Tiftickjian

•  These four micrographs were all made of living cheek cells. The two in the top row should look similar to what you observed in lab.

•  The top left picture is an unstained cell.

•  The top right picture is a cell that has been stained with methylene blue dye. Note that is stands out from the background much more distinctly because it has absorbed the dye.

•  Special microscope techniques

•  Although we only used bright field microscopy in lab, the bottom two pictures are included to illustrate special microscope methods.

•  These two pictures show living cells (in fact, they are pictures of the same cell seen at the upper left), but using a microscope with special optics. The left picture was made using phase contrast; the right using differential interference. These are special methods that can increase the contrast of living specimens without having to use stains.

•  Plants

•  Onion epidermis

Allium epidermis
Epidermal peel from red onion showing pigmented cells. Note that pigment is located within the vacuole. Nuclei are visible in several cells.
Micrograph by John Tiftickjian

•  These cells exhibit the typical plant cell characteristics: cell wall and large central vacuole. The red pigment in these cells is located entirely in the vacuole. The entire cell appears to be red because the vacuole makes up about 95% of the cell volume. In most plant cells, the vacuole is the largest organelle.

•  Elodea

Elodea leaf cells
Living leaf cells of the aquatic plant Elodea.
Micrograph by John Tiftickjian

•  These cells have cell walls and large vacuoles like the onion cells, but also contain chloroplasts, another plant characteristic. Each green organelle is a single chloroplast.

•  Why don't you see chloroplasts in the onion cells?

•  How is the location of chlorophyll in these plant cells different from its location in the cells of the cyanobacteria?

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