Classroom Explorations: Characteristics of Life
All cells show some ability to move at some stage of their lives. Some cells are highly active, such as immune system cells and amoebae. The basis for all cell movement arises from the cell's internal skeleton that's made of proteins called tubulin and actin. Using structures made from these proteins, cells can move internal material, divide, crawl, and swim.
In this video, Amoeba proteus is stained with a pH-dependent dye. Amoebae are single-celled organisms familiar to many high school students. Despite their tiny size, they're giant in comparison to other types of cells. While sharing many characteristics with other organisms, amoebae are primarily studied for their ability to move about. The molecular mechanisms that amoebae use to crawl are nearly identical to the molecular mechanisms that cells in all organisms use to move. Scientists have used this commonality to discover how our own cells move. (The video has an elapsed time of about 5 minutes.)
Amoebae stained with a pH-dependent dye were mounted in pondwater between a slide and coverslip using a silicon spacer. The movie was taken on an compound inverted microscope using a 20x objective and digital camera.