Reference no: EM133505652
Case Study:
Prokaryotic Cells:
Prokaryotic cells are considered to be the less complex cell type, containing no organelles and no nucleus. Each cell is an individual organism (there are no multicellular prokaryotes), though the cells may form colonies. Within a colony, cells may specialize in performing different tasks. Individual cells of a colony can survive independently if they are separated.
Autotrophic Bacteria: Cyanobacteria.
Some organisms are autotrophs, making their own food via photosynthesis (or other measures). The chlorophyll and other pigments required for photosynthesis give cyanobacteria a green or blue-green color, and no special staining is required to view these organisms under the microscope. Although these cells possess chlorophyll and have the ability to carry out photosynthesis, they do not have chloroplasts - remember prokaryotes do not possess organelles.
A colony of the cyanobacteria species Anabaena can be viewed in Figure 4.1a. Note the shape of each cell, the overall shape of the colony, how the cells are connected to one another, and any other distinctive features. For comparison, a eukaryotic alga is in Figure 4.1b.
Figure 4.1a: Anabaena colony; b: eukaryotic alga. Imaged by a light microscope at 400X magnification. Credit: scienceprofonline.com.
Heterotrophic bacteria:
Heterotrophic organisms must ingest their forms of energy. This includes many prokaryotic species, animals, fungi, and many protists. While most bacteria are free living, some rely on a host, and can be mutualistic (helpful) or pathogenic (harmful) to the host. The following images show a pathogenic bacterial species with the immune cells of the human host, and free-living soil bacteria.
Figure 4.2a: Colorized scanning electron micrograph of human macrophage (grey) ingesting the pathogenic bacteria Streptococcus pyogenes, in orange. The red cell is a lymphocyte, another human immune cell. b: Scanning electron micrograph of Pseudomonas aeruginosa, a free-living soil bacterium. Credit: cellsalive.com.
Questions:
1a and compare the Anabaena cells in the colony, which is a long chain of individual cells attached to each other. Describe any variation you see in cell shape or any other visible characteristics.
Compare the inside of an Anabaena cell with the cell of the eukaryotic algae. How do they compare in the complexity of the structure? What does the eukaryotic cell have inside it that the prokaryotic cell does not?
If you placed the strands next to each other, approximate how many Anabaena cells would fit next to one of an eukaryotic algal cell:
a and compare the orange Streptococcus pyogenes cells to the grey human cell. Describe any variation you see in cell shape or any other visible characteristics.
b. Are these Pseudomonas aeruginosa individuals single or multicellular? How do you know?
b. Why do some of these Pseudomonas aeruginosa individuals appear to be twice as large as others? Hypothesize what might cause this size difference.