ANSWERS
Process of Science
What Causes Infections in AIDS Patients?
Lab Notebook
Data Collection Table
Infected lung tissue / Several black spots appear to be lesions in the lung tissue.Micrograph of infected lung cells / The cells of the pathogenic organisms are spherical and dark, with a distinct dark spot in the center. They tend to be grouped in clusters.
The infected cells appear to have a true nucleus, as in eukaryotic cells. The infected cells are almost the same size as the human cells, which are eukaryotic.
Photo of skin lesions / The nodules appear to be hardened, darkened areas of the patient's own skin.
Micrograph of skin lesions / The abnormal cells are organized in a similar fashion to the normal cells. The nuclei of the abnormal cells are darker and more irregularly shaped than those of the normal cells.
Questions
1. After examining the lung tissue, describe what you would do next if you were the physician investigating this condition.
I would get a closer look at the cells in the black spots that make up the lesions.
2. Are the invading cells prokaryotic or eukaryotic? Include evidence to support your conclusion.
Eukaryotic cells.
These invaders have many characteristics of eukaryotic cells. Eukaryotic cells have a true nucleus, a membrane-enclosed structure inside the cell that contains DNA, the genetic material. Prokaryotic cells lack a true nucleus. The invading cells appear to have a nucleus, which is evidence that they are eukaryotic. Other evidence is the size of the invading cells: about the same as the human cells. Because humans are eukaryotes, and because typical eukaryotic cells are much larger than typical prokaryotic cells, the invading cells appear to be eukaryotic.
3. Describe the physical nature of the cells in the nodules. What do you think may be happening? Are the nodules caused by an invading cell or the patient's own cells growing abnormally? List evidence that supports your diagnosis.
Abnormal growths of the patient's own cells.
Most pathologists would probably agree with you. While the abnormal cells seem to be invading the surrounding normal tissue, they do not appear to be a disorganized colony of microorganisms. The cells do not have the thick cell walls expected of fungi. They are the size of the normal human cells on the right of the image, not small as prokaryotic bacterial cells would be. They have nuclei, so they are eukaryotic. And the cells in the growth seem to have some tissue organization in places. For example, cells are organized in a stream about four cells wide along the upper left edge of the image. In the lower part just left of center, cells are organized around a triangular-shaped space that may be a blood vessel. Blood cells hemorrhaged from blood vessels are visible as red clumps near this triangular space.
The nuclei of the cells in the growth look distinctly different from those in the normal tissue. The normal nuclei are round or oval shaped and only slightly more darkly staining than the cytoplasm. In contrast, nuclei in the cells of the growth are intensely staining and are often have a spindle shape. These characteristics suggest abnormal growth characteristics. All this evidence -- proliferation of cells into a growth and invasion of normal tissue -- suggests that these are cancer cells.
______
Copyright © 2010 Pearson Education, Inc., publishing as Pearson Benjamin Cummings