Plasma Membrane, Cell Surface, Cell Adhesion, And Extracellular Matrix

Observation under a Microscope for Cell-Dissection or an Inverted Phase-Contrast Microscope

Items 1-5

Suppose we have a typical bacterial cell with various structures labeled.

1. The genetic information for replication of this organism is found inside the nucleus.
2. Rapid movement of this structure propels the entire organism through its aqueous milieu
3. This organelle prevents macrophages from engulfing the organism.
4. Food reserves are stored in this organelle.
5. As this structure extends, the bacterium divided into two daughter cells.

ANSWERS AND TUTORIAL ON ITEMS 1-5

The answers are: 1-B; 2-F; 3-E 4-1; 5-C. Tissue-culture microscope 1.1 shows a typical bacterial cell. Procaryotes are functionally compartmentalized, but lack the well-defined membrane bound organelles of eukaryotic cells. Area of high DNA content appear as areas of high electron density in electron micrographs. This nucleoid region (B) contents the bacterial DNA and newly transcribed RNA’s. Translation of the information in mRNA into proteins takes place throughout the cell cytoplasm on ribosomes (A). After DNA replication and the separation of the duplicated chromosome to opposite ends of the cell, cytoplasmic division occurs as the result of growth of the septum (C).

Bacteria move by rotation of flagella (F), which may be situated at one end or long the entire length of the bacterium. Smaller appendages called pill are found on some bacteria. They are not involved in motility but probably play a role in conjugation or adherence to tissue receptors.

The Bacterial capsule (E), when present, usually consists of complex peptidoglycans. It serves as a virulence factor that prevents phagocytosis by host macrophages or mediates adhesion to host tissue receptors. The antigenic properties of the capsule are sometimes useful in identifying different species and strains.

Many bacteria contain a variety of intracytoplasmic storage vacules (I).Polymerized metaphosphates or lipids are examples of inclusions which serve to store energy reserves for the organism. The presence of different inclusions or granules or granules can be detected using special stains. Other structures represented within the diagram are a cell wall (D), mesosome (G), pili (H) and sexual pili (J). professional-high-power microscope.