The nuclear region of the prokaryotic cell is primitive and a striking contrast to that of the eucaryotic cell (Figure 8.3). Prokaryotic cells lack a distinct nucleus; the function of the nucleus is carried out by a single, long, double strand of DNA that is efficiently packaged to fit within the nucleoid. The nucleoid is attached to the plasma membrane. A cell can have more than one nucleoid when cell division occurs after the genetic material has been duplicated.
The bacterial cytoplasm is often packed with ribosomes (Figure 8.3). Ribosomes are minute, rounded bodies made of RNA that are loosely attached to the plasma membrane. Ribosomes are estimated to account for about 40% of the dry weight of a bacterium; a single cell may have as many as 10,000 ribosomes. Ribosomes are the site of protein synthesis and are part of the translation process.
Inclusions (or storage granules) are often seen within bacterial cells (see Figure 8.3). Some inclusion bodies are not bound by a membrane and lie free in the cytoplasm. A single-layered membrane about 2 to 4 pm thick encloses other inclusion bodies. Many bacteria produce polymers that are stored as granules in the cytoplasm.
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