2. The differences between eukaryotic and prokaryotic cells, summarized in Table 6-1, are the basis for antimicrobial drugs.
|Characteristic||Prokaryotic Cells||Eukaryotic Cells|
|Size (approximate) (μm)||0.5–3||>5|
|Cell wall||Complex structure composed of proteins, peptidoglycan, and lipids||Only in fungal and plant cells; composition differs from that of bacterial cell wall|
|Plasma (cytoplasmic) membrane||Contains no sterols (except in Mycoplasma species)||Contains sterols|
|Genome||Single, circular DNA molecule in nucleoid||Multiple, linear DNA molecules in nucleus|
|Ribosomes||70S (50S + 30S subunits)||80S (60S + 40S subunits)|
|Cell division||Via binary fission||Via mitosis and meiosis|
6-2 Gram-positive and gram-negative bacteria. Internal structures and the plasma membrane are similar in all bacteria, but the cell wall is more complex in gram-negative than in gram-positive bacteria. Motile bacteria possess a flagellum. Pili, which are shorter and thinner than flagella, are present on some gram-positive and gram-negative species.
3. Because bacteria lack a nuclear membrane, transcription and translation are coupled (i.e., ribosome-mediated protein synthesis can begin while a messenger RNA [mRNA] is being produced and is still attached to the DNA).
• Membrane contains enzymes and other proteins that carry out energy production (e.g., electron transport chain, F1 adenosine triphosphatase), transport of nutrients (e.g., permeases), and synthesis of structural components.