Cell Biology
Prokaryotic cells are single-celled organisms belonging to the domains Bacteria and Archaea. These cells lack nuclei and can come in different shapes. Bacteria contain various cellular structures, including a cell membrane, cytoplasm, and ribosomes. Their genetic material is organized into a single molecule of circular DNA located in a membrane-less area called the nucleoid region. Some bacteria also contain plasmids, which are small, circular DNA molecules external to the bacterial genome.
Bacteria may have other cellular structures, such as a cell wall outside the cell membrane and flagella for movement. Prokaryotic flagella differ from their eukaryotic counterparts in structure and function. Unlike eukaryotic cells, bacteria do not have membrane-bound organelles or a mitotic apparatus. Instead, they reproduce through a process called binary fission. Bacterial morphology encompasses the size, shape, and arrangement of bacterial cells, with the three most common shapes being cocci (spherical), bacilli (rod-shaped), and spirilla (spiral-shaped).
Lesson Outline
<ul> <li>Introduction to Prokaryotes <ul> <li>Domains: Bacteria and Archaea</li> <li>Prokaryotes are single-celled organisms</li> <li>Similarities and differences with Eukaryotes</li> </ul> </li> <li>Focus on Bacteria domain <ul> <li>Cellular structures <ul> <li>Cell membrane</li> <li>Cytoplasm</li> <li>Ribosomes</li> <li>Genome: single circular DNA molecule</li> <li>Nucleoid region</li> <li>Plasmids</li> <li>Cell wall</li> <li>Flagellum</li> </ul> </li> <li>Structures bacteria do not have <ul> <li>No membrane-bound organelles</li> <li>No mitotic apparatus</li> <li>Reproduce via binary fission</li> </ul> </li> <li>Bacterial morphology <ul> <li>Spherical: cocci</li> <li>Rod-shaped: bacilli</li> <li>Spiral-shaped: spirilla</li> </ul> </li> </ul> </li> </ul>
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FAQs
Prokaryotic cells, which include Bacteria and Archaea, differ from eukaryotic cells mainly by their lack of a nucleus and other membrane-bound organelles. Prokaryotes have a simpler internal organization, with most of their genetic material found in a single, circular DNA molecule called a nucleoid. Additionally, prokaryotic cells are generally smaller than eukaryotic cells and have different mechanisms of gene expression and protein synthesis.
Bacterial morphology refers to the size, shape, and arrangement of bacterial cells. There are three main bacterial shapes: cocci (spherical), bacilli (rod-shaped), and spirilla (spiral-shaped). Some bacteria also exhibit unique morphological features such as stalks, flagella, or fimbriae. The cell wall structure, which can be either gram-positive or gram-negative, is another important aspect of bacterial morphology, as it influences factors like antibiotic susceptibility and immune response.
The simpler structure of prokaryotic cells allows for faster growth and reproduction rates compared to eukaryotic cells, as they have fewer internal compartments and process their genetic material more directly. The reduced complexity also enables prokaryotes to adapt rapidly to different environmental conditions, and their diverse metabolic capabilities allow them to inhabit a wide range of environments. Furthermore, many prokaryotes have specialized structures like flagella for motility, pili for attachment, or various enzymes for the degradation and utilization of complex substrates.
Prokaryotes typically reproduce asexually through a process called binary fission, in which a single cell divides into two genetically identical daughter cells. However, prokaryotes can also exchange genetic material with other cells via horizontal gene transfer mechanisms, such as transformation, conjugation, and transduction. This transfer of genetic material between individual prokaryotes contributes to their adaptability and evolution.
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