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EXAM#1

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  • What are prokaryotes?

    Prokaryotes are organisms that lack membrane-bound organelles and a true nucleus, including bacteria and archaea.

  • How do prokaryotes differ from eukaryotes in cell structure?

    Prokaryotes have no nucleus, smaller size (0.5-5µm), always have a cell wall, and lack membrane-bound organelles, unlike eukaryotes.

  • What are the common shapes of prokaryotes?

    Bacilli (rod-shaped), cocci (spherical), and spirilla (spiral-shaped) are common prokaryotic shapes.

  • What is peptidoglycan and where is it found?

    Peptidoglycan is a network of sugar polymers cross-linked by polypeptides found in bacterial cell walls.

  • How do gram-positive and gram-negative bacteria differ?

    Gram-positive bacteria have thick peptidoglycan walls and stain purple; gram-negative have thin peptidoglycan and an outer membrane, staining pink/red.

  • What are endospores in prokaryotes?

    Endospores are metabolically inactive, highly resistant structures that allow bacteria to survive harsh conditions for centuries.

  • What are fimbriae and pili in bacteria?

    Fimbriae help bacteria stick to surfaces; pili (sex pili) are longer and enable DNA exchange between bacteria.

  • What is chemotaxis in bacteria?

    Chemotaxis is bacterial movement toward or away from chemical stimuli, often using flagella for motility.

  • Describe the prokaryotic genome structure.

    Prokaryotes have a circular chromosome located in the nucleoid region and may have smaller DNA rings called plasmids.

  • How do prokaryotes reproduce and generate genetic diversity?

    Prokaryotes reproduce asexually by binary fission; diversity arises from rapid reproduction, mutations, and genetic recombination.

  • What are the three modes of genetic recombination in bacteria?

    Transformation: uptake of external DNA; transduction: virus-mediated DNA transfer; conjugation: direct DNA transfer via pili.

  • What are archaea and where do they live?

    Archaea are prokaryotes without peptidoglycan, often extremophiles living in high salt, temperature, or anaerobic environments.

  • What roles do prokaryotes play in ecosystems?

    Prokaryotes recycle chemical elements, decompose organic matter, enhance soil nutrients, and form symbiotic relationships with plants and animals.

  • What is the significance of the Gram stain in microbiology?

    The Gram stain differentiates bacteria by cell wall composition, aiding identification and treatment decisions.

  • What is the function of the bacterial flagellum?

    The flagellum is a rotary motor structure that enables bacterial motility through liquid environments.

  • What is the nucleoid region in prokaryotes?

    The nucleoid is the region in prokaryotic cells where the circular chromosome DNA is located, not enclosed by a membrane.

  • What are plasmids and their role in bacteria?

    Plasmids are small, circular DNA molecules that carry genes beneficial for survival, such as antibiotic resistance.

  • How do prokaryotes contribute to nitrogen cycling?

    Some prokaryotes fix atmospheric nitrogen into forms usable by plants, playing a key role in the nitrogen cycle.

  • What is the difference between autotrophic and heterotrophic prokaryotes?

    Autotrophs produce their own energy (e.g., photosynthesis), while heterotrophs obtain energy by consuming organic compounds.

  • What is the importance of prokaryotic metabolic diversity?

    Metabolic diversity allows prokaryotes to inhabit diverse environments and utilize various energy and carbon sources.