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Functional Anatomy of Prokaryotic Cells in Microbiology

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  • What are the main differences between prokaryotic and eukaryotic cells?

    Prokaryotes lack a true nucleus and membrane-bound organelles, have one circular chromosome, no histones, and divide by binary fission. Eukaryotes have a nucleus with paired chromosomes, histones, organelles, and divide by mitosis.

  • Name the common shapes of bacterial cells.

    Bacillus (rod-shaped), Coccus (spherical), Spiral forms: Vibrio (curved rods), Spirillum (rigid spirals), Spirochete (flexible spirals), plus star-shaped and rectangular.

  • What are the typical arrangements of cocci bacteria?

    Diplococci (pairs), Streptococci (chains), Tetrads (groups of four), Sarcinae (cubelike groups of eight), Staphylococci (clusters).

  • What is the glycocalyx and its functions in bacteria?

    A viscous polymer outside the cell wall, existing as a capsule or slime layer. It prevents phagocytosis, aids adherence, and facilitates biofilm formation.

  • Describe the structure and function of bacterial flagella.

    Flagella are filamentous appendages made of flagellin with filament, hook, and basal body parts. They provide motility and are used for identification (H antigens).

  • List the types of flagellar arrangements in bacteria.

    Peritrichous (all over), Monotrichous (single polar), Lophotrichous (tuft at one pole), Amphitrichous (both poles).

  • What are axial filaments and archaella?

    Axial filaments are endoflagella in spirochetes causing corkscrew movement. Archaella are motility structures in Archaea, rotating like flagella and powered by ATP.

  • Differentiate fimbriae and pili in bacteria.

    Fimbriae enable attachment and biofilm formation. Pili are involved in motility and DNA transfer (conjugation).

  • What is the main component of the bacterial cell wall and its function?

    Peptidoglycan, a polymer of NAG and NAM linked by peptides, provides rigidity, shape, and protection from osmotic lysis.

  • How do Gram-positive and Gram-negative cell walls differ?

    Gram-positive have thick peptidoglycan with teichoic acids and high penicillin susceptibility. Gram-negative have thin peptidoglycan, outer membrane with LPS, and lower penicillin susceptibility.

  • What are atypical bacterial cell walls?

    Acid-fast bacteria have waxy mycolic acid; Mycoplasmas lack cell walls; Archaea have walls of pseudomurein or none.

  • How do lysozyme and penicillin damage bacterial cell walls?

    Lysozyme hydrolyzes peptidoglycan bonds; penicillin inhibits peptide cross-bridge formation, weakening the wall.

  • What are protoplasts, spheroplasts, and L forms?

    Protoplasts are wall-less Gram-positive cells; spheroplasts are wall-less Gram-negative cells; L forms are wall-less cells with irregular shapes.

  • Describe the plasma membrane of prokaryotic cells.

    A phospholipid bilayer with proteins, responsible for selective permeability, ATP production, and sometimes photosynthesis.

  • What are the passive and active transport processes across bacterial membranes?

    Passive: simple diffusion, facilitated diffusion, osmosis. Active: active transport using ATP to move substances against gradients.

  • What is the nucleoid in prokaryotic cells?

    The nucleoid contains the circular, double-stranded DNA chromosome, not membrane-bound and lacking histones.

  • What are plasmids and their significance?

    Small extrachromosomal DNA circles carrying nonessential genes like antibiotic resistance; replicate independently and transfer between cells.

  • What is the structure and function of prokaryotic ribosomes?

    70S ribosomes made of protein and rRNA, responsible for protein synthesis and targeted by some antibiotics.

  • Name types of bacterial inclusions and their functions.

    Metachromatic granules (phosphate), polysaccharide granules, lipid inclusions, sulfur granules, carboxysomes (CO2 fixation), gas vacuoles (buoyancy), magnetosomes (iron oxide).

  • What are endospores and their importance?

    Highly resistant dormant structures formed by some bacteria under nutrient depletion, surviving extreme conditions and important in sterilization.