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Microbiology: Prokaryotic Cells and Biochemistry Basics

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Terms in this set (37)

  • Two prokaryotic domains

    Bacteria and Archaea are the two prokaryotic domains; they differ in cell wall composition but both lack membrane-bound organelles.

  • Why are prokaryotes small?

    Prokaryotes tend to be small because most nutrients enter by diffusion, which is limited by the surface area-to-volume ratio.

  • Common prokaryotic shapes

    Bacilli (rod-shaped), cocci (spherical), vibrio (comma-shaped), stella (star-shaped), coccobacilli (ovoid), and spirochetes (spiral-shaped).

  • Definition of pleomorphic bacteria

    Bacteria that can take on different shapes, which may enhance their ability to cause infection.

  • Binary fission process

    DNA is copied, cell grows, chromosomes move to opposite ends, septum forms at midpoint, and two daughter cells separate.

  • Prokaryotic plasma membrane structure

    A thin, flexible phospholipid bilayer with embedded proteins functioning as transporters, anchors, receptors, and enzymes.

  • Difference between bacterial and archaeal cell walls

    Bacteria have peptidoglycan in their cell walls; archaea have pseudopeptidoglycan.

  • Gram-positive vs Gram-negative cell walls

    Gram-positive: thick peptidoglycan layer, stains purple, no outer membrane. Gram-negative: thin peptidoglycan, outer membrane with LPS, stains pink/red.

  • Clinical significance of Gram-negative outer membrane

    Acts as a selective barrier protecting against lysozyme, drugs, detergents, and disinfectants, making Gram-negative bacteria harder to kill.

  • Acid-fast bacteria and staining

    Contain mycolic acid in cell walls; stain red/pink with acid-fast stain; examples include Mycobacterium and Nocardia.

  • Mycoplasma bacteria characteristics

    Lack a cell wall, have sterol-enriched plasma membranes, are pleomorphic, and usually live inside other cells.

  • Passive transport types in prokaryotes

    Simple diffusion (small non-charged molecules) and facilitated diffusion (using channel or carrier proteins).

  • Osmosis effects on bacterial cells

    Hypertonic: water leaves cell causing plasmolysis; hypotonic: water enters causing swelling or lysis if cell wall is damaged; isotonic: no net water movement.

  • Primary active transport

    Uses ATP to move substances across the membrane against their concentration gradient.

  • Secondary active transport types

    Symport: ions and solutes move in the same direction; antiport: ions and solutes move in opposite directions, driven by ion gradients.

  • Flagella function and structure

    Filamentous structures made of flagellin that rotate like a propeller to enable bacterial motility.

  • Flagella arrangements

    Monotrichous (single), lophotrichous (tuft at one pole), amphitrichous (flagella at both poles), peritrichous (all over cell surface).

  • Periplasmic flagella (axial filaments)

    Located between plasma membrane and cell wall; enable spirochetes to move with corkscrew motion.

  • Fimbriae and pili differences

    Fimbriae are short, numerous, and help adhesion; pili are longer, fewer, rigid, and aid in adhesion, movement, and gene transfer.

  • Glycocalyx types and functions

    Slime layer (loose, unorganized) and capsule (well-organized); both aid in adhesion, protection from desiccation, and immune evasion.

  • Nucleoid in prokaryotes

    Region containing a single, circular chromosome of DNA, not membrane-bound.

  • Prokaryotic ribosome structure

    70S ribosomes composed of 50S large and 30S small subunits; synthesize proteins.

  • Function of prokaryotic cytoskeleton

    Provides cell structure and support through long protein filaments.

  • Examples of inclusion bodies

    Carboxysomes (carbon-fixing enzymes) and magnetosomes (magnetic iron accumulation).

  • Endospores and their significance

    Dormant, highly resistant structures formed by some bacteria (e.g., Bacillus, Clostridium) to survive harsh conditions.

  • Sporulation process

    DNA replication, packaging into spore coat, formation of resistant layers, and release of mature endospore.

  • Atoms and their parts

    Atoms consist of a nucleus with protons and neutrons, surrounded by electrons in shells.

  • Difference between cations and anions

    Cations are positively charged ions (lost electrons); anions are negatively charged ions (gained electrons).

  • Isotopes definition

    Atoms of the same element with different numbers of neutrons.

  • Organic vs inorganic molecules

    Organic molecules contain carbon and hydrogen; inorganic molecules may contain carbon but lack hydrogen.

  • pH scale basics

    Measures acidity/basicity from 0-14; pH 7 is neutral, below 7 acidic, above 7 basic.

  • Buffers in biological systems

    Compounds that stabilize pH by absorbing or releasing H+ ions.

  • Ionic vs covalent bonds

    Ionic bonds form by transfer of electrons creating charged ions; covalent bonds form by sharing electrons.

  • Hydrogen bonds

    Noncovalent electrostatic attractions between polar molecules or within a molecule, important for structure.

  • Hydrophobic, hydrophilic, amphipathic molecules

    Hydrophobic repel water; hydrophilic attract water; amphipathic have both properties (e.g., phospholipids).

  • Four main classes of biomolecules

    Carbohydrates, lipids, nucleic acids, and proteins.

  • Protein structure levels

    Primary (amino acid sequence), secondary (alpha helices, beta sheets), tertiary (3D folding), quaternary (multiple polypeptides).