Pro and eu

• Eukaryotic cells


  Cells that have a nucleus and membrane-bound organelles

  
• Prokaryotic cells


  Cells that lack a nucleus and membrane-bound organelles
• Prokaryotes


  • Lack cell nucleus or any other membrane bound organelles
  • DNA and sites of metabolic activity are not collected in a discrete membrane-enclosed area, but are freely accessible within the cell

  
• Macromolecules that make up prokaryotic cell material

  • DNA
  • RNA
  • Proteins
  • Polysaccharides
  • Phospholipids

  
• Primary subunits


  Nucleotides, amino acids, sugars
• Primary structure


  The sequence in which the subunits are put together in the macromolecule
• Prokaryotic structural components


  • Nucleoid (DNA)
  • Ribosomes
  • Cell membrane
  • Cell wall
  • Surface layer

  
• Appendages on the prokaryotic cell surface


  • Flagella
  • Pili (fimbriae)

  
• Components of the prokaryotic cell envelope

  • Capsule
  • Cell wall
  • Plasma membrane

  
• Components of the prokaryotic cytoplasmic region

  • Chromosome (DNA)
  • Ribosome
  • Cellular inclusions

  
• Flagella


  • Filamentous protein structures that provide swimming movement
  • Powered by proton motive force rather than ATP hydrolysis
• Tactic behavior


  • Ability to move (swim) in response to environmental stimuli like chemotaxis, phototaxis, aerotaxis, magnetotaxis
• Fimbriae and pili


  Short, hair-like structures on the prokaryotic cell surface
• Functions of fimbriae and pili

  • Stabilize bacteria during DNA transfer by conjugation
  • Attachment to surfaces
  • Protection against phagocytosis

  
• Fimbriae are shorter and stiffer than flagella, and slightly smaller in diameter
• Properties of pili and fimbriae

  • Number on cell
  • Distribution on cell surface
  • Function
• Cell envelope


  The several layers of material that enclose the protoplasm of the prokaryotic cell

  
• Capsules


  A polysaccharide layer outside of the cell wall polymer
• Slime layer or biofilm

  A less discrete structure or matrix which embeds the cells
• Glycocalyx


  A thin layer of tangled polysaccharide fibers on the cell surface
• Cell wall


  An essential structure that protects the cell protoplast from mechanical damage and osmotic rupture
• Gram-positive bacterial cell wall


  • Consists of multiple layers of peptidoglycan with teichoic acids running perpendicular

  
• Gram-negative bacterial cell wall


  • Consists of a single layer of peptidoglycan surrounded by an outer membrane containing lipopolysaccharide

  
• Cell wall-less form


  Bacteria that can live without a cell wall, like mycoplasmas
• Plasma membrane


  The most dynamic structure of a prokaryotic cell, acts as a selective permeability barrier

  
• Functions of the prokaryotic plasma membrane

  • Osmotic/permeability barrier
  • Transport of solutes
  • Energy generation
  • Lipid synthesis
  • Cell wall synthesis
  • Protein secretion
  • DNA replication coordination
  • Chemotaxis
  • Enzyme systems

  
• Cytoplasm


  Aqueous solution containing macromolecules, small molecules, and inorganic ions/cofactors

  
• Nucleoid


  The bacterial chromosome, typically a single large circular DNA molecule

  
• Plasmids


  Smaller extrachromosomal pieces of DNA in prokaryotes
• Ribosomes


  Composed of proteins and RNA, involved in protein synthesis

  
• Inclusions


  Distinct granules in the cytoplasm, often containing reserve materials
• Molecules


  • Macromolecules such as proteins (enzymes), mRNA and tRNA
  • Small molecules that are energy sources, precursors of macromolecules, metabolites or vitamins
  • Various inorganic ions and cofactors
• Bacterial cell


  • Nucleoid - bacterial chromosome is typically one large circular molecule of DNA, more or less free in the cytoplasm, although coiled and supercoiled and anchored by proteins
  • Prokaryotes sometimes possess smaller extrachromosomal pieces of DNA called plasmids
  • The total DNA content of a prokaryote is referred to as the cell genome

  
• Bacterial cell


  • Ribosomes - are composed of proteins and RNA, involved in the process of translation (protein synthesis)

  
• Bacterial cell inclusions


  • Glycogen - polyglucose, reserve carbon and energy source
  • Polybetahydroxybutyric acid (PHB) - polymerized hydroxy butyrate, reserve carbon and energy source
  • Polyphosphate (volutin granules) - linear or cyclical polymers of PO4, reserve phosphate; possibly a reserve of high energy phosphate
  • Sulfur globules - elemental sulfur, reserve of electrons (reducing source) in phototrophs; reserve energy source in lithotrophs
  • Gas vesicles - protein hulls or shells inflated with gases, buoyancy (floatation) in the vertical water column
  • Parasporal crystals - protein, unknown but toxic to certain insects
  • Magnetosomes - magnetite (iron oxide) Fe3O4, orienting and migrating along geo-magnetic field lines
  • Carboxysomes - enzymes for autotrophic CO2 fixation, site of CO2 fixation
  • Phycobilisomes - phycobiliproteins, light-harvesting pigments
  • Chlorosomes - lipid and protein and bacteriochlorophyll, light-harvesting pigments and antennae
• Endospores


  • Formed by vegetative cells in response to environmental signals that indicate a limiting factor for vegetative growth
  • Endospores exhibit no signs of life, being described as cryptobiotic
  • Endospores germinate and become vegetative cells when the environmental stress is relieved
  • Endospore-formation is a mechanism of survival rather than a mechanism of reproduction
• Differences between endospores and vegetative cells


  • Surface coats
  • Microscopic appearance
  • Calcium dipicolinic acid
  • Cytoplasmic water activity
  • Enzymatic activity
  • Macromolecular synthesis
  • Heat resistance
  • Resistance to chemicals and acids
  • Radiation resistance
  • Sensitivity to lysozyme
  • Sensitivity to dyes and staining
• Archaea


  • Many features in common with Eukarya, genes encoding protein: replication, transcription, translation
  • Features in common with Bacteria, genes for metabolism
  • Unique rRNA gene structure, capable of methanogenesis
• Archaea


  • Highly diverse with respect to morphology, physiology, reproduction, and ecology
  • Best known for growth in anaerobic, hyper saline, pH extremes, and high-temperature habitats
  • Also found in marine arctic temperature and tropical waters
• Archaeal size, shape, arrangement

  • Much like bacteria, cocci and rods are common shapes
  • Other shapes can also exist, no spirochetes or mycelial forms yet
  • Branched/flat shapes
  • Sizes vary, typically 1-2 x 1-5 μm for rods, 1-5 μm in diameter for cocci
  • Smallest observed is 0.2 μm in diameter
  • Largest is a multicellular form that can reach 30 mm in length