Unit 2-7

• Bacterial cell


  Small, circular, no nuclear membrane, contains membrane-bound organelles in some species, cell wall made of peptidoglycan, has single RNA polymerase, has histone-like proteins
• Eukaryal cell


  Much larger than bacterial cells, has nuclear membrane, has membrane bound organelles, has cell wall in some species, 3 main RNA polymerases (I, II, and III), has histones, contains cholesterol in plasma membrane
• Size comparison


  • Proteins
  • Viruses
  • Bacteria
  • Eukaryote
• Bacteria


  • 0.5-5um in size
• Eukarya


  • 80-100um in size
• Bacterial cell morphology


  • Spherical (coccus/cocci)
  • Rod-shaped (bacillus, bacci)
  • Comma-shaped (vibrio/vibrio)
  • Spiral (spirillum, spirilla)
  • Pleiomorphic (varying shaped)
• Mycoplasma has no cell wall
• Cytoplasm


  Aqueous (watery) environment in plasma membrane and very densely packed; most catalyzed metabolic reactions occur here; crowded
• Components of the cytoplasm

  • Nucleoid
  • Chromosome-packing proteins
  • Synthesis enzymes (DNA, RNA)
  • Regulatory factors
  • Ribosomes
  • Plasmid(s)
  • Enzymes
  • Inclusion bodies
  • Gas vesicles
  • Magnetosomes
  • Cytoskeletal structures
• Nucleoid


  Convoluted mass of DNA that are coated with proteins and RNA; genetic information storage and gene expression
• Chromosome-packing proteins


  Protection and compaction of genomic DNA
• Synthesis enzymes (DNA, RNA)


  Replication of the genome, transcription
• Regulatory factors


  Control of replication, transcription, and translation
• Ribosomes


  Site of Translation (protein synthesis)
• Plasmid(s)


  Extra chromosomal DNA molecules that encode non-chromosomal genes for a variety of functions
• Enzymes

  Break down substrates; provide energy production and anabolic precursors
• Inclusion bodies

  Storage of carbon, phosphate, nitrogen, and sulfur; no membrane
• Gas vesicles


  Protein-encased "compartment" that provides buoyancy
• Magnetosomes


  Membrane enclosed organelle that orients the cell during movement
• Cytoskeletal structures


  Guides cell wall during synthesis, cell division
• Cell wall


  Provides structural support and maintains cell shape; protects cell from osmotic lysis
• Plasma membrane


  Separates the interior of the cell from the external environment; composed of phospholipid bilayer with embedded proteins; controls access to cytoplasm, captures/stores energy, senses and transduces signals
• Differences between gram-positive and gram-negative bacteria

  • Gram-positive: No outer membrane, thick peptidoglycan layer, narrow periplasm, form endospores
  • Gram-negative: Contains outer membrane, thin peptidoglycan layer, larger periplasm, contains porins and TonB receptors
• Import/export and secretion systems


  • Active transport
  • Passive transport (facilitated diffusion, symport, antiport)
  • ABC transporter
  • Sec pathway
  • TAT pathway
  • Porins
  • TonB dependent receptors
  • Type III secretion system
• Gram staining


  Categorizes bacteria into gram-negative (pink) and gram-positive (purple)
• Gram-positive staining


  Alcohol decolorization shrinks pores, helping crystal violet to lock in
• Gram-negative staining


  Alcohol may strip some outer membrane lipids, making them more likely to lose the crystal violet stain
• Beta-lactam antibiotics


  Inactivate transpeptidase enzymes, affecting cross-linking in the cell wall; inhibition causes problems for growing bacterial cells
• Lysozyme


  Cleaves the backbone of peptidoglycan, hydrolyzing the beta-1,4-glycosidic bond between NAM and NAG, leading to a weakened cell wall
• Lysostaphin


  Acts on the cross bridges of certain Staphylococcus species
• Cellular components and functions

  • Flagella (motility)
  • Fimbriae (attachment, biofilm, conjugation)
  • Capsules (protection, biofilm, adherence)
  • Surface arrays (protection from bacteriophages)
  • Endospores (protection under stress)
• Nucleus


  Holds the cell's DNA, site of transcription, surrounded by double membrane
• Endoplasmic reticulum


  Site of translation and protein folding
• Golgi apparatus


  Modifies, sorts, and transports proteins; connected to the endoplasmic reticulum
• Mitochondria


  Energy production - ATP synthesis through ATPase; cellular respiration, surrounded by double membrane
• Chloroplasts


  Photosynthesis - use the ATP they produce to fix carbon into organic compounds
• Plasma membrane


  Surrounds the eukaryotic cell, composed of a double membrane
• Cell wall


  Fungal cell wall: chitin; Plant cell wall: cellulose
• Lysosome


  Digestion of macromolecules
• Peroxisome


  Breakdown of fatty acids