Micro: Chapter 4 – Flashcards

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Prokaryote?
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  • prenucleus
  • one circular chromosome, not in a membrane
  • no histones
  • no organelles
  • bacteria: peptidoglycan cell walls
  • Archaea: pseudomurein cell walls
  • binary fission
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Eukaryote
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  • Paired chromosomes, in nuclear membrane
  • histones
  • organelles
  • polysaccharide cell walss
  • mitotic spindle

 

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Basic shapes
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  • bacillus (rod-shaped)
  • cocuss (sperical)
  • Spiral
    • Spirillum
    • Vibrio
    • Spirochete
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Arrangements
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  • Pairs: diplococci, diplobacilli
  • Clusters: staphylococci
  • Chains: streptococci, streptobacilli
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Glycocalyx
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  • Outside cell wall
  • Usually sticky
  • Capsule: neatly organized
  • Slime layer: unorganized and loose
  • Extracellular polysaccharide allows cell to attach
  • Capsules prevent phagocytosis
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Flagella
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  • Outside cell wall
  • Made of chains of flagellin
  • Attached to a protein hook
  • Anchored to the wall and membrane by the basal body
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Motile cells
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  • Rotate flagella to run or tumble 
  • Move toward or away from stimuli (taxis)
  • Flagella proteins are H antigens
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Axial Filaments
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  • Also called endoflagella
  • In spirochetes
  • Anchored at one end of a cell
  • Rotation causes cell to move
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Fimbriae
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  • allow attachment 
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Pili
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  • Facilitate transfer of DNA from one cell to another
  • Gliding motility
  • Twitching motility
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Cell Wall
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  • Prevents osmotic lysis
  • Made of peptidoglycan (in bacteria)
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Peptidoglycan
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  • Polymer of disaccharide:
    • N-acetylglucosamine (NAG)
    • N-acetylmuramic acid (NAM)
  • Linked by polypeptides in Gram-Positive bacteria
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Gram-Positive Cell Walls
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  • Thick peptidoglycan
  • Teichoic acids
  • May regulate movement of cations
  • Polysaccharides provide antigenic variation
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Gram-Negative Cell Wall
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  • Thin peptidoglycan
  • Outer membrane
  • Periplasmic space
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Teichoic Acids
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  • Lipoteichoic acid links to plasma membrane
  • Wall teichoic acid links to peptidoglycan
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Gram-Negative Outer Membrane
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  • Lipopolysaccharides, lipoproteins, phospholipids
  • Forms the periplasm between the outer membrane and the plasma membrane
  • Protection from phagocytes, complement, and antibiotics
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O polysaccharide
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  • antigen present in the outer membrane of gram negative cells
  • examples include E. coli O157:H7
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Lipid A
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  • An endotoxin present in the outer membrane of gram negative cells
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Porins
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  • proteins that form channels through the outer membrane of gram-negative cells
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The Gram Stain Mechanism
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  • Crystal violet-iodine crystals form in cell
  • Gram-positive
    • alcohol dehydrates peptidoglycan
    • CV-I crystals do not leave
  • Gram-negative
    • alcohol dissolves outer membrane and leaves holes in peptidoglycan
    • CV-I washes out
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Gram-Positive cell wall
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  • 2-ring basal body
  • Disrupted by lysozyme
  • Penicillin sensitive
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Gram-Negative cell wall
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  • 4-ring basal body
  • Endotoxin
  • Tetracycline sensitive
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Atypical cell walls
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  • Acid-fast cell walls
  • Mycoplasms
  • Archaea
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Acid-fast cell walls
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  • Like gram-positive cell walls
  • waxy lipid (mycolic acid) bound to peptidoglycan
  • Mycobacterium
  • Nocardia
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Mycoplasmas
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  • Lack cell walls
  • Sterols in plasma membrane
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Archaea
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  • Wall-less, or
  • walls of pseudomurein (lack NAM and D-amino acids)
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Damage to the Cell Wall
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  • Lysozyme digests disaccharide in peptidoglycan
  • Penicillin inhibits peptide bridges in peptidoglycan
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Protoplast
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  • wall-less cell
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Spheroplast
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  • wall-less gram-positive cell
  • protoplasts and spheroplasts are susceptible to osmotic lysis
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L forms
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  • wall-less cells that swell into irregular shapes
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The Plasma Membrane
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  • Phospholipid bilayer
  • Peripheral proteins
  • Integral proteins
  • Transmembrane
  • Proteins
  • Contain enzymes for ATP production
  • Selective permeability allows passage of some molecules
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Fluid Mosaic Model
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  • Membrane is viscous as olive oil
  • Proteins move to function
  • Phospholipids rotate and move laterally
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Selective permeability
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  • allows passage of some molecules
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Chromatophores
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  • Also called thylakoids
  • present in the plasma membrane
  • Photosynthetic pigments on foldings in the plasma membrane
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Damage to the plasma membrane
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  • Damage done by alcohols, quaternary ammonium (detergents), and polymyxin antibiotics cause leakage of cell contents
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simple diffustion
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  • movement of a solute from an area of high concentration to an area of low concentration
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Facilitated diffusion
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  • solute combines with a transporter protein in the membrane
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Osmosis
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  • the movement of water across a selectively permeable membrane from an area of high water to an area of lower water concentration
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Osmotic pressure
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  • the pressure needed to stop the movement of water across the membrane
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Movement of materials across membranes
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  • Through lipid layer
  • Aquaporins (water channels)
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Ative transport
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  • requires a transporter protein and ATP
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Group translocation
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requires a transporter protein and PEP
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Cyoplasm
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  • The substance inside the plasma membrane
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The Prokaryotic Ribosome
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  • Protein synthesis
  • 70s
    • 50s + 30s subunits
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Inclusions
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  • Metachromatic granules (volutin)
  • Polysaccharide granules
  • Lipid inclusions
  • Sulfur granules
  • Carboxysomes
  • Gas vacuoles
  • Magnetosomes
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Metachromatic granules
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  • Also called Volutin
  • Phosphate reserves
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Polysaccharide granules
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  • energy reserves
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Lipid inclusions
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  • energy reserves
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Sulfur granules
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  • energy reserves
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Carboxysomes
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  • Ribulose 1,5-diphosphate carboxylase for CO2 fixation
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Gas vacuoles
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  • protein-covered cylinders
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Magnetosomes
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  • Iron oxide (destroys H2O2)
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Endospores
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  • Resting cells
  • Resistant to desiccation, heat, chemicals
  • Bacillus, Clostridium
  • Sporulation and Germination
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Sporulation
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  • endospore formation
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Germination
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  • Return to vegetative state
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Endospore formation
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  1. Spore septum begins to isolate newly replicated DNA and a small portion of cytoplasm
  2. Plasma membrane starts to surround DNA, cytoplasm, and membrane isolated in step 1
  3. Spore septum surrounds isolated portion, forming forespore
  4. Peptidoglycan layer forms between membranes
  5. Spore coat forms
  6. Endospore is freed from cell
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Flagella and Cilia
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  • Microtubules
  • Tublin
  • 9 pairs + 2 array
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Endocytosis
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  • energy using process by which cells absorb molecules by engulfing them
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Phagocytosis
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  • pseudopods extend and engulf particles
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Pinocytosis
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  • membrane folds inward, bringing in fluid and dissolved substances
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Cytoplasm membrane
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  • substance inside plasma and outside nucleus
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Cytosol
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  • fluid portion of cytoplasm
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Cytoskeleton
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  • microfilaments, intermediate filaments, microtubules
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Cytoplasmic streaming
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  • Movement of cytoplasm throughout cells
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Ribosomes
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  • Protein synthesis
  • 80S
    • Membrane-bound: attached to ER
    • Free: in cytoplasm
  • 70S
    • In chloroplasts and mitochondria
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Organelles
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  • Nucleus
  • Endoplasmic Reticulum
  • Golgi complex
  • Lysosome
  • Vacuole
  • Mitochondrion
  • Chloroplast
  • Peroxisome
  • Centrosome
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Nucleus
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  • contains chromosomes
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Endoplasmic Reticulum
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  • also called ER
  • transport network
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Golgi complex
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  • membrane formation and secretion
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Lysosome
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  • Digestive enzymes
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Vacuole
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  • Brings food into cells and provides support
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Mitochondrion
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  • cellular respiration
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Chloroplast
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  • photosynthesis
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Peroxisome
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  • oxidation of fatty acids; destroys H2O2
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Centrosome
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  • consists of protein fibers and centrioles
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