Prokaryotes vs. Eukaryotes Quiz

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Questions and Answers

What is a distinguishing characteristic of prokaryotes?

  • Associated with histones
  • Single circularly arranged chromosome (correct)
  • DNA enclosed within a membrane
  • Lack cell walls

What are the distinguishing characteristics of eukaryotes?

DNA is in nucleus, multiple chromosomes, associated with histones, has membrane-enclosed organelles, and undergoes mitosis.

Bacteria range in size from _____ in diameter and ______ in length.

0.2-2.0 micrometers, 2-8 micrometers

What are the three possible shapes of bacteria?

<p>Coccus, Bacillus, Spiral</p> Signup and view all the answers

Cocci are usually ______ and are elongated and flattened on one side.

<p>Round</p> Signup and view all the answers

How do cocci reproduce?

<p>Divide</p> Signup and view all the answers

Match the type of cocci with their arrangement after division:

<p>Pairs = Diplococci Chainlike patterns = Streptococci Groups of four = Tetrads Groups of eight = Sarcinae Clusters = Staphylococci</p> Signup and view all the answers

How do bacilli appear and divide?

<p>As single rods and divide only across their short axis</p> Signup and view all the answers

What do diplobacilli look like after division?

<p>Appear in pairs</p> Signup and view all the answers

What is the structure of streptobacilli?

<p>Occur in chains</p> Signup and view all the answers

What is the appearance of coccobacilli?

<p>Oval, look very similar to cocci</p> Signup and view all the answers

'Bacillus' has how many meanings?

<p>Two meanings (D)</p> Signup and view all the answers

What do vibrios look like?

<p>Curved rods</p> Signup and view all the answers

What is the shape of spirilla?

<p>Helical shape</p> Signup and view all the answers

What is special about spirochetes?

<p>Helical and flexible</p> Signup and view all the answers

What are some additional bacterial shapes?

<p>All of the above (D)</p> Signup and view all the answers

What determines the shape of bacteria?

<p>Heredity</p> Signup and view all the answers

Most bacteria are monomorphic.

<p>True (A)</p> Signup and view all the answers

What does it mean for bacteria to be pleomorphic?

<p>Can have many shapes</p> Signup and view all the answers

What are the three basic components of a prokaryotic cell?

<p>Structures external to the cell wall, the cell wall, structures internal to the cell wall</p> Signup and view all the answers

List some structures external to the cell wall.

<p>Glycocalyx, Flagella, Axial filaments, Pili, Fimbriae</p> Signup and view all the answers

Describe the glycocalyx.

<p>Substance secreted by prokaryotes, viscous, gelatinous polymer composed of polysaccharide or polypeptide.</p> Signup and view all the answers

What is a capsule?

<p>Substance organized and firmly attached to the cell wall</p> Signup and view all the answers

How can the presence of a capsule be detected?

<p>Negative staining</p> Signup and view all the answers

What defines a slime layer?

<p>Unorganized and loosely attached to the cell wall</p> Signup and view all the answers

Capsules contribute to bacterial virulence by protecting against _____

<p>Phagocytosis by the cells of the host</p> Signup and view all the answers

What is glycocalyx important for?

<p>Biofilms</p> Signup and view all the answers

What is extracellular polymeric substance?

<p>Glycocalyx that helps cells in a biofilm attach to their environment and to each other.</p> Signup and view all the answers

What does glycocalyx protect a cell against?

<p>Dehydration, prevents nutrients from leaving the cell</p> Signup and view all the answers

What are flagella?

<p>Long, filamentous appendages that propel bacteria</p> Signup and view all the answers

What are bacteria without flagella called?

<p>Atrichous</p> Signup and view all the answers

Match the types of flagella with their distribution:

<p>Peritrichous = Distributed over the entire cell Polar = At one or both poles/ends of cells</p> Signup and view all the answers

Match polar flagella types:

<p>Monotrichous = Single flagellum at one pole Lophotrichous = A tuft of flagella from one pole Amphitrichous = Flagella at both poles</p> Signup and view all the answers

What are the three basic parts of flagella?

<p>Filament, Hook, Basal Body</p> Signup and view all the answers

Describe the filament of the flagellum.

<p>Long, outermost region, constant in diameter, contains globular protein flagella in chains.</p> Signup and view all the answers

What is the basal body of the flagellum?

<p>Anchors flagellum to the cell wall and plasma membrane.</p> Signup and view all the answers

What characterizes the gram-negative basal body?

<p>Two pairs of rings</p> Signup and view all the answers

What characterizes the gram-positive basal body?

<p>Only inner pair is present</p> Signup and view all the answers

How do flagella move?

<p>Rotation from the basal body</p> Signup and view all the answers

What can bacterial cells alter regarding flagella?

<p>Speed and direction of rotation</p> Signup and view all the answers

What is motility?

<p>Ability of an organism to move by itself</p> Signup and view all the answers

Movement in one direction for any length of time is called _____

<p>Run or swim</p> Signup and view all the answers

Runs are interrupted by random changes called _____

<p>Tumbles</p> Signup and view all the answers

What causes tumbles?

<p>Reversal of flagella rotation</p> Signup and view all the answers

What is taxis?

<p>The movement of bacterium toward/away from a stimulus</p> Signup and view all the answers

What are the two types of stimuli that spur taxis?

<p>Both A and B (C)</p> Signup and view all the answers

What do motile bacteria have to detect chemical stimuli?

<p>Receptors</p> Signup and view all the answers

What are the two types of signals bacteria can receive?

<p>Both A and B (C)</p> Signup and view all the answers

What is H antigen?

<p>Flagellar protein useful for distinguishing among serovars.</p> Signup and view all the answers

What are axial filaments?

<p>Structures similar to flagella, enabling movement in spirochetes.</p> Signup and view all the answers

What do spirochetes exhibit?

<p>Unique structure and motility</p> Signup and view all the answers

What type of bacteria have hairlike appendages that are shorter than flagella?

<p>Gram-negative bacteria</p> Signup and view all the answers

What is fimbriae?

<p>Hairlike appendages used for attachment and DNA transfer.</p> Signup and view all the answers

What are pili?

<p>Longer than fimbriae, involved in motility and DNA transfer.</p> Signup and view all the answers

Describe twitching motility.

<p>Pili extend, make contact with surfaces, then retracts for movement.</p> Signup and view all the answers

What is gliding motility?

<p>Smooth, gliding movement of myxobacteria.</p> Signup and view all the answers

What is the function of the cell wall in bacteria?

<p>To provide shape and protect the cell from adverse changes.</p> Signup and view all the answers

What are the typical functions of the cell wall?

<p>Preventing cells from rupturing due to water pressure.</p> Signup and view all the answers

The cell wall is composed of what macromolecule?

<p>Peptidoglycan</p> Signup and view all the answers

How do peptide cross-bridges interact with cell walls?

<p>They weaken the cell wall, causing lysis.</p> Signup and view all the answers

What happens during lysis?

<p>Rupture of plasma membrane and loss of cytoplasm.</p> Signup and view all the answers

Describe gram-positive cell walls.

<p>Many layers of peptidoglycan, thick and rigid structure.</p> Signup and view all the answers

What are the two classes of teichoic acids?

<p>Lipoteichoic and wall teichoic</p> Signup and view all the answers

What do negatively charged teichoic acids do?

<p>Regulate movement of cations.</p> Signup and view all the answers

What are teichoic acids involved in?

<p>Cell growth, preventing wall breakdown, and preventing cell lysis.</p> Signup and view all the answers

What covers the cell walls of gram-positive streptococci?

<p>Polysaccharides</p> Signup and view all the answers

Describe gram-negative cell walls.

<p>Thin layer of peptidoglycan and an outer membrane.</p> Signup and view all the answers

What does the outer membrane of gram-negative cell walls contain?

<p>Lipopolysaccharides (LPS)</p> Signup and view all the answers

What are the specialized functions of the outer wall?

<p>Evade phagocytosis, provides barrier to antibiotics and enzymes.</p> Signup and view all the answers

What makes the outer wall slightly permeable?

<p>Porins</p> Signup and view all the answers

What is lipopolysaccharides composed of?

<p>Lipid A, core polysaccharide, O polysaccharide</p> Signup and view all the answers

What is Lipid A?

<p>Lipid portion of LPS, functions as an endotoxin when released.</p> Signup and view all the answers

What does the core polysaccharide provide?

<p>Stability</p> Signup and view all the answers

What role does the O polysaccharide play?

<p>Functions as an antigen useful for distinguishing gram-negative species.</p> Signup and view all the answers

What is the Gram stain mechanism based on?

<p>Differences in the structure of the cell walls of gram-positive and gram-negative bacteria.</p> Signup and view all the answers

What does crystal violet stain?

<p>Both gram-positive and gram-negative bacteria purple.</p> Signup and view all the answers

What does iodine (mordant) do?

<p>Causes crystals to form.</p> Signup and view all the answers

What effect does alcohol wash have on gram-positive walls?

<p>Dehydrates the peptidoglycan, making it impermeable to the crystal violet-iodine.</p> Signup and view all the answers

What happens to gram-negative bacteria during alcohol wash?

<p>Dissolves the outer membrane, leaving holes in the peptidoglycan layer.</p> Signup and view all the answers

What defines atypical cell walls?

<p>No walls or very little material.</p> Signup and view all the answers

What do archaea lack in terms of their cell wall?

<p>Lack walls or have walls that contain polysaccharides/proteins, not peptidoglycan.</p> Signup and view all the answers

What can enzymatic treatment do to cell walls?

<p>Can damage cell walls, especially in the presence of lysozyme.</p> Signup and view all the answers

Describe lysozyme.

<p>Digestive enzyme that occurs naturally in tears, mucus, and saliva.</p> Signup and view all the answers

What occurs if lysis does not occur?

<p>Cell remains surrounded by plasma membrane as a protoplast.</p> Signup and view all the answers

What can happen to cells in the genus Proteus?

<p>Can lose their cell walls and swell into irregularly shaped cells.</p> Signup and view all the answers

What are L forms?

<p>Cells that can live and divide without cell walls.</p> Signup and view all the answers

What happens to gram-negative walls when lysozyme is applied?

<p>Wall is not destroyed to the same extent as gram-positive walls.</p> Signup and view all the answers

What do protoplasts and spheroplasts undergo in pure water?

<p>Osmotic lysis.</p> Signup and view all the answers

Describe the plasma membrane.

<p>Thin structure enclosing the cytoplasm, primarily phospholipids.</p> Signup and view all the answers

What is the most important function of the plasma membrane?

<p>Serve as a selective barrier through which materials enter/exit.</p> Signup and view all the answers

What includes movement across membranes?

<p>Both A and B (C)</p> Signup and view all the answers

What is simple diffusion?

<p>Net movement of molecules from high to low concentration without energy.</p> Signup and view all the answers

What is facilitated diffusion?

<p>Proteins assist in moving ions across membranes without energy.</p> Signup and view all the answers

What is osmosis?

<p>Net movement of solvent molecules across a selectively permeable membrane.</p> Signup and view all the answers

What does osmotic pressure refer to?

<p>Pressure required to prevent movement of water into a solution.</p> Signup and view all the answers

What are the three types of osmotic solutions?

<p>Isotonic, Hypotonic, Hypertonic (A)</p> Signup and view all the answers

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Study Notes

Prokaryotes vs. Eukaryotes

  • Prokaryotes have DNA in a singular circular chromosome, not enclosed within a membrane, while eukaryotes have multiple chromosomes within a nucleus.
  • Prokaryotic DNA is not associated with histones, whereas eukaryotic DNA is associated with histones and non-histones.
  • Prokaryotes lack membrane-bound organelles; eukaryotes contain organelles such as mitochondria, ER, Golgi complex.
  • Prokaryotic cell walls are primarily made of peptidoglycan, while eukaryotic cell walls, if present, are simpler.
  • Prokaryotes reproduce via binary fission; eukaryotes use mitosis.

Bacterial Size and Shape

  • Bacteria typically range from 0.2-2.0 micrometers in diameter and 2-8 micrometers in length.
  • Common bacterial shapes include cocci (spherical), bacilli (rod-shaped), and spiral.

Bacterial Arrangement

  • Cocci can exist as:
    • Diplococci: pairs
    • Streptococci: chains
    • Tetrads: groups of four
    • Sarcinae: groups of eight
    • Staphylococci: clusters
  • Bacilli divide only across their short axis and can form:
    • Diplobacilli: pairs
    • Streptobacilli: chains
    • Coccobacilli: oval shapes resembling cocci.

Glycocalyx and Its Functions

  • Glycocalyx is a substance secreted by prokaryotes, serving as a biofilm's component; it is viscous and sticky.
  • Encapsulated bacteria are organized and firmly attached, while slime layers are unorganized and loosely attached.
  • Capsules can enhance bacterial virulence and protect pathogenic bacteria from phagocytosis.

Flagella Structure and Function

  • Flagella are long, filamentous appendages crucial for bacterial movement.
  • There are two types of flagella arrangements: peritrichous (around the entire cell) and polar (at one or both ends).
  • The basic structure of flagella includes a filament, hook, and basal body, with movement achieved through rotation of the basal body.

Cell Wall Characteristics

  • Prokaryotic cell walls are complex, semirigid structures composed mainly of peptidoglycan.
  • Gram-positive bacteria have thick layers of peptidoglycan, while gram-negative bacteria have a thin layer surrounded by an outer membrane containing lipopolysaccharides (LPS).
  • Peptidoglycan consists of alternating NAM and NAG linked by peptide cross-bridges; this forms a network providing shape and strength to the cell wall.

Antibiotic Action

  • Penicillin targets the peptidoglycan structure, weakening the cell wall and potentially causing lysis.
  • Lysis is the destruction induced by the rupturing of the plasma membrane, which can lead to cell death.

Osmotic Responses

  • Protoplasts (gram-positive) and spheroplasts (gram-negative) form when exposure to lysozyme or other agents damages the cell wall.
  • Osmotic lysis occurs when the cell swells due to internal pressure exceeding external pressure, often in dilute solutions.

Plasma Membrane Role

  • The plasma membrane is a selective barrier that controls the flow of materials in and out of the cell, primarily composed of a phospholipid bilayer.
  • The movement across membranes can occur through passive processes like simple diffusion and facilitated diffusion, as well as osmosis, which specifically involves solvent movement (mostly water).

Types of Osmotic Solutions

  • Isotonic: equal solute concentration inside and outside the cell.
  • Hypotonic: lower solute concentration outside the cell; may cause cell swelling.
  • Hypertonic: higher solute concentration outside the cell; may lead to cell shrinkage.

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