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Servsafe Alcohol Exam Explained Questions With Correct Answers., Exams of Microbiology

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Microbiology Chapter 3 2025 2026
Questions And Answers.
Prokaryotes can be distinguished from eukaryotes by
The way their DNA is packaged (lack of nucleus and histones) Bacteria & Archaea have genetic
material that is free inside the cell - The makeup of their cell wall (peptidoglycan (Bacteria) and other
unique chemicals (Archaea) providing sturdy cell walls) - Their internal structure (lack of membrane
bounded organelles)
All bacterial cells possess:
-cell membrane
-cytoplasm
-ribosomes
-cytoskeleton
-one (or a few) chromosomes
cell membrane
Surrounds cytoplasm
cytoplasm
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Microbiology Chapter 3 2025 2026

Questions And Answers.

Prokaryotes can be distinguished from eukaryotes by

The way their DNA is packaged (lack of nucleus and histones) → Bacteria & Archaea have genetic material that is free inside the cell - The makeup of their cell wall (peptidoglycan (Bacteria) and other unique chemicals (Archaea) providing sturdy cell walls) - Their internal structure (lack of membrane bounded organelles)

All bacterial cells possess:

  • cell membrane
  • cytoplasm
  • ribosomes
  • cytoskeleton
  • one (or a few) chromosomes

cell membrane

Surrounds cytoplasm

cytoplasm

Water-based solution filling cell

Ribosomes

Sites of protein synthesis

Cytoskeleton

Encircle cell inside cell membrane contributing to the shape of the cell

One (or a few) chromosome(s)

Composed of condensed DNA molecules

•Most bacterial cells possess

cell wall

glycocalyx (surface coating)

cell wall

Semirigid casing providing structural support

Surface coating called a glycocalyx

Stored nutrient such as fat, phosphate, or glycogen

Endospores

Dormant body formed within some bacteria that allows for their survival in adverse conditions

prokaryotic cell

A type of cell lacking a membrane-enclosed nucleus and membrane-enclosed organelles; found only in the domains Bacteria and Archaea.

•Most prokaryotes (talking primarily about bacteria) exist as unicellular organisms

Sometimes they can act as a group, in colonies or in biofilms (communicating with one another via chemicals that cause the, to behave differently than if they were living singly) - Also capable of communicating nanotubes or nanowires (appendages used for transferring electrons or other substances)

On average, prokaryotic cells are

1 mm (microns) - Can range from 0.05 - 0.2 mm ("nanobes") to 750 mm

•Cells of one species may vary in shape and size

This is pleomorphism caused by variations in cell wall structure

coccus (cocci)

berry-shaped bacteria/bacterium

rod/bacillus

cylindrical shaped bacteria

Vibrio

a curved, rod-shaped bacterial cell

Spirillum

Spiral-shaped bacterial cell (rigid)

Spirochetes

spiral-shaped bacteria that have flexible walls and are capable of movement

branching filaments

a few bacteria produce multiple branches off of a basic rod structure

Bacterial cells can also be categorized according to arrangement, or style of grouping. The greatest variety in arrangement occurs in cocci:

Monotrichous

Single flagellum

Lophotrichous

small bunches or tufts of flagella

Amphitrichous

flagella at both poles of the cell

Peritrichous:

flagella distributed over the entire cell

All spirilla, about half of the rods, and a small number of the cocci are

flagellated

Flagella are often difficult to see via light microscopy. However, because the primary function of flagella is motility, simply knowing is a microbe is motile or not can aid in

identification.

If the flagella are found on the ends of a cell, they are termed

polar

•Bacteria move in response to chemical signals

(chemotaxis) → Positive (moving towards) vs. Negative (moving away from)

•Receptors bind extracellular molecules, which triggers flagellum to

rotate

•The actual "fuel" for the flagellum to turn is a gradient of protons (hydrogen ions) that are generated by the metabolism of the bacterium and that bind to an detach from parts of the flagellar

motor

•Runs

Smooth linear movement toward a stimulus

•Tumbles

Flagellar rotation reverses, causing the cell to stop and change its course

CAPSULE

Bound more tightly to the cell, denser and thicker than a slime layer • Visible by negative staining • Produces a sticky (mucoid) character to colonies • Encapsulated bacterial cells generally have greater pathogenicity.

Cell Envelope •Lies outside of the cytoplasm •Composed of two or three basic layers:

Cell wall - Cell membrane - Outer membrane in some bacteria • Although each envelope layer performs a distinct function, together they act as a single protective unit.

peptidoglycan cell wall

Repeating framework of long glycan (sugar) chains cross-linked by short peptide (protein) fragments → Provides the relatively rigid quality • Present in most bacteria • Provides strength to resist rupturing due to osmotic pressure (Antibacterial drugs operate on this premise, breaking down the peptide cross-links, leading to a weakened cell wall and ultimately lysis. Lysozyme acts similarly naturally in the body

Gram Positive Cell

Thick peptidoglycan → Several layers of peptidoglycan • Also contains teichoic acid, lipoteichoic acid (Tightly-bound, acidic polysaccharides) → Function in cell wall maintenance and enlargement during cell division • One membran

The differences in the peptidoglycan layer of the cell envelope is what is largely responsible for the designations of

gram-negative vs. gram-positive bacteria.

Gram Negative Cell

Thin peptidoglycan → One layer •Lipopolysaccharide •Two membranes •Porins

The Gram Stain: Developed by Hans Christian Gram (

  1. Crystal violet First, crystal violet is added to the cells in a smear. It stains them all the same purple color.
  2. Gram's iodine Then, the mordant, Gram's iodine, is added. This is a stabilizer that causes the dye to form large complexes in the peptidoglycan meshwork of the cell wall. The thicker gram-positive cell walls are able to more firmly trap the large complexes than those of the gram-negative cells.
  3. Alcohol Application of alcohol dissolves lipids in the outer membrane and removes the dye from the peptidoglycan layer—only in the gram-negative cells.
  4. Safranin (red dye) Because gram-negative bacteria are colorless after decolorization, their presence is demonstrated by applying the counterstain safranin in the final step

Acid-Fast Bacteria

•Mycobacterium sp. and Nocardia sp. •Bulk of the cell wall is composed of mycolic acid (a wax) → Contributes to the pathogenicity of this group •Modified Gram-positive structure

Acid-Fast Bacteria is highly-resistant to certain chemicals and dyes, so they must use the acid-fast stain to ID important pathogens causing:

Tuberculosis - Leprosy

70 - 80% water → Serving as a solvent for the contents of the cell •Soluble proteins, salts, carbohydrates •Site of nearly all chemical reactions •Contains the DNA in the nucleoid •Some distinguish between the cytoplasm and the cytosol

•DNA of most bacteria exists in the form of a single circular

bacterial chromosome

•DNA is aggregated in a dense area of the cell called the

nucleoid (No nucleus, no nuclear membrane)

Many bacteria contain other, nonessential pieces of DNA called

plasmids (Exist as separate, doublestranded pieces of DNA) → Not essential to bacterial growth and metabolism, but do provide protective traits such as resisting drugs and producing toxins and enzymes

Prokaryotic Ribosome

•Site of protein synthesis •Often occur in chains called polysomes •Two subunits (30S and 50S) •Total size is 70S (versus 80S in eukaryotes) •60% rRNA and 40% protein •Translates mRNA into proteins

Inclusions or Granules: Storage Bodies

Non-membrane bound granules that respond to the environmental conditions of a bacteria • Usually for storage of nutrients, storage of gas, and even storage of crystals of iron oxide with magnetic properties

The Cytoskeleton

Peptidoglycan layer determines shape of many bacteria, but in some, the cytoskeleton contributes as well • Others use protein fibers composed of actin and tubulin to alter cell shape

Bacterial Endospores

Dormant bodies that can withstand hostile conditions and facilitate survival

  • Heat resistance due to calcium and dipicolinic acid content removing water in the protoplasm
  • The thick cortex and endospore coats protect against radiation and chemicals
  • Metabolically active vegetative cells can undergo

sporulation when environmental conditions become challenging

Sporulation is not

a reproductive function for most bacteria

When spores of Clostridium sp. are embedded in a wound with dead tissue, they can

germinate, grow, and release toxins

A Typical Sporulation Cycle in Bacillus Species

e refers to representatives of a species that stimulate a distinct pattern of antibody (serum) responses in their hosts, because of distinct surface molecules