Microbiology - Ch. 4 Prokaryotic and Eukaryotic Cell Anatomy - flashcards 2

Why do we need to know average bacterial size?

For identification purposes.

What unit is bacterial size measured in?

Microns (μm) — e.g., ~2.0 μm diameter × ~8 μm length.

What does "monomorphic" mean?

One shape present in the visual field — all bacteria are identical.

What does "pleomorphic" mean?

Several shapes present in visual field — more than one type of bacteria present.

What is a coccus?

Round/spherical bacterium.

What is a bacillus?

Rod-shaped bacterium.

What is a coccobacillus?

Oval-shaped bacterium (between coccus and bacillus).

What are the 3 types of spiral bacteria?

Vibrio, Spirillum, Spirochete.

What shape is Vibrio?

"Comma"-shaped.

Are all spiral bacteria motile?

Yes.

Compare Spirilla vs Spirochetes: rigidity.

Spirilla = rigid; Spirochetes = flexible.

Compare Spirilla vs Spirochetes: size/thickness.

Spirilla = short/thick; Spirochetes = longer/thin.

Compare Spirilla vs Spirochetes: coiling.

Spirilla = loosely-coiled; Spirochetes = tightly-coiled.

How do Spirilla move?

Via (external) flagella.

How do Spirochetes move?

Via endoflagella (internal flagella).

What arrangement term means "pairs"?

Diplo- (e.g., diplococci, diplobacilli).

What arrangement term means "clusters"?

Staphylo- (e.g., staphylococci).

What arrangement term means "chains"?

Strepto- (e.g., streptococci, streptobacilli).

What is a tetrad?

A group of four bacteria arranged together.

What is a sarcina?

A cube-like group of eight bacteria.

Is the glycocalyx present in all bacteria?

No — it may or may not be present (optional).

Where is the glycocalyx located?

External to the cell wall; surrounds the bacterium.

What is the glycocalyx made of?

Polysaccharide (carbohydrate) or polypeptide (protein).

What are the two types of glycocalyces?

Capsule and slime layer.

What is a capsule made of, and what's its structure?

Made of polysaccharide; thick, organized, and tightly attached to the cell wall.

What is a slime layer made of, and what's its structure?

Made of protein; thin, unorganized, and loosely attached to the cell wall.

How does a capsule help bacteria attach to host tissue?

Its "stickiness" (due to carbohydrate composition) lets it adhere.

How does a capsule help bacteria evade the immune system?

It makes the bacterium look bigger, so it escapes phagocytosis (engulfment).

Name two examples of encapsulated bacteria.

Streptococcus mutans and Streptococcus pneumoniae.

What protein are flagella made of?

Flagellin.

What are two functions of flagella?

Movement/propulsion — to find nutrient sources and escape phagocytosis.

What structural hierarchy do flagellin proteins form?

Flagellin proteins arrange into filaments; filaments make up a flagellum.

What is an "H antigen"?

A flagellin protein that acts as a surface marker, helping distinguish bacterial subspecies/strains.

Give an example of an H antigen designation.

E. coli O157:H7 — H7 refers to a specific flagellar (H) antigen type.

What are the three parts of a flagellum?

Filament (outermost region), hook (attaches to filament), basal body (anchors flagellum).

What connects the filament to the basal body?

The hook.

Which bacterial shapes have flagella?

Some bacilli and all spirilla.

What are axial filaments also known as?

Endoflagella.

Where are axial filaments found?

In spirochetes.

Where are axial filaments located relative to the cell?

Internal (intracellular), anchored at one end, within the cell wall.

How does rotation of the endoflagellum cause movement?

It causes the cell to move in a corkscrew/spiral motion.

What is the function of fimbriae?

Hair-like appendages that allow for attachment.

What is fimbriae made of, and where located?

Made of protein; external to the cell.

What is the function of pili?

"Twitching" motility and DNA transfer from one cell to another.

What is an example of a pilus used in DNA transfer?

Conjugation pilus.

In conjugation, what happens to the recipient cell after DNA transfer?

It receives inserted DNA from the donor bacterium and becomes genetically different.

What is the outermost layer of a bacterial cell if no capsule is present?

The cell wall.

What are the two main functions of the cell wall?

Prevents osmotic lysis and protects the cell membrane.

What molecule makes up the cell wall structurally?

Peptidoglycan (rows of carbohydrates connected to proteins).

What determines Gram-positive vs. Gram-negative classification?

Amount of peptidoglycan in the cell wall — more = Gram-positive, less = Gram-negative.

Describe the Gram-positive cell wall.

Thick peptidoglycan layer, has teichoic acids, no outer membrane, sensitive to penicillin.

Describe the Gram-negative cell wall.

Thin peptidoglycan layer, no teichoic acids, has an outer membrane with LPS, resistant to penicillin.

Why is penicillin effective against Gram-positive but not Gram-negative bacteria?

PCN destroys the peptidoglycan layer/cell wall — Gram-negatives are protected by their outer membrane and thin peptidoglycan resists destruction.

What does LPS stand for and where is it found?

Lipopolysaccharide; major component of the outer membrane of Gram-negative cell walls.

What are LPS's two chemical components?

Lipids and carbohydrates.

Name the 3 components of LPS.

Lipid A, Core polysaccharide, O polysaccharide.

What is the function of Lipid A?

Functions as a toxin; embedded in the cell wall's outer membrane.

What is the function of core polysaccharide?

Joins Lipid A and O polysaccharide.

What is the function of O polysaccharide?

Functions as an antigen (surface marker); sticks out; helps distinguish subspecies/strains (e.g., E. coli O157 in O157:H7).

What is the purpose of Gram staining?

To classify and identify bacteria by staining the peptidoglycan-containing cell wall.

List the 4 steps of Gram staining in order.

1) Crystal violet (purple dye), 2) Iodine (mordant), 3) Alcohol wash (decolorization), 4) Safranin (counterstain).

What color do all cells start as during Gram staining?

Purple/violet.

Why doesn't iodine alone decolorize Gram-positive bacteria?

Iodine acts as a mordant that helps crystal violet bind — the thick peptidoglycan traps the dye so alcohol can't wash it out.

What color does a Gram-positive cell wall appear after staining?

Purple/violet (keeps the purple dye).

What color does a Gram-negative cell wall appear after staining?

Red/pink (does NOT keep purple dye; picks up safranin instead).

What 4 criteria are used to identify bacteria under a microscope?

Gram reaction, shape, arrangement, size.

What is unique about the Genus Mycobacterium cell wall?

Has a waxy lipid (mycolic acid) bound to peptidoglycan; uses acid-fast stain instead of Gram stain.

How does mycolic acid protect Mycobacterium from phagocytes?

It prevents digestion of the bacterium after being engulfed — the phagocyte engulfs it, but it's not destroyed.

What is unique about Genus Mycoplasma?

It lacks a cell wall entirely.

What is unique about Domain Archaea's cell wall?

No peptidoglycan present.

Where is the plasma membrane located relative to the cell wall?

Deep to the cell wall.

What is the plasma membrane's basic structure?

Phospholipid bilayer enclosing the cytoplasm.

What's the difference between peripheral and integral/transmembrane proteins?

Peripheral proteins sit on the membrane surface; integral/transmembrane proteins penetrate the membrane.

What are the 3 functions of the plasma membrane?

Transport (selective permeability), site of ATP production, site of photosynthesis (in certain bacteria only).

Why is the plasma membrane the site of ATP production in bacteria?

Because bacteria lack mitochondria.

Why is the plasma membrane the site of photosynthesis in some bacteria?

Because bacteria lack chloroplasts (only possible in certain photosynthetic bacteria).

What direction does passive transport move particles?

High concentration to low concentration.

Does passive transport require energy?

No.

What direction does active transport move particles?

Low concentration to high concentration.

Does active transport require energy?

Yes (ATP).

What is simple diffusion?

Movement of small, uncharged particles across the cell membrane (no protein channel needed).

What is facilitated diffusion?

Movement of large, charged particles across the membrane, requiring a protein channel or carrier.

What is osmosis?

Movement of water across a membrane; requires a concentration difference.

What is an isotonic solution?

Same concentration of particles inside and outside the cell.

What is a hypotonic solution?

Low particle concentration outside the cell relative to inside.

What happens to a cell in a hypotonic solution?

It swells because water enters the cell.

What is a hypertonic solution?

High particle concentration outside the cell relative to inside.

What happens to a cell in a hypertonic solution?

It shrinks because water leaves the cell.

In osmosis, which direction does water move relative to solute concentration?

Water moves from low solute concentration to high solute concentration.

What is bacterial cytoplasm mostly composed of?

80% water plus proteins, carbohydrates, lipids, and ions.

What organelles are present in bacterial cytoplasm?

None, except ribosomes.

What are bacterial ribosomes called?

70S ribosomes.

Are bacterial ribosomes membrane-bound?

No — not surrounded by a membrane.

What is the function of ribosomes?

Sites of protein synthesis.

What are the two subunits of a 70S ribosome?

Large subunit and small subunit.

What is the nucleoid?

A "nucleus-like" region containing the bacterial chromosome (vs. a true nucleus in eukaryotes).

Describe the bacterial chromosome's structure.

Circular thread of DNA, supercoiled/compacted, contains most of the cell's genetic info, NOT surrounded by a nuclear membrane.

What is a plasmid?

Small, circular, extrachromosomal genetic material (in addition to the nucleoid).

What kind of genes do plasmids carry?

"Non-crucial" genes that aid adaptability and survival.

Give two examples of what plasmid genes encode.

Antibiotic resistance and toxin production.