Lect 28 - prokaryotic cells - structural components and their roles

Flashcards about Prokaryotic Cells - Structural Components and Their Roles, covering topics like the bacterial genome, cell wall, Gram stain, flagella, adherence factors, glycocalyx, and endospores.

What is the structure and location of the bacterial chromosome?

Singular, circular chromosome located in the nucleoid region without a nuclear membrane.

What are plasmids?

Small, circular, self-replicating DNA molecules found in the cytosol, separate from the main chromosome.

What is the function of the peptidoglycan cell wall in bacteria?

Provides strength to the cell, protects against osmotic lysis, and confers cell shape.

What are mycoplasmas?

Prokaryotes that lack a cell wall and are groups of pathogenic bacteria.

What is the function of transpeptidase in bacteria?

It is the enzyme that cross-links the peptidoglycan chains to form rigid cell walls.

What is the Gram stain used for, and in what year was it developed?

Used to differentiate bacteria based on their cell wall structure; developed in 1877.

Outline the steps of the Gram stain procedure.

1. Apply crystal violet dye; 2. Apply iodine solution (mordant); 3. Wash with alcohol (decolorize); 4. Apply safranin (counterstain).

How does the Gram stain differentiate between Gram-positive and Gram-negative bacteria?

Gram-positive bacteria retain the crystal violet dye due to a thick peptidoglycan layer, while Gram-negative bacteria lose the dye due to a thin peptidoglycan layer.

What is the structure of Gram-positive bacterial cell walls?

Thick peptidoglycan layer (20-80 nm) that traps crystal violet dye.

What is the structure of Gram-negative bacterial cell walls?

Thin peptidoglycan layer (5-10 nm) with inner and outer membranes, allowing crystal violet to be easily rinsed away.

What is the function of bacterial flagella?

Enable motility by rotating like a propeller to move the cell through a liquid medium.

What is chemotaxis?

A tactic response where bacteria move along a concentration gradient towards a chemical attractant or away from a chemical repellent.

What are fimbriae?

Adherence pili or adhesins; structures with adhesive properties that cause bacteria to stick to surfaces.

What is the function of pili (sex pili or F pili)?

Attachment to other bacteria for the transfer of genetic material (conjugation).

What is conjugation?

A form of horizontal gene transfer that occurs when genetic material is transferred from one bacterial cell to another.

What is the glycocalyx?

A gelatinous polysaccharide and/or polypeptide outer covering that forms a sticky meshwork of fibers.

What is a slime layer?

A glycocalyx that is disorganized, without cell shape, and attached loosely to the cell wall.

What is a capsule?

A glycocalyx that is organized into a defined structure and attached firmly to the cell wall.

What are the functions of the glycocalyx?

Virulence factors, protecting bacteria from phagocytosis and engulfment by immune cells, and preventing cell drying (desiccation).

What are bacterial endospores?

Dormant, tough, and non-reproductive structures formed during unfavorable growth conditions to protect cells from stress; germinate under favorable conditions.

In what type of bacteria are endospores present?

Only in some Gram-positive bacteria, such as members of the genus Bacillus and Clostridium.

What stressors trigger endospore formation?

Nutrient starvation and high cell density.