Chapter 4: A Survey of Prokaryotic Cells and Microorganisms - Practice Flashcards

A set ofQUESTION_AND_ANSWER style flashcards covering key concepts from the notes on prokaryotic cells, cell structures, staining, and taxonomy.

What are the two basic cell types found in organisms?

Eukaryotic and prokaryotic.

Which cell type contains a true nucleus and membrane-bound organelles?

Eukaryotic cells.

Which organisms are prokaryotic?

Bacteria and archaea.

What is the primary component of the Gram-positive cell wall?

Peptidoglycan.

What structural feature distinguishes Gram-negative from Gram-positive cell walls?

Gram-negative have an outer membrane with a thin peptidoglycan layer and a periplasm; Gram-positive have a thick peptidoglycan layer without an outer membrane.

What is the function of fimbriae?

Adhesion to surfaces and other cells.

What is the function of pili in Gram-negative bacteria?

Conjugation; joining cells for DNA transfer.

What is glycocalyx and its two forms?

A coating outside the cell wall made of sugars/proteins; slime layer and capsule.

Name two general functions of the glycocalyx.

Protection from dehydration and phagocytosis; attachment and biofilm formation.

What are endospores and which genera commonly form them?

Inert, resting spores formed by some Gram-positive genera (e.g., Clostridium, Bacillus, Sporosarcina); highly resistant; sporulation and germination.

What is the Gram stain used for?

Differential stain to distinguish Gram-positive from Gram-negative cells and aid classification and diagnosis.

How do Gram-positive and Gram-negative cells appear after Gram staining?

Gram-positive appear purple; Gram-negative appear red/pink.

What is teichoic acid and where is it found?

Teichoic and lipoteichoic acids found in Gram-positive cell walls; function in wall maintenance, ion transport, and immune stimulation.

What components are found in the Gram-negative outer membrane?

Lipopolysaccharides (LPS), porins, and an outer membrane.

What is LPS and its role?

Lipopolysaccharide in the Gram-negative outer membrane; endotoxin component and can trigger immune responses.

What are porins?

Protein channels in the Gram-negative outer membrane that regulate molecule passage.

What is the basic structure of a bacterial ribosome?

Two subunits (large and small); about 60% rRNA and 40% protein; differs from eukaryotic ribosomes.

What is the nucleoid?

Region in a prokaryotic cell where the single circular chromosome resides; no true nucleus.

What is a plasmid?

A small circular double-stranded DNA molecule; not essential for growth; can be transferred between cells and used in genetic engineering.

What is the bacterial cytoskeleton?

Internal network of protein polymers associated with the cell wall; provides structure.

What are endospores and which genera form them?

Dehydrated, metabolically inactive spores formed by some Gram-positive genera (e.g., Clostridium, Bacillus, Sporosarcina).

What are endospore features?

Thick coat; highly resistant to heat, desiccation, radiation, and chemicals; germination returns to vegetative growth.

What are the basic shapes of bacteria?

Coccus (spherical), Bacillus (rod), Coccobacillus (short rod), Vibrio (curved), Spirillum (spiral), Spirochete (spring-like).

What are common cocci arrangements?

Singles, diplococci, tetrads, irregular clusters.

What are common bacilli arrangements?

Diplobacilli, chains, palisades.

Name the three major prokaryotic taxonomic groups mentioned.

Domain Archaea; Domain Bacteria (Phyla Proteobacteria, Firmicutes, Actinobacteria).

What is the Gram-positive cell wall thickness range?

About 20–80 nm.

What is the periplasmic space and where is it found?

Space between the inner and outer membranes in Gram-negative bacteria; may be present in Gram-positive as well; contains enzymes and solutes.

What is the Gram stain sequence?

Crystal violet → iodine → alcohol → safranin.

Which bacteria are non-typical and acid-fast due to mycolic acids?

Mycobacterium and Nocardia; require acid-fast staining (cord factor).

What is Mycoplasma?

Bacteria that lack a cell wall and are stabilized by sterols; pleomorphic.

What is the function of the cell membrane?

Phospholipid bilayer with embedded proteins; fluid mosaic model; site of energy reactions, nutrient processing, and selective permeability.

What is the role of endospores in survival?

Desiccated, dormant cells that are highly resistant to extreme conditions.

What makes endospores extremely resistant?

Thick coat and dehydration; resistant to heat, drying, radiation, and chemicals.

What is germination?

Return of an endospore to vegetative growth when conditions improve.

What is the significance of Gram staining in clinical microbiology?

Helps classify bacteria and guide treatment by distinguishing Gram-positive from Gram-negative.

What is the cord factor in mycobacteria?

Mycolic acid in the cell wall; associated with virulence and acid-fast staining.

What is the universal phylogenetic tree?

A diagram showing evolutionary relationships among prokaryotes and other life forms.

Flagella

Whip-like appendages primarily responsible for bacterial motility, varying in arrangement such as monotrichous (single), lophotrichous (tuft at one pole), amphitrichous (one at each pole), or peritrichous (all over the cell surface).

Pili and Fimbriae

Fimbriae are short, bristle-like proteins for adhesion to surfaces and host tissues. Pili are longer, less numerous appendages mainly involved in bacterial conjugation for genetic transfer.

Glycocalyx

An external coating made of polysaccharides or proteins that protects the cell from dehydration and nutrient loss, aids in adhesion to surfaces (biofilm formation), and offers protection against host immune cells.