Prokaryotic Cell Structure and Microscopic Taxonomy

Vocabulary practice flashcards generated from lecture material covering prokaryotic cell structures, microbial taxonomy, transport mechanisms, and cellular appendages.

Taxonomy

The classification of organisms based on their evolutionary history, originally proposed by Carolus Linnaeus.

Bacteria

Prokaryotic. Single-celled. No nuclei. Circular chromosome (DNA). example: Escherichia coli.

Archaea

Prokaryotic. Single-celled. No nuclei. Circular chromosome (DNA). example: Haloferax volcanii. Unique cell membranes. DNA/Protein synthesis like eukaryotes

Eukarya

Eukaryotic. Single- and multi-cellular. Nuclei. (Typically) linear chromosomes. Membrane-bound organelles. Homo sapiens, Lavandula spica, Giardia duodenalis

What is the difference in size of microbial entities?

viruses < bacteria/archaea < eukaryotic cell

Who proposed the idea of taxonomy and what does it represent?

Carolus Linnaeus

What do we use, today, to display evolutionary history (binomial nomenclature) ?

phylogenies

Binomial Nomenclature

The formal system of naming species by combining their Genus and species names (e.g., Escherichia coli).

circular morphology; round shaped

Coccus

Rod morphology; rod shaped

Bacillus

Spiral morphology; long, loose, helical spiral

Spirochete

Diplococcus

pair of two cocci

Tetrad

grouping of four cells arranged in a square.

Streptococcus

chain of cocci

Staphylococcus

cluster of cocci

Cytoplasm

A gel-like, nutrient-rich suspension within the cell that suspends internal structures, provides structural support, and acts as a transport medium.

What is the function of cytoplasm in prokaryotes?

serves as the medium that suspends internal structures, acts as the medium for transporting nutrients and genetic information, and provides structural support.

Osmosis

The net movement of water across a selective membrane from an area of higher water concentration to an area of lower water concentration.

Osmotic Pressure

the difference in solute concentration between the solution and the solvent.; pressure required to prevent the flow of solvent into a solution via osmosis

Isotonic Solution

A solution that has equal solute concentration inside and outside the cell, resulting in no net movement of water.

Hypertonic Solution

A solution with a higher solute concentration outside the cell, causing water to move out of the cell and leading to crenation or plasmolysis.

Hypotonic Solution

A solution with a lower solute concentration outside the cell, causing water to move into the cell and leading to expansion or cell lysis.

Plasmolysis

The shrivel of a bacterial cytoplasm away from the rigid cell wall in hypertonic solutions, creating “empty” space within itself

Nucleoid-Associated Proteins (NAPs)

Proteins in prokaryotes that interact with genomic DNA to organize and concentrate it into the nucleoid region.

Nucleoid

The non-membrane-bound region in a prokaryotic cell where the single circular chromosomal DNA is concentrated.

Plasmid

A small, circular, extrachromosomal DNA molecule found in bacteria that replicates independently of the bacterial chromosome.

Used during transport in Horizontal Gene Transfer

plasmids

Endospores

Highly resistant dormant structures formed by certain bacteria through sporulation, allowing them to survive extreme environmental conditions until favorable conditions return and they can germinate to a metabolically active state.

Vegetative Cell

The normal, metabolically active and growing state of a bacterial cell.

Sporulation

The process by which a vegetative bacterial cell forms a dormant endospore to survive harsh environmental conditions.

Germination

The process by which a dormant endospore breaks dormancy and returns to a metabolically active vegetative state.

Inclusions

Intracellular storage sites in prokaryotes that collect nutrients like glycogen, starch, or phosphate to help regulate osmotic pressure.

glycogen

storage form of glucose

Inclusion Bodies

Intracellular aggregations of misfolded or non-functional proteins that can be toxic to the cell.

Ribosome

A non-membrane-bound structure responsible for protein synthesis, composed of a $70S$ complex in prokaryotes and an $80S$ complex in eukaryotes.

Prokaryotes Ribosome

70S (50S + 30S)

Eukaryotes

80S (60S + 40S)

Svedberg Unit (S)

A unit measuring sedimentation rate during centrifugation used to characterize ribosomal subunits and complexes.

Fluid Mosaic Model

the idea of the plasma membrane as a fluid phospholipid bilayer where its internal components are constantly adjusting within the membrane itself.

Simple Diffusion

The energy-free movement of small, uncharged molecules directly through a membrane down their concentration gradient.

Facilitated Diffusion

The energy-free transport of larger or charged molecules across a membrane down their concentration gradient using transmembrane protein channels.

Active Transport

An energy-requiring mechanism that uses ATP to move molecules or ions across a membrane against their concentration gradient.

Adenosine Triphosphate (ATP)

The chemical energy currency of the cell, converted to ADP via phosphorylation to power cellular functions.

Phospholipid Bilayer

The core structural lattice of the cell membrane, consisting of hydrophobic fatty acid tails facing inwards and hydrophilic phosphate heads facing outwards.

Phosphorylates

The action of adding a phosphate group to a molecule, typically used to modulate the activity of proteins or convert (ATP) into (ADP)

Peptidoglycan (Murein)

A rigid polymer layer composed of repeating NAG and NAM sugar subunits cross-linked by peptide chains, found exclusively in bacterial cell walls.

Gram-Positive Cell Wall

A bacterial cell wall type characterized by a thick peptidoglycan layer containing teichoic acids for structural stability and adhesion.

Gram-Negative Cell Wall

A bacterial cell wall type characterized by a thin peptidoglycan layer enclosed by an outer membrane rich in lipopolysaccharides (LPS).

Which type of gram cell has a thin peptidoglycan layers and an outer membrane?

gram negative cell walls

Lipopolysaccharide (LPS)

A major component of the Gram-negative outer membrane that acts as a potent antigen/endotoxin and enhances bacterial pathogenicity.

What provides structural support and environmental protection, much like teichoic acid?

LPS

Important structures of gram-negative peptidoglycan?

repeating N-acetylglucosamine (NAG), N-acetylmuramic acid (NAM), tetrapeptide crosslinkers, pentapeptide crosslinkers and teichoic acid

Important structures of gram-positive peptidoglycan?

Repeating NAG and NAM units, tetrapeptide links, and LPS instead of teichoic acid

Teichoic Acid

An acidic carbohydrate polymer embedded in Gram-positive peptidoglycan that stabilizes the cell wall and facilitates bacterial surface adhesion.

Glycocalyx

An outer sugar layer secreted beyond the cell wall that facilitates protection, environmental interactions, attachment, and biofilm formation.

Capsule

Rigid, highly organized glycocalyx structure firmly attached to the cell wall that cannot be easily washed away.

Slime Layer

An unorganized, loosely attached glycocalyx structure that can easily be washed off the cell surface.

Biofilm

A complex, structured community of microorganisms attached to a surface and enclosed in a protective self-produced extracellular matrix.

Fimbriae

Short, hair-like surface projections that allow bacteria to attach to surfaces and host cells, contributing to biofilm creation and pathogenicity.

Pili

Medium-sized surface appendages involved in cellular interactions, transfer of toxins, and horizontal gene transfer.

Flagella

Long, whip-like structures that provide motility to certain bacteria by rotating and allowing the cell to swim through its environment.

Sex Pilus (F Pilus)

A specialized pilus structure that connects bacterial cells during conjugation to mediate horizontal gene transfer.

Flagella Arrangements

The structural classification patterns of bacterial flagella based on their placement and count across the cell surface.

Monotrichous

Having a single flagellum located at one polar end of a bacterial cell.

Amphitrichous

Having a single flagellum or cluster of flagella located at both poles of a bacterial cell.

Lophotrichous

Having a tuft or cluster of multiple flagella situated at one polar end of a bacterial cell.

Peritrichous

Having flagella distributed across the entire outer surface of a bacterial cell.

Running (Flagellar Motion)

The counter-clockwise rotation of flagella that bundles them together to move a bacterium forward smoothly toward or away from a stimulus.

Tumbling (Flagellar Motion)

The clockwise rotation of flagella that causes them to separate, resulting in a temporary, random reorientation of the bacterial cell.