BIO 111: General Characteristics of Prokaryotic Life

Comprehensive vocabulary flashcards detailing the cellular structures, molecular differences, and genetic mechanisms of prokaryotic organisms based on BIO 111 lecture notes.

Prokaryote

A unicellular organism whose cells lack a membrane-bound nucleus (derived from Greek "pro" meaning before, and "karyo" meaning nucleus).

LUCA

Last Universal Common Ancestor; the ancient ancestral lineage dating back $3.5\text{--}4\text{ bya}$ from which the domains Bacteria, Archaea, and Eukarya originated.

Human Microbiome Ratio

The cellular composition of an average human body, consisting of approximately $40\text{ trillion}$ bacterial cells and $30\text{ trillion}$ human cells.

Cytoplasm

All the internal contents of a cell bounded by the plasma membrane, excluding the nucleus in eukaryotic organisms.

Cytosol

The fluid portion of the cytoplasm in which cellular components and solutes are suspended.

Nucleoid

The region in a prokaryotic cell where the single, circular chromosome is localized without being enclosed by a membrane.

Plasmid

Small, circular accessory DNA molecules in prokaryotes found in addition to the main chromosome.

Central Dogma

The fundamental framework of molecular biology describing the flow of genetic information: Deoxyribonucleic acid (DNA) to Ribonucleic acid (RNA) to Protein.

Ribosome Subunit Functions

The two primary components of ribosomes where the small subunit reads mRNA transcripts and the large subunit synthesizes peptide bonds joining amino acids.

Bacterial Ribosome

A protein-synthesizing ribonucleoprotein complex composed of RNA and $58$ proteins.

Archaeal Ribosome

A protein-synthesizing ribonucleoprotein complex composed of RNA and $68$ proteins.

Eukaryotic Ribosome

A protein-synthesizing ribonucleoprotein complex composed of RNA and $78$ proteins.

Archaeal Phospholipid

A membrane lipid consisting of branched isoprenoid tails joined to L-glycerol via ether linkages, conferring enhanced thermal stability in high-stress environments.

Bacterial Phospholipid

A membrane lipid composed of unbranched fatty acid tails connected to D-glycerol via ester linkages.

Peptidoglycan (Murein)

A mesh-like polymer of repeating sugars and amino acids in bacterial cell walls with $\beta(1\text{-}4)$ linkages that maintains cell shape and protects against osmotic stress.

Gram-Positive Cell Wall

A bacterial cell envelope characterized by a thick peptidoglycan layer that retains crystal violet dye, appearing purple under microscopy.

Gram-Negative Cell Wall

A bacterial envelope composed of a thin peptidoglycan layer surrounded by an outer phospholipid bilayer; it does not retain crystal violet dye (staining pink) and is resistant to antibiotics targeting peptidoglycan synthesis.

Pseudomurein

A peptidoglycan-like cell wall polymer present in methanogenic Archaea containing $\beta(1\text{-}3)$ glycosidic bonds and distinct peptide cross-links.

Osmotic Lysis

The swelling and rupture of a cell that occurs when water enters by osmosis in a hypotonic solution due to a weak or damaged cell wall.

Plasmolysis

The shrinkage of a cell's cytoplasm away from the cell wall caused by net water loss when exposed to a hypertonic environment.

Flagellum (Bacterial)

A rigid, rotating external filament powered by a molecular motor that enables bacterial motility at speeds up to $60\text{ cell lengths per second}$.

Fimbriae

Short, bristle-like surface appendages occurring in large numbers that enable bacteria to adhere to host tissues and surfaces to establish infections.

Pilus (Pili)

A specialized, longer surface filament present singly or in pairs that facilitates the transfer of genetic material between bacteria during conjugation.

Bacterial DNA Replication

A bidirectional process occurring on a single circular chromosome initiated at a single origin of replication and carried out by two replication forks until termination.

Binary Fission

The mode of asexual reproduction in bacteria where duplicated DNA copies separate with the help of protein filaments, followed by a contractile protein ring constricting the membrane to split the cell into two identical daughters.

Horizontal Gene Transfer

The lateral transmission of genetic information between individual cells of the same generation via conjugation, transformation, or transduction.

Conjugation

A form of lateral gene transfer where a donor cell ($F^+$) transfers plasmid DNA (such as the F factor) to a recipient cell ($F^-$) through a conjugative pilus and junction.

Hfr (High Frequency of Recombination) Cell

A bacterial cell that has integrated the fertility factor (F factor) plasmid directly into its main circular chromosome.

Transformation

A genetic recombination mechanism in which a competent, living bacterial cell takes up fragments of naked extracellular DNA or plasmids released from a lysed (dead) donor cell.

Transduction

A mechanism of horizontal gene transfer where a bacteriophage virus mistakenly incorporates host bacterial DNA into its capsid and injects it into a recipient bacterium.

Formylmethionine

The modified initiator amino acid utilized by Bacteria to begin protein translation, contrasting with unformylated methionine used by Archaea and Eukarya.

Archaeal RNA Polymerase

A complex transcription enzyme in Archaea composed of $13\text{ subunits}$, resembling eukaryotic RNA polymerase rather than the $5\text{-subunit}$ bacterial enzyme.