Prokaryotic Cell Structure & Function

Key vocabulary terms related to the structure and function of prokaryotic cells.

Prokaryotic Cell

Cellular organism that lacks a nucleus.

Eukaryotic Cell

Cellular organism that contains a nucleus.

Bacteria

Single-celled organisms with a cell wall made of peptidoglycan.

Archaea

Single-celled organisms with a cell wall distinct from bacteria and eukaryotes.

Coccus

Spherical or oval-shaped bacteria.

Bacillus

Cylindrical or rod-shaped bacteria.

Vibrio

Curved or comma-shaped bacteria.

Pleomorphism

Variations in size and shape among cells of a single species.

Diplococci

Pairs of cocci cells.

Tetrads

Groups of four cocci cells.

Staphylococci

Irregular clusters of cocci cells.

Streptococci

Chains of cocci cells.

Sarcina

Cubical packet of 8, 16, or more cocci cells.

Diplobacilli

Pairs of bacilli cells with their ends attached.

Streptobacilli

Chains of bacilli cells.

Palisades

Cells of a chain that remain partially attached and fold back, creating a side-by-side row of cells.

Flagella

Appendages that provide motility.

Fimbriae

Appendages that provide attachment points.

Pili

Appendages that provide attachment points or channels.

Chemotaxis

Movement in response to chemical signals.

Phototaxis

Movement toward light.

Axial filament

Internal flagellum enclosed between the cell wall and the outer membrane in spirochetes that imparts a twisting or flexing motion to the cell.

Glycocalyx

Sticky carbohydrate-enriched layer including slime layer and capsule.

Slime layer

A form of glycocalyx that forms loosely around the cell; protects the cell from loss of water and nutrients.

Capsule

A form of glycocalyx that is more tightly bound to a cell than a slime layer; denser and thicker than a slime layer.

Biofilms

A surface coating providing protection to bacteria.

Peptidoglycan

Unique macromolecule that provides a strong but flexible support framework, found in the cell walls of most bacteria.

Gram-positive

Bacteria with a thick cell wall composed of peptidoglycan and inner cytoplasmic membrane.

Gram-negative

Bacteria with an outer membrane, thin cell wall (less peptidoglycan), and inner cytoplasmic membrane.

Mycolic acid

Very-long-chain fatty acid that makes the surface hydrophobic and waxy.

Mycoplasmas

Bacteria that naturally lack a cell wall.

Plasmids

Nonessential small pieces of DNA.

Endospores

The hardiest of all life forms that withstand hostile conditions and facilitate survival.

Sporulation

Spore formation induced by environmental conditions (depletion of nutrients).

Germination

The breaking of dormancy in the presence of water and a specific organic or inorganic molecule (amino acid, salt).

Methanogens

Convert CO2 and H2 into methane gas (CH4).

Extreme Halophiles

Require salt to grow; can multiply in 36% NaCl that would destroy most cells.

Psychrophiles

Grow at very low temperatures.

Hyperthermophiles

Grow at very high temperatures.