4.2 Prokaryotic Cells

capsule

A form of glycocalyx that consists of a gelatinous layer; found in blue-green algae and certain bacteria.

bacillus

A rod-shaped bacterium; also a genus of bacteria, Bacillus.

coccus

A spherical-shaped bacterium.

prokaryotic cells

Cells that generally lack a membrane-bound nucleus and organelles; the cell type within the domains Bacteria and Archaea.

cell wall

Cellular structure that surrounds a plant, protistan, fungal, or bacterial cell and maintains the cell's shape and rigidity; composed of polysaccharides.

plasmids

Extrachromosomal ring of accessory DNA in the cytoplasm of prokaryotes.

thylakoid

Flattened sac within a granum of a chloroplast; membrane contains chlorophyll; location where the light reactions of photosynthesis occur.

glycocalyx

Gel-like coating outside the cell wall of a bacterium. If compact, it is called a capsule; if diffuse, it is called a slime layer. This coating helps protect the bacterium against drying out and evade the host's immune system.

conjugation pilus

In a bacterium, elongated, hollow appendage used to transfer DNA to other cells.

cell envelope

In a prokaryotic cell, the portion composed of the plasma membrane, the cell wall, and the glycocalyx.

spirochete

Long, rod-shaped bacterium that is twisted into a flexible spiral; if the spiral is rigid rather than flexible, it is called a spirillum.

spirillum

Long, rod-shaped bacterium that is twisted into a rigid spiral; if the spiral is flexible rather than rigid, it is called a spirochete.

flagellum

Long, slender extension used for locomotion by some bacteria, protozoans, and sperm.

plasma membrane

Membrane surrounding the cytoplasm that consists of a phospholipid bilayer with embedded proteins; functions to regulate the entrance and exit of molecules from cell.

cyanobacteria

Photosynthetic bacterium that contains chlorophyll and releases oxygen; formerly called a blue-green alga.

cytoplasm

Region of a cell between the nucleus, or the nucleoid region of a bacterium, and the plasma membrane. It is composed of a semifluid solution composed of water and organic and inorganic materials.

nucleoid

Region of prokaryotic cells where DNA is located; it is not bound by a nuclear envelope.

ribosomes

Site of protein synthesis in a cell; composed of proteins and ribosomal RNA (rRNA).

fimbriae

Small, bristlelike fiber on the surface of a bacterial cell, which attaches bacteria to a surface; also fingerlike extension from the oviduct near the ovary.

eukaryotic cells

Type of cell that has a membrane-bound nucleus and membranous organelles; found in organisms within the domain Eukarya.