Cell Structure

Archaea

One of two domains of prokaryotes; single-celled and metabolically diverse; closest prokaryotic relatives of eukaryotes.

Bacilli (singular, bacillus)

Rod-shaped bacteria.

Bacteria

One of two domains of prokaryotes; single-celled and metabolically diverse; oldest and most numerous organisms on Earth.

Calibration slide (stage micrometer)

Microscope slide etched with precise scale lines of true length.

Cell

Small membrane-bound compartment that is the basic unit of living organisms and that performs all the processes of life.

Cell membrane

Lipid-rich barrier that encloses all cells and regulates the passage of substances into and out of cells.

Cell wall

Rigid, protective layer surrounding cells of many prokaryotes, protists, fungi, and plants.

Cellular respiration

Group of cellular reactions that extracts energy from food molecules.

Central vacuole

Membrane-bounded organelle in plant cells that stores water, ions, sugars, and other molecules.

Chloroplasts

Organelles that are the sites of photosynthesis in eukaryotes; found in the cells of plants and some protists.

Cocci (singular, coccus)

Spherical-shaped bacteria.

Cyanobacteria

Group of aquatic and photosynthetic bacteria; include Anabaena, and played an important role in contributing oxygen to the ancient earth’s atmosphere.

Cytoplasm

Semifluid matrix that fills interior of cell and contains a cell’s molecules, structures, and, in eukaryotes, organelles.

Eukaryotes

Organisms composed of one or more cells containing a membrane-bounded nucleus and other membrane-bounded organelles; includes protists, fungi, plants, and animals.

Eukaryotic cells

Complex cells that contain a nucleus and other membrane-bounded organelles.

Mitochondria

Organelles that are the sites of cellular respiration reactions in eukaryotes.

Nucleoid

Area in a prokaryotic cell where the DNA is located.

Nucleus

Membrane-bounded compartment that contains the DNA in a eukaryotic cell.

Ocular scale (ocular micrometer)

Row of lines etched into the eyepiece of a compound microscope; can be calibrated and used to measure size of specimens being viewed. 

Organelle

Membrane-bounded compartment of a eukaryotic cell that performs a specialized function.

Photosynthesis

Group of cellular reactions that capture light energy and use it to power the production of organic molecules; oxygen is a by-product.

Plasmodesmata (singular, plasmodesma)

Channels in the cell walls of adjacent plant cells that act as tunnels for the exchange of materials between cells.

Plasmolysis

Process in which plant cells lose water to their surroundings, causing the cell to shrink and the cell membrane to pull away from the cell wall.

Prokaryotes

Organisms composed of a cell that lacks a nucleus and other membrane-bounded organelles; includes bacteria and archaea.

Prokaryotic cells

Cells that have a nucleoid area containing the DNA but lack a membrane-bounded nucleus.