Nuceolus

(nū-klē′-ō-lus) (plural, nucleoli)

A specialized structure in the nucleus, consisting of chromatin regions containing ribosomal RNA genes along with ribosomal proteins imported from the cytoplasmic site of rRNA synthesis and ribosomal subunit assembly.

Nucleus

(1) An atom’s central core, containing protons and neutrons. (2) The chromosome-containing organelle of a eukaryotic cell. (3) A cluster of neurons.

Vacuole

(vak′-yū-ōl′)

A membrane-bounded vesicle whose function varies in different kinds of cells.

Chloroplast

(klōr′-ō-plast)

An organelle found in plants and photosynthetic protists that absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide and water.

Golgi Apparatus

(gol′-jē)

An organelle in eukaryotic cells consisting of stacks of flat membranous sacs that modify, store, and route products of the endoplasmic reticulum and synthesize some products, notably noncellulose carbohydrates.

Ribosome

(rī′-buh-sōm′)

A complex of rRNA and protein molecules that functions as a site of protein synthesis in the cytoplasm; consists of a large and a small subunit. In eukaryotic cells, each subunit is assembled in the nucleolus. See also nucleolus.

Endoplasmic Reticulum (ER)

(en′-dō-plaz′-mik ruh-tik′-yū-lum)

An extensive membranous network in eukaryotic cells, continuous with the outer nuclear membrane and composed of ribosome-studded (rough) and ribosome-free (smooth) regions.

Cytoplasm

(sī′-tō-plaz′-um)

The contents of the cell, exclusive of the nucleus and bounded by the plasma membrane.

Mitochondrion

(mī′-tō-kon′-drē-un) (plural, mitochondria)

An organelle in eukaryotic cells that serves as the site of cellular respiration.