Mitochondrion Spherical or elongated structures found in most eukaryotic cells that produce most of the ATP in the cell.

Golgi Apparatus In eukaryotic cells, a series of flattened, hollow sacs surrounded by phospholipid bilayers and functioning to package large molecules for export in secretory vesicles.

Vacuole General term for a membranous sac that stores or carries a substance in a cell.

Cell Membrane The cell membrane serves as a barrier and gatekeeper. It comprises a bilayer of phospholipids and encloses the semiliquid, gelatinous material called cytoplasm inside a cell.

Endoplasmic Reticulum Netlike arrangement of hollow tubules continuous with the outer membrane of the nuclear envelope and function as a transport system.

Rough ER (RER) Type of endoplasmic reticulum with ribosomes adhering to its outer surface; these produce proteins for transport throughout the cell.

Smooth ER (SER) Type of endoplasmic reticulum that lacks ribosomes and plays a role in lipid synthesis and transport.

Nucleus Spherical to ovoid membranous organelle containing a eukaryotic cell’s primary genetic material (DNA).

Nucleolus It is a specialized region in a cell nucleus where RNA is synthesized and assembled.

Ribosomes A non-membranous organelle in prokaryotes and eukaryotes, composed of protein and ribosomal RNA and functions to make polypeptides.

Vesicles A cytoplasmic organelle bounded by a single membrane and containing oxidative enzymes. Lysosomes are digestive animal cell vesicles that recycle worn-out cell parts, debris and food.

Centrioles They are a pair of barrel-shaped organelles close to the nuclear envelope and help determine the skeletal framework of the cell by aiding in pinpointing where the cell's nucleus and other organelles are located.