Cell Organelles

Cell organelles are specialized structures within which particular cell processes occur. Their functions are described in the following table and their structures are depicted in the illustration.

STRUCTURE DESCRIPTION FUNCTION
STRUCTURAL ELEMENTS
Cytosketeton Network of protein filaments Structural support; cell movement
Flagella(cilia, microvilli) Cellular extensions Motility or moving fluids over surfaces
Centrioles Hollow microtubules Moving chromosomes during cell division
ENDOMEMBRANE SYSTEM
Plasma membrane Lipid bilayer in which proteins are embedded Regulates what passes into and out of cell; cell-to-cell communication
Endoplasmic reticulum Network of internal membranes; forms compartments and vesicles Rough type processes proteins for secretion and synthesizes phospholipids; smooth type synthesize fats and steroids
Nucleus Structure bounded by double membrane; contains chromosomes Control center of cell; directs protein synthesis and cell reproduction
Golgi complex Stacks of flattened vesicles Modifies and packages proteins for export from cell; forms secretory vesicles
Lysosomes Vesicles derived from Golgi complex that contain hydrolytic digestive enzymes Digest worn-out mitochondria and cell debris; play role in cell death
ENERGY-PRODUCTING ORGANELLES
Mitochondria Bacteria-like elements with inner membrane Power plant of the cell; site of oxidative metabolism; synthesis of ATP
ORGANELLES OF GENE EXPRESSION
Chromosomes Long threads of DNA that form a complex with protein Contain hereidtary information
Nucleolus Site of rRNA synthesis Assembles ribosomes
Ribosomes Small, complex assemblies of protein, often bound to ER Site of protein synthesis
Cell Organelles