Non-Membrane-Bound Organelles

Ribosomes

Dense cytoplasmic granules with 2 subunits (large and small); may be free in cytoplasm (free ___) or bound to rough ER (bound ___)

Function: synthesizes proteins for use in the cell (free ____) AND secretion, incorporation into plasma membrane, or lysosomes (bound ____)

Cytoskeleton

Organized network of protein filaments or hollow tubules throughout the cell

Function: structural support; facilitates cytoplasmic streaming, organelle, and cellular motility; transport of materials, chromosomal movement, and cell division

Microfilaments

Cytoskeleton Component

Actin protein monomers formed into filaments

Function: maintain cell shape; aid in muscle contraction and intracellular movement; separates dividing cells

Intermediate filaments

Cytoskeleton Component

Structure with various protein components

Function: structural support; stabilizes cell junctions

Microtubules

Cytoskeleton Component

Hollow cylinders of tubulin protein; ability to lengthen and shorten

Function: support cell; hold organelles in place; maintain cell shape/rigidity; direct organelle movement within cell and cellular motility as cilia and flagella; move chromosomes at cell division

Centrosome

Amorphous region adjacent to nucleus; contains a pair of centrioles

Function: organizes microtubules; participates in spindle formation during cell division

Centrioles

Centrosome Component

Paired perpendicular cylindrical bodies; composed of microtubule triplets

Function: organize microtubules during cell division for movement and separation of chromosomes

Cilia

Short, membrane-attached projections containing microtubules; occur in large numbers on some mucous membrane surfaces

Function: move fluid, mucus, and materials over the cell surface

Flagellum

Long, singular membrane extension containing microtubules

Function: propels sperm in human male

Microvilli

Numerous thin membrane folds projecting from the free cell surface

Function: increase membrane surface area for absorption and/or secretion