Membrane-Bound Organelles

Smooth endoplasmic reticulum (smooth ER)

Interconnected network of membrane tubules and vesicles; no ribosomes; continuous with rough ER

Function: synthesizes lipids, metabolizes carbohydrates, detoxifies alcohol/drugs

Rough endoplasmic reticulum (rough ER)

Flattened intracellular network of membrane sacs (cisternae); ribosomes attached on cytoplasmic surface; continuous with the nuclear envelope

Function: synthesizes proteins for secretion, new proteins for the plasma membrane, and lysosomal enzymes; transports and stores molecules

Golgi apparatus

Stacked series of flattened, smooth membrane sacs with associated transport vesicles (shuttle vesicles)

Function: modifies, packages, and sorts newly synthesized proteins for secretion, inclusion in new plasma membrane, or lysosomal enzyme synthesis

Lysosomes

Membrane-enclosed sacs containing digestive enzymes

Function: digest materials or microbes ingested by the cell; remove old/damaged organelles; self-destruct (autolyze)

Peroxisomes

Membrane-enclosed sacs; usually contain large amounts of specific enzymes to break down harmful substances

Function: converts hydrogen peroxide formed during metabolism to water

Mitochondria

Double membrane structures with cristae; fluid matrix contents at center, contains its own DNA (mtDNA)

Function: synthesizes most ATP during cellular respiration; cell’s powerhouse