Endoplasmic reticulum – mode of membranous-walled canals and flat, curving sacs arranged in parallel rows throughout the cytoplasm; extend from the plasma membrane to the nucleus.
Proteins move through the canals. There are two typesRough endoplasmic reticulumRibosomes dot the outer surface of the membranous wallsRibosomes synthesize proteins, which move toward the Golgi apparatus and then eventually leave the cellFunction in protein synthesis and intracellular transportationSmooth endoplasmic reticulumNo ribosomes border the membranous wallFunctions are less well established and probably more varied than for the rough endoplasmic reticulumSynthesizes certain lipids and carbohydrates and creates membranes for use throughout the cellRemoves and stores Ca++ from the cell’s interiorRibosomesMany are attached to the rough endoplasmic reticulum and many lie free, scattered through the cytoplasmEach ribosome is a nonmembranous structure made of two pieces, a large subunit and a small subunit; each subunit is composed of rRNA and proteinRibosomes in the endoplasmic reticulum make proteins for “export” or to be embedded in the plasma membrane; free ribosomes make proteins for the cell’s domestic useGolgi apparatusMembranous organelle consisting of cisternae stacked on one another and located near the nucleusProcesses protein molecules from the endoplasmic reticulumProcessed proteins leave the final cisterna in a vesicle; contents may then be secreted to outside the cellLysosomesMade of microscopic membranous sacs that have “pinched off” from Golgi apparatusThe cell’s own digestive system; enzymes in lysosomes digest the protein structures of defective cell parts, including integral membrane proteins and particles that have become trapped in the cellProteasomesHollow, protein cylinders found throughout the cytoplasmBreak down abnormal/misfolded proteins and normal proteins no longer needed by the cellBreak down protein molecules one at a time by tagging each one with a chain of ubiquitin molecules, unfolding it as it enters the proteasome, and then breaking apart the peptide bondsPeroxisomesSmall membranous sacs containing enzymes that detoxify harmful substances that enter cellsOften seen in kidney and liver cellsMitochondriaPlasma membrane – separates the cell from its surrounding environmentMade of microscopic sacs; wall composed of inner and outer membranes separated by fluid; thousands of particle make up enzyme molecules attached to both membranesThe “power plants” of cell; mitochondrial enzymes catalyze series of oxidation reactions that provide almost all of a cell’s energy supplyEach mitochondrion has a DNA molecule, which allows it to produce its own enzymes and replicate copies of itselfCytoplasm – gel-like internal substance of cells that includes many organelles suspended in watery intracellular fluid called cytosolNucleus – large membranous structure near center of the cellpages 73-78 Anatomy & Physiology 8th edition Patton Thibodeau
