Eucaryotic Cell Structure and Cell Components

Diagram of a Eucaryotic cell -- see text for identification

Eucaryotic cells are organized into different compartments
The cytoplasm: site of protein synthesis and many metabolic events
The Nucleus: locus of DNA & RNA synthesis and protein assembly
The Endomembrane system: moving materials into different compartments
Endomembrane system = set of interconnected compartments: endoplasmic reticulum (ER), Golgi body, lysosomes, cell membrane
Organelles involved in energy transformations are separate from the endomembrane system
Endosymbiont theory: All organelles seem to share many properties with bacteria: contain 70S ribosomes (whereas rest of eukaryote cells contain 80S ribosomes), divide by binary fission, contain circular DNA without nucleus, etc. Lynn Margulis proposed endosymbiont hypothesis: that organelles derived from ancient colonization of large bacteria (became the eucaryotic cell) by smaller bacteria (became the mitochondria, chloroplast, etc.) Symbiosis = "living together". Eventually, organelles lost ability to exist as separate organisms, cannot be separated from cell. Recent evolutionary taxonomy by comparing ribosomal RNA shows that this idea has lots of merit. Mitochondrial and plastid ribosomes are very similar to current bacteria, very different from eukaryotes.
Build a cell (Campbell website activity)

Cytoskeletal system provides internal fibrous structure to cells
Cell is not "just a bag in a bubble". Lots of internal fibers = internal "skeleton". Not rigid like bone; capable of being assembled, broken down in minutes. Allows cell movement, cell division, internal motion of compartments.
Cell walls provide rigid structure around cells
Cells don't end at their outer membrane; they possess an extracellular matrix (ECM)
Cells are joined by a variety of intracellular junctions

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