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Unlike prokaryotic cells, eukaryotic cells have a number of membrane-bound components, called organelles. The difference between the two cell types is typically defined by the presence or absence of a nucleus. While eukaryotic cells have nuclei, or sacs of genetic material, the genetic material of a prokaryotic isn’t membrane-encased. But the differences extend beyond the nucleus and other membrane-bound organelles.
Eukaryotic cells are much larger than prokaryotic cells. And while prokaryotic cells make up simple organisms, like bacteria, eukaryotic cells compose more complex structures, such as plants and animals.
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The Organelles of a Eukaryotic Cell
Eukaryotic cells—like prokaryotic cells—are enclosed by membranes. These membranes regulate the transfer of particles into and out of the cell.
Plasma membranes enclose the compartments contained within the cell as well. The nucleus houses the genetic material - chromosomes, which contain DNA and protein. The nucleus also contains a smaller component, the nucleolus, which synthesizes RNA. This RNA is incorporated into ribosomes, which create protein.
Ribosomes, in turn, line the walls of another organelle—the rough endoplasmic reticulum, or RER, a passageway that transports materials throughout the cell. The ribosomes covering the RER’s membrane make it look bumpy, or “rough," hence the name. The smooth endoplasmic reticulum, or SER—which doesn’t have ribosomes—also forms passageways through the cell, but serves to produce lipids.
Materials in the RER are enclosed in vesicles, taken up by the Golgi apparatus. This organelle restructures the proteins in these vesicles, which carry the reformed proteins to other parts of the cell. Lysosomes, in contrast, deconstruct proteins within the cell.
Mitochondria are the only organelles besides nuclei that contain DNA. These components produce the energy that a eukaryotic cell needs to survive.
Plant eukaryotic cells house several organelles that animal eukaryotic cells do not. These include chloroplasts, which convert light energy into sugar through photosynthesis; vacuoles, which store water and other materials; and cell walls, tough structures that encase the cells’ outer membranes.