Cells Cells have many different sizes, shapes, and functions Most are microscopic Some are large - egg cell Some are long - nerve cell (nerve cell in giraffe leg is 2+ meters long!) Flat cells – skin cells cover the body Long cells – nerve cells transmit messages to different areas Shape changers – white blood cells move through narrow openings to track down diseases. Cells contain many small organs or organelles (“elle” = small/tiny) Like organs in a body, they all have specific functions. Ex: Brain controls body, nucleus in cell controls cell.

Prokaryotic Cells “Pro” – before, “karyo” – nucleus Does NOT have a membrane-enclosed nucleus Has 1 long, circular chromosome not contained within a nucleus Does NOT have membrane-enclosed organelles Have organelles: Cell Wall, Cell Membrane, Ribosomes, Flagella, Cytoplasm, & Chromosome Cell size is usually small Less complex cells First cell on earth, 3.5 billion years ago Bacteria is the only type of prokaryote currently living

Eukaryotic Cells “Eu” – true, “karyo” – nucleus Contains a “true” nucleus – nucleus is membrane enclosed DNA is wrapped with proteins to make chromosomes Most organelles are membrane enclosed Cell size is generally larger than prokaryotic cells Complex cells Evolved 1.5 billion years ago Evolved from prokaryotic cells All cells other than bacteria