Prokaryotes vs. Eukaryotes  Prokaryotes: *NO NUCLEUS, but do have nucleiod region with DNA present *Small and Simple – few organelles *Have cell membranes and cytoplasm Ex. Bacteria  Eukaryotes: *Contain nuclei *Contains organelles that perform specialized functions *Uni-or multicellular Ex. Plant and animal cells

Figure 7.4 A prokaryotic cell

Figure 7.7 Overview of an animal cell

Figure 7.8 Overview of a plant cell

Basic cell parts: cell membrane and cytoplasm  Cell membrane – *provides barrier between internal and external environment of cell *is semi-permeable (some things can go in, some cannot; some things can exit, some never can) *made up of phospholipid bilayer with proteins embedded that allow for needed passage of large molecules

 Major job of cell membrane is to maintain the cell’s environment – establish homeostasis

Surface Area to Volume Ratio  Surface area acts as limiting factor in size of cell because is a two dimentional unit  Volume is three dimentional, so increases more quickly than the surface area can accomodate

Figure 7.5 Geometric relationships explain why most cells are microscopic

Figure 8.6 The detailed structure of an animal cell’s plasma membrane, in cross section

Fluid Mosaic Model  Cell membrane and embedded proteins are not locked into position – they flow against one another as the cytoplasm and the external liquid environment dictate

Figure 8.7 The structure of a transmembrane protein

Figure 8.6 The detailed structure of an animal cell’s plasma membrane, in cross section

Cytoplasm  Entire region between the nucleus and the cell membrane  The semifluid substance that fills this area is called CYTOSOL, and this is what the organelles are suspended in

Cell Wall  Found in plant cells (another barrier in ADDITION to the cell membrane)  Protects the cell  Gives support to cell  Made of polysaccharide called cellulose  Is very porous and allows molecules to pass through, but is NOT SELECTIVELY PERMEABLE