Cell Structure and Function. Pattern #3: Life Needs an Inside and an Outside. Background Cell Theory Prokaryotes vs. Eukaryotes Surface Area vs. Volume Form vs. Function Cell Membrane Cytoplasma Nucleus. Endoplasmic Reticulum Ribosomes Golgi Apparatus Lysosomes Vacuoles
Pattern #3: Life Needs an Inside and an Outside
Some cells are much larger than others. Given the constraints imposed by the S.A. to volume ratio, how would you expect the level of activity in large cells to compare with that in small cells?
1972 – Singer and Nicolson
The membrane is made of a phospholipid bilayer that is viscous and free to move. Globular proteins are embedded in the bilayer and move about as well. The Hydrophobic ends of the lipids create a non-polar region within the membrane. This region impedes the passage of all water soluble molecules. Hydrophilic heads exist at the inner and outer surfaces and allow specific chemical interactions to take place.
The cytoplasm of most eukaryotic cells is filled with membranous structures that extend to every nook and cranny of the cell’s interior.
While the membranes of the cytoplasm have the same basic structure, the particular proteins embedded in the lipid bilayer vary and give specialized functions.
The membranes of the cytoplasm form a highly interdependent network within the cell.
Nucleus with Pores
Liver Cell Nucleus
Electron Microscope View
Brum, Gilbert D., L. McKane, and G. Karp. 1994. Biology: Exploring Life, 2d ed. New York: Wiley.
Raven, Peter H. and G.B. Johnson. 1999. Biology, 5th ed. New York: McGraw-Hill.