Cell is the basic structural and functional unit of all organisms. Subcellular structures the principle of complementarity of structure and function of biochemical reactions. Plasma membrane: boundary, 7-10nm, very thin, phospholipid bilayer, embedded membrane proteins and cholesterol (stabilizes the plasma membrane maintains integrity of plasma membrane, fluid mosaic model. Cytoplasm- interior of the cell between the plasma membrane and the nucleus contains the cytoplasmic organelles. Nucleus- contains the genes which control activities of the cell. Transport, enzymatic activity, receptors for signal transduction, intercellular joining, cell-cell recognition, attachment to the cytoskeleton. Integral proteins: embedded in the plasma membrane, exposed on one/two surfaces, transmembrane proteins- go all the way through the proteins. Peripheral proteins: attached to integral proteins or the phospholipids heads on the face of the plasma membrane. Tight junction- impermeable junction: fusion of integral proteins in plasma membrane of adjacent cells.