8. Transport: Protein channels and pumps transport specific substances into the cell Enzymatic Activity: Some enzymes are at the membrane, supplying products where they are needed Signal Transduction: Some membrane proteins are receptors that receive external signals and initiate cascades of chemical reactions
9. Intercellular Joining: Cell adhesion molecules (CAMS) provide binding sites for cell-cell interactions Cell-Cell Recognition: Some glycoproteins serve as cellular “ID” tags that allow cells to recognize each other Attachment to the cytoskeleton and ECM: Some membrane proteins act as anchors for the cell, binding the cell to its environment and supporting the cytoskeleton
23. Tonicity Hypertonic: Osmotic pressure outside the cell is higher, water leaves cell faster than it enters Isotonic: Osmotic pressure in and out of cell are equal, water enters and leaves cell at same rate Hypotonic: Osmotic pressure inside cell the higher, water enters the cell faster than it leaves