Chapter 5 Lecture Enrichment Ideas
Describe how the sugar residues of glycoproteins and glycolipids are located only on the outside face of the plasma membrane and how these residues are important in cellular recognition.
Examine scanning electron micrographs of freeze-fractured plasma membrane, and determine which face is the cytoplasmic and which the external side of the membrane (the proteins are more frequent in the cytoplasmic face). Ask students why that would be so.
Ask students how we can test if a lipid bilayer is a "two-dimensional fluid." Question why proteins and phospholipids that are able to move about freely in two layers are very unlikely to switch from one face of the bilayer to the other.
Describe the function of cholesterol in the plasma membranes of animal cells, and consider why it is missing in plant cells. (There are other lipids that serve the same function in plant membranes.)
Describe the different kinds of proteins that are located in and attached to the plasma membrane along with their different functions. Ask why these membrane-associated proteins are also found in membrane-bounded organelles such as vesicles, vacuoles, mitochondria, and chloroplasts. Compare how they function there with their function in the plasma membrane.
Use dialysis bags containing different molar solutions of saline, and place them in different molar solutions in beakers at the start of class for examination at the end of class. Then determine which beakers represent a cell in a hypotonic, hypertonic, or isotonic solutions.
Compare the functions of the different kinds of junctions that hold cells together and what kinds of cells they would be likely to link.
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