Student Activities - Chapter 2

• 1. Emphasize the process of science by having students devise an experiment to determine how proteins pass through the Golgi apparatus. Currently, two different hypotheses are under consideration:

  • a. Proteins move in vesicles from the ER to the Golgi forming face, where the vesicles coalesce to a saccule. Each saccule gets pushed to the secretory face as more saccules are added. At the secretory face, vesicles bud off and carry the modified proteins to the plasma membrane, where secretion by exocytosis occurs.

  • b. Proteins move in vesicles from the ER directly to the secretory face, where proteins are modified and repackaged.

  A simple experiment involves providing a cell with radioactive amino acids and then tracing the path of the resulting radioactive proteins from the ER to the plasma membrane. This can be done by autoradiography: After cells have taken up radioactive amino acids, any excess is removed, and the radioactive tissue or cells are sectioned and coated with a layer of photographic emulsion. The radioactive particles emitted from the tissue interact with silver bromide crystals in the emulsion, creating silver grains when the slide is photographically developed. If available, show an appropriate illustration.

Do Onions Make You Cry?

• 2. Enzymes trigger metabolic reactions in cells. It is also true that cells compartmentalize different compounds, an asset of eukaryotic cells that prokaryotes do not possess. To illustrate both the action of enzymes and of cell compartmentalization, consider the following:

  Plants, such as onions and garlic, produce compounds aimed at deterring predators. These same compounds are what make onions and garlic so appealing to us as flavorings and food. In onions and garlic, one enzyme is stored between cells, and another compound is stored within cells. When the bulb of either plant is cut, either with a knife or from a grazing predator, the enzyme and the compound mix, producing a chemical reaction that releases a lachrymator--a potent compound that stings human eyes. Tears result when the lachrymator contacts moist eye tissues, producing sulfuric acid. A demonstration of this reaction in the classroom is useful.

Johnson Explorations in Human Biology CD-ROM

• 3. Study the Johnson Explorations in Human Biology CD-ROM as a way to understand active transport and how a genetic mistake in a transport protein can set the stage for the potentially deadly disease cystic fibrosis.

  Within the Interactive Exploration of #1, Cystic Fibrosis, students can examine one of three patterns of dominance to see how it affects chloride ion transfer across a membrane and results in mucus buildup.

  Within the Interactive Exploration of #2, Active Transport, students can vary an initial amino acid level and the ATP expenditure and see the effects on amino acid transport rate and concentrations on both sides of the membrane.

  Under Graphics and Photos of #2, Active Transport, students can examine diagrams of the sodium-potassium pump, ATP reaction, semipermeable membrane, diffusion, and other related topics.