Mader/Inquiry into Life, 9/e

Lecture Enrichment Ideas - Chapter 3

3.0. The Cell Theory and Microscopy

Few modern students can understand the mind set of people living at a time before microscopic structures and cells were recognized. Readings from various history-of-science books will demonstrate the flavor of mysticism prevalent at this time. Discovery of cells with mysteriously moving contents did not dispel this "vitalist" view of life but merely focused it on a "life essence" presumed to reside in "protoplasm" (and thus a term to be avoided today). This set the public's perspective for acceptance of the storyline in "Frankenstein" where poorly understood electric forces were presumed to restore life to dead cells. For a brief description of vitalism, see the introduction to "New Concepts in the Evolution of Complexity" by Jacob Bronowski in A Sense of the Future (MIT Press).

Student labwork is critical in allowing students to gain an understanding of the working of the compound light microscope, experience however that is unlikely for the electron microscope. Modern students are however familiar with the general structure of the modern television where electrons are boiled off the back of the picture tube by high voltage (electrical "pressure") and fired at the front screen while being targeted by magnets at the top, bottom, and sides. The technology is essentially the same; in great simplification, the electron microscope is a TV-style electron gun with additional focusing devices.

3.1 - 6. Eukaryotic Cells and Organelles

Freezer burn helps explain several cell functions. Slow freezing forms sharp ice crystals that puncture the plasma membrane and destroy the cell walls of plants (hence, frozen and thawed lettuce loses its structure). Repeated freezing of meat likewise ruptures lysosomes and the self digestion changes the taste of the meat. Fast-freezing of small lumps of tissue or small animals prevents ice crystal formation and damage, but the insulating tissues of larger animals insure inner ice crystal formation--thus freezing dead people for future revival poses cell damage problems.

3.7. Prokaryotic Cells

Project a series of cell cross sections of various organisms, asking students to determine if they are prokaryote or eukaryote and why? Point out the telltale features, although oftentimes the nucleus and cell organelles will vary from textbook perfection; such variation is also an important science lesson.

Back