Cell respiration can be viewed as a series of enzyme catalyzed reactions in which carbohydrates, proteins, and fats are broken down to carbon dioxide and water with the release of energy. During the process, hydrogen is removed from the fuel molecules and oxygen is consumed. With this background information, students measure oxygen consumption and hydrogen liberation in germinating barley at different temperatures. The program provides eight calibrated respirometers for measurement of oxygen consumption and the chemicals required to perform a graphic dye reduction assay.
Acid phosphatase is present in many plant tissues where it catalyzes the removal of phosphate groups from macromolecules at low pH. In this exercise, students prepare a cell-free extract from wheat germ and determine the amount of the enzyme present in the extract. The experiment offers practical experience with enzyme extraction procedures and is an excellent introduction to the analysis of enzyme activity and basic enzyme kinetics.
A colorimeter is desirable but not absolutely necessary for this exercise.
The primary level of chromosome structure in eukaryotes occurs when the DNA molecule is wrapped around histone proteins into particles called nucleosomes. Evidence for this "beads on a string" model is derived from nuclease digestion studies. When nuclei are incubated with micrococcal nuclease, the enzyme cleaves the linker DNA between nucleosomes (the string) but not the nucleosomal core DNA (the beads).
Peroxidase is associated with the plant cell wall and different forms of peroxidase are found in different plant tissues. These tissue-specific differences are revealed by this exercise where students examine the electrophoretic patterns of peroxidase in corn root and shoot extracts.
This miniprogram was designed to give students a basic understanding of enzyme kinetics. In the first experiment in this series, students prepare an extract from wheat germ. They then determined the initial velocity (Vo) of the reaction catalyzed by purified acid phosphatase and by the acid phosphatase activity present in the extract. From these data, they estimate the amount of the enzyme that is present in the wheat germ. In the second experiment, the student examines the effects of substrate concentration on the reaction velocity.
Locating specific proteins and nucleic acid molecules in tissue sections is an important goal in cell biology. An effective and simple technique for this purpose is tissue printing which permits the localization of specific macromolecules in animal and plant tissues. Here students perform this technique to examine the tissue distribution of the enzyme peroxidase in plants. First, students section carrots, celery, and other vegetables with razor blades and transfer the proteins from the cut sections to nitrocellulose membranes by application of gentle pressure.