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To promote understanding of the authority of the primary literature in students taking our biochemistry laboratory courses, a biochemistry laboratory exercise on the determination of an acceptable molar absorptivity value of 2-nitrophenol (2-NP) was developed. This made the laboratory course much more relevant by linking to a thematic thread, [beta]-galactosidase, that scaffolds concepts in one exercise with those in later exercises. The substrate for the continuous assay of [beta]-galactosidase is the chromogenic 2-nitrophenyl-[beta]-D-galactopyranoside that produces 2-NP. In an early laboratory exercise, students determine the wavelength of maximum absorption for the protonated and deprotonated form of 2-NP at various pH values and then determine the molar absorptivity of 2-NP. Students were encouraged to discuss apparent discrepancies not only in their own determinations of molar absorptivity values for 2-NP, but also in the published molar absorptivity values for 2-NP (2,150-21,300 M[superscript -1] cm[superscript -1]) at almost the same pH and at 420 nm. Finally, the students were led to a publication that serves as an authentic source for molar absorptivity of 2-NP. (Contains 3 figures, 2 tables, and 1 footnote.)

Students' reactions to classroom learning and the mastery of science vary along a wide spectrum of attitudes and emotions. In particular, we argue here that how learners encounter and learn subject matter is a function of their level of cognitive development. We describe the stages of cognitive development based on the work of William Perry and demonstrate their relevance to the undergraduate science classroom. With examples drawn from biochemistry, we attempt to show that, depending on the student's developmental level, there will be different abilities to handle the range of assignments and activities s/he can expect to experience in the average classroom. The college science instructor can benefit from knowledge of these stages and can work through their implications to develop strategies and techniques to regulate collective student learning.

The discussion board feature that is included with most course management software packages is a potentially valuable tool to augment instructor-student interactions in science lecture courses and increase student motivation. However, many teachers seem to have been frustrated that students do not readily make use of this feature when it is added to the course resources. The author has been using a discussion board in undergraduate biochemistry lecture courses for six years and has learned to use it to evolve a system that students use and that seems to increase interaction with students while requiring less time than traditional face-to-face meetings outside of the lecture. The aspects that the author emphasizes for efficient discussion board use are timing, creating a safe virtual environment for the students, "seeding" with simulated questions, setting boundaries, and being self-conscious about the attitude that the instructor projects to the students.

We describe a simple undergraduate exercise involving the titration of a weak acid by a strong base using a pH meter and a micropipette. Students then use their data and carry out graphical analyses with a spreadsheet. The analyses involve using mathematical concepts such as first-derivative and semi-log plots and provide am opportunity for collaboration between biochemistry and mathematics instructors. By focusing on titration data, rather than the titration process, and using a variety of graphical transformations, we believe that students achieve a deeper understanding of the concept of buffering. [ABSTRACT FROM AUTHOR]

Skepticism, when promoted as a desirable trait amongst undergraduate students, can effect a marked increase in their cognitive development. We will describe a biochemistry laboratory exercise that can be utilized to promote student skepticism. The individual exercises in our laboratory course are made more relevant by providing a thematic thread, β-galactosidase, that links concepts in one exercise with those in latter exercises. The substrate for the continuous assay of β-galactosidase is the ehromogenic 2-nitrophenyl-β-D-galactopyranoside that produces 2-nitrophenol (2-NP). In one of the laboratory exercises, students prepare a series of ten differently buffered solutions by using KH2PO4 and K2HPO4, mixed with 50 µM 2-NP, to determine the wavelength of maximum absorption for the protonated and deprotonated form of each molecule. After determining the pH of the individual solution they determine the pKa value for 2-NP. The molar absorptivity of 2-NP is then determined, by preparing different dilutions of 5mM 2-NP in a solution of K2HPO4. The average molar absorptivity value for 2-NP determined by 38 students in one semester was 3560 ± 1060 at 420 nm, at a pH of 9.2. Students are encouraged to discuss that apparent discrepancies in the published molar absorptivity values for 2-NP (2150 to 21,300) at almost the same pH and at 420 nm with their own molar absorptivity values for 2-NP. [ABSTRACT FROM AUTHOR]