Manuel Alonso

A Simple Chemical Method for Rendering Wild-Type Yeast Permeable to Brefeldin A That Does Not Require the Presence of an erg6 Mutation

The present work aims to develop a growth medium to render a wild-type strain of Saccharomyces cerevisiae permeable to the antifungal drug Brefeldin A. In the current study, a synthetic medium containing 0.1% L-proline and supplemented with 3.0 × 10-3% SDS is employed. When Brefeldin A is added to this medium, a wild-type strain shows increased growth sensitivity and a diminished transport of the amino acid L-leucine. Since Brefeldin A exerts its effect on the endoplasmic reticulum and the Golgi apparatus, the medium permits the study of the drug effect on the intracellular traffic of L-leucine permeases.

Student assessment in large‐enrollment biology classes

Enrollments into first‐year university biology courses may be very large, and therefore evaluating student learning can represent quite a challenge. In this article, we present our experience in assessing students by means of an assessment instrument called “Understand Before Choosing” (UBC). It has been used for six semesters, and its performance has been compared with two other common means of assessment, the use of multiple‐choice questions and the use of open‐ended questions. UBC consists of a text (100 lines, nearly 700 words) on the subject being tested, and a set of carefully worded questions that require the selection of one of five crafted options to be answered. To choose the best option, a student needs to understand the concepts embedded in the text.

Teaching lactose metabolism

We developed an experimental didactic proposal to teach both carbohydrate metabolism and lactose intolerance as the disease related to that metabolism. Therefore, we implemented an empirical strategy consisting of inexpensive and nontoxic components for which students do not need to know any of the laboratory techniques. The fact that students were able to discuss their own results obtained from the experiments performed in their classroom gave them an additional motivation to learn the subject.

Teaching nutritional biochemistry: an experimental approach using yeast

In this report, we present a practical approach to teaching several topics in nutrition to science students at the high school and college freshmen levels. This approach uses bakers yeast (Saccharomyces cerevisiae) as a biological system model. The diameters of yeast colonies, which vary according to the nutrients present in the medium, can be observed, compared, and used to teach metabolic requirements. The experiments described in this report show simple macroscopic evidence of submicroscopic nutritional events. This can serve as a useful base for an analogy of heterotrophic human cell nutrition.

Redes semánticas poblacionales: un instrumento metodológico para la investigación educativa

We report a qualitative, innovative and original methodology for research in science education. We use the concept of Semantic Network as idea for displaying students´ responses to a problem on a given topic. We proposed a problem with multiple resolutions on the metabolism of carbohydrates to university students of Biology and Biological Chemistry from different careers. Students’ answers were organized in cognitive pathways, using a methodology derived from the Information Processing Model. Graphical representation of all individual cognitive pathways allowed us to construct semantic networks from each studied population. In this way the declarative knowledge of each population could be easily represented. These networks allowed us to detect: (a) answering strategies, (b) general trends of mistakes, and (c) mistakes that appeared in specific populations.

Brefeldin a decreases the activity of the general amino acid permease (GAP1) and the more specific systems for L-leucine uptake in Saccharomyces cerevisiae

Brefeldin A is a commonly used antifungal agent that reversibly blocks protein transport from the endoplasmic reticulum to the Golgi complex. In this study, we aimed to characterize L-leucine uptake in Saccharomyces cerevisiae in the presence of brefeldin A. For this purpose, we used a synthetic medium, containing L-proline and the detergent SDS, which allows the agent to permeate into the yeast cell. The results obtained with a wild type strain and a gap1 mutant indicate that BFA causes either direct or indirect modification of the transport and/or processing of L-leucine permeases. The presence of BFA affects the kinetic parameter values for L-leucine uptake and decreases not only the uptake mediated by the general system (GAP1), but also that through the specific BAP2 (S1) and/or S2 systems.