Observação de diferentes células e de suas estruturas ácidas: uma aula prática de biologia celular no ensino médio

Abstract

Basophilia is a practical microscopy lesson in the subject of General Cell Biology, which is common in many undergraduate courses such as Biological Sciences and Agronomy, but can also be carried out in 1st year high school biology practicals. This lesson presents a basic dye to help visualize the acidic structures of cells, which is indispensable for students' understanding of this microscopic universe. Thus, the focus of the practice is mainly on animal and plant cells, which are observed in the human buccal mucosa and onion epidermis and visualized under the optical microscope using methylene blue. This dye acts by binding to the acidic structures of cells due to their affinity with basic molecules. However, the lack of a greater diversity of cells and the restriction to textbooks can be a limitation for students to understand more about this microscopic universe. The aim of this paper is to describe a cell biology lesson for the first year of secondary school in a public school, which involves observing and identifying the various cells and their acid structures. In addition to the onion and mucous membrane slides already described, slides were made of specimens of protozoa, fungi and bacteria. The semi-permanent bacterial slides were prepared using Escherichia coli and the fungal slides using Saccharomyces cerevisiae yeast microcultures. The protozoan slides were made from cultures of Paramecium sp., which were grown in a beaker containing dead yeast. The practical lesson on basophilia allowed the students to observe different specimens stained with methylene blue in order to compare the similarities and differences between them. Finally, two questionnaires, one qualitative physical and the other quantitative on Google Forms, were applied as a form of evaluation. We conclude that the activity contributed to the 1st year students' learning of cell biology content, and we hope that this work will inspire other teachers to use the content presented as a tool for observing the diversity of living beings beyond the classic cells presented in textbooks.