Practical - Plasma Membrane (structure) and Cytoskeleton (components)

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PRACTICAL CLASS 3 -Plasma Membrane: Structure and Specializations 
Cytoskeleton: component characterization
General objectives:
This practical class aims to demonstrate to the student, through simple experiments, one of the physicochemical properties of 
biomembranes, in addition to the identification, under the light microscope and in electron micrographs, of the specializations of 
the plasma membrane, the constituent elements of the cytoskeleton, microtubular organelles and the organization of the 
cytoskeleton in striated muscle cells.
PART 1
Physicochemical properties of biomembranesThe cell manages to maintain, inside, an extremely different composition 
from the environment that surrounds it thanks to the compartmentalization generated by the plasma membrane and other 
internal biomembranes. Thus, it is assumed that biological membranes have physicochemical properties specialized in 
selectively or differentially controlling the inlet and outlet of solute and solvent.
In this part of the class, the student must perform a simple experiment that demonstrates one of these properties of the biological 
membrane:Effect of organic solvent on the selective permeability of membranes.
Procedure:
1. Label two test tubes with numbers 1 and 2.
2. Put 4 ml of water in tube 1 and 2 ml of water in tube 2
3. Add 2 ml of acetone to tube 2
4. Add in each of the tubes a “cube” (+ 1cm3) of beetroot properly dried on absorbent paper.
5. Wait until the end of the class (about two hours) to see the results. After observing the results, answer: What can be 
concluded when comparing the results obtained in the two tubes? How did acetone act on the cells to produce what 
was observed?
PART 2
Plasma membrane specializations
1.small intestine slide: try to identify in the small intestine preparation, using the 40X objective, and then 
the immersion objective, the intestinal villi whose cells have microvilli (under the light microscope called 
striated border or brush border). What is the role of this specialization of the plasma membrane in this 
cell type? Sketch just one detail of the villus.
Translated from Portuguese to English - www.onlinedoctranslator.com
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two.epididymis blade: try to identify in epididymis preparation, the stereocilia. Locate them initially with the 10X objective, 
and with the 40X and immersion objective observe greater details of the morphological and structural aspects of the 
stereocilia. What is the role of this specialization of the plasma membrane in this cell type? Sketch only one detail of the 
epididymis cut.
Observation of electron micrographs.On the bench will be available an album containing electron micrographs among 
which some refer to the plasma membrane and its specializations. Observe them, identify the structures and try to correlate 
them with the slides you analyzed.
websites
http://www.anatomyatlases.org/MicroscopicAnatomy/MicroscopicAnatomy.shtml http://www.ulb.ac.be/
sciences/biolhc/ainz.de/FB/Medizin/Anatomie/workshop/EM/EMAtlas.htmlOn these sites you will find several 
light microscopy and electron microscopy images that can help you understand about cell structure.
what they can to be Useful:
http://www.uni-
PART 3 - CYTOSKELETON
a) Tracheal Blade:try to identify the cilia on the apical surface of the tracheal epithelial cells in cross-section. What is 
the role of these structures in the trachea? Layout only at 40X magnification.
Answer:1. Is it possible to observe the eyelash as an individualized structure?
2. What is the intensely colored structure at the base of each eyelash called?
3. What is the fundamental difference between these structures? Sketch these differences.
b) Organization of the cytoskeleton (microfilaments) of muscle cells.
Rabbit Tongue Cutting Observationcorada pelo método do Tricrômico de Gömöri. Nesta lâmina o aluno perceberá uma 
abundância de fibras musculares esqueléticas estriadas. As estrias transversais presentes nestas células são devidas à 
disposição organizada dos microfilamentos do citoesqueleto. Esquematize. Responda: 1. Quais são os elementos do 
citoesqueleto responsável pela aparência estriada das fibras musculares esqueléticas estriadas? 2. Como ocorre a 
movimentação destes componentes para que ocorra a contração do músculo?
c) Eletromicrografias Serão distribuídos nas bancadas alguns álbuns de eletromicrografias, e caberá ao aluno verificá-las de acordo 
com as instruções do docente. Nessas eletromicrografias deverão conter os principais elementos do citoesqueleto. Analise e 
estabeleça comparações entre as estruturas observadas.
-Don't forget that on the Internet you have a lot of information that can help you in this matter. Just browse the 
search engines with the keywords: Cytoskeleton; actin filament; microtubules; intermediary filament.
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