The plasma membrane or cell membrane comprises a lipid bilayer with a hydrophilic (water-loving) head and hydrophobic (water-hating) tail. These amphipathic lipids form a spherical lipid bilayer in an aqueous environment where the hydrophilic heads face outward toward the outer environment. In contrast, the hydrophilic tail is concealed inside the lipid bilayer. The most abundant lipid in the cell membrane is phospholipid; however, other lipids like glycolipids, sphingolipids, and cholesterol are also present in the cell membrane. Lipids are known for their elastic and fluid properties; hence, the cell membrane is fluid and flexible.
The membrane with high cholesterol levels is more rigid, especially in low temperatures. Protein is another honorable mention in discussing the structure of plasma membranes. Proteins move laterally across the membrane and take care of many key biological functions. Proteins act as a gateway allowing or not allowing the transport of some molecules into and out of the cell, making the membrane a selective barrier. The cell membrane is known as the fluid mosaic model owing to its fluidity and lateral movement of proteins across the membrane.
This was a brief overview of the plasma membrane structure, which is sometimes difficult for students to comprehend. Many more components of this topic are tiring or boring for the students. Educators are always looking for fun ways to teach this fundamental topic in biology.
This article aims to introduce five fun and practical strategies that educators could use in their classrooms to make the structure and function of cell membranes a rather interesting topic for students. But first, let's look at the top three reasons that make this topic trickiest for educators and students.
Figure: GIF from Labster's simulation, Cell Membrane and Transport: Modifying the cell membrane.
Many reasons make teaching and learning about cell membranes crafty at the college/university level. Here we'll discuss the top three reasons experienced by most educators while dealing with this subject.
The structure and function of cell membranes could be tricky as there are many components. Students don't realize the significance of the plasma membrane without seeing the molecules in action. The modification of plasma membrane includes Free Surface Modification (Microvilli) and Junctional Complex (Inter digitations, tight junction, gap junction, desmosomes, and plasmodesmata). The modifications help with additional functions like microvilli (finger-like projections) and increase the surface area for absorption in epithelial cells of kidneys and gall bladder.
Many more significant roles are associated with the plasma membrane and its modification that makes students at the college/university level feel overwhelmed. It is impossible to visualize everything we discuss in class as some processes occur at the molecular level, making it a tricky topic for educators.
Most molecules, like nutrients or waste products, depending on the specialized proteins to enter or leave the cells. The membrane structure (discussed above) only allows small hydrophobic molecules to pass through the membrane readily. This transport across the membrane is enabled by either facilitated diffusion, active transport, or transporters' help.
The unequal distribution of electrons between both sides of the membrane creates an electrochemical gradient. This gradient drives the molecules from a region of high to low concentration to balance the charge or concentration of molecules across the membrane. The molecules move through a specific channel or carrier proteins; hence the process is known as passive transport or facilitated diffusion. Contrary to this, active transport is an energy-driven process using either ATP or a different electrochemical gradient. It occurs when the molecules need to move against the concentration gradient (i.e., low to high). Students often find it challenging to understand the concept of gradient formation and diffusion of molecules.
The membrane transport gets more complicated at college/university with the introduction of additional mechanisms like transporter-mediated transport or vesicle formation. The bulky molecules need transporter proteins to cross the membrane. These proteins spread over the membrane are categorized into aquaporins, carrier proteins, pumps, and channel proteins. Transport proteins are specific in their action and only help transfer the compatible molecule. During vesicle formation, the membrane forms enclosed vesicles that either help send molecules outside the cell (exocytosis) or take up molecules inside the cell (endocytosis). It is challenging for educators to explain these terms and connect the transport mechanism with regulating many biological processes.
We've already discussed the significance of cell membrane permeability in transporting molecules. Scientists are interested in finding ways of artificially altering the membrane's permeability to improve the process of drug delivery at specific targets. These artificial modifications of cell membranes could be tricky for students.
One method to play around the permeability is to design conjugating compounds complementing the transporter substrates on the membrane. It would improve the permeability of a specific drug making its way inside the membrane easier. Peptides are essential therapeutics but cannot readily or passively pass the membrane; therefore, scientists have changed their physical properties and polarity to fool the membrane. Such engineered peptides could easily pass through the membrane and target the desired component inside the cell.
It is not possible for therapeutic proteins to effortlessly cross the plasma membrane; therefore, scientists use methods like the mechanical disruption of the membrane. The physical techniques to disrupt plasma membranes include microinjection and electroporation. Another interesting method is pore-forming toxins or human proteins with a high net positive charge. The exogenous proteins could efficiently translocate inside the cell following these pores- or channel-forming proteins of bacterial origin. We could also use engineered bacteriophages and package the proteins inside its head, improving protein delivery to the cytoplasm. Such complex processes make it difficult for educators to explain the plasma membrane modifications increasing the potential of the specific drug.
The vast scope of this topic makes it challenging for students to comprehend. We'll discuss five effective and practical ways educators could use to make cell membrane morphology, structure, function, and transportation more approachable.
Sharing interesting facts is a great way to get students' attention and make your lecture fun. The few fun facts about cell membranes that you can share with your class are as follows:
The cell is the basic unit of life, and the door to its entrance is the cell membrane, but not every molecule has the key to its lock. Or we can say that the plasma membrane guards the cell with a proper defensive apparatus. Cell membrane could hypothetically be called the skin of the cell.
Did you know in animals and humans, the only layer that keeps the inside and outside of cell material separated is the cell membrane? As in plant cells, there is another protective layer outside the plasma membrane knowns as the cell wall.
It is a sandwich of two phospholipids layers with cholesterol and protein molecules embedded in between, with carbohydrates as the cherry on the top.
The carbohydrates on the cell surface are essential for identifying the cell. Carbohydrates also maintain a friendly environment creating links to the nearby cells.
Larger substances require energy (ATP) or carrier proteins to enter the cell, while smaller substances readily pass (following the concentration gradient) through the membrane without energy expenditure.
Did you know there are a lot of cell membranes in our body? It will equal four football fields of 300,000 square feet if all membranes are compiled and counted.
Interestingly cell membranes are so small that we will have to stack about 10,000 cell membranes over each other to attain something as thick as a piece of paper.
Introducing fun facts is a great way to make students interested in the topic. Educators could use the role-play method to create structure and permeability of cell membrane fun. Make students participate in the game preparation, for instance, by writing labels (like water, proteins, lipids, etc.) on the white paper. Ask them to choose to be parts of the molecule or components of the cell membrane. Students will get engaged in learning their roles as proteins or any other molecule. Ask the students playing molecules to try to pass through the membrane, while the students' imposter membrane should only allow the correct ones to pass. The large molecules would need an additional friend (ATP) to cross the membrane, while small molecules will readily pass through the membrane. It would help educators notably explain the modes of transport.
Learning about a structure unseen to the naked eye can be a little boring. Educators could use the advantages of technology to develop interests among students.
The 3D model of the plasma membrane, as shown in a gif below, would help students to understand the arrangement of lipids, proteins (intrinsic or extrinsic), and carbohydrates. Such visual representations help make such an abstract biological topic more approachable for students.
Figure: GIF from Labster's Cell Membrane and Transport: Learn how transporters keep cells healthy Virtual Lab available at the high school and university levels.
We've discussed the significance of real-world examples and visual representations in making a topic more approachable, but students also need to memorize the topics for exams. Word-play is a fun way of making complex terms easier to remember. Following are a few concepts in the plasma membrane topic, which we've made easy with meanings or word-play.
Active and passive transport could be memorized by linking the word active with "energy" and passive with "dull or no energy." This meaningful trick would help students remember that the former transport mechanism is energy-dependent while the latter needs no external/internal energy source.
The fluid mosaic model could be compared with a sandwich where slices of bread would be two layers of lipid (upper and lower), and items inside the lipid bread would be proteins.
The intrinsic proteins are present wholly embedded inside the membrane, while extrinsic proteins are on the surface. Peripheral proteins are found at the periphery (edge) of the cell. They are responsible for signaling between different parts of the membrane.
A virtual laboratory simulation is a great way to teach about cell membranes and transport. At Labster, we're dedicated to delivering fully interactive advanced laboratory simulations that utilize gamification elements like storytelling and scoring systems inside an immersive and engaging 3D universe.
Check out Labster's simulations for Cell Membrane and Transport: Learn how transporters keep cells,Modifying the cell membrane, and Types of transporter proteins. You will identify the transporter proteins that can transport molecules against a chemical gradient and how they work by launching molecules at the virtual cell. By the end of the simulation, you will have learned how ions and molecules can cross the cell membrane by using different types of transporter proteins. Moreover, you would be able to apply your learning to improve the health of synthetic cells that the lead researcher wants to use to produce insulin.
Please take a look at the following snippets taken from the Labster simulations or get in touch to find out how you can start using virtual labs with your students.
Figure: GIF from Labster's simulation, Cell Membrane and Transport: Types of transporter proteins.
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