Learn: Cell Membranes and the Fluid Mosaic Model

Welcome!Welcome back! You’ve already learned about gas exchange surfaces and how ventilation supports efficient diffusion. Now, we’ll build on that by exploring cell membranes and their structure, which plays a key role in controlling what enters and leaves the cell.

What is the Fluid Mosaic Model?The Fluid Mosaic Model describes the structure of the cell membrane. It is called 'fluid' because the phospholipids can move within the bilayer, and 'mosaic' because of the diverse proteins embedded in it. This model explains how membranes are flexible and selectively permeable.

Phospholipid BilayerThe phospholipid bilayer is the foundation of the cell membrane. It consists of two layers of phospholipids. Each phospholipid has a hydrophilic (water-attracting) head and hydrophobic (water-repelling) tails. This arrangement forms a barrier that allows small, non-polar molecules like oxygen to pass through while blocking large or polar molecules.

Proteins in the MembraneProteins are embedded in the phospholipid bilayer. These include channel proteins (allowing specific molecules to pass through) and carrier proteins (helping transport substances). Proteins are essential for communication and transport across membranes.

CholesterolCholesterol is found within the bilayer. It stabilises the membrane, keeping it fluid at low temperatures and reducing fluidity at high temperatures. This helps the cell membrane maintain its functionality in varying conditions.

CarbohydratesCarbohydrates are attached to proteins (glycoproteins) or lipids (glycolipids) in the membrane. They are involved in cell recognition and signalling, helping the immune system identify cells and communicate with other cells.

Review Time!Great work! You’ve learned about the phospholipid bilayer, proteins, cholesterol, and carbohydrates in the membrane. Let’s test your understanding with a few questions.

Final ThoughtsWell done! You’ve mastered the Fluid Mosaic Model and the key components of the cell membrane. Remember, the membrane’s structure is integral to its function, ensuring cells can interact with their environment effectively.