Learn: Cell Membranes and the Fluid Mosaic Model

Welcome!Great to see you again! Building on what you've learned about gas exchange and the mammalian lung, we'll now explore cell membranes and the fluid mosaic model. This will help you understand how substances move in and out of cells.

What is the Fluid Mosaic Model?The fluid mosaic model describes the structure of cell membranes. It shows how the membrane is flexible ('fluid') and made up of different components like proteins and phospholipids ('mosaic'). This model explains how membranes control what enters and leaves the cell.

Phospholipid BilayerThe phospholipid bilayer forms the foundation of the cell membrane. It has two layers of phospholipids, with hydrophobic tails facing inward and hydrophilic heads facing outward. This arrangement creates a barrier that is selectively permeable to certain substances.

Proteins in the MembraneMembrane proteins have various roles. Some act as channels or carriers to help transport substances, while others are receptors for signalling molecules. These proteins are embedded within or attached to the phospholipid bilayer.

CholesterolCholesterol is found within the phospholipid bilayer and helps maintain membrane fluidity. It prevents the membrane from becoming too rigid or too fluid, adapting to changes in temperature.

Passive TransportPassive transport occurs when substances move across the membrane without energy input. This includes diffusion (movement from high to low concentration) and osmosis (water movement through a selectively permeable membrane).

Active TransportActive transport requires energy (ATP) to move substances against their concentration gradient. Carrier proteins often play a role in this process, ensuring cells can take in essential nutrients or remove waste.

Endocytosis and ExocytosisEndocytosis is the process by which cells engulf substances to bring them inside. Exocytosis is the opposite, where substances are expelled from the cell. Both processes involve vesicles and require energy.

Review Time!Great work! You've learned about cell membranes, the fluid mosaic model, and transport mechanisms. Let's test your understanding with a few questions.