Cell Membrane Structure and Function

Phospholipid

A type of lipid that makes up the cell membrane, with a hydrophilic (water-loving) head and two hydrophobic (water-fearing) tails. These help form the structure of the cell membrane, like a two-sided sticker where one side loves water and the other avoids it.

Hydrophilic

Describes something that is attracted to water. The hydrophilic heads of phospholipids face the watery environments both inside and outside the cell.

Hydrophobic

Describes something that avoids or repels water. The hydrophobic tails of phospholipids hide inside the membrane, away from water.

Plasma Membrane

The outer boundary of a cell that controls what enters and leaves. It acts like a protective bubble around the cell, regulating the passage of substances.

Amphipathic

Refers to a molecule that has both hydrophilic (water-loving) and hydrophobic (water-fearing) parts. Phospholipids are amphipathic because they have a head that likes water and tails that avoid it.

Bilayer

A double layer of phospholipids that makes up the cell membrane, where the hydrophilic heads face outwards towards water and the hydrophobic tails face inward away from water. This structure is like two rows of people holding hands, with heads facing the water and tails hidden inside.

Selective Permeability

The property of the cell membrane that allows it to control what enters and exits the cell, letting some things through while blocking others, much like a picky gatekeeper.

Fluid Mosaic Model

A model that describes the cell membrane as flexible (fluid) and made of many different parts, like proteins and carbohydrates (mosaic). The components move around within the membrane, keeping it functional and dynamic.

Cholesterol (in Membranes)

A type of lipid in the cell membrane that helps keep it stable across different temperatures, preventing it from becoming too stiff when cold or too loose when hot.

Integral Proteins

Proteins that span the entire cell membrane, acting like tunnels or gates to help substances move in and out of the cell.

Peripheral Proteins

Proteins that sit on the surface of the membrane, loosely attached and not embedded in it. They're like toppings on a pizza, playing a role in signaling and support.

Glycolipids

Carbohydrates attached to lipids in the membrane, helping cells recognize each other, like a name tag for the cell.

Glycoproteins

Carbohydrates attached to proteins in the membrane, also helping with cell recognition and communication, acting like special labels between cells.

Cell Wall (in Plants)

A tough outer layer found in plant cells that gives them shape, structure, and protection. It's like a rigid box around the cell that helps control how much water it takes in.

Cellulose

A strong material that makes up the plant cell wall. It provides the cell wall's strength, much like the bricks in a wall give it structure.

Plasmodesmata

Small channels in plant cell walls that connect neighboring cells, allowing them to communicate and share materials, like tiny tunnels between houses.

Unsaturated Hydrocarbon Tails

The fatty acid chains in some phospholipids that have bends or kinks, preventing them from packing tightly together. This helps keep the cell membrane fluid, especially in cold temperatures.

Aquaporins

Specialized proteins in the cell membrane that allow water to pass through quickly, like water slides that help water molecules move in and out of the cell.

Diffusion

The movement of molecules from an area where there are many of them to an area where there are fewer, like people spreading out in an empty room. This happens naturally to balance concentrations.

Osmosis

The movement of water across a membrane from an area of high water concentration to low water concentration. It's like water moving through a sponge to balance out the levels on both sides of the membrane.