Cell Membrane

Plasma Membrane

The semi-permeable barrier that surrounds the cell, made of a phospholipid bilayer with embedded proteins.

Phospholipid Bilayer

A double-layered membrane structure where hydrophilic heads face outward and hydrophobic tails face inward.

Integral Proteins

Proteins that span across the membrane, functioning as channels or carriers for molecules.

Fluid Mosaic Model

Describes the plasma membrane's structure as a dynamic arrangement of lipids and proteins.

Selective Permeability

The property of the plasma membrane that allows only certain molecules to pass through.

Passive Transport

The movement of substances across the membrane without energy, including diffusion and osmosis.

Active Transport

The movement of substances across the membrane against their concentration gradient, requiring energy.

Diffusion

The movement of molecules from higher concentration to lower concentration.

Facilitated Diffusion

A form of passive transport where molecules cross the membrane with the help of a protein channel.

Osmosis

The diffusion of water across a semi-permeable membrane from lower to higher solute concentration.

Concentration Gradient

The difference in concentration of a substance between two areas.

Endocytosis

The process by which a cell engulfs substances to bring them into the cell.

Exocytosis

The process by which a cell expels substances using vesicles that fuse with the plasma membrane.

Ion Channels

Protein channels that allow specific ions to pass through the membrane.

Sodium-Potassium Pump

An active transport pump that moves sodium out and potassium into the cell, using ATP.

Endoplasmic Reticulum (ER)

A network of membranes involved in protein and lipid synthesis, with rough ER having ribosomes.

Golgi Apparatus

An organelle that modifies, sorts, and packages proteins and lipids for transport.

Vesicles

Small membrane-bound sacs that transport materials within and outside the cell.