cell membrane structure

Facilitated diffusion

The movement of molecules across a cell membrane through protein channels from high concentration to low concentration, without using energy.

Diffusion

The natural movement of molecules from an area of high concentration to an area of low concentration.

Osmosis

The diffusion of water across a selectively permeable membrane from high water concentration to low water concentration.

Equilibrium

A balanced state where molecules are spread out evenly and there is no net movement of particles.

Selectively permeable membrane

A membrane (like the cell membrane) that allows some substances to pass but not others.

Hypotonic

A solution with less solute (more water) compared to the cell; water moves into the cell.

Hypertonic

A solution with more solute (less water) compared to the cell; water moves out of the cell.

Isotonic

A solution with equal solute concentration compared to the cell; water moves equally in both directions.

Cholesterol

A lipid found in the cell membrane that helps keep the membrane flexible and stable.

Phospholipid bilayer

The double layer of phospholipids that makes up the cell membrane.

Fatty Acid Tails

The hydrophobic (water-fearing) parts of a phospholipid that face inward, away from water.

Phosphate Heads

The hydrophilic (water-loving) parts of a phospholipid that face outward, toward water.

Peripheral Protein

Proteins that sit on the surface of the cell membrane and help with signaling or structure.

Vesicle

A small, bubble-like sac used by the cell to transport materials.

Integral Protein

Proteins that are embedded through the membrane and help transport molecules across it.

Glycoprotein

A membrane protein with a carbohydrate chain attached; used for cell recognition.

Glycolipid

A membrane lipid with a carbohydrate chain attached; also helps with cell recognition.

Passive Transport

Movement of molecules across the membrane without energy, from high to low concentration.

Active Transport

Movement of molecules across the membrane using energy, usually from low to high concentration.

Exocytosis

The process where a cell uses a vesicle to export materials out of the cell.

Endocytosis

The process where a cell uses a vesicle to bring materials into the cell.