Cell membranes

Plasma Membrane

A barrier that surrounds the cell, controlling the entry and exit of substances.

Fluid Mosaic Model

A model describing the plasma membrane as a flexible layer of lipids with embedded proteins.

Phospholipid Bilayer

A double layer of phospholipids that makes up the primary structure of the plasma membrane.

Selectively Permeable

A property of cell membranes that allows certain molecules to pass through while restricting others.

Membrane Proteins

Proteins embedded in the lipid bilayer that perform various functions such as transport and signaling.

Glycoproteins

Proteins that have carbohydrates attached, playing roles in cell recognition and signaling.

Glycolipids

Lipids attached to carbohydrates, found on the extracellular surface of the plasma membrane.

Peripheral Proteins

Proteins located on the outer or inner surface of the membrane, not embedded within the lipid bilayer.

Integral Proteins

Membrane proteins that span the entire lipid bilayer and can function as channels or transporters.

Passive Transport

Movement of substances across a cell membrane without the use of energy.

Facilitated Diffusion

Transport of substances across a membrane via protein channels or carriers, driven by concentration gradients.

Osmosis

The diffusion of water across a selectively permeable membrane.

Hypertonic Solution

A solution with a higher concentration of solutes compared to the cell, causing the cell to lose water.

Hypotonic Solution

A solution with a lower concentration of solutes compared to the cell, causing the cell to swell.

Isotonic Solution

A solution with an equal concentration of solutes compared to the cell, maintaining cell shape.

Active Transport

Movement of substances against their concentration gradient, requiring energy input.

Sodium-Potassium Pump

A primary active transport mechanism that moves Na+ out of and K+ into the cell.

Exocytosis

The process by which a cell expels materials in vesicles that fuse with the plasma membrane.

Endocytosis

The process by which a cell takes in materials by engulfing them in a vesicle.

Cholesterol Role in Membrane

Cholesterol molecules are interspersed among phospholipids to regulate membrane fluidity.

Transport Proteins

Proteins that facilitate the movement of substances across the plasma membrane.