Chapter 5

Phospholipid Bilayer

A double layer of phospholipids that forms the fundamental structure of cell membranes, characterized by hydrophobic tails and hydrophilic heads.

Sphingolipids

A class of lipids that contain sphingosine instead of glycerol and are involved in biological recognition, such as blood type determination.

Fluid Mosaic Model

A model describing the structure of cell membranes as a mosaic of various components (lipids, proteins) that are fluid and can move laterally within the layer.

Integral Proteins

Proteins that span the entire membrane and are involved in transport and communication across the membrane.

Peripheral Proteins

Proteins that are attached to the exterior or interior surfaces of the membrane and play roles in signaling and maintaining the cell's shape.

Glycoproteins

Proteins that have carbohydrate chains attached, functioning as cell-surface markers for recognition and signaling.

Glycolipids

Lipids with carbohydrate chains that contribute to cell recognition and signaling on the cell surface.

Active Transport

The process of moving substances against their concentration gradient, requiring energy (usually from ATP).

Passive Transport

The movement of molecules across a membrane without the use of energy, typically down their concentration gradient.

Facilitated Diffusion

A type of passive transport that uses specific proteins to help move substances across the membrane.

Osmosis

The diffusion of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration.

Aquaporins

Specialized channel proteins that facilitate the rapid transport of water across cell membranes.

Hypertonic Solution

A solution with a higher solute concentration compared to another solution, leading to cell shrinkage.

Hypotonic Solution

A solution with a lower solute concentration compared to another solution, leading to cell swelling.

Isotonic Solution

A solution with equal solute concentration compared to another solution, resulting in no net movement of water.

Sodium-Potassium Pump

A type of active transport mechanism that moves sodium ions out of the cell and potassium ions into the cell, crucial for maintaining membrane potential.

Endocytosis

The process of taking substances into the cell by engulfing them in a membrane-bound vesicle.

Exocytosis

The process of expelling materials from the cell by vesicles fusing with the plasma membrane.

Receptor-Mediated Endocytosis

A selective form of endocytosis where cells take in specific molecules after they bind to receptors on the cell surface.