BI108 Cell Membranes

Fluid mosaic model

describes the cell membrane as a dynamic, flexible bilayer of phospholipids with embedded proteins, cholesterol, and carbohydrates

Transmembrane protein

protein that spans the lipid bilayer of a cell membrane; amphipathic

Peripheral membrane protein

protein found on the inner or outer surface of a cell membrane

Integral membrane protein

protein embedded into the lipid bilayer of cell membranes, with parts exposed in both the internal and external cellular compartments

Anchored membrane protein

hydrophobic lipid; proteins that are covalently attached to lipids embedded into biological membranes

Membrane fluidity

the viscosity and flexibility of the lipid bilayer, allowing lipids and proteins to move laterally

Selective permeability

allowing hydrophobic and small nonpolar molecules to pass directly while restricting ions and large polar molecule

Transport proteins

integral membrane proteins that act as a channel for specific ions or molecules

Membrane permeability

the ability of a lipid bilayer or cell membrane to control the passage of substances, such as molecules, ions, and water, into and out of the cell

Diffusion

the spontaneous movement of atoms, ions, and molecules from areas of HIGHER concentration to areas of LOWER concentration

Concentration gradient

difference in concentration; occurs without the input of energy

Entropy

the tendency of a system to tend toward a state of greater randomness or disorder

Osmosis

water will move across the membrane from areas of HIGH water concentration to areas of LOW water concentration

Hypertonic

higher solute concentration; cell will shrink

Isotonic

equal solute concentrations; no net movement of water

Hypotonic

lower solute concentration; cell will burst (“lyse”)