Cell Membranes: Structure & Function

Flashcards covering cell membrane structure, function, evolution, proteins, and permeability based on lecture notes.

Plasma Membrane

Separates the living cell from its surroundings and exhibits selective permeability.

Phospholipid

The most abundant lipid in most membranes, possessing both hydrophobic and hydrophilic regions.

Amphipathic

Having both hydrophilic and hydrophobic regions.

Fluid Mosaic Model

States that the membrane is a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids.

Cholesterol

Maintains membrane fluidity at cool temperatures by preventing tight packing.

Evolution of Differences in Membrane Lipid Composition

Variations in lipid composition of cell membranes of many species that appear to be evolutionary adaptations to specific environmental conditions.

Integral Proteins

Penetrate the hydrophobic interior of the lipid bilayer, with transmembrane proteins spanning the membrane.

Peripheral Proteins

Loosely bound to the surface of the membrane.

Passive Transport

Passing of molecules through cell membrane in a process driven by kinetic (thermal) energy of molecules

Active Transport

Passing of molecules through cell membrane in a process that requires cell to expend energy (ATP)

Glycoproteins

Identification tags specifically recognized by membrane proteins of other cells.

Glycolipids

Membrane carbohydrates covalently bonded to lipids.

Sidedness of Membranes

The asymmetrical arrangement of proteins, lipids, and associated carbohydrates in the plasma membrane, determined as the membrane is built by the ER and Golgi apparatus.

Selective Permeability

Regulating the cell’s molecular traffic.

Diffusion

Movement of molecules from an area of high concentration to an area of lower concentration.

Osmosis

Net movement of water molecules across a semipermeable membrane.

Tonicity

The ability of a surrounding solution to cause a cell to gain or lose water.

Isotonic

Solutions that have the same solute concentrations.

Hypotonic

Water enters the cell faster than it leaves, causing the cell to swell.

Hypertonic

Cell loses water and shrivels.

Osmoregulation

The control of solute concentrations and water balance.

Facilitated Diffusion

Passive transport aided by proteins where transport proteins speed the passive movement of molecules across the plasma membrane.

Channel Proteins

Provide corridors that allow specific molecules or ions to cross the membrane with hydrophilic passageways.

Aquaporins

Transport water molecules.

Ion Channels

Transport specific ions.

Gated Channels

Open or close in response to stimulus.

Carrier Proteins

Undergo subtle change in shape that translocates the solute-binding site across the membrane