Taylor Chapter 6

Lipid

A carbon containing compound that is insoluble in water, most prominent for its role in cell membranes.

Hydrocarbons

Nonpolar molecules because electrons are shared equally in C-H bonds.

Fatty acid

A lipid consisting of a hydrocarbon chain bonded to a polar carboxyl functional group.

Amphipathic

Containing both hydrophobic and hydrophilic regions, such as phospholipids and cholesterol.

Micelles

Formed when hydrophilic heads interact with water and hydrophobic tails interact with one another.

Lipid bilayers

Layers in which hydrophilic heads interact with water while hydrophobic tails interact with each other, forming the foundation of cellular membranes.

Vesicles

Small bubble-like structures consisting of lipid bilayers with tails shielded from water and heads in contact with it.

Permeability

The tendency to allow a given substance to pass through a membrane.

Selective permeability

The ability of a membrane to allow some substances to cross more easily than others.

Diffusion

The spontaneous movement of molecules and ions across a membrane.

Concentration gradient

The difference in solute concentrations across a membrane.

Passive transport

The diffusion of substances across a membrane without the need for external energy.

Osmosis

The diffusion of water across a selectively permeable membrane.

Protocells

Simple vesicle-like structures that harbor nucleic acids.

Integral membrane proteins

Membrane proteins that span the entire lipid bilayer.

Peripheral membrane proteins

Proteins that bind to membrane lipids or integral proteins without passing through the membrane.

Ion channels

Specialized transmembrane proteins that allow ions to routinely cross the membrane.

Electrochemical gradient

A combined concentration and electrical gradient.

Aquaporin

A channel protein that allows water to cross the plasma membrane while excluding other molecules and most ions.

Gated channels

Channels that open or close in response to a specific signal.

Facilitated diffusion

The passive transport of substances across a membrane with the assistance of transmembrane proteins.

Active transport

The movement of molecules against their concentration gradient.

Secondary active transport (cotransport)

Transport that uses an ATP pump's gradient to move a different solute in a directed manner, often against its gradient.