LMS Glossary - The working units of life - Exploring cell types (Cell membranes and Organelles)

active transport

The energy-dependent transport of a substance across a biological membrane against a concentration gradient—that is, from a region of low concentration (of that substance) to one of high concentration

anchored membrane proteins

Proteins that are associated with the membrane by covalent attachments to lipids.

cell junctions

Specialized structures associated with the cell membranes of epithelial cells. Some contribute to cell adhesion, others to intercellular communication.

concentration gradient

A difference in concentration of an ion or other chemical substance from one location to another, often across a membrane.

diffusion

The random movement of molecules or other particles, resulting in even distribution of the particles when no barriers are present.

Endocytosis

A process by which liquids or solid particles are taken up by a cell through invagination of the cell membrane

facilitated diffusion

Passive movement through a membrane involving a specific carrier protein; does not proceed against a concentration gradient.

fluid mosaic model

A molecular model for the structure of biological membranes consisting of a fluid phospholipid bilayer in which suspended proteins are free to move in the plane of the bilayer.

glycolipid

A lipid to which sugars are attached.

glycoprotein

A protein to which sugars are attached.

Hypertonic

Having a higher solute concentration; said of one solution in comparing it with another.

Hypotonic

Having a lower solute concentration; said of one solution in comparing it with another.

Integral membrane proteins

Proteins that are at least partially embedded in the cell membrane.

Isotonic

Having the same solute concentration; said of two solutions

osmosis

The movement of water across a differentially permeable membrane, from one region to another region where the water potential is more negative.

passive transport

Diffusion across a membrane; may or may not require a channel or carrier protein

Peripheral Membrane proteins

Proteins associated with but not embedded within the cell membrane.

phospholipid

A lipid containing a phosphate group; an important constituent of cellular membranes.

pinocytosis

Endocytosis by a cell of liquid containing dissolved substances within vesicles.

selective permeability

The characteristic of membranes that allows certain substances to pass through while other substances are excluded.

transmembrane protein

An integral membrane protein that spans the phospholipid bilayer.