Membrane Structure (1.7) – Vocabulary Flashcards

40 vocabulary flashcards summarising essential terms and definitions related to membrane structure, components, and transport processes.

Plasma (Cell) Membrane

A selectively permeable phospholipid bilayer that regulates movement of substances into and out of all cells.

Phospholipid

An amphipathic lipid with a hydrophilic phosphate-glycerol head and two hydrophobic fatty-acid tails.

Amphipathic

Describes a molecule that contains both hydrophilic and hydrophobic regions.

Hydrophilic

Water-loving; attracted to and soluble in water (polar).

Hydrophobic

Water-fearing; repelled by water and non-polar.

Phospholipid Bilayer

Double layer of phospholipids with heads facing outward toward water and tails tucked inward away from water.

Fluid Mosaic Model

The accepted model of membrane structure depicting a dynamic bilayer with dispersed proteins and lipids.

Integral Protein

Membrane protein embedded within—or spanning—one or both lipid layers; often involved in transport or signaling.

Peripheral Protein

Membrane protein temporarily attached to the bilayer’s surface; commonly for signaling or support.

Channel Protein

Integral protein forming hydrophilic pores for passive diffusion of specific ions or molecules.

Pump Protein

Integral transport protein that uses ATP to move particles against their concentration gradient (active transport).

Glycoprotein

Protein with an attached oligosaccharide; functions in cell recognition and adhesion (e.g., ABO antigens).

Glycolipid

Phospholipid with an attached carbohydrate chain; contributes to cell recognition and membrane stability.

Cholesterol

Steroid lipid interspersed among phospholipids in animal membranes; modulates fluidity and stability.

Vesicle

Small membrane-bound sac that transports or stores substances within a cell.

Endocytosis

infolding of membrane/formation of vesicles, bringing molecules into the cell using ATP.

Exocytosis

infolding of membrane/formation of vescles, releasing molecules from cells using ATP.

Phagocytosis

Type of endocytosis where solid particles are engulfed to form a food vacuole (phagosome).

Pinocytosis

Type of endocytosis that internalises liquids or dissolved substances.

Receptor-Mediated Endocytosis

Endocytosis triggered by ligand binding to specific membrane receptors in coated pits.

Selectively Permeable

Property of membranes that allows some molecules to cross more easily than others.

Self-Repair

Ability of the lipid bilayer to reseal minor tears due to phospholipid attraction.

Binary Fission

Asexual reproduction in prokaryotes where the cell splits into two daughter cells.

Micelle

Spherical aggregate of phospholipids in water with tails inward; formed when single-layered.

Liposome

Closed phospholipid bilayer vesicle enclosing an aqueous compartment.

Smooth Endoplasmic Reticulum

Organelle that synthesises phospholipids and transports them in vesicles to membranes.

Membrane-Bound Organelle

Eukaryotic cell compartment surrounded by a phospholipid bilayer (e.g., nucleus, ER, Golgi).

Junction (Adhesion Protein)

Membrane protein that connects neighbouring cells to form tissues.

Anchorage Protein

Membrane protein that attaches cytoskeleton or extracellular matrix to the membrane.

Signal Transduction Receptor

Membrane protein that binds extracellular signals and initiates intracellular responses.

MHC (Major Histocompatibility Complex)

Glycoprotein markers on vertebrate cells distinguishing self from non-self to the immune system.

Zona Pellucida

Glycoprotein coat around mammalian eggs responsible for species-specific sperm recognition.

ABO Antigens

Blood-group glycoproteins on red blood cells determining A, B, AB, or O type.

Sheet-Like Bilayer Formation

Spontaneous arrangement of amphipathic lipids into continuous bilayers when in aqueous solution.

Transmembrane Domain

Hydrophobic region of an integral protein that spans the phospholipid bilayer.

Amphipathic Lipid

Lipid possessing both hydrophilic and hydrophobic parts, enabling bilayer formation.

Self-Sealing Property

Characteristic of lipid bilayers to close spontaneously after small disruptions.

Membrane Fluidity

Lateral movement of lipids and proteins within the bilayer; influenced by temperature, cholesterol, and fatty-acid saturation.

Saturated Fatty Acid

Fatty acid with no double bonds; decreases membrane fluidity.

Unsaturated Fatty Acid

Fatty acid containing one or more double bonds; increases membrane fluidity.