Cell Membrane Structure and Fluidity (Vocabulary)

Vocabulary flashcards covering the key components and concepts of the cell membrane, including phospholipids, cholesterol, proteins, carbohydrates, and membrane dynamics such as fluidity, permeability, diffusion, and osmosis.

Phospholipid bilayer

Two-layered membrane structure formed by phospholipids with hydrophilic heads facing outward and hydrophobic tails facing inward; forms the flexible, fluid-like cell membrane.

Cell membrane

The boundary of the cell composed of a phospholipid bilayer, proteins, carbohydrates, and cholesterol; components are in constant lateral motion.

Glycerol

Three-carbon backbone of phospholipids to which fatty acids and a phosphate group attach.

Phosphate group

Polar, negatively charged group in phospholipids forming the hydrophilic head.

Fatty acid

Hydrocarbon chain attached to glycerol that forms the phospholipid tails; can be saturated or unsaturated.

Saturated fatty acid

Fatty acid with no double bonds; straight chains that pack tightly, decreasing membrane fluidity.

Unsaturated fatty acid

Fatty acid with one or more double bonds causing kinks; prevents tight packing and increases membrane fluidity.

Cholesterol

Lipid embedded between phospholipid tails; fills gaps and stabilizes membranes; high temps lower fluidity, low temps increase rigidity.

Amphipathic (cholesterol context)

Molecule with both hydrophobic and small hydrophilic regions; cholesterol is mostly hydrophobic with a small polar hydroxyl group.

Membrane proteins

Proteins embedded in or attached to the membrane; include transporters, anchors, receptors, and enzymes.

Integral protein

Membrane protein that is embedded within the lipid bilayer.

Transmembrane protein

Integral protein that spans the entire phospholipid bilayer.

Channel protein

Membrane protein forming pores that allow specific substances to cross the membrane (amphipathic).

Transporter

Membrane protein that moves substances across the membrane, often by facilitated diffusion or active transport.

Anchor (protein)

Membrane protein that anchors other structures to the membrane or cytoskeleton.

Signal receptor

Membrane protein that binds signaling molecules to trigger cellular responses.

Enzyme (membrane-bound)

Enzyme located in or near the membrane that catalyzes reactions relevant to membrane function.

Carbohydrate chains

Sugar chains attached to the outer surface of the membrane or to a protein; act as ID tags and enable recognition and communication.

Glycoprotein

Protein with carbohydrate chains attached on the extracellular surface; involved in cell recognition.

Glycolipid

Lipid with carbohydrate chains attached on the extracellular surface; involved in cell recognition.

ID tags (carbohydrate chains)

Carbohydrate components that serve as identification markers for cells.

Carbohydrates on membrane (outer surface)

Sugar chains on the outer surface or attached to proteins/ lipids; participate in recognition and communication.

Fluidity

The ease with which membrane components move within the bilayer; influenced by temperature and lipid composition.

Permeability

The ability of substances to cross the membrane; related to membrane composition and fluidity.

Lateral movement

Side-to-side movement of lipids and proteins within the same leaflet of the bilayer.

Diffusion

Movement of a solute from high concentration to low concentration until equilibrium is reached.

Solute

Substance present in smaller amount that diffuses or is redistributed to reach equilibrium.

Concentration gradient

Difference in solute concentration that drives diffusion (high to low).

Osmosis

Diffusion of water across a selectively permeable membrane from areas of low solute concentration to high solute concentration.

Water movement (osmosis context)

Water moves from regions of lower solute concentration (higher water potential) to higher solute concentration across membranes.