Module 3: Transport of Materials Across the Cell Membrane

Vocabulary flashcards covering membrane structure (fluid mosaic model, components) and transport mechanisms (diffusion, osmosis, endocytosis, exocytosis, active transport).

Fluid Mosaic Model

The cell membrane model proposed by Singer and Nicolson in 1972 describing a fluid phospholipid bilayer with embedded proteins, glycoproteins, glycolipids, and cholesterol.

Fluidity

The property of the membrane that allows its components to move laterally within the phospholipid bilayer.

Phospholipid

Amphipathic molecule with a hydrophilic (polar) head and a hydrophobic (nonpolar) tail that forms the bilayer.

Hydrophilic head

The phosphate-containing region of a phospholipid that has an affinity for water.

Hydrophobic tail

The fatty acid region of a phospholipid that lacks affinity for water.

Cholesterol

A sterol located between phospholipids that buffers membrane fluidity by restricting movement at high temperatures and preventing tight packing at low temperatures.

Glycoprotein

Membrane protein with carbohydrate chains attached.

Glycolipid

Lipid with attached carbohydrate chains.

Carbohydrate chain

Sugars attached to glycoproteins or glycolipids involved in cell recognition.

Integral membrane protein

Proteins that span the phospholipid bilayer (intrinsic proteins).

Peripheral membrane protein

Proteins attached to the membrane surface, not spanning the bilayer.

Phospholipid bilayer

Two-layer arrangement of phospholipids that forms the core structure of the cell membrane.

Lateral diffusion

Sideways movement of phospholipids within a single layer of the bilayer.

Rotational diffusion

Rotation of a phospholipid around its axis.

Transverse diffusion (flip-flop)

Movement of a phospholipid from one leaflet to the other across the bilayer.

Simple diffusion

Passive transport down the concentration gradient without transport proteins.

Facilitated diffusion

Passive transport aided by membrane proteins that allow specific substances to cross down their concentration gradient.

Osmosis

Diffusion of water across a selectively permeable membrane from higher water concentration to lower.

Hypertonic solution

Higher solute outside the cell; water moves out; the cell shrinks.

Isotonic solution

Equal solute and water concentrations inside and outside; no net water movement.

Hypotonic solution

Lower solute outside the cell; water moves in; the cell swells.

Endocytosis

Process by which cells take in substances via vesicle formation from the plasma membrane.

Endocytic vesicle

Vesicle formed from the plasma membrane that engulfs ingested material during endocytosis.

Phagocytosis

Cell drinking? No—cell eating; engulfing large solid particles or organisms.

Pinocytosis

Cell drinking; uptake of small droplets of extracellular fluid.

Receptor-mediated endocytosis

Endocytosis triggered by binding of specific ligands to receptors in clathrin-coated pits.

Exocytosis

Release of substances from the cell via vesicle fusion with the plasma membrane.

Active transport

Energy-requiring movement of substances against their concentration gradient; includes nerve impulse-related transport and the sodium-potassium pump.

Sodium-potassium pump

ATP-powered pump that exchanges Na+ for K+ across the membrane, essential for impulse transmission.

Bulk transport

Movement of large substances into or out of the cell via endocytosis or exocytosis.

ABO glycolipids

Glycolipids on red blood cells that contribute to the ABO blood types.

Semipermeable membrane

A membrane that allows some substances to pass more easily than others, enabling selective permeability.