Plasma Membrane & Cellular Transport – Vocabulary Flashcards

A comprehensive set of vocabulary flashcards covering the structure and function of the plasma membrane and the various mechanisms of cellular transport.

Plasma Membrane

The flexible boundary of a cell composed of a phospholipid bilayer with embedded proteins, cholesterol, and carbohydrates that regulates what enters or exits the cell.

Phospholipid Bilayer

Double layer of phospholipids whose hydrophilic heads face outward and hydrophobic tails face inward, forming the basic structure of cell membranes.

Phospholipid

A lipid molecule with a hydrophilic (water-loving) phosphate head and two hydrophobic (water-fearing) fatty acid tails.

Fluid Mosaic Model

Concept that describes the plasma membrane as a dynamic, flexible structure where proteins float within or are attached to a shifting phospholipid sea.

Selectively Permeable

Property of the plasma membrane that allows some substances to cross more easily than others while blocking certain molecules entirely.

Permeability

The ability of a substance to pass through a membrane.

Protein Channel

Membrane protein that forms a tunnel allowing specific molecules or ions to cross the membrane during facilitated diffusion.

Cholesterol (in membranes)

Lipid embedded in animal cell membranes that stabilizes the bilayer, maintaining fluidity and integrity.

Carbohydrate (Cell ID Tag)

Short sugar chain on membrane proteins or lipids that functions in cell recognition and communication.

Passive Transport

Movement of substances across a membrane without the use of cellular energy (ATP); includes diffusion, facilitated diffusion, and osmosis.

Active Transport

Energy-requiring process (uses ATP) that moves substances across a membrane against their concentration gradient (low → high).

Diffusion

Passive movement of molecules from an area of high concentration to an area of low concentration.

Facilitated Diffusion

Passive transport in which molecules cross the membrane through protein channels or carriers down their concentration gradient.

Osmosis

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

Concentration Gradient

Difference in the concentration of a substance between two regions; drives diffusion.

ATP (Adenosine Triphosphate)

Energy-carrying molecule used to power cellular processes such as active transport.

Sodium-Potassium Pump

Membrane protein that uses ATP to move Na⁺ out of and K⁺ into the cell against their concentration gradients.

Endocytosis

Active transport process in which a cell engulfs external material by wrapping the plasma membrane around it and forming a vesicle.

Exocytosis

Active transport process that releases materials out of the cell when vesicles fuse with the plasma membrane.

Tonicity

Relative concentration of solutes in two solutions separated by a semipermeable membrane, affecting water movement.

Isotonic Solution

Environment with equal solute and water concentration inside and outside the cell, resulting in no net water movement.

Hypotonic Solution

Environment with lower solute (higher water) concentration outside the cell, causing water to enter and the cell to swell or burst.

Hypertonic Solution

Environment with higher solute (lower water) concentration outside the cell, causing water to leave and the cell to shrink.

Hydrophilic

Describes molecules or parts of molecules that are attracted to water (water-loving).

Hydrophobic

Describes molecules or parts of molecules that repel water (water-fearing).