Plasma Membrane Structure and Function

Vocabulary flashcards covering the structure and function of the plasma membrane, membrane proteins, passive and active transport mechanisms, and solution tonicity.

Plasma Membrane

The cellular structure that regulates the entrance and exit of substances to and from the cell to help maintain homeostasis.

Fluid-Mosaic Model

A model describing the plasma membrane as a phospholipid bilayer with hydrophilic polar heads facing outward and hydrophobic tails facing inward, embedded with laterally moving proteins.

Hydrophilic Heads

The polar ends of membrane phospholipids that face outward toward the cellular exterior and the intracellular fluid.

Hydrophobic Tails

The nonpolar ends of membrane phospholipids that face inward toward each other, away from water.

Peripheral Proteins

Membrane proteins partially embedded on one side of the membrane that play a structural role by helping to stabilize and shape the plasma membrane.

Integral Proteins

Membrane proteins that span the entire membrane, can protrude from both sides, move laterally, and determine the membrane's specific functions.

Channel Proteins

Integral proteins involved in the passage of molecules through the cell membrane by allowing them to cross through an open pore.

Carrier Proteins

Membrane proteins involved in the passage of molecules through the cell membrane by combining with the specific substance being transported.

Cell Recognition Proteins

Glycoproteins in the plasma membrane involved in cell recognition of pathogens.

Receptor Proteins

Membrane proteins with shapes that bind to specific molecules, which causes a cellular response.

Selectively Permeable

A characteristic of the plasma membrane that allows only certain substances to pass into and out of the cell.

Diffusion

The movement of molecules down their concentration gradient without requiring energy, affected by factors such as temperature, pressure, and molecule size.

Concentration Gradient

The gradual difference in solute concentration between two regions, where molecules naturally move from high concentration to low concentration.

Facilitated Transport

The movement of molecules across the membrane by binding to carrier proteins down their concentration gradient without requiring energy (ATP).

Active Transport

The movement of molecules across the membrane against their concentration gradient via carrier proteins (pumps), requiring energy usually in the form of ATP.

Sodium-Potassium Pump

An active transport carrier protein pump that moves sodium ions to the outside of the cell and potassium ions to the inside of the cell.

Bulk Transport

An energy-dependent process (membrane-assisted transport) in which macromolecules are moved into or out of the cell via vesicle formation.

Exocytosis

A bulk transport process by which substances exit a cell when an intracellular vesicle fuses with the plasma membrane and secretes its contents outside.

Endocytosis

A bulk transport process by which substances enter a cell through the inward folding and formation of vesicles from the plasma membrane.

Phagocytosis

A form of endocytosis where the cell brings large material (such as a food particle or another cell) into the cell, common in unicellular organisms and certain human white blood cells.

Pinocytosis

A form of endocytosis where vesicles form around liquids or very small particles, common in blood cells, intestinal cells, and plant root cells.

Receptor-Mediated Endocytosis

A specific type of pinocytosis involving receptor proteins in coated pits that bind only to particular molecules before forming a vesicle.

Osmosis

The diffusion of water molecules across a selectively permeable membrane due to differences in solute concentration.

Isotonic Solution

A solution that has the same concentration of solute and solvent as the inside of the cell, resulting in no net movement of water.

Hypotonic Solution

A solution that has a lower concentration of solute than the inside of the cell, causing water to enter the cell.

Hypertonic Solution

A solution that has a higher concentration of solute than the inside of the cell, causing water to leave the cell.