Chapter 5: Membranes and Transport Vocabulary Flashcards

Comprehensive vocabulary flashcards covering cell membrane structure, passive and active transport mechanisms, osmosis, and bulk transport based on Chapter 5.

CFTR (Cystic Fibrosis Transmembrane Conductance Regulator)

A transport protein that pumps $Cl^-$ ions out of epithelial cells; mutations in its gene lead to cystic fibrosis.

Phospholipid

A lipid molecule featuring a polar, hydrophilic head with a phosphate group and a nonpolar, hydrophobic end with two fatty-acid tails.

Sterol

A type of lipid possessing nonpolar carbon rings, a nonpolar side chain at one end, and a single polar hydroxyl group ($-OH$) at the other end.

Cholesterol

The main sterol present in animal cell membranes, responsible for maintaining membrane fluidity.

Transport Proteins

Membrane proteins that form channels or carriers to allow selected polar molecules and ions to cross the membrane.

Recognition Proteins

Plasma membrane proteins that identify a cell as belonging to the same individual or as foreign.

Receptor Proteins

Proteins in the plasma membrane that recognize and bind extracellular chemical signaling molecules, such as hormones.

Cell Adhesion Proteins

Membrane proteins that attach cells to one another by recognizing and binding receptors or chemical groups on adjacent cells.

Glycolipid

A lipid molecule on the outer surface of cell membranes that has attached carbohydrate groups.

Glycoprotein

A membrane protein molecule on the outer surface with attached carbohydrate groups.

Glycocalyx

A cell surface coat in many animal cells formed by the carbohydrate chains of glycolipids and glycoproteins.

Fluid Mosaic Model

A structural model proposing that biological membranes consist of a fluid phospholipid bilayer in which proteins float freely and are embedded.

Integral Proteins

Proteins that are embedded directly within the phospholipid bilayer.

Peripheral Proteins

Proteins positioned on the surfaces of biological membranes held by noncovalent bonds.

Passive Transport

The movement of ions and molecules across a membrane along their concentration gradient without energy input.

Active Transport

The movement of substances across a membrane against their concentration gradient, requiring energy input directly or indirectly from ATP.

Diffusion

The net movement of ions or molecules from an area of higher concentration to an area of lower concentration.

Concentration Gradient

A difference in solute concentration between two areas that serves as a form of potential energy driving diffusion.

Simple Diffusion

The passive movement of nonpolar inorganic gases, water, and small organic molecules directly through the lipid portion of a membrane.

Facilitated Diffusion

Passive transport of polar and charged molecules across a membrane mediated by specific transport proteins.

Aquaporins

Specific channel proteins in biological membranes that facilitate the rapid transport of water molecules.

Gated Channels

Ion channel proteins that open, close, or transition through intermediate states in response to specific signals.

Uniport Transport

A transport process where a carrier protein binds and transports a single specific solute across the membrane.

Osmosis

The diffusion of water across a selectively permeable membrane in response to concentration gradients.

Osmotic Pressure

The hydrostatic pressure that balances the tendency of water molecules to move across a semipermeable membrane via concentration gradients.

Tonicity

The property of a solution measured by its ability to cause water to enter or leave a cell based on relative nonpenetrating solute concentrations.

Hypotonic

A solution surrounding a cell that has a lower concentration of nonpenetrating solutes than the cell interior, causing water to enter and the cell to swell.

Hypertonic

A solution surrounding a cell that has a higher concentration of nonpenetrating solutes than the cell interior, causing water to exit and the cell to shrink.

Isotonic

A condition in which the solute concentrations inside and outside the cell are equal, resulting in no net movement of water.

Turgor Pressure

Osmotic pressure in plant cells placed in a hypotonic environment that pushes the cytoplasm against the rigid cell wall to support soft plant tissues.

Plasmolysis

The extreme shrinkage and retraction of the plant cell cytoplasm away from the cell wall when placed in a hypertonic solution.

Membrane Potential

An electrical voltage difference across the plasma membrane created by the active transport and distribution of ions.

Primary Active Transport

Active transport in which the transport protein directly hydrolyzes ATP to power the movement of ions against a concentration gradient.

Sodium/Potassium Pump ($Na^+/K^+$ Pump)

A primary active transport protein in animal cell plasma membranes that exports $3$ $Na^+$ and imports $2$ $K^+$ per pumping cycle using ATP.

Electrochemical Gradient

A combined store of potential energy resulting from both electrical charge differences and concentration differences across a biological membrane.

Secondary Active Transport

Active transport powered indirectly by ATP, utilizing an ion gradient established by primary active transport to move another solute.

Symport

Cotransport mechanism where the target solute and driving ion move through the membrane protein in the same direction.

Antiport

Cotransport mechanism where the target solute and driving ion move through the membrane protein in opposite directions.

Exocytosis

An active bulk transport mechanism where secretory vesicles fuse with the plasma membrane to release cargo to the cell exterior.

Endocytosis

An active transport mechanism where extracellular substances are engulfed in membrane depressions that pinch off as intracellular vesicles.

Bulk Endocytosis (Pinocytosis)

A non-specific endocytic process by which a cell engulfs droplets of extracellular fluid into small vesicles.

Receptor-Mediated Endocytosis

A specific endocytic mechanism where specific target molecules bind to surface receptor proteins gathered in coated pits before internalization.

Clathrin

A protein network that coats and reinforces the cytoplasmic side of coated pits during receptor-mediated endocytosis.

Phagocytosis

A form of endocytosis where cells use extended cytoplasmic lobes to engulf large particles or whole organisms into vesicles.