Ch07 Membrane Structure and Function Study Guide

Vocabulary flashcards covering key membrane structure and function terms and their definitions.

active transport

Energy-requiring movement of substances across the plasma membrane, typically via pumps, against their concentration or electrochemical gradient.

amphipathic

Describes a molecule that has both hydrophilic (water-loving) and hydrophobic (water-fearing) regions, such as phospholipids.

aquaporin

A channel protein that facilitates rapid water movement across the cell membrane.

bulk transport

Movement of large cargo into or out of a cell via vesicles; includes endocytosis and exocytosis.

carrier protein

A membrane protein that binds a specific substance and changes shape to shuttle it across the membrane.

channel protein

A membrane protein that forms a pore allowing ions or small molecules to pass; can be gated.

cholesterol

A lipid in animal cell membranes that modulates fluidity and stability of the bilayer.

concentration gradient

Difference in solute concentration across a membrane; substances tend to move down this gradient.

cotransport

Secondary active transport: the transport of a solute against its gradient coupled to the downhill movement of another substance.

diffusion

Passive movement of particles from high to low concentration, down their gradient.

electrochemical gradient

The combined effect of a concentration gradient and a membrane potential that drives ion movement.

osmosis

Diffusion of water across a selectively permeable membrane.

passive transport

Movement of substances across a membrane without energy input; includes diffusion and facilitated diffusion.

facilitated diffusion

Passive transport of substances down their concentration gradient via transport proteins (carrier or channel).

flaccid

Plant cell that is limp due to loss of turgor when in isotonic surroundings.

fluid mosaic model

Model describing the plasma membrane as a fluid phospholipid bilayer with embedded and peripheral proteins.

gated channel

Ion channel that opens or closes in response to a stimulus, regulating ion flow.

glycolipid

Carbohydrate attached to a lipid on the outer surface of the plasma membrane involved in cell recognition.

glycoprotein

Carbohydrate attached to a protein on the cell surface involved in recognition and signaling.

hydrophilic

Water-loving; polar or charged, and typically attracted to water.

hydrophobic

Water-fearing; nonpolar and repelled by water.

hypertonic

Solution with higher solute concentration than another solution, causing water to move out of a cell.

hypotonic

Solution with lower solute concentration than another; water moves into the cell.

ion channel

Membrane protein that forms a pore for specific ions to pass; often gated.

isotonic

Solution with equal solute concentration to another solution; no net water movement.

integral protein

A membrane protein permanently embedded in the bilayer, often spanning the membrane.

lysed

Condition in which a cell has burst due to excessive water intake, typically in a hypotonic solution.

membrane potential

The voltage difference across a cell membrane resulting from ion distribution.

osmoregulation

Regulation of water and solute balance in an organism.

peripheral protein

Protein bound to the membrane surface, not embedded through the bilayer.

phagocytosis

Endocytosis that engulfs large particles or cells via vesicle formation.

pinocytosis

Endocytosis of extracellular fluid and dissolved substances (cell drinking).

plasmolysis

Contraction of a plant cell’s cytoplasm away from the cell wall due to water loss in a hypertonic solution.

proton pump

Pumps that use energy (usually ATP) to move protons across a membrane, creating a gradient.

receptor-mediated endocytosis

Endocytosis triggered by the binding of a molecule to specific cell-surface receptors.

selective permeability

Property of membranes that allows some substances to cross more easily than others.

sodium-potassium pump

Na+/K+-ATPase; actively transports 3 Na+ out and 2 K+ in, contributing to membrane potential.

solite

Substance dissolved in a solvent.

transmembrane protein

A protein that spans the entire lipid bilayer, linking the interior and exterior of the cell.

transport protein

General term for proteins that move substances across membranes (carriers, channels, pumps).

turgid

swollen plant cell due to uptake of water, pressing the plasma membrane against the cell wall.

endocytosis

Process by which cells take in material by forming vesicles from the plasma membrane.

exocytosis

Process by which cells secrete substances by vesicle fusion with the plasma membrane.

electrogenic pump

A pump that contributes to the membrane potential by moving charge across the membrane.