Cell Membrane Structure, Dynamics, and Transport Mechanisms Flashcards

Vocabulary flashcards covering cell membrane structures, dynamics, protein components, passive and active transport mechanisms, and cellular pressure regulation mechanisms based on the lecture material.

Amphipathic

Describes a molecule that possesses both hydrophilic (water-loving) and hydrophobic (water-fearing) regions in a single structure.

Micelles

Spherical lipid structures formed by wedge-shaped lipids with bulky head groups and a single hydrophobic fatty acid tail.

Bilayer

A two-layered lipid structure formed by rectangular-shaped lipids with less bulky heads and two hydrophobic fatty acid tails sandwiched in the middle.

Liposomes

Spherical bilayer structures that spontaneously form when phospholipids are added to a test tube of water at neutral pH, enclosing a central space.

Fluid (Membrane Fluidity)

The property of cell membranes that allows lipids and embedded proteins to dynamically move within the plane of the membrane.

Saturated Fatty Acids

Fatty acid chains lacking double bonds that form straight structures, favoring tight packing and decreasing membrane fluidity.

Unsaturated Fatty Acids

Fatty acid chains containing one or more double bonds that create kinks, reducing the tightness of packing and increasing membrane fluidity.

Cholesterol

A major lipid component of animal cell membranes (accounting for 30% of membrane mass) containing a hydroxyl group that modulates membrane fluidity based on temperature.

Lipid Rafts

Defined, specialized patches within the membrane formed by assembled groups of lipids such as sphingolipids.

Transporter Proteins

Membrane proteins responsible for moving ions or specific molecules across the cell membrane.

Receptor Proteins

Membrane proteins that bind specific molecules and allow the cell to receive environmental signals.

Membrane Enzymes

Membrane-bound proteins that serve as catalysts to kick-start chemical reactions.

Anchor Proteins

Membrane proteins that attach to other proteins to help maintain cell shape and structural stability.

Integral Membrane Proteins

Permanent membrane proteins that cannot be separated from the lipid membrane without destroying it.

Peripheral Membrane Proteins

Temporary membrane proteins that can be separated from the membrane without destroying it because they are non-permanently bonded.

Fluid Mosaic Model

A model proposed by S. Jonathan Singer and Garth Nicolson in 1972 stating that the membrane is a dynamic mosaic of laterally moving lipids, proteins, and carbohydrates.

Plasma Membrane

The defining boundary of all cells, composed of phospholipids with embedded proteins, which separates internal cell contents from the external environment.

Homeostasis

The active maintenance of a stable internal environment within a cell or organism.

Selectively Permeable

The characteristic of a membrane that allows specific molecules to pass freely, under certain conditions, or not at all.

Diffusion

The net movement of substances from an area of higher concentration to an area of lower concentration driven by random molecular motion.

Passive Transport

The movement of molecules across a cell membrane by diffusion down a concentration gradient without requiring energy.

Facilitated Diffusion

Passive transport where molecules cross a cell membrane down their concentration gradient through specialized protein transporters.

Channel Proteins

Transport proteins that provide an open passage between the inside and outside of a cell, which may be gated by chemical or electrical signals.

Carrier Proteins

Transport proteins that bind specific molecules and change conformation to move them across the membrane.

Aquaporins

Channel proteins that facilitate the rapid movement of water molecules across the hydrophobic core of the membrane.

Osmosis

The net movement of a solvent like water across a selectively permeable membrane from an area of lower solute concentration to higher solute concentration.

Osmotic Pressure

The pressure generated as a solution draws in water by osmosis until an equilibrium balance is established.

Active Transport

The movement of substances across a membrane against their concentration gradient ('uphill'), requiring cellular energy.

Primary Active Transport

Active transport that directly utilizes energy, such as ATP, to move molecules against a concentration gradient.

Secondary Active Transport

Active transport driven by potential energy stored in an electrochemical gradient built up by primary active transport, rather than direct ATP usage.

Electrical Gradient

A difference in electrical charge across a membrane driving ions to move toward areas of opposite charge.

Electrochemical Gradient

A combined driving force consisting of both an electrical gradient (charge difference) and a chemical gradient (concentration difference) across a membrane.

Contractile Vacuoles

Specialized organelles found in single-celled eukaryotes like Paramecium that absorb excess intracellular water and pump it into the environment to prevent bursting.

Cell Wall

A rigid external structure composed of carbohydrates and proteins surrounding the plasma membrane in bacteria, fungi, protists, and plants that prevents water loss and provides structural support.

Turgor Pressure

The hydrostatic force exerted by water inside a plant or walled cell against its cell wall as a result of water moving in by osmosis.

Vacuole

A plant organelle that absorbs water and swells to maintain internal turgor pressure against the cell wall.

Cytoskeleton

An internal system of protein filaments within a cell that helps maintain structural shape and provides rigid support equivalent to bones.