Biology Week 11 Lecture 26: Cell Membrane Structure and Transport Mechanisms

Vocabulary flashcards covering cell membrane composition, membrane proteins, passive diffusion mechanisms, osmosis and tonicity, and active transport processes based on the lecture notes.

Peripheral proteins

Membrane proteins that do not interact with the hydrophobic region of the lipid bilayer and instead make contact with the hydrophilic, phosphate-containing heads on either surface of the membrane.

Integral proteins

Membrane proteins that penetrate into the hydrophobic hydrocarbon tail region of the lipid bilayer, often spanning completely across the membrane as transmembrane proteins.

Transmembrane proteins

Integral proteins that span entirely across the phospholipid bilayer, contacting both the interior and exterior environments of the cell or organelle.

Oligosaccharides

Carbohydrate chains consisting of several linked sugars attached to proteins or lipids on the extracellular surface of the membrane.

Glycoproteins

Proteins with attached oligosaccharide chains located on the cell exterior that function in recognizing neighboring cells and facilitating cell-to-cell adhesion.

Semi-permeable

The property of a biological membrane that allows certain substances to cross while preventing others from passing through.

Passive transport

The movement of substances across a membrane from an area of high concentration to low concentration without the direct input of cellular energy.

Simple diffusion

The passive movement of small, non-polar molecules or gases directly through the phospholipid bilayer down their concentration gradient until equilibrium is reached.

Equilibrium

The state where solute concentrations become equal on both sides of a membrane, resulting in no net movement of molecules while individual molecules continue to move.

Facilitated diffusion

A form of passive transport where hydrophilic, polar, or charged substances move down their concentration gradient through a transmembrane channel or carrier protein without energy expenditure.

Channel proteins

Transmembrane proteins with an interior hydrophilic pore that allows specific molecules, such as ions or water, to flow continuously across the membrane from high to low concentration.

Gated channels

Channel proteins that open or close in response to a specific signal or ligand binding, regulating the passage of materials like ions across the membrane.

Aquaporins

Channel proteins that facilitate the rapid movement of large amounts of water into and out of the cell.

Carrier proteins

Membrane proteins that specifically bind a target substance, undergo a conformational shape change to move it across the membrane, and return to their original shape after releasing the substance.

Osmosis

The diffusion of water across a membrane from an area of higher water concentration (lower solute concentration) to an area of lower water concentration (higher solute concentration).

Isotonic solution

An external environment having the exact same total solute concentration as the inside of a cell, resulting in zero net movement of water.

Hypertonic solution

An external solution with a higher solute concentration (and lower water concentration) relative to the cell interior, causing net movement of water out of the cell and causing it to shrivel.

Hypotonic solution

An external solution with a lower solute concentration (and higher water concentration) relative to the cell interior, causing water to enter the cell and potentially causing animal cells to lyse or burst.

Active transport

The movement of substances across a membrane against their concentration gradient (from low to high concentration), requiring direct energy input.

Primary active transport

Active transport directly powered by ATP hydrolysis to move molecules against their concentration gradient, as seen in the sodium-potassium pump.

Secondary active transport

Active transport powered by an existing electrochemical or ion gradient previously created by primary active transport, driving the movement of another molecule against its concentration gradient without directly hydrolyzing ATP at that protein.