Diffusion, Osmosis, and Carrier-Mediated Transport

Vocabulary flashcards covering key terms related to diffusion, osmosis, and carrier-mediated transport as discussed in the lecture.

Solution

A uniform mixture in which dissolved substances (solutes) are evenly dispersed throughout a liquid (solvent).

Solute

Particles such as ions, proteins, carbohydrates, or gases that are dissolved in a solvent.

Solvent

The liquid portion of a solution; in the body, water is the primary solvent.

Concentration

The amount of a solute present in a given volume of solvent, often expressed as a percentage.

Concentration Gradient

A difference in solute concentration between two regions separated by a membrane.

Diffusion

Passive movement of solute molecules from an area of higher concentration to an area of lower concentration (down the gradient).

Down the Concentration Gradient

Directional flow from high solute concentration toward low solute concentration without energy input.

Plasma Membrane

A phospholipid bilayer that encloses the cell and regulates substance movement in and out.

Channel Protein

Membrane protein forming a hydrophilic passage that allows specific ions or water to cross the membrane.

Selectively Permeable Membrane

A barrier that allows certain substances to pass while restricting others.

Osmosis

Net movement of water molecules across a selectively permeable membrane from lower solute concentration to higher solute concentration.

Aquaporin

Channel protein specifically facilitating rapid water movement across the plasma membrane.

Hydration Sphere

Loose association of water molecules around an ion or polar molecule, reducing those water molecules’ ability to diffuse back across a membrane.

Passive Transport

Membrane transport that requires no cellular energy (e.g., diffusion, osmosis, facilitated diffusion).

Active Transport

Membrane transport that requires cellular energy (ATP) to move substances against their concentration gradients.

Carrier-Mediated Transport

Transport process in which specific solutes bind to membrane carriers that change shape to move the solute across the membrane.

Facilitated Diffusion

Carrier-mediated transport of a solute down its concentration gradient without energy expenditure.

Transport Maximum (Tm)

The rate at which carrier proteins are saturated and cannot transport solute any faster.

Primary Active Transport

Carrier-mediated transport that directly uses ATP to move solutes against their gradients.

Adenosine Triphosphate (ATP)

High-energy molecule whose phosphate bonds provide energy for cellular processes, including active transport.

Sodium-Potassium Ion Pump (Na⁺/K⁺-ATPase)

Primary active transport protein that expels three Na⁺ from the cell and imports two K⁺, maintaining essential ion gradients.

Secondary Active Transport

Carrier-mediated transport that relies on gradients created by primary active transport; does not directly use ATP.

Cotransport

Simultaneous carrier-mediated movement of two substances in the same direction, often pairing Na⁺ influx with glucose uptake.

Cytosol

The fluid component of cytoplasm inside the cell, containing dissolved ions, proteins, and other solutes.

Interstitial Fluid

The extracellular fluid that bathes and surrounds tissue cells outside the bloodstream.