Transport Across Membranes: Overcoming the Permeability Barrier

These flashcards cover key vocabulary and concepts related to transport across cell membranes, focusing on mechanisms and types of transport processes.

Selectively permeable membrane

A membrane that allows certain molecules to pass through while blocking others.

Simple diffusion

The unassisted movement of solutes from a region of higher concentration to a region of lower concentration.

Facilitated diffusion

A process where molecules pass across the membrane through cell membrane channels without the use of energy.

Active transport

The movement of molecules across a membrane against their concentration gradient, requiring energy, usually in the form of ATP.

Homeostasis

The maintenance of a stable internal environment in an organism.

Osmosis

The diffusion of water across a selectively permeable membrane.

Osmolarity

The concentration of solute particles in a solution, expressed in osmoles per liter (Osm/L).

Tonicity

The ability of a surrounding solution to cause a cell to gain or lose water.

Uniport

A transport process where one solute is transported across the membrane by a carrier protein.

Cotransport

Simultaneous transport of two or more solutes across a membrane, which can be either symport or antiport.

Na+/K+ pump

An active transport mechanism that pumps sodium out of a cell and potassium into the cell, essential for maintaining electrochemical gradients.

Aquaporins

Channel proteins that facilitate the rapid transport of water across cell membranes.

Competitive inhibition

A process where similar molecules compete for the same binding site on a transport protein, affecting transport efficiency.

Exergonic

A process that releases energy, typically associated with movements down a concentration gradient.

Endergonic

A process that requires energy, typically associated with movements against a concentration gradient.

ATP hydrolysis

The reaction that involves the breakdown of ATP to release energy.

Channel proteins

Membrane proteins that facilitate the movement of ions and other small molecules. They include ion channels and aquaporins.

Carrier proteins

Integral membrane proteins that transport specific molecules across the membrane by undergoing a conformational change.

Saturation kinetics

The phenomenon where transport proteins become saturated and can no longer transport additional solute molecules as their concentration increases.

Indirect active transport

Transport that is driven by the energy created via the gradients established by direct active transport.

MDR Transport Proteins

Proteins that pump out drugs and toxins from cells, contributing to multidrug resistance in cancer therapy.

Bacteriorhodopsin

An integral membrane protein that uses energy from light to transport protons, generating an electrochemical gradient.