Cell Membrane Transport Vocabulary Flashcards

A set of vocabulary flashcards covering key terms and concepts related to cellular membrane structure, passive and active transport mechanisms, driving forces, osmosis, endocytosis, and exocytosis from the lecture notes.

Semi-Permeable Membrane

A property of the plasma membrane that allows small or nonpolar molecules to freely diffuse across, while large or polar molecules require carrier proteins to move across.

Passive Transport

Transport across the cell membrane that does not require energy, moving molecules from higher energy (higher concentration) to lower energy (lower concentration).

Active Transport

Transport across the cell membrane that requires energy to move molecules against their concentration or electrochemical gradient.

Chemical Driving Force

A force created by a concentration gradient across a membrane that pushes molecules from an area of higher concentration to an area of lower concentration.

Electrical Driving Force

A force affecting charged molecules (ions) that depends on the membrane potential (voltage difference across the plasma membrane).

Membrane Potential

The difference in electrical potential or voltage across the plasma membrane, which is negative in most healthy cells due to excess anions in the intracellular fluid.

Electrochemical Driving Force

The total force acting on an ion, determined by combining the chemical driving force and electrical driving force, set by the difference between an ion's equilibrium potential and the membrane potential.

Equilibrium Potential

The membrane potential at which the electrical driving force on a specific ion is equal and opposite to its chemical driving force.

Simple Diffusion

The passive movement of molecules freely across a membrane down their electrochemical gradient as a result of random thermal motion.

Facilitated Diffusion

Passive transport mechanism in which molecules bind to specific protein carriers or transporters in the membrane to move down their electrochemical gradient.

Diffusion Through Ion Channels

Passive movement where ions or molecules flow down their electrochemical gradient through pores in specific transmembrane channel proteins.

Primary Active Transport

Active transport mechanism that uses ATP directly to provide energy for moving molecules against their electrochemical gradient.

Na+/K+ ATPase

A primary active transport protein pump that directly consumes ATP to transport $\text{Na}^+$ out of the cell and $\text{K}^+$ into the cell against their electrochemical gradients.

Secondary Active Transport

Active transport mechanism where one molecule moves passively down its electrochemical gradient to provide the energy needed to drive another molecule up its electrochemical gradient.

Cotransport

A form of secondary active transport in which the transported molecule and the driving molecule move in the same direction across the membrane.

Countertransport

A form of secondary active transport in which the transported molecule and the driving molecule move in opposite directions across the membrane.

Osmosis

The passive transport of water across a membrane from an area of low solute concentration to an area of high solute concentration to equalize solute concentration.

Osmolarity

The total solute particle concentration of a solution.

Isotonic

A state in which the intracellular solution and extracellular solution have equal solute particle concentrations.

Hypertonic Solution

A solution state characterized by a higher solute concentration and lower water concentration relative to another solution.

Hypotonic Solution

A solution state characterized by a lower solute concentration and higher water concentration relative to another solution.

Phagocytosis

A form of endocytosis in which the plasma membrane engulfs a particle to form a phagosome, which subsequently fuses with a lysosome to form a phagolysosome.

Pinocytosis

A form of endocytosis in which dissolved extracellular molecules are brought into the cell enclosed within an endosome.

Receptor-Mediated Endocytosis

Endocytosis process in which the binding of a specific molecule to a membrane receptor protein in a clathrin-coated pit triggers internalization into the cell.

Selective Serotonin Reuptake Inhibitors (SSRIs)

Depression medications (e.g., Prozac) that block receptor-mediated endocytosis of serotonin back into presynaptic neurons, enhancing serotonin binding to postsynaptic receptors to promote well-being.

Exocytosis

A transport process in which a secretory vesicle within the cell fuses with the plasma membrane to release its contents into the extracellular fluid.