Cellular Transport and Membrane Potentials

Vocabulary flashcards generated from lecture notes on cell transport mechanisms, membrane potential states, and cellular signal integration.

Simple Diffusion

The passive transport of small, nonpolar molecules, nonpolar gases, water, or lipid-soluble steroid hormones directly across the phospholipid bilayer.

Fick's Law of Diffusion

The physical law dictating the rate of diffusion across a cell membrane, influenced by factors such as membrane surface area and temperature.

Carrier Protein

A membrane transport protein that moves molecules in and out of the cell across the phospholipid bilayer via facilitated diffusion or active transport.

Channel

A membrane protein structure that exclusively allows ions to pass through via facilitated diffusion without active pumping.

Uniport

A transport process where a membrane transporter moves a single type of solute in one direction across the membrane.

Symport

A transport process in which two or more solutes are transported across the membrane in the same direction.

Antiport

A transport process in which solutes move across the cell membrane in opposite directions.

Primary Active Transport

Active transport that directly utilizes ATP hydrolysis at the location of the membrane protein to pump solutes against their concentration gradient.

Secondary Active Transport

Active transport that utilizes energy stored in an ionic disequilibrium gradient to move a solute against its concentration gradient without directly consuming ATP at the transporter.

Endocytosis

An active bulk transport process where the cell membrane indents to form an internal vesicle, bringing materials inside the cell.

Exocytosis

An active bulk transport process in which a secretory vesicle fuses with the cell membrane to export contents out of the cell.

Clathrin

A specialized lipophilic protein that forms indents called coated pits in the cell membrane to initiate receptor-mediated endocytosis.

Phagocytosis

A specialized form of endocytosis where extensions of the cell membrane called pseudopods engulf target particles like bacteria to form an internal phagosome.

Macrophage

A type of leukocyte whose name translates to 'big eater,' responsible for engulfing pathogens through phagocytosis.

Transcytosis

A vesicular transport process combining endocytosis on one side of a cell and exocytosis on the opposite side to move substances rapidly across a cellular barrier.

Resting Membrane Potential

The electrical gradient or difference in electrical charge across the plasma membrane when a cell is at rest, typically equal to $-70\,mV$ in neurons.

Depolarization

A shift in membrane potential making the inside of the cell less negative or more positive relative to rest, driving the cell into an active state.

Repolarization

The return of the cell membrane potential to its negative resting value following a period of depolarization.

Hyperpolarization

A change in membrane potential that makes the inside of the cell more negative than its resting state, inhibiting cellular activity.

Pancreatic Beta Cell

An endocrine cell located in the pancreas that secretes the hormone insulin when blood glucose levels are elevated.

Potassium ATP Channel

A chemically gated ion channel in pancreatic beta cells that remains open at rest but closes when bound by high levels of ATP, leading to cell depolarization.