Introduction to Cell Membrane Structure and Transport

Vocabulary flashcards covering cell membrane components, membrane transport mechanisms (passive, active, and vesicular), and tonicity concepts.

Plasma membrane

The outermost barrier of a cell, also referred to as the cell membrane or phospholipid bilayer.

Cytoplasm

All of the organelles and the fluid inside the cell.

Cytosol

The fluid portion inside the cell, located within the cytoplasm, that is primarily composed of water.

Fluid mosaic model

The accepted model of the plasma membrane, described as fluid because it is movable and slippery, and mosaic because it is composed of multiple different molecules.

Hydrophilic

Water-loving; describes polar, charged structures such as phosphate heads that interact with water molecules.

Hydrophobic

Water-hating; describes nonpolar, uncharged structures such as fatty acid tails that will not interact with water.

Integral proteins

Proteins that are directly embedded within the cell membrane.

Transmembrane protein

A subclassification of integral proteins that extends all the way across the cell membrane.

Peripheral proteins

Proteins attached to the outer edges of the cell membrane rather than being embedded within it.

Passive transport

Membrane transport that does not require the cell to use energy (ATP) and depends on the concentration gradient.

Concentration gradient

An imbalance or difference in the concentration of solutes between two distinct areas.

Simple diffusion

A form of passive transport where small, nonpolar, lipid-soluble molecules pass directly through the phospholipid bilayer down their concentration gradient.

Facilitated diffusion

Passive transport of solutes across a cell membrane down their concentration gradient with the assistance of transport proteins.

Leakage channels

Channel proteins embedded in the membrane that remain open to allow the continuous flow of specific ions down their concentration gradient.

Voltage gated channel

A type of gated channel protein that opens or closes in response to changes in electrical charge or voltage.

Chemically gated channels

Gated channel proteins that open or close when a specific chemical messenger, such as a neurotransmitter, binds to them.

Mechanically gated channels

Gated channel proteins that open or close in response to physical touch or mechanical pressure.

Osmosis

The passive movement or diffusion of water across a membrane from an area of higher water concentration to an area of lower water concentration.

Aquaporins

Specific membrane transport proteins dedicated exclusively to facilitating the movement of water.

Filtration

A transport process driven by fluid pressure against vessel walls, forcing water and dissolved solutes through tiny spaces between cells.

Tonicity

The ability of an extracellular solution to alter a cell's volume by affecting the movement of water.

Isotonic solution

A solution in which the concentration of solutes and water outside the cell equals the concentration inside the cell, maintaining cell volume.

Hypertonic solution

A solution with a higher solute concentration and lower water concentration than the inside of a cell, causing water to leave the cell.

Crenation

The shrinking and shriveling of a cell resulting from water leaving the cell when placed in a hypertonic solution.

Hypotonic solution

A solution with a lower solute concentration and higher water concentration than the inside of a cell, causing water to enter the cell.

Lysing

The bursting of a cell that occurs when excessive water enters it while in a hypotonic solution.

Active transport

Membrane transport that requires the cell to consume energy (ATP) to move solutes against their concentration gradient.

Sodium potassium pump

A transmembrane active transport protein (sodium potassium ATPase) that moves three sodium ions out of the cell and two potassium ions into the cell using ATP.

Secondary active transport

A form of active transport where the movement of one solute down its concentration gradient drives the transport of another solute across the membrane via a cotransporter.

Transcytosis

A vesicular transport process that brings material into a cell, transports it across the cell cytoplasm, and releases it on the opposite side.

Phagocytosis

A type of endocytosis known as cell eating, where the cell uses pseudopods to engulf large particles or molecules.

Pseudopod

A temporary extension of the cell membrane used during phagocytosis to surround and capture large substances.

Phagosome

A specific vesicle formed around food or large particles engulfed during phagocytosis.

Pinocytosis

A type of endocytosis known as cell drinking, where the cell membrane invaginates to take in extracellular fluid and dissolved solutes.

Receptor mediated endocytosis

A selective form of endocytosis where specific target solutes bind to specialized protein receptors on the cell membrane to trigger vesicle formation.

Exocytosis

A vesicular transport process where internal vesicles fuse with the plasma membrane to release waste or cell-produced substances to the outside of the cell.