WEEK 2 Pre3: Membrane Structure and Function

Vocabulary flashcards covering cellular membrane structure, passive and active transport, osmosis, tonicity, and bulk transport mechanisms.

Fluid Mosaic Model

A structural model of cellular membranes describing them as selectively permeable lipid bilayers composed of a mosaic of lipids (mainly phospholipids), proteins, and carbohydrates.

Membrane Fluidity

The dynamic quality of a cell membrane influenced by its lipid composition, where unsaturated hydrocarbon tails prevent packing to increase fluidity, saturated tails pack tightly to increase viscosity, and cholesterol modulates fluidity.

Membrane Carbohydrates

Carbohydrates attached to membrane components, including glycoproteins and glycolipids, that function in cell-cell recognition and serve as recognition targets for several viruses.

Glycoproteins

Membrane carbohydrates covalently linked to proteins that play a role in cell-cell recognition.

Glycolipids

Membrane carbohydrates covalently linked to lipids that participate in cell-cell recognition.

Integral Proteins

Membrane proteins that penetrate the hydrophobic interior of the lipid bilayer, including transmembrane proteins that completely span the membrane.

Peripheral Proteins

Membrane proteins loosely bound to the membrane surface, often associated with integral proteins, involved in functions such as transport and signal transduction.

Diffusion

The movement of particles so that they spread out across available space and down their concentration gradient until dynamic equilibrium is reached.

Electrochemical Gradient

The combined diffusion gradient of an ion influenced by both its ion concentration gradient and the membrane potential across the membrane.

Osmosis

The diffusion of free water molecules across a selectively permeable membrane.

Tonicity

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

Isotonic Solution

A solution whose solute concentration causes no net movement of water into or out of a cell, maintaining normal shape in animal cells and a flaccid state in plant cells.

Hypertonic Solution

A solution with a higher solute concentration than the cytoplasm, causing water to move out of the cell, leading animal cells to shrivel and plant cells to become plasmolyzed.

Hypotonic Solution

A solution with a lower solute concentration than the cytoplasm, causing water to enter the cell, leading animal cells to lyse and plant cells to become turgid.

Turgor Pressure

The force exerted by the cell membrane against the cell wall in plant cells placed in a hypotonic solution, maintaining structural firmness.

Passive Transport

The diffusion of a molecule across a biological membrane down its electrochemical gradient without requiring energy input.

Facilitated Diffusion

A form of passive transport where molecules move down their concentration gradient across a membrane aided by highly selective channel or carrier proteins.

Channel Proteins

Transport proteins that provide a hydrophilic passageway across the membrane for specific molecules or ions, including gated channels.

Carrier Proteins

Transport proteins that translocate specific molecules across a cell membrane by undergoing a shape change.

Active Transport

The energy-requiring process that moves compounds across a cell membrane against their electrochemical gradient using carrier proteins, directly or indirectly powered by ATP hydrolysis.

Cotransport

A transport mechanism where the movement of one molecule down its gradient provides the energy to move another molecule against its gradient.

Symport

A type of cotransport where both transported molecules move in the same direction across the cellular membrane.

Antiport

A type of cotransport where the transported molecules move in opposite directions across the cellular membrane.

Bulk Transport

The export (exocytosis) or import (endocytosis) of large molecules across cell membranes via vesicles.

Exocytosis

The bulk transport process by which a cell exports large molecules by fusing intracellular vesicles with the plasma membrane.

Endocytosis

The bulk transport process by which a cell imports large molecules or particles by forming vesicles from the plasma membrane.

Phagocytosis

A type of endocytosis where a cell engulfs solid food or other particles using pseudopodia to package them into a food vacuole.

Pinocytosis

A type of endocytosis where a cell continuously takes in droplets of extracellular fluid containing solute molecules within coated vesicles.

Receptor-Mediated Endocytosis

A specific type of endocytosis triggered when specific ligands bind to receptor proteins on the cell membrane, forming a coated vesicle.