Cell Membranes and Transport

These flashcards cover key concepts associated with cell membranes and transport processes in biology.

Plasma Membrane (PM)

The boundary that separates the living cell from its non-living surroundings.

Selective Permeability

The ability of the plasma membrane to allow some substances to cross it more easily than others.

Phospholipid Bilayer

A double layer of phospholipids that forms the main structure of the plasma membrane.

Amphipathic Molecules

Molecules that contain hydrophobic (water-repelling) and hydrophilic (water-attracting) regions.

Fluid Mosaic Model

A model stating that the membrane is a fluid structure with a mosaic of various proteins embedded in it.

Flippase

An enzyme that moves an outer phospholipid leaflet to the inner phospholipid leaflet.

Fluidity of Membranes

The ability of membranes to remain flexible and not solidify at lower temperatures.

Cholesterol

A steroid that plays a pivotal role in maintaining the structural integrity and regulating the fluidity of cell membranes.

Integral Proteins

Proteins that span the membrane, also known as transmembrane proteins.

Peripheral Proteins

Proteins that are not embedded in the lipid bilayer but are attached to the surface of the membrane.

Passive Transport

The movement of substances across a membrane without the use of energy.

Diffusion

The tendency for molecules to spread out evenly into the available space.

Osmosis

The diffusion of water across a selectively permeable membrane.

Tonicity

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

Hypertonic Solution

A solution with a solute concentration greater than that inside the cell, causing the cell to lose water.

Hypotonic Solution

A solution with a solute concentration less than that inside the cell, causing the cell to gain water.

Facilitated Diffusion

The process in which transport proteins speed the movement of molecules across the plasma membrane.

Active Transport

The movement of substances against their concentration gradient, requiring energy (usually in the form of ATP).

Sodium-Potassium Pump

An important active transport system in animal cells that moves Na+ out and K+ into the cell.

Endocytosis

An active cellular process in which substances are brought into the cell by forming vesicles from the plasma membrane.

Exocytosis

An active process of moving materials from inside a cell to the exterior by vesicle fusion.

Phagocytosis

A type of endocytosis where the cell engulfs particles in a vacuole.

Pinocytosis

A type of endocytosis where extracellular fluids or small particles are ingested by the cell.

Receptor-Mediated Endocytosis

A type of endocytosis triggered by the binding of ligands to receptors.