Cell Membranes and Transport Mechanisms

These flashcards cover key concepts related to cell membrane structure and transport mechanisms.

Membrane Structure

Permits the passage of substances into and out of the cell, consisting of a phospholipid bilayer with embedded proteins.

Fluid Mosaic Model

Describes the structure of cell membranes where a mosaic of proteins floats in or on the fluid lipid bilayer.

Phospholipid Bilayer

A flexible matrix in membranes that acts as a barrier to permeability consisting of phospholipids.

Integral Membrane Proteins

Proteins that span the lipid bilayer, responsible for transporting molecules across the membrane.

Transmembrane Proteins

Integral membrane proteins that extend across the bilayer and have regions that are hydrophobic and hydrophilic.

Channel Proteins

Proteins that create a selective tunnel that allows certain molecules to pass through the membrane.

Facilitated Diffusion

Movement of molecules through membrane proteins from higher to lower concentration without energy use.

Osmosis

A specific kind of facilitated diffusion concerning the net diffusion of water across a membrane toward higher solute concentration.

Active Transport

Movement of substances against their concentration gradient that requires energy, usually in the form of ATP.

Sodium-Potassium Pump

An antiporter that uses ATP to move Na+ out of the cell and K+ into the cell against their concentration gradients.

Endocytosis

Movement of substances into the cell; includes phagocytosis, pinocytosis, and receptor-mediated endocytosis.

Exocytosis

Process of moving substances out of the cell, typically using vesicles that fuse with the plasma membrane.

Hydrophobic Interior

The main barrier to crossing a biological membrane, which repels polar molecules but allows nonpolar molecules to pass.

Aquaporins

Channel proteins that facilitate the transport of water across the cell membrane.

Peripheral Membrane Proteins

Proteins that are attached to the external or internal part of the membrane and play roles in signaling and maintaining cell shape.