Cell Membrane and Transport Vocabulary

Vocabulary flashcards covering membrane structure, components, and transport processes from the lecture notes.

Cell membrane

The boundary that defines the cell, formed by a phospholipid bilayer with embedded proteins and carbohydrates; regulates exchange with the environment.

Phospholipid bilayer

Two-layer structure that forms the core of the cell membrane; phospholipids have hydrophilic heads and hydrophobic tails.

Glycoprotein

Protein with carbohydrate attached; involved in cell signaling and cell-cell recognition.

Glycolipid

Lipid with carbohydrate attached; involved in cell recognition, signaling, and intercellular adhesion.

Integral membrane protein

Protein permanently associated with the membrane, often forming channels or transporters.

Peripheral membrane protein

Protein temporarily associated with the membrane, not embedded.

Cholesterol

A membrane lipid that buffers fluidity, preventing too much movement at high temperatures and too tight packing at low temperatures.

Phytosterols

Plant sterols (e.g., sitosterol, stigmasterol) that help maintain membrane fluidity and stability.

Amphipathic

Molecules with both hydrophilic (water-loving) and hydrophobic (water-fearing) regions.

Hydrophilic

Water-loving; polar region of a phospholipid head.

Hydrophobic

Water-fearing; nonpolar tail region of a phospholipid.

Polar head group

Hydrophilic head region of a phospholipid (phosphate-containing).

Glycerol backbone

The glycerol-derived backbone of phospholipids to which head group and tails attach.

Liposome

Spherical vesicle formed when phospholipids spontaneously assemble into a bilayer in water.

Fluid mosaic model

Model describing the membrane as a fluid, dynamic mosaic of lipids and proteins.

Osmosis

Diffusion of water across a semipermeable membrane toward higher solute concentration.

Isotonic

Solution with equal solute concentration to the cell's interior.

Hypotonic

Solution with a lower solute concentration outside than inside; water tends to enter the cell.

Hypertonic

Solution with a higher solute concentration outside the cell; water tends to leave the cell.

Diffusion

Movement of particles from high to low concentration due to random molecular motion.

Simple diffusion

Passive transport directly through the lipid bilayer, no proteins.

Facilitated diffusion

Passive transport via membrane proteins (channels or carriers); no energy required.

Channel protein

Transmembrane protein forming a pore for specific ions or molecules; may be gated (e.g., aquaporins for water).

Carrier protein

Transmembrane protein that binds a molecule and changes shape to shuttle it across.

Active transport

Movement of substances across the membrane using energy, usually against the concentration gradient.

Primary active transport

Direct use of ATP to power transport (e.g., Na+/K+ pump).

Sodium-potassium pump

A primary active transporter that pumps Na+ out and K+ in, maintaining gradients.

Secondary active transport

Uses electrochemical gradients created by primary active transport to move substances.

Electrochemical gradient

Combined chemical and electrical gradient used to drive transport.

Solution

Homogeneous mixture of solute and solvent; e.g., salt water.

Solute

Dissolved substance in a solution.

Solvent

Dissolving agent; typically water in biological systems.

Concentration gradient

Difference in solute concentration across space or a membrane; drives diffusion.

Cytoskeleton filaments

Internal protein filaments that anchor the membrane and support cell shape.

Aquaporin

Channel protein that specifically facilitates water movement across membranes.

Homeostasis

Maintenance of stable internal conditions by the cell.