Plasma Membrane and Membrane Permeability

Vocabulary practice flashcards covering membrane structure, components of the fluid mosaic model, membrane proteins and carbohydrates, selective permeability, and cell walls.

Plasma Membrane

A selectively permeable boundary comprised primarily of phospholipids that separates the internal cell environment from the external environment.

Amphipathic

A characteristic of having both hydrophilic (polar) and hydrophobic (nonpolar) regions, as seen in phospholipids forming a bilayer.

Fluid Mosaic Model

A model describing the plasma membrane as a fluid structure held together by weak hydrophobic interactions, composed of a mosaic of diverse macromolecules.

Unsaturated Hydrocarbon Tails

Phospholipid tails featuring kinks that prevent the tight packing of lipids, thereby helping to maintain membrane fluidity at low temperatures.

Cholesterol

A lipid component that buffers membrane fluidity by reducing phospholipid movement at high temperatures and preventing tight packing at low temperatures.

Integral Proteins

Proteins embedded into the lipid bilayer whose hydrophilic regions form channels or face aqueous cytosol and whose hydrophobic regions interact with fatty acid tails.

Peripheral Proteins

Membrane proteins that are not embedded within the lipid bilayer, remaining loosely bound to the inner or outer surface of the membrane.

Glycolipids

Carbohydrates covalently bonded to lipids on the cell surface that participate in cell-to-cell recognition.

Glycoproteins

The most abundant category of cell-surface carbohydrates, formed by carbohydrates covalently bonded to proteins, which function in cell-to-cell recognition.

Selective Permeability

The property of the plasma membrane that allows it to regulate the passage of substances entering and exiting the cell, largely governed by its hydrophobic interior.

Cell Wall

An extracellular structure found in bacteria, Archaea, fungi, and plants that provides a structural boundary, acts as a permeability barrier, and prevents osmotic lysis.

Osmotic Lysis

The rupturing or bursting of a cell resulting from the excessive uptake of water.

Cellulose

The primary carbohydrate material that forms plant cell walls, creating a structural layer that is thicker than the underlying plasma membrane.

Plasmodesmata

Cytosol-filled, hole-like channels traversing plant cell walls that physically connect the interiors of adjacent cells.

Channichthyidae

The crocodile ice fish inhabiting the Southern Ocean around Antarctica in temperatures between $-2.2$ to $1.7$ ($28$ to $35$), adapted to cold environments through modified membrane lipid composition.