Membrane

Phospholipid

A molecule that comprises a glycerol backbone, a phosphate group, and two fatty acid chains; essential for forming lipid bilayers in cell membranes.

Lipid bilayer

A double layer of phospholipids, with hydrophilic heads facing outward and hydrophobic tails facing inward, forming cell membranes.

Amphipathic molecule

A molecule that has both hydrophilic (water-attracting) and hydrophobic (water-repelling) regions.

Simple diffusion

The movement of non-polar molecules across a membrane from an area of higher concentration to an area of lower concentration without the use of energy.

Facilitated diffusion

The process by which molecules pass through the membrane via the aid of transport proteins, moving down their concentration gradient.

Osmosis

The diffusion of water across a selectively permeable membrane from a region of lower solute concentration to a region of higher solute concentration.

Active transport

The movement of molecules across a membrane against their concentration gradient, requiring energy, typically from ATP.

Channel proteins

Transmembrane proteins that form pores in the membrane, allowing specific ions or water to pass through.

Carrier proteins

Proteins that bind to specific molecules and change shape to shuttle them across the membrane.

Glycolipids

Lipids with a carbohydrate attached, found in cell membranes, helping with cell recognition and stability.

Glycoproteins

Proteins with carbohydrate chains attached, important for cell recognition and signaling in the immune response.

Fluid mosaic model

A model describing the structure of cell membranes as a mosaic of various proteins embedded in a fluid lipid bilayer.

Resting membrane potential

The electrical potential difference across the cell membrane when a neuron is not actively transmitting a signal.

Aquaporins

Channel proteins that facilitate the fast transport of water across cell membranes.

Sodium-potassium pump

An enzyme that uses ATP to actively transport sodium ions out of and potassium ions into the cell, crucial for maintaining membrane potential.

Indirect active transport

Transport mechanism where the movement of one solute down its concentration gradient drives the transport of another solute against its concentration gradient.

Endocytosis

The process by which cells engulf material from the external environment by enclosing it in a vesicle.

Exocytosis

The process by which cells expel material by packaging it in vesicles that fuse with the plasma membrane.

Integral proteins

Proteins that are embedded in the lipid bilayer and have hydrophobic regions that interact with the membrane.

Peripheral proteins

Proteins that are not embedded but rather associate with the membrane's surface, often interacting with integral proteins.

Selectively permeable membrane

A membrane that allows certain molecules or ions to pass through while blocking others.

Transport proteins

Proteins that facilitate the movement of ions and molecules across the cell membrane.

Steroids

A class of lipids with a structure characterized by four fused carbon rings, including hormones like testosterone and cholesterol.

Cholesterol

A type of steroid that is a crucial component of cell membranes, affecting fluidity and serving as a precursor to steroid hormones.

Saturated fatty acids

Fatty acids that have no double bonds between carbon atoms, typically solid at room temperature and found in animal fats.

Unsaturated fatty acids

Fatty acids that have one or more double bonds in their carbon chain, typically liquid at room temperature and found in plant oils.

Membrane potential

The voltage difference across the cell membrane due to the distribution of ions, critical for the function of neurons and muscle cells.