Lipids and Biological Membranes - Vocabulary Review

Vocabulary flashcards covering lipids, their structures, types, and membrane-associated concepts discussed in the lecture.

Lipid

A broad class of biological molecules defined more by insolubility in water than by a single chemical structure; includes triglycerides, phospholipids, glycolipids, and steroids.

Triglyceride

Energy-storage lipid formed when glycerol (a three-carbon backbone) is esterified with three fatty acids.

Glycerol

A three-carbon backbone alcohol used in lipids (phospholipids and triglycerides); a sugar-alcohol rather than a carbohydrate.

Fatty acid

A carboxylic acid attached to a hydrocarbon tail; tail is hydrophobic; designation X:Y indicates total carbons (X) and carbon–carbon double bonds (Y).

Ester linkage

Covalent bond formed when fatty acids attach to glycerol (acid–alcohol condensation) in triglycerides and phospholipids.

Saturated fatty acid

Fatty acid with no carbon–carbon double bonds; chains are straight and pack tightly.

Unsaturated fatty acid

Fatty acid with one or more carbon–carbon double bonds; introduces kinks that prevent tight packing.

Phospholipid

Lipid with a glycerol backbone, two fatty acids, and a phosphate group; often has an additional head group; amphipathic.

Phosphatidylcholine

A common membrane phospholipid with a choline-containing head group.

Phosphatidylethanolamine

Membrane phospholipid with an ethanolamine head group.

Phosphatidylserine

Membrane phospholipid with a serine head group.

Phosphatidylinositol

Membrane phospholipid with an inositol head group.

Single myelin

A phospholipid-like lipid that uses serine as its backbone instead of glycerol; similar function in membranes but non-glycerol backbone.

Glycolipid

Lipid with a sugar-containing head group (no phosphate); can have one or more monosaccharides or oligosaccharides.

Cholesterol

A sterol steroid with a four-ring structure and a small hydroxyl group; modulates membrane fluidity and acts as a membrane component.

Steroid

A lipid class with a four-ring isoprenoid core; includes cholesterol and steroid hormones; varies in head region and function.

Amphipathic

Molecule with both hydrophobic (water-fearing) and hydrophilic (water-loving) regions; typical of membrane lipids.

Hydrophobic

Nonpolar regions or interiors that repel water; essential for the lipid bilayer interior.

Hydrophilic

Polar or charged regions that interact with water; typically found on lipid head groups facing aqueous environments.

Liposome

Spherical vesicle formed when lipid bilayers seal into a sphere; used to study membranes and encapsulate substances.

Lipid bilayer

Two leaflets of lipids with hydrophobic interiors; forms the basic structure of cellular membranes.

Asymmetry (membranes)

Unequal distribution of lipid types between the two leaflets; allows different chemistry on each side of the membrane.

Integral membrane proteins

Proteins embedded in the membrane; includes transmembrane, lipid-anchored, and membrane-associated proteins under one umbrella.

Transmembrane protein

Integral membrane protein that spans the lipid bilayer, with segments on both sides.

Lipid-linked protein

Protein covalently attached to a lipid, anchoring it to the membrane.

Membrane-associated protein

Protein associated with the membrane but not spanning it; located on one side via noncovalent interactions.

Peripheral membrane protein

Protein not covalently attached to the membrane; bound by noncovalent forces and does not insert into the interior.

Phospholipid definition (backbone, fatty acids, phosphate)

A membrane phospholipid has a three-carbon backbone (often glycerol), two fatty acids, and a phosphate group, with possible additional head-group chemistry.