Structural Properties of Lipids and Their Biological Roles

Vocabulary flashcards covering the structural characteristics, biological signaling functions, and pharmaceutical applications of lipids.

Lipids

A diverse group of organic compounds—including fats, oils, hormones, and membrane components—that group together because they contain highly hydrophobic regions and do not interact with water.

Palmitic acid

The simplest fatty acid, consisting of a long alkyl chain with a carboxylic acid head group, which deprotonates to form palmitate at physiological $\text{pH } 7.4$.

Amphipathic

The property of molecules that have a dual chemical nature, possessing both a hydrophilic, polar head that interacts with water and a lipophilic, hydrophobic tail that interacts with oils or grease.

Surfactants

Amphipathic agents that reduce the surface tension of water by orienting at interfaces and disrupting the hydrogen bonding network of water molecules.

Glycerophospholipids

Abundant membrane lipids composed of a glycerol backbone (propane-$1,2,3$-triol) linked to two fatty acid alkyl chains via ester bonds and a phosphate-based polar head group.

Sphingolipids

Membrane lipids built around a sphingosine unit that act as structural scaffolding to provide shape to cell membranes and break down to produce signaling molecules.

Micelles

Monolayer spherical lipid aggregates whose lipophilic tails cluster inward and hydrophilic heads face outward, helping solubilize and transport dietary fats and fat-soluble vitamins across membranes.

Liposomes

Bilayer spherical lipid structures containing an internal aqueous channel, capable of encapsulating and transporting polar molecules such as messenger RNA around the body.

Sphingosine-1-phosphate (S1P)

A phosphorylated signaling lipid that exits the cell and binds receptors on lymph nodes to stimulate the release of inflammatory fluid containing platelets and white blood cells.

Fingolimod

A drug modulator designed to structurally mimic sphingosine-1-phosphate to block receptor signaling for the treatment of autoimmune conditions such as multiple sclerosis.

Prostaglandins

Signaling lipid mediators (such as $\text{PGH}_2$) generated from arachidonic acid via cyclooxygenase ($\text{COX}$) enzymes that act as key regulators of immune response, pain, and inflammatory edema.

Aldosterone

A steroid hormone synthesized in the adrenal glands from cholesterol, containing an enone and an aldehyde group, which acts on the kidneys to control salt secretion.

Cortisol

A cholesterol-derived steroid hormone featuring a $6,6,6,5$ fused ring system that exerts immunosuppressive and anti-inflammatory activity while keeping the body alert and awake under stress.