Lipids: Structure and Function

Lipids that contain fatty acids and can undergo a saponification reaction.

Lipids that do not contain fatty acids and cannot undergo a saponification reaction.

Amphipathic molecules consisting of a long hydrocarbon chain with a carboxyl group (COOH) at one end.

Fatty acids with no double bonds in their hydrocarbon chains.

Fatty acids with at least one double bond in their hydrocarbon chain.

Fatty acids with one double bond in their hydrocarbon chain.

Fatty acids with two or more double bonds in their hydrocarbon chain.

The degree of unsaturation (number of double bonds) and length of the hydrocarbon chain influence the fluidity of lipids and cell membranes.

The main energy storage form of fats.

The process of breaking down triglycerides into glycerol and fatty acids.

A molecule with both hydrophobic and hydrophilic regions.

The polar (hydrophilic) head of a fatty acid.

The non-polar (hydrophobic) tail of a fatty acid.

The main structural component of cell membranes.

A type of phospholipid that is derived from sphingosine, an amino-alcohol with a long hydrocarbon chain.

A ceramide molecule is formed when a fatty acid is linked to the amino group of sphingosine.

Sphingolipids are amphipathic molecules, meaning they have both hydrophilic (water-loving) and hydrophobic (water-repelling) regions. This property makes them crucial for cell membrane structure.

Myelin sheath, the protective covering around nerve cells, is enriched in sphingomyelin. This type of sphingolipid has phosphorylcholine attached to the hydroxyl group of sphingosine.

Glycolipids are lipids with sugar molecules attached to them. They are found on the outer surface of cell membranes, contributing to cell recognition and immunity.

Glycolipids play a significant role in the immune system, blood typing, and cell-cell interactions.

In contrast to phospholipids, glycolipids have a sugar motif instead of a phosphate group attached to the third hydroxyl group of glycerol (or the hydroxyl group of sphingosine).

Glycolipids make up a significant portion of the outer lipid layer of the plasma membrane.

Glycerol-derived glycolipids are found mainly in bacteria and plants. They have two fatty acids attached to glycerol, with the third position occupied by a carbohydrate.

Sphingosine-derived glycolipids are found mostly in animal cells. They share a similar structure to sphingophospholipids, but lack a phosphate group and instead feature a carbohydrate.

Cerebrosides are the simplest glycolipids. They have a single sugar unit (like glucose or galactose) attached to the lipid backbone.

Gangliosides are more complex glycolipids with a branched or unbranched oligosaccharide attached. These oligosaccharides may also include modified sugars.

Cerides are esters of fatty acids and fatty alcohols, with a long hydrocarbon tail ending in a hydroxyl group (OH).

Eicosanoids are derived from the oxidation and cyclization of certain C20 polyunsaturated fatty acids (like arachidonic acid). They act as hormone-like molecules involved in various processes.

Nonsaponifiable lipids are lipids that do not contain fatty acids. They are primarily composed of steroids and terpenes, both derived from isoprene units.

Terpenes are a diverse group of organic compounds found in many plants and some animals. They often have a characteristic fragrance and are responsible for many colors, scents, and flavors.

Terpenes are derived from isoprene units, which are small five-carbon molecules that can be linked together in various combinations.

Many terpenes are characterized by a cyclic structure at one end of the molecule, created through an internal reaction within the isoprene chain.

Steroids are a vital class of lipids with a complex cyclic structure based on a four-ring framework.

Steroids are derived from cholesterol, a key molecule involved in cell membranes and hormone production.

Steroids function as hormones, vitamins, and structural components in living organisms.

Cholesterol, a steroid, is a crucial component of cell membranes, affecting their fluidity and stability.

While cholesterol is abundant in animal products, it also plays an essential role in the body and is not entirely harmful.

These interactions are the main force behind the formation and stability of cell membranes. Nonpolar hydrocarbon tails cluster together to avoid water, while polar heads interact with the watery environment.

These tiny, spherical structures have polar heads facing outward, interacting with water through ionic and hydrogen bonds. The hydrophobic tails point inward, avoiding water.

These layers within a solution keep hydrophobic tails far away from water. They form a barrier against large, water-loving molecules.

These artificial spherical vesicles are formed when a lipid bilayer folds back on itself. They have a hydrophilic lumen inside, which means it is water-loving.

This central region, made of hydrophobic tails in the lipid bilayer, prevents large, water-loving molecules from passing through.

The hydrophobic tails of amphipathic lipids are directed away from water, because they don't like water, thus forming these structures.

Water is a great solvent for polar molecules but not for lipids.