Question

Draw the structure of a glycerophospholipid that contains palmitic acid and ethanolamine. What is another name for this type of glycerophospholipid?

Short answer

Phosphatidylethanolamine is the glycerophospholipid containing palmitic acid and ethanolamine.

Step-by-step solution

Understand the Basic Structure

A glycerophospholipid is composed of glycerol, two fatty acids, phosphoric acid, and an alcohol.

Attach the Fatty Acids to Glycerol

Attach two fatty acids to the first and second hydroxyl groups of glycerol. In this case, one of the fatty acids is palmitic acid (C16:0).

Add the Phosphate Group

Attach a phosphate group to the third hydroxyl group of glycerol, completing the phosphatidic acid backbone.

Attach the Ethanolamine

Link ethanolamine to the phosphate group via a phosphodiester bond, forming the final glycerophospholipid structure.

Define and Name the Glycerophospholipid

The resulting structure is known as phosphatidylethanolamine, which is the glycerophospholipid containing palmitic acid and ethanolamine.

Key concepts

glycerol

Glycerol is a simple molecule, also known as glycerin. It consists of a three-carbon chain, where each carbon atom is bonded to a hydroxyl group (-OH). This triol (an alcohol with three hydroxyl groups) forms the backbone of glycerophospholipids.

• The first and second hydroxyl groups attach to fatty acids.
• The third hydroxyl group bonds with a phosphate group.

Glycerol is the central scaffold for forming complex lipids. This structure allows glycerophospholipids to be amphipathic (having both hydrophilic and hydrophobic parts).

palmitic acid

Palmitic acid is a saturated fatty acid consisting of 16 carbon atoms (C16:0). It is one of the most common saturated fatty acids found in animals and plants. In the context of glycerophospholipids:

• A fatty acid like palmitic acid connects to the first hydroxyl group of glycerol.

This fatty acid tail is hydrophobic, contributing to the lipid's non-polar nature. The union of glycerol and palmitic acid helps form part of the cell membrane's structure, adding rigidity and strength.

ethanolamine

Ethanolamine is a simple amino alcohol with the formula HOCH2CH2NH2. It is a key component of glycerophospholipids like phosphatidylethanolamine (PE). Ethanolamine's properties include:

• A water-soluble part, owing to the hydroxyl (-OH) and amine (-NH2) groups.
• When linked to the phosphate group, ethanolamine forms a polar head.

This polar head faces the aqueous environment, making phosphatidylethanolamine an essential structural component of cell membranes.

phosphate group

The phosphate group (PO4) is crucial in forming glycerophospholipids. It attaches to the third hydroxyl group of glycerol. The unique traits of the phosphate group include:

• The ability to form strong bonds with other molecules.
• Interaction with alcohols like ethanolamine to form phosphodiester bonds.

The addition of the phosphate group imparts a negative charge to the molecule, enhancing its ability to interact with water and forming the hydrophilic head of the phospholipid.

phosphatidylethanolamine

Phosphatidylethanolamine (PE) is a type of glycerophospholipid formed when ethanolamine attaches to a glycerol backbone through a phosphate group. Its main characteristics are:

• Aglycerol backbone connected to two fatty acid tails (like palmitic acid) and a phosphate-ethanolamine head group.

This structure forms the amphipathic nature of PE, with the polar head group interacting with water and the non-polar tails facing inward. Phosphatidylethanolamine is a major component of biological membranes, contributing to membrane fluidity and function.