Question

Draw the structure of a triacylglycerol composed of equal amounts of palmitic acid, stearic acid, and oleic acid

Short answer

A triacylglycerol consists of a glycerol backbone esterified with palmitic, stearic, and oleic acids.

Step-by-step solution

Understand Triacylglycerols

A triacylglycerol (or triglyceride) is a lipid molecule made of one glycerol molecule and three fatty acid molecules. The fatty acids attach to the glycerol backbone via ester bonds.

Identify Fatty Acids

Clarify the structure of each fatty acid component: - Palmitic acid: A saturated fatty acid with the formula C15H31COOH. - Stearic acid: A saturated fatty acid with the formula C17H35COOH. - Oleic acid: An unsaturated fatty acid with one double bond and the formula C17H33COOH.

Draw the Glycerol Backbone

The glycerol molecule consists of a three-carbon chain, where each carbon has an -OH (hydroxyl) group. Begin by sketching the three carbon atoms, each bonded to two hydrogens and one hydroxyl group.

Attach Fatty Acids to Glycerol

Connect each fatty acid to the glycerol backbone. - The palmitic acid esterifies with the first hydroxyl (-OH) group. - The stearic acid connects with the second hydroxyl group. - The oleic acid attaches to the third hydroxyl group. To form these ester bonds, remove the -H from each glycerol hydroxyl group and an -OH from the carboxyl (COOH) end of each fatty acid.

Complete the Triacylglycerol Structure

Ensure all ester links are formed, resulting in: - Glycerol backbone linked via ester bonds to palmitic, stearic, and oleic acids. - Check that each fatty acid chain correctly contains its specific number of carbons and adheres to the required saturation or unsaturation (double bond for oleic acid).

Key concepts

Triacylglycerol Structure

Triacylglycerol, commonly known as a triglyceride, is an essential lipid molecule that forms a significant part of our daily diet. Consider it as a combination of a simple molecule called glycerol with three fatty acids. The glycerol provides the backbone of this structure.
It is a three-carbon compound where each carbon is attached to an -OH group (hydroxyl). This simple structure enables it to bond with fatty acids readily.

The three fatty acids attach to each of these hydroxyl groups on the glycerol via a special kind of linkage known as an ester bond. This bond forms when the -OH group of the glycerol and the -COOH (carboxyl group) of fatty acids combine, releasing water (a process called esterification). This fundamental structure allows for variability in the nature and order of fatty acids, which can influence the physical properties of the triacylglycerol.

• The specific arrangement and type of fatty acids in a triacylglycerol determine if it is a solid or liquid at room temperature.
• They play a crucial role in energy storage and insulation in living organisms.

Fatty Acids

Fatty acids are critical components attached to the glycerol backbone in triacylglycerols. These organic acids contain a long carbon chain and a carboxyl group (-COOH) at one end. Fatty acids can be saturated or unsaturated, giving them distinct chemical properties.
Saturated fatty acids have no double bonds between the carbon atoms, leading to a straight chain that packs closely with other chains. Palmitic acid and stearic acid are classic examples of saturated fatty acids.

On the other hand, unsaturated fatty acids have one or more double bonds, creating kinks in their structure that prevent tight packing. An example is oleic acid, which has one double bond (monounsaturated).

• The length and degree of saturation in fatty acids greatly influence the functionality and metabolism of the triacylglycerol.
• Fatty acids are also essential biological molecules for cell membrane formation and signaling.

Recognizing the structure and characteristics of fatty acids is essential for understanding their role in nutrition and biochemistry.

Lipid Molecules

Lipid molecules encompass a diverse group of compounds unified by their insolubility in water. Among these, triacylglycerols are the most well-known. They serve as long-term energy storage molecules, storing more energy per gram than carbohydrates.
Lipid molecules can be classified broadly into simple and complex lipids. Triacylglycerols are simple lipids since they're primarily composed of glycerol and fatty acids without additional components.

Besides energy storage, lipids perform several key biological functions:

• They make up the structural components of cell membranes, primarily in the form of phospholipids.
• Lipids are involved in signaling pathways that regulate various biological processes.

Understanding lipids is crucial for grasping their role in metabolism and cellular function, as well as their importance in nutrition and health.