Which one of the following options describes a triglyceride?
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Pay close attention to the prefixes.
"Tri-" refers to the three fatty acid chains (acyl groups), while "glyceride" refers to the single glycerol backbone.
Three fatty acid chains linked to a molecule of glycerol
Three glycerol molecules linked to a fatty acid chain
Three saturated fatty acid chains linked to a molecule of cholesterol
Three glyceride molecules linked to a molecule of phospholipid
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The Correct Option isA
Solution and Explanation
Step 1 : Understanding the Question:
This question tests the biochemical definition and structural composition of a triglyceride molecule, which is a major type of lipid found in organisms. Step 2 : Key Formulas and Approach:
The approach involves understanding the esterification reaction that occurs between alcohol groups and carboxylic acid groups during lipid synthesis.
A triglyceride is chemically known as a triacylglycerol. Step 3 : Detailed Explanation:
• Glycerol Backbone: Glycerol is a simple three-carbon compound containing three hydroxyl ($-OH$) groups, represented chemically as $CH_2OH-CHOH-CH_2OH$.
• Fatty Acids: Fatty acids consist of long hydrocarbon chains terminating in a carboxyl group ($-COOH$).
• Esterification: During the synthesis of a triglyceride, each of the three hydroxyl groups of the single glycerol molecule undergoes a condensation reaction with the carboxyl group of a fatty acid chain.
• This process results in the formation of three ester bonds and the release of three water molecules, linking three fatty acid chains to one glycerol molecule.
• The other options describe chemically incorrect combinations, such as multiple glycerol molecules attached to a single fatty acid, or connections involving cholesterol or phospholipids. Step 4 : Final Answer:
Thus, a triglyceride is composed of three fatty acid chains linked to one molecule of glycerol.
This corresponds to Option (A).
