Hydrolysis of triacylglycerol — which product is water soluble? If the ester bonds of a triacylglycerol are hydrolyzed completely, which resulting molecule is readily soluble in water?

Introduction / Context:
Triacylglycerols are storage lipids composed of glycerol esterified with three fatty acids. Enzymatic or chemical hydrolysis cleaves the ester bonds to yield glycerol and free fatty acids. Knowing the solubility of the products is important for understanding digestion, absorption, and metabolism.

Given Data / Assumptions:

• Complete hydrolysis generates one glycerol and three fatty acids.
• Water solubility depends on polarity and hydrogen bonding capability.
• Free fatty acids are amphipathic but poorly soluble as long chain species.

Concept / Approach:

Glycerol is a small, highly polar triol with three hydroxyl groups that hydrogen bond extensively with water, making it very soluble. In contrast, long chain fatty acids possess long hydrophobic tails that limit solubility; they form micelles or bind to albumin rather than dissolving freely. Steroids and cholesteryl esters are hydrophobic lipids, while glycogen is a carbohydrate polymer not derived from triacylglycerol hydrolysis.

Step-by-Step Solution:

Verification / Alternative check:

Solubility tables show glycerol is miscible with water, confirming the conclusion. Physiological transport uses glycerol freely in blood, whereas fatty acids require carriers.

Why Other Options Are Wrong:

Fatty acids are sparingly soluble and typically require micelles or proteins. Steroids and cholesteryl esters are hydrophobic. Glycogen is unrelated to triacylglycerol hydrolysis.

Common Pitfalls:

Assuming the carboxyl group alone makes long chain fatty acids very soluble; the long hydrocarbon tail dominates solubility behavior.

Final Answer:

Glycerol