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Ch.23 Lipids
McMurry - Fundamentals of General, Organic, and Biological Chemistry 8th Edition
McMurry8th EditionFundamentals of General, Organic, and Biological ChemistryISBN: 9780134015187Not the one you use?Change textbook
All textbooksMcMurry 8th EditionCh.23 LipidsProblem 15
Chapter 23, Problem 15

Draw the structure of the glycerophospholipid that contains a stearic acid acyl group, an oleic acid acyl group, and a phosphate bonded to ethanolamine.

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Step 1: Understand the structure of a glycerophospholipid. A glycerophospholipid consists of a glycerol backbone with two fatty acid chains esterified to the first and second hydroxyl groups, and a phosphate group attached to the third hydroxyl group. The phosphate group is further bonded to a polar head group, in this case, ethanolamine.
Step 2: Identify the fatty acids involved. Stearic acid is a saturated fatty acid with the formula CH₃(CH₂)₁₆COOH, and oleic acid is an unsaturated fatty acid with one double bond, with the formula CH₃(CH₂)₇CH=CH(CH₂)₇COOH. These will be attached to the glycerol backbone via ester bonds.
Step 3: Attach the fatty acids to the glycerol backbone. The stearic acid acyl group will be attached to the first hydroxyl group of glycerol, and the oleic acid acyl group will be attached to the second hydroxyl group of glycerol. This forms the hydrophobic tail region of the glycerophospholipid.
Step 4: Add the phosphate group and ethanolamine. The third hydroxyl group of glycerol is bonded to a phosphate group (PO₄³⁻) via a phosphoester bond. The phosphate group is then bonded to ethanolamine (CH₂CH₂NH₂) to form the polar head group.
Step 5: Assemble the complete structure. Combine the glycerol backbone, the two fatty acid chains (stearic acid and oleic acid), and the phosphate group with ethanolamine to form the full glycerophospholipid structure. Ensure the hydrophobic tails (fatty acids) and hydrophilic head (phosphate and ethanolamine) are clearly represented in the structure.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Glycerophospholipid Structure

Glycerophospholipids are a class of lipids that consist of a glycerol backbone, two fatty acid chains, and a phosphate group. The glycerol serves as the foundation, with the fatty acids attached to the first and second carbon atoms, while the phosphate group is attached to the third carbon. This structure is crucial for forming cell membranes, providing both structural integrity and fluidity.
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Fatty Acid Composition

Fatty acids are long hydrocarbon chains that can be saturated or unsaturated. Stearic acid is a saturated fatty acid with no double bonds, while oleic acid is an unsaturated fatty acid with one double bond. The specific combination of these fatty acids in a glycerophospholipid influences its physical properties, such as fluidity and melting point, which are essential for membrane functionality.
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Ethanolamine and Phosphate Group

Ethanolamine is an amine that can be attached to a phosphate group, forming phosphoethanolamine. In glycerophospholipids, this combination serves as a polar head group, contributing to the molecule's amphipathic nature, which is vital for membrane formation. The presence of this head group affects the lipid's interactions with water and other molecules, influencing membrane dynamics and signaling.
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Related Practice
Textbook Question

Which of the following terms apply to the compound shown below? (Hint: Look at the functional groups and the bonds involved to begin analyzing the compound part by part in comparison to the lipids discussed in this chapter.)

a. A phospholipid

Textbook Question

As noted earlier (Section 22.3), he first step in glycolysis, which occurs within cells, is phosphorylation of glucose to glucose 6-phosphate. Why does this step prevent passive diffusion of glucose back out of the cell?

Textbook Question

Identify the products formed by complete hydrolysis of all ester bonds in (a) the phosphatidylcholine on page 726.

Textbook Question

Draw the structure of the sphingomyelin that contains a myristic acid acyl group. Identify the hydrophilic head group and the hydrophobic tails in this molecule.

Textbook Question

Identify the products formed by complete hydrolysis of all ester bonds in (b) the sphingomyelin in Figure 23.5.

Textbook Question

Which of the following terms apply to the compound shown below? (Hint: Look at the functional groups and the bonds involved to begin analyzing the compound part by part in comparison to the lipids discussed in this chapter.)

e. A lipid