Question3 Which one of the following statements regarding lipids is CORRECT? Select one alternative: A phospholipid is comprised of 3 fatty acids esterified to a glycerol backbone Naturally occurring unsaturated fatty acids usually contain trans-double bonds Cholesterol's sole role is as a structural component in membranes Docosahexaenoic acid (22:6n-3) is a major fatty acid in the brain Both phospholipids and cholesteryl esters can be considered amphipathic lipids ResetMaximum marks: 1 Flag question undefined

Question

BlackTom AI · Accepted Answer

Let’s break down the statement set by set to understand which one truly reflects lipid biology.
Option 1: 'A phospholipid is comprised of 3 fatty acids esterified to a glycerol backbone.' In reality, a typical phospholipid has two fatty acids esterified to a glycerol backbone and a phosphate-containing head group. This makes the assertion incorrect because it overcounts the fatty acid moieties for standard phospholipids.
Option 2: 'Naturally occurring unsaturated fatty acids usually contain trans-double bonds.' This is a common misconception. Most naturally occurring unsaturated fatty acids have cis double bonds, which create kinks that affect membrane fluidity. Trans double bonds are more associated with industrial hydrogenation and partially hydrogenated fats, not typical natural fatty acids. Therefore this option is incorrect due to the cis preference in biology.
Option 3: 'Cholesterol's sole role is as a structural component in membranes.' While cholesterol is indeed a major membrane component that modulates fluidity and stability, it has several other roles, including serving as a precursor for steroid hormones, bile acids, and vitamin D synthesis. The claim of a sole role is too narrow, so this statement is not entirely accurate and thus incorrect.
Option 4: 'Docosahexaenoic acid (22:6n-3) is a major fatty acid in the brain.' Docosahexaenoic acid (DHA) is indeed highly enriched in brain tissue and plays critical roles in neural membranes and cognitive function. This aligns with established knowledge about brain fatty acid composition, making this option a correct statement.
Option 5: 'Both phospholipids and cholesteryl esters can be considered amphipathic lipids.' Amphipathic means having both hydrophilic and hydrophobic regions. Phospholipids are classic amphipathic molecules with a polar head and fatty acid tails. Cholesteryl esters, however, lack a polar head group and are largely hydrophobic, so they do not display amphipathic character. Consequently, this statement is inaccurate.
In summary, options 1, 2, 3, and 5 each contain a specific factual inaccuracy or overgeneralization, while option 4 presents a fact that correctly reflects brain lipid composition, particularly the prominence of DHA in neural membranes.

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