Petitpas et al. (2001) noted in their 1GNJ structure that a polyunsaturated fatty acid with four double bonds (C20:4) had far from a linear conformation and in fact could adopt several different configurations. You can review the structure of this molecule here
Links to an external site.
.

While this structure is sometimes depicted as being extremely curved, they showed in their albumin structure that the C20:4 fatty acid was able to adopt a variety of conformations. Some examples of this molecule captured within a few different albumin binding sites are shown here; you can ignore the arrows (they were meant to highlight some of the widest parts of the binding sites):

Thinking back to earlier in the module, which one of the following best indicates a reason why we want to make sure that we have some unsaturated (not just saturated) fatty acids available to incorporate into our membrane lipids?

Question

Petitpas et al. (2001) noted in their 1GNJ structure that a polyunsaturated fatty acid with four double bonds (C20:4) had far from a linear conformation and in fact could adopt several different configurations. You can review the structure of this molecule here
Links to an external site.
.

While this structure is sometimes depicted as being extremely curved, they showed in their albumin structure that the C20:4 fatty acid was able to adopt a variety of conformations. Some examples of this molecule captured within a few different albumin binding sites are shown here; you can ignore the arrows (they were meant to highlight some of the widest parts of the binding sites):

Thinking back to earlier in the module, which one of the following best indicates a reason why we want to make sure that we have some unsaturated (not just saturated) fatty acids available to incorporate into our membrane lipids?

BlackTom AI · Accepted Answer

Contextualizing the question, we are asked to identify why having some unsaturated fatty acids in membrane lipids is advantageous. The core concept is that double bonds in unsaturated tails introduce kinks, preventing tight, orderly packing of lipid tails and thereby increasing membrane fluidity.

Option 1: 'They serve as a precursor for cytochrome c, an electron transport chain component.' While lipids and lipoproteins can participate in carries or contacts related to electron transport in certain contexts, this statement does not address the primary physical reason for unsaturation in membrane lipids. It misstates the functional role as a chemical precursor, which is not the central rationale for membrane fluidity.

Option 2: 'Their properties prevent tight packing of the tails which increases membrane fluidity.' This directly links the presence of double bonds to the structural effect—kinks from cis double bonds disrupt tight packing, reducing van der Waals interactions between tails, and thus raise fluidity. This is the fundamental and widely taught rationale for including unsaturated fatty acids in membranes.

Option 3: 'Their properties allow necessary ion movement through membranes.' While membrane fluidity can influence permeability and protein function that govern ion movement, this choice overstates and obliquely credits unsaturation with enabling ion movement directly. The primary, established link is to fluidity via tail packing, not an explicit assertion that unsaturation alone creates ion channels or movement.

Option 4: 'They serve as an anchor for ribosomal proteins.' Ribosomes are not anchored to lipid bilayers via unsaturated fatty acids in the way described here; this option misattributes a membrane lipid property to a role in ribosome binding, which is not supported by typical membrane biology.

Option 5: 'They serve as electron donors for the citric acid cycle.' This is inaccurate for fatty acids in membranes; fatty acids are not electron donors for the citric acid cycle in this context. The citric acid cycle relies on acetyl-CoA oxidation and related coenzymes, not the unsaturation state of membrane lipids.

In summary, the most accurate statement that aligns with the established reasoning about membrane lipid composition is that unsaturated fatty acids prevent tight tail packing and thereby increase membrane fluidity. The other options describe roles or effects that are not the primary rationale for including unsaturated fatty acids in membranes, or they describe incorrect functions altogether.

类似问题

If a bacterial cell increases the average length of its phospholipid tails from 16 carbons to 20 carbons, how has the environment likely changed?

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