Regarding membrane fluidity

[JA Prufrock]

This question deals with the integration of saturated and unsaturated fatty acids into membranes.

My understanding is that, at higher temperatures, fatty acid unsaturation goes down since the cell wants to decrease fluidity. Saturated fatty acids pack closer together, and so they would be better at decreasing fluidity.

Ek Bio 1001, question 241 on page 45 says the opposite. It says, at lower temperatures, you will have more saturated fatty acids. But wouldn't the cell want to increase fluidity at a lower temperature (and so produce more unsaturated fatty acids)?

Can anyone shed some light on this? Thanks.

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[Quantum Chem]

When I answered this question I just referred to the passage. In the second paragraph it says "At low temp cell membrane fluidity decreases." Then in the last paragraph it states "...increase membrane fluidity by elevating the extent of fatty acid unsat." So according to the passage a high level of unsat fats results in a higher fluidity. The question wants a low ratio of unsat to sat fat, so low amounts of unsat fat according to the passage would be seen in membranes that have decreased fluidity, which is at lower temps.

 

[JA Prufrock]

When I answered this question I just referred to the passage. In the second paragraph it says "At low temp cell membrane fluidity decreases." Then in the last paragraph it states "...increase membrane fluidity by elevating the extent of fatty acid unsat." So according to the passage a high level of unsat fats results in a higher fluidity. The question wants a low ratio of unsat to sat fat, so low amounts of unsat fat according to the passage would be seen in membranes that have decreased fluidity, which is at lower temps.

At lower temperatures, cell membrane fluidity does decrease. However, I thought the cell tries to compensate for this by adding unsaturated fatty acids so that fluidity increases, in order to balance out the effects from temperature. At higher temperatures, cell membrane fluidity is increased, so to keep fluidity at an optimal range, the cell would increase the amount of saturated fatty acids (which pack together nicely), and lower the amount of unsaturated fatty acids.

Is my understanding of this concept wrong?