examkrackers biology question

[tido88]

I was doing passage 303 in the EK Biology 1001 book, and can't seem to understand the solution too the question asking about when the ratio of unsaturated to saturated fatty acids would be lowest.

My understanding is that there would be a low ratio of unsat/sat fatty acids at high temperatures (because unsaturated fatty acids aid in keeping the membrane fluid). However, the book says that there would be a low ratio at low temperatures. Does anyone mind explaining this to me? I would really appreciate it!

Thanks.

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[Dr Gerrard]

That is correct.

Because unsaturated fatty acids increase fluidity of the membrane.
High temperature increase fluidity of the membrane.

Thus, at higher temperatures, you don't want the membrane to be TOO fluid, so you want higher concentrations of saturated fatty acids.

Similarly, at low temperatures, you want more unsaturated fatty acids to increase the fluidity and make up for the lower temperatures.