Various factors influences the fluidity of the phospholipid bilayer of the cell membrane. If we were to chart the composition of cell membranes in organisms as we move north from the equator to higher latitudes around the Arctic circle, we would expect to find
phospholipids with
A)
fewer hydrophilic heads.
B)
fewer interspersed cholesterol molecules.
both saturated and unsaturated fatty acid tails.
D
an increase in the length of the fatty acid tails.

D

an increase in the length of the fatty acid tails.

Explanation:

As average annual temperatures decrease, we would expect to find phospholipids within the cell membranes of organisms to have both saturated

and unsaturated fatty acid tails. Saturated fatty acids tails are arranged linearly, in a way that maximizes interactions between the tails and

decreases bilayer fluidity. Unsaturated fatty acids, on the other hand, have more distance between the tails, fewer intermolecular interactions and

more membrane fluidity. Longer tails and decreased cholesterol also decrease fluidity

we would need to see the picture to answer it

"1. it should be, it has been for about 20 years, and it's really not much different in the end than breeding animals to have particular traits. there are always concerns about genetically engineered animals/plants affecting the environment in unexpected negative ways, but i can't think of an example where the fears didn't turn out to be baseless.  

first, as you point out, it would be a great advance in pharmacology, to be able to tailor drugs and their doses to me. the pros involve better medical treatment. the cons involve privacy issues like insurance companies denying coverage to people with genetic risk factors. looking at dna markers wouldn't affect the frequency of genetic diseases, but it would allow detection of them earlier. and ok, actually i suppose that if people used this information to avoid having children with genetic diseases, some might decrease in frequency."