Factors affecting cell fluidity

[linuxzhen]

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My quandary stems from BR Ochem PART I Page 294 Qestion 18 “which fatty acid would most reduced membrane's fluidity?”

When I review the answer of Question 18 in Page 297 . Cell fluidity depends on packing of the alkyl groups, and saturated alkyl groups pack best, which indicates that unsaturated alkyl groups reduce cell fluidity. ....

But...

The answer of Question 21 reveals that Arctic Salmon have more unsaturated fats to raise cell fluidity, which contradicts answers above.

Is part of the answer of Question 18 wrong?

SOS~~

 

[sdm33]

Because of the kinks in the carbon chains at the cis double bonds of unsaturated fatty acids, the glycerophospholipids do not fit closely together. As a result, the lipid bilayer is not a rigid, fixed structure, but one that is dynamic and fluid like. So it is the unsaturation fat should increase the dynamic fluid. Furthermore, saturated fat is sold at room temp, and unsautratred fat is more health and has a lower melting point, that is why olive oil is better then butter. As of the contradiction of the questions may be it is better if you ask BR.
Good luck

 

[BerkReviewTeach]

My quandary stems from BR Ochem PART I Page 294 Qestion 18 "which fatty acid would most reduced membrane's fluidity?"

When I review the answer of Question 18 in Page 297 . Cell fluidity depends on packing of the alkyl groups, and saturated alkyl groups pack best, which indicates that unsaturated alkyl groups reduce cell fluidity. ....

But...

The answer of Question 21 reveals that Arctic Salmon have more unsaturated fats to raise cell fluidity, which contradicts answers above.

Is part of the answer of Question 18 wrong?

SOS~~

You should look back at explanation #18 and double check if it's saying what you just paraphrased. Here is the exact statement.

Explanation to 18:
Cell fluidity depends on the packing of the alkyl groups in the cell membrane. Saturated alkyl groups pack best, as evident by the higher melting points of saturated alkanes relative to unsaturated alkanes of the same size. Cell fluidity is more reduced by a long alkyl chain than a short alkyl chain. Arachidic acid is twenty carbons in length and contains no pi-bonds, so it will reduce cell fluidity more than arachadonic acid (which has four pi-bonds), lauric acid (which only has twelve carbons), and linioleic acid (which has three pi-bonds).

The answer does not state that cell fluidity is reduced by unsaturation. In fact, it alludes to the idea that unsaturated hydrocarbons don't pack as well to explain their lower melting points. Unsaturated hydrocarbons (with pi-bonds) reduce packing and thereby make the cell more fluid (just as sdm33 has explained). Both the answer for 18 and the answer for 21 agree with this idea.

 

[pacer]

Cell fluidity depends on:

degree of unsaturation
concentration of cholestrol
length of fatty acids

If more unsaturated lipids are present in the cell membrane, they will have lots of kinks and will not stack properly, allowing the membrane to be loosely structured and highly fluid.

 

[adrakdavra]

Some of the most amazing doctors I know, the ones who've started clinics for the underserved and reached out from their hearts to help others, didn't do all that well on the MCAT. Maybe because they had to work so hard to become a doctor, they work that much harder as a doctor

That sounds deep. I read a lot of stories about the MCAT on this website, and I realized one thing , that some students have posted that they scored 25 and study for another 3 months and scored 27 , other students scored less than the first time they took the MCAT. Is this normal for the Mcat.

I read a lot of MCAT stories that make me wonder why?

 

[PlumbLine]

What is this I don't even