Warm/Cold Enviroment Fatty Acid

[TexasFluoride]

I don't understand 2 concepts in Greenwaves notes (AKA alan's notes).

Concept #1:

• In a warmer environment, the organism will want to increase its % of unsaturated fatty acids, so that fatty acids will be more fluid and the melting point will decrease.

^^^^^^
Why would a organism want its fatty acid to be more fluid in warmer enviroment? It seems like the opposite to me.
Also how would this statement be true for a cold enviroment?

Concept #2:

• For each subsequent level in the energy pyramid, the energy increases by 101.

Shouldn't this statement be that the energy decreases by 10 for each subsequent level????? Looking at the picture below it looks like energy decrease as we go up each level.

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[TexasDDS]

I have no explanation, but I was wondering where can I get those notes from?

 

[TK2006]

1. Unsaturated fatty acids have higher boiling point but lower melting point compared to saturated fatty acids. This is due to increased "kinks" in packing of the molecules as a result of the double bonds. Double bonds increase bond polarity, increasing boiling point due to polarity but decreasing melting point due to less efficient packing.

In general,

cis vs trans double bonds:
-cis isomer has lower melting point and higher boiling point

less bonds (e.g. single) vs more bonds (e.g. double):
-more bonds allow lower melting point and higher boiling point

You want boiling point to be higher so that the acid chains can withstand the heat better in a warm environment. If you still have questions, feel free to PM me. I'll do my best to answer.

2. As you go up the energy pyramid, you "lose" energy by 10-fold. If energy is 1000 kcal at level 2, then energy will be 100 kcal at level 3 (one level higher). That must be a typo in the notes.

Extra: a little mnemonic that I use for bp/mp trend is: "Cis depresses and elevates; more bonds do the same"
- cis isomer depresses freezing point but elevates boiling point. Adding more bonds create the same effect.

 

[rmm30]

concept #2: typo, you have the right idea

concept #1: Alans notes got this one wrong, you have it right. Cell membranes need to maintain a certain degree of fluidity and are capable of changing membrane fatty acid composition to do so. In cold weather, to avoid rigidity, cells incorporate more mono and polyunsaturated fatty acids into the membrane as they have lower melting points and are kinked to increase fluidity. Warm weather climates show the opposite trend. Also you are probably aware the cell membranes contain cholesterol which adds rigidity to the lipid bilayer. In cold weather there is a decrease in cholesterol and an increase in cholesterol in warm weather