Reef Chemistry Question of the Day #193 Membrane Penetration

[Randy Holmes-Farley]

Reef Chemistry Question of the Day [HASHTAG]#193[/HASHTAG]

Which of the following chemicals in a reef aquarium is most likely to travel across a biological membrane (such as on the surface of a coral) without any special transport proteins being present?

A. Phosphate
B. Nitrate
C. Ammonia
D. Copper

Good luck!






























.

 

[donnievaz]

Ammonia, because it's slippery. lol

 

[fab]

Copper... deadly to corals.
fab

 

[Salty1962]

A

 

[JimWelsh]

I'm going with "C. Ammonia", because it's the only one without a charge.

 

[Myka]

Ammonia. It's the only one listed that makes it through a reverse osmosis membrane.

 

[Hunter S Thompson]

You would think it would be Phosphate because it is on both sides of the membrane and of coarse it's coral food, but I have no idea what "special transport proteins" are.

 

[SROPE]

I guess ammonia.

 

[Cory]

Ill guess copper. My reasoning is:

1) hard corals hate po4 and cabt build caco3 with too much of it, and wouldnt like it getting through easily, consequently adapting to its presence, thus the need to control its entry via transport proteins. So its not po4.

2) copper is smaller than those molecules (maybe not), so maybe it gets through easily because of its size. Considering durring millions of years evolution probably had low concentrations of copper due to photosythysizing algaes and thus corals wouldnt need to adapt to it much, due to it being low. Thus any amount passes through.

3) ammonia is loved by algae maybe corals evolved to suck it up as quick as possible for survival reasons. So their zoox can get a tasty treat.

Its gotta be copper or ammonia

 

[beaslbob]

traveling across do you mean thru the membrane to the other side? Of just slipping along the surface?

 

[Randy Holmes-Farley]

traveling across do you mean thru the membrane to the other side? Of just slipping along the surface?

Through.

 

[beaslbob]

Through.

either way I don't know.

 

[Randy Holmes-Farley]

either way I don't know.

Glad I answered.

 

[Randy Holmes-Farley]

And the answer is...C. Ammonia

In its uncharged form, NH3, ammonia crosses cell membranes fairly readily, and that is why ammonia toxicity is much worse at higher pH (because more of it is present as ammonia rather than ammonium, NH4+, which is charged and does not cross membranes as well).

The other chemicals are all charged and a charge makes it very hard to cross the oil like middle of a cell membrane. Same reason salt does not dissolve in olive oil: the oil cannot stabilize the charges well at all, while water can. Consequently, salts dissolve in water but not oil.