Reef Chemistry Question of the Day #142 Food Sources of N and P

[Randy Holmes-Farley]

As reefers we all are (or should be) aware of the importance of striking a proper balance between the additions of nitrogen and phosphorus to our aquaria, and the export.

Most of the time, foods are by far the biggest source of nitrogen and phosphorus, but which food components contribute?

This question of the day has two parts.

Which of the following are NOT known to contain a significant amount of nitrogen?

Which of the following are NOT known to contain a significant amount of phosphorus?

A. Proteins
B. Bone (not including marrow)
C. Fat (triglyceride)
D. Genetic material (DNA)
E. Cell membranes
F. Chitin (shrimp and crab shells)

Good luck and feel free to explain your answer, if needed.



















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[redfishbluefish]

I struggle with the word, "significant," but here's my shot:

A. Proteins: Proteins are composed of amino acids. By definition, the amino group contains nitrogen and therefore I would surmised is in "significant" amounts.
B. Bone (not including marrow): A major component of bone is hydroyapatite....for simplist terms, a calcium triphosphate.....so significant amounts of P
C. Fat (triglyceride): Nope, no N or P here
D. Genetic material (DNA): DNA is made of a pinch of sugar, a P and one of four nucliotides, all of which contain mulpiple N's.....so definitely significant N, and I would say significant P, but that could be argued not knowing what significant is.
E. Cell membranes: Membranes could contain a crap load of stuff, but the major components are phospholipids.....so significant P's.
F. Chitin (shrimp and crab shells): A long chain organic compound with an amine group.....is it significant.....I say yes, because it's there!.....so N for this guy.


So to summarize:

Significant N and P: DNA
Significant N only: Proteins, Chitin
Significant P only: Bone, Cell Membranes
No N or P: Fat

 

[Randy Holmes-Farley]

I struggle with the word, "significant," but here's my shot:

It was intentionally a bit vague, but the focus is intended to be the primary material and not the one bacteria that was found somewhere that has N or P in some chemical where other organisms do not.

That said, at least one of the categories above has significant wiggle room on the answer, and hence the potential need to explain.

 

[ahmed.boomer]

a) Proteins have to have chains of amino acids, so they would have multiple nitrogen components.
b) Bones have a Ca to P ratio of about 5:3, but that's for human bones, I don't think it's quite the same for every species.
c) Fats are just hydrocarbon chains.
d) Genetic material is made of amino acids and proteins, so it does have multiple nitrogen components. But I thought the helix structure was reinforced with phosphate compounds.
e) Most cell membranes are my of phospholipid and proteins. So it is made of fats, proteins, and phosphate.
f) Chitin isn't very digestible, but I have no clue what it's made of

a) Bones, fats, chitin
b) Proteins, fats, chitin

 

[beaslbob]

what they said.

 

[Habib(Salifert)]

There is a tricky one, not knowing if that was the intention or not.

 

[Randy Holmes-Farley]

There is a tricky one, not knowing if that was the intention or not.

A is trickier than it might seem.

 

[redfishbluefish]

A is trickier than it might seem.

Significant!!! Yes, there are a few proteins that undergo post RNA production phosphorylation, but they are few and far between, and therefore insignificant. Don't confuse stuff like ATP and ADP as being proteins....they are not.

I'm struggling more with cell membranes......certainly loads of P with the phospholipids, but they also contain proteins (which contain the N stuff), so is that significant? I'm leaning more towards cell membranes having both significant N and P for this reason.


So my updated summary:

Significant N and P: DNA, Cell Membranes
Significant N only: Proteins, Chitin
Significant P only: Bone
No N or P: Fat

 

[Randy Holmes-Farley]

Maybe not so few...

"It is now known that more than 80% of the different proteins encoded by genes (over 17,000) are subjected to protein phosphorylation, and that the vast majority of these are phosphorylated at multiple sites per protein."

"We believe that the vast majority of the 21,000 proteins encoded by the human genome are in fact phosphorylated. Moreover, the average protein would seem to be phosphorylatable on more than 40 amino acid residues."

both come from:

http://www.kinexus.ca/scienceTechnology/phosphorylation/phosphorylation.html


Also, dietary guidelines for people requiring low phosphate diets are always low in protein. It's a problem for dialysis patients. That may in part be due to other compounds correlated with protein, but phosphorylation is part of the explanation.

 

[Habib(Salifert)]

A is trickier than it might seem.

I was actually thinking about B but you are right A is also tricky (I would have had that one wrong)

 

[Randy Holmes-Farley]

Yes, bones are very complicated. Just the title of this article shows that:

Chemical composition, mineral content and amino acid and lipid profiles in bones from various fish species"

http://www.sciencedirect.com/science/article/pii/S1096495906004210

Abstract
The chemical composition, content of minerals and the profiles of amino acids and fatty acids were analyzed in fish bones from eight different species of fish. Fish bones varied significantly in chemical composition. The main difference was lipid content ranging from 23 g/kg in cod (Gadus morhua) to 509 g/kg in mackerel (Scomber scombrus). In general fatty fish species showed higher lipid levels in the bones compared to lean fish species. Similarly, lower levels of protein and ash were observed in bones from fatty fish species. Protein levels differed from 363 g/kg lipid free dry matter (dm) to 568 g/kg lipid free dm with a concomitant inverse difference in ash content. Ash to protein ratio differed from 0.78 to 1.71 with the lowest level in fish that naturally have highest swimming and physical activity. Saithe (Pollachius virens) and salmon (Salmo salar) were found to be significantly different in the levels of lipid, protein and ash, and ash/protein ratio in the bones. Only small differences were observed in the level of amino acids although species specific differences were observed. The levels of Ca and P in lipid free fish bones were about the same in all species analyzed. Fatty acid profile differed in relation to total lipid levels in the fish bones, but some minor differences between fish species were observed.

 

[JonasRoman]

1) B and C
2)A and C

 

[Randy Holmes-Farley]

So this did end up being an unusually complicated question.

Here's my discussion.

A. Proteins are polymers of amino acids, each of which contains at least one nitrogen (some have two, three or even four), so it is a very big source of nitrogen. It is generally a small source of phosphorus because some of the amino acids will be phosphorylated. That is, a phosphate is attached to them. But, as noted, it is only an occasional amino acid in a protein which is phosphorylated.

B. Bones are the most complicated. The inorganic mineral structure of bones has a LOT of phosphate. The inorganic structure can be approximated by Ca10(PO4)6(OH)2. But bones also have a lot of organic matter all through them. Proteins, whole cells, etc. So there is also a lot of N in bone. Fish foods with bone meal may be high in phosphate for this reason.

C. Fat (as a pure triglyceride) contains no N or P. The structures vary, but look something like

D. DNA has lots of N and P. It is a big part of the structure:

E. Cell membranes contain phospholipids, which contain phosphate. Some membrane components will also contain nitrogen (such as proteins which can be imbeded in the membrane).

F. Chitin is a polymer of N-acetyl glucosamine, so it has a lot of N. Not much P in it.