Reef Chemistry Question of the Day #287: Sources of Color

[Randy Holmes-Farley]

Reef Chemistry Question of the Day #287

There are many sources of color in reef aquaria, and many questions I could ask about them.

Let's start with a hard one.

Which of the following is not true?

1. The spines of some sea urchins are purple due to the presence of iodine in them.
2. The most common fluorescent chemical in corals is green fluorescent protein (GFP). The critical part of the GFP molecule for fluorescence contains cobalt.
3. Percula clownfish (A. percula) will become more orange/red if fed a diet containing the natural pigment astaxanthin found in shrimp.
4. Most photosynthetic organisms use chlorophyll to absorb light. Chlorophyll contains a magnesium ion in its core.

Pick all that you think are WRONG.

Good luck!

Previous Reef Chemistry Question of the Day:

Reef Chemistry Question of the Day #286: Pi Day!

Reef Chemistry Question of the Day #286 Today is March 14, pi day! In honor of the day, we have a reef chemistry question about pi. Which of the following chemicals contain pi bonds? 1. Nitrate, NO3- 2. Chloride, Cl- 3. Phosphate, PO4--- 4. Calcium, Ca++ 5. Ethanol, CH3CH2OH Pick all you...

www.reef2reef.com

 

[John Bolden]

I'm going to take a stab and say 3. I recently learned about the photosynthesis process in my biology class and can rule out 4.

 

[Randy Holmes-Farley]

And the answer is:

Which of the following is not true?

1. The spines of some sea urchins are purple due to the presence of iodine in them.
2. The most common fluorescent chemical in corals is green fluorescent protein (GFP). The critical part of the GFP molecule for fluorescence contains cobalt.
3. Percula clownfish (A. percula) will become more orange/red if fed a diet containing the natural pigment astaxanthin found in shrimp.
4. Most photosynthetic organisms use chlorophyll to absorb light. Chlorophyll contains a magnesium ion in its core.

Pick all that you think are WRONG.

Answers 1 and 2 are wrong.

1. While I2 is purple, it is not the color forming agent in sea urchins. Sea urchin spines are mostly calcium carbonate, and the color generally comes from various organic chromophores in them. This article has a lot more discussion of that topic:

Sea Urchins: A Chemical Perspective by Randy Holmes-Farley - Reefkeeping.com

2. While GFP and related structures are prevalent in corals, the actual chromophore is pure organic and contains no metals.

GFP Chromophore

www.cryst.bbk.ac.uk

3. Percula clownfish can color up based on their diet:

https://onlinelibrary.wiley.com/doi/10.1111/are.15920

4. Magnesium is at the core of chlorophyll. It is a little unexpected from a chemistry perspective since magnesium itself does not absorb light (unlikely many other metal ions).

Chlorophyll a - Wikipedia

en.wikipedia.org

 

[John Bolden]

And the answer is:

Which of the following is not true?

1. The spines of some sea urchins are purple due to the presence of iodine in them.
2. The most common fluorescent chemical in corals is green fluorescent protein (GFP). The critical part of the GFP molecule for fluorescence contains cobalt.
3. Percula clownfish (A. percula) will become more orange/red if fed a diet containing the natural pigment astaxanthin found in shrimp.
4. Most photosynthetic organisms use chlorophyll to absorb light. Chlorophyll contains a magnesium ion in its core.

Pick all that you think are WRONG.

Answers 1 and 2 are wrong.

1. While I2 is purple, it is not the color forming agent in sea urchins. Sea urchin spines are mostly calcium carbonate, and the color generally comes from various organic chromophores in them. This article has a lot more discussion of that topic:

Sea Urchins: A Chemical Perspective by Randy Holmes-Farley - Reefkeeping.com

2. While GFP and related structures are prevalent in corals, the actual chromophore is pure organic and contains no metals.

GFP Chromophore

www.cryst.bbk.ac.uk

3. Percula clownfish can color up based on their diet:

https://onlinelibrary.wiley.com/doi/10.1111/are.15920

4. Magnesium is at the core of chlorophyll. It is a little unexpected from a chemistry perspective since magnesium itself does not absorb light (unlikely many other metal ions).

Chlorophyll a - Wikipedia

en.wikipedia.org

I was completely wrong

 

[Randy Holmes-Farley]

I was completely wrong

lol

Thanks for playing.

 

[John Bolden]

lol

Thanks for playing.

Thanks for posting!