L2. Mineral salts in organisms

On Monday 29th of September we started an experiment called "Mineral salts in organisms", the main objectives were to identify mineral salts in organisms and to understand the function of inorganic biomolecules in skeletal structures of organisms.

First we gathered all the materials that we needed: 
-Molluscs's shells
-Dried cleaned chicken bones
-Distilled water
-Acetic acid
-Vinegar
-250 ml Beaker
-Clock glass

PROCEDURE

Chicken bones:
1- We took the chicken bone and made sure that there was no meat remaining on it, also we cleaned it with water.
2- After that we weighed the bone, the weight was 13,5 g.
3- Then we tried to bend the bone to check it's flexibility, it was not flexible at all.
4- We took the beaker and put vinegar in there, with a small amount of acetic acid.
5- Then we dropped the bone in the solution that we made and covered the beaker with the clock glass to protect it.
6- All that we had to do is wait 24-48 hours to see what happens to the bones but we decided to wait a week because the bone is really thick.

Results and observations: We left the bones in the solution for a week and when we tried to bend them again with the tongs, they did.

Conclusions: The bones are now flexible! They lost their stiffness because they don't have calcium carbonate anymore, and only the organic material is left.

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Mollusks shells:
1-We took another beaker and put acid acetic and distilled water in there.
2-Then we put the shells in the beaker.

Results and observations: When we put the shells in the beaker a lot of bubbles started forming and soon the entire beaker was covered with bubbles (it was very fizzy) , it looked like an effervescent pill. Then we decidded to leave the solution for a few days to see what happens, on the third day there was no signs of the small shell in the beaker and the big shell was disolving. Ignacio decided to try this experiment with and egg shell and the same happened to it, but there were brown rests of egg shell and the membrane.

Conclusions: What happened is that the shells contain Ca CO3 (calcium carbonate), when it combines with acetic acid a chemical reaction takes place and CO2 (carbon dioxide) is released (those are the bubbles) and (Ca (CH3COO)2) calcium acetate is formed. So the inorganic materials dissolve and all that there's left are the organic materials.

 QUESTIONS

1- Write the reaction that takes place when the acid acectic reacts with the calcium carbonate.
CH3 COOH + Ca CO3 --> CO2 + (Ca (CH3COO)2)
When calcium carbonate reacts with acetic acid it produces carbon dioxide and calcium acetate.

2-What is happening when the shells are soaking of acetic acid? What are the bubbles that you can see? When the shells are soaking of acetic acid they make a lot of bubbles and the soulution is fizzy. The bubbles are CO2.

3- What is happening to the bone after some days of soaking it in acetic acid? Why is the bone flexible now?
The bone become more flexible, we can now bend it with the tongs. The acetic acid dissolves the calcium carbonate of the bone and only the organic material is left, so the bone looses it's stiffness.

4-So, what is the function of the calcium carbonate in the skeletal structures? To give rigidity.

5- Increases in carbon dioxide to the atmosphere from the burning fossil fuels and deforestation threaten to change the chemistry of the seas. Evidence suggests that this increase in atmospheric carbon dioxide is lowering the pH of the oceans in a process called ocean acidification. How can acidification affect coral reefs?
The coral reefs are made of calcium carbonate (CaCo3), if the acidity is higher they will disolve. The lowering of the pH will disolve the CaCo3.