Thursday, 29 September 2016
Have you ever noticed that fruits turn brown when you cut them? They turn brown when they are in contact with the air. The fruit's skin protects them, but if it breaks or is cut or damaged the fruit goes brown faster. Fruits contain enzymes (polyphenol oxidase and catechol oxidase are two common examples) that react with the O2 and with iron or copper cofactors in the fruit. A cofactor is a component that is necessary for a certain enzymatic reaction to happen. The fruit starts to oxidize and turn brown. Electrons are lost to another molecule, in this case the air. In other words, it's like an edible rust on your food!
Antonio Agustin has done the following experiment to study the effects of different substances on fruit oxidation. Oxidation can be prevented or slowed down by not allowing O2 to get to the surface of the fruit or by reducing the oxidase enzymes in them. For example, cooking fruit destroys the oxidase enzymes in them but it's also possible to prevent browning or oxidation by covering the fruit to avoid its contact with air or by lowering the pH on the surface, that is making it more acidic.
Antonio covered the food with different substances to try to find which prevents the food from turning brown best and why.
He tested 4 foods: apple, avocado, potato and banana. He submerged them in different solutions: lemon juice, vinegar, clear soda, olive oil, water, salt water and a control sample.
After observing his experiment for a few minutes he came to the following conclusion. Lemon juice, vinegar and clear soda prevent food from turning brown quickly. These liquids are acidic, they lower the pH of the food surface. Olive oil also prevents from browning because it doesn't let the oxygen reach the fruit. Water and salt water are the least effective.
Acids prevent oxidation because they react with the O2 that comes into contact with the surface of the sample. Once all of the acid covering the surface has reacted with the O2 or it has washed off or degraded, the sample will start to go brown. Stronger acids, like lemon juice, can even destructure the oxidase enzyme. This means that the enzyme can no longer perform its original function.
Antonio showed great interest and dedication doing this interesting experiment and explained it well at the Science Fair.
Wednesday, 28 September 2016
DNA or deoxyribonucleic acid is the molecule of life. DNA exists in every organism, from the smallest virus to the largest mammal, in every single cell. It is the only known molecule that has the ability to replicate itself.
DNA is made up of two very long and thin fibres twisted together. Genes are located along the fibre, there are proteins attached to the genes that activate or deactivate them at different moments or in different cells. Other proteins help coil the DNA into chromosomes.
In this experiment Sonsoles has extracted the DNA fibres form the nuclei of strawberry cells. A white cloudy substance (DNA) soon developed in the test tube above the strawberry layer. The colour contrast between the strawberries and the DNA fibres made it easier to see.
For this, she used strawberries, water, beakers, test tubes, dish detergent, salt, filter paper, alcohol and a plastic bag. Sonsoles repeated the experiment several times until she was familiar with the procedure and the results were how we expected.
Sonsoles carried out the experiment several times at the Science Fair not only showing the results but also the method to the visitors at her stand.
19 students from ESO1 and 2 presented their experiments in the Science fair in May 2016. This was the result of many weeks of hard work in the Biology and Geology class, and also many lunch breaks! Some of the experiments had to be done several times before the expected results were obtained. These students showed a lot of interest and enthusiasm and made sure that everything was perfectly ready for the big day.
Friday, 23 September 2016
|Cachalot - By Silvia Pacheco E1|
|Turtle - By Silvia Pacheco E1|
|Peacock - By Silvia Pacheco E1|
|Cachalots - By Silvia Pcheco E1|
Thursday, 22 September 2016
Here are some of the dates you should remember during this term. If you haven't written them in your agenda you should do it now.
GROUPS A,E,D - Monday 26th September
GROUPS B,C,F - Wednesday 28th September
GROUPS A,E,D - Monday 24th October
GROUPS B,C,F - Wednesday 26th October
GROUP C - Tuesday 18th October
GROUP B - Wednesday 19th October
GROUP A,D,E,F - Thursday 20th October