Science for kids - The Iodine Clock

Some of the best parts of my day are when I get to go to a school or organization and talk about science with kids.  Just the other week I went to Davis Drive Middle School with a colleague (Thanks Mandy!!) to talk about chemistry.   We visited an after school chemistry club and it was obvious these kids were passionate about science and chemistry.

We talked a lot about pH and how it can affect plants.  We also talked about how certain molecules can interfere with other molecules.  This is important in the plant world because certain nutrients can suppress or even increase uptake of other nutrients.  It is important in human health as well.  Many of us have taken medicine and heard from our doctors certain rules we need to apply while on the medicine.  For instance don't eat grapefruit while on this medicine because it can interfere.

So one experiment we did was to try to show how certain components in a solution can interact with other components in a solution.  It is a very visual experiment and done with household supplies.

The supplies you need are Vitamin C (1000 mg), Iodine (2%), Hydrogen Peroxide (3%), and liquid starch.

You will be making two separate solutions.

Solution 1 is a combination of the vitamin C and Iodine tincture in water.

Solution 1 - Step 1.  Mix 1000 mg of vitamin C in 60 mL of water.  The vitamin C we had is 500 mg tablets.  We crushed 2 tablets pretty easily and mixed the powder in water.  We had colored tablets which will work fine.  If you can find non-colored vitamin C that will work just great as well.

Solution 1 - Step 2:  Next add the Iodine to the Vitamin C and water.   You will add 5 mL of the Iodine to the solution.

At this point solution 1 is done!

Next we will make Solution 2 which is a combination of water, hydrogen peroxide, and liquid starch.  

Solution 2 - Step 1:  Add 15 mL of hydrogen peroxide to 60 mL of water.

Solution 2 - Step 2:  Add 5 mL of liquid starch to the water and hydrogen peroxide mixture.

We are now done with solution 2.

Once you have your two solutions, we can start the reaction.

Grab a new clear container and pour solution 1 and 2 together in the new container.  You can pour the new solution back and forth between empty containers a few times to be sure it is well mixed.

At first it will look like nothing is happening.

Over time (hence the clock), the solution will instantaneously turn dark blue-black!!

So what is going on?  Well when starch and iodine molecules mix you get a dark blue.  However we added some other things that interfere with this reaction.

One reaction that is going on is production of I2 molecules.  The hydrogen peroxide was added to the household iodine and it forms Iodine molecules.  When iodine meets starch it turns blue-black.  

+ 2I – (aq) + H2O2(aq) ->I2(aq) + 2H2O(l)

However we did not get a blue-black color immediately. This is because a second reaction was underway due to the addition of the Vitamin C powder.   The I2 produced from the hydrogen peroxide should react with the starch, but instead it immediately reacts with ascorbic acid (from the vitamin C tablets).  This prevents the I2 from reacting from the starch.  In essence it is shielding the I2 from the starch.

I2(aq) + C6H8O6(aq)-> 2H+ (aq) + 2I – (aq) + C6H6O6(aq)

Eventually the ascorbic acid is used up and there will be enough I2 react with the starch and get a color change.  This is a great example of how certain molecules can hinder other molecules.

It was a fun day at Davis Drive middle.   This reaction can be sped up or slowed down by certain variables as well.  We actually split into two groups.  One group used 60 ml of water for solution 1 and 2.  The other group only used 30 ml of water for each solution and we compared which reaction went the fastest.   What do you think?   If you want to experiment or read more at home here is a great resource:  http://www.greeningschools.org/docs/VitaminCClockReaction.pdf

The Arctic Apple - A GMO apple that does not brown

I have 3 kids and as many of you know getting them to eat the healthy stuff can be challenging.  If I give them a bag of M&Ms then they gobble them right up.  Giving them some broccoli can be a different story, at least with my 7 year old.   He is a very picky eater and even fruit can be a challenge to get him to eat.

At least one study shows that one thing to do to help kids eat fruit is to have it sliced.  You can find the abstract and more info here:  http://www.ajpmonline.org/article/S0749-3797(13)00105-0/fulltext

It's conclusions were:

"Sliced fruit is more appealing to children than whole fruit because it is easier and tidier to eat. This study applies the principle of convenience from behavioral economics and provides an example of a scalable, low-cost environmental change that promotes healthy eating and decreases waste."

I know my kids prefer sliced or cut up fruit.  Yet even that does not always solve the problem.  "Ewwww, that banana has a brown spot."   "Yuck, that apple is brown,"     I hear this type of talk with certain foods so I am a fan of anything that can help get my kids to eat healthy food.

Well when it comes to apples I might just get my wish.  There is a new apple in town that is being introduced in midwestern grocery stores called the Arctic apple.  Hopefully more introductions to other grocery stores will follow in the near future.  The Arctic apple is special in that it does not brown when sliced and exposed to air like other apples.  

This is a great story, yet for some this is not a happy story at all.  The reason is because the Arctic apple is a GMO.    Since the first mention of this apple there has been a lot of false information and fear about the apple.  Even Dr. Oz was throwing around his skepticism in 2015 when the apples were finally getting started.

Let's start by going over the science.  How does this apple work?  Many people stop at the word GMO.  Instead let's explore the science and see exactly what is going on with this apple and compare it to other DNA changes in the world that we don't really think twice about.

The first answer to this question is to investigate why apples turn brown in the first place.  When a fruit or vegetable such as an apple or potato are damaged (sliced), an enzyme called polyphenol oxidase is released.  This enzyme causes the browning we see.   There are many plants that will exhibit this color change effect from PPO including lettuce, mushrooms, and potatoes.

So if you can inhibit the production of PPO production, then you reduce the browning that occurs.  The Arctic apple does this through a GMO approach.  A question and answer from the Arctic Apple website states:

"Joel June 12, 2015 at 12:35 am

Hi there, and sorry for the delayed response!

The specific genes that stop Arctic® apples from turning brown come from apples. Apples have a small number of genes that control the production of polyphenol oxidase (PPO), the enzyme that initiates the browning reaction when an apple is bitten, sliced, or bruised. We insert apple PPO genes that make Arctic® apples produced less PPO, and therefore they don’t have enough PPO to turn brown."

http://www.okspecialtyfruits.com/how-we-introduce-the-nonbrowning-trait-in-arctic-apples/


What the Arctic apple team did was take some DNA sequences from other apples and get them into the Arctic apples plant genome.  You can see some of my previous posts to see how genes are inserted.  These sequences actually turn up the production of PPO to a very high level.   So how in the world does adding genes that increase PPO production actually decrease PPO and browning?  This sounds counter intuitive. Shouldn't increasing  PPO production actually make the apples brown even more?  That is a good question.  Well the world is an amazing place and we (plants and animals) have lots of feedback mechanisms to help control our genes.  One of these mechanisms is called gene silencing.   There are different forms of gene silencing, but in the case of Arctic apples by having such high expression of the PPO genes, it actually causes the plant to say "Whoa!  This is too much.  Shut it down Scotty!"

There is a nice graphic I found of this mechanism by Kevin Folta (and another great read on the arctic apple):

http://www.science20.com/kevin_m_folta/the_hard_science_behind_the_nonbrowning_arctic_apple-224898


Segment C shows what is happening at the molecular level in the Arctic apple.

The result is you get an apple that does not brown!

http://www.arcticapples.com/how-did-we-make-nonbrowning-apple/

If you are interested in diving into more science here is a science paper on reducing the browning in potatoes through inhibiting PPO in potato:  Reduced polyphenol oxidase gene expression and enzymatic browning in potato (Solanum tuberosum L.) with artificial microRNAs

Well that is the science behind the Arctic apple.  It is pretty neat stuff I think.  And in reality it was a very small change in the apples genome.    I know some still argue that it is unnatural to mess with genes even if it just one change.  I have a couple arguments to try and convince you otherwise.

One of the best visuals I can give as a counter argument deals with some foods we all the time and never think twice about it.  These include broccoli, cauliflower, cabbage, and turnips among others.   These foods are not "natural" in the sense no one ever just discovered them in the wild.   Humans tinkered with a plant called Brassica oleracea.  Through breeding over years and years they selected for the best leaves of the wild mustard plant to get kale.   They selected for the flower buds to get broccoli and cauliflower.     How many changes to DNA sequences do you think were involved in this process?   Broccoli looks nothing like wild mustard because it was human made.  It is healthy and humans have been eating it for thousands of years.  In fact humans were figuring out how to make these mutations to get broccoli in the 6th century BC.  It made its way to America in the 1700s, but never gained great acceptance until the 1920s.  Wow, does this trend sound familiar?

Secondly, we are using gene silencing and other technologies that change how genes are expressed to help with human health too.  A company called  Ionis has many drugs in development that can help with some awful diseases.

Remember that PPO gene that causes browning in an apple.  What if there were a protein that causes a disease in humans and you could turn that gene off so you limit the protein production that causes the disease.   I would certainly use this to help ease the suffering of a loved one or even cure them.   Well one drug in development for Huntington's disease would do just this.

http://www.ionispharma.com/

Humans have been manipulating plant genes for thousands of years.  Our technology has just gotten much better and we can be more specific with those changes in both plants and humans.   When you breed and make something like broccoli with thousands of DNA changes it just goes on  the market.  When you make a couple gene changes with a GMO approach it gets tested for years!! for safety before entering the market.   I can't wait to get hold of an Arctic Apple.  Science is an amazing thing and I can't wait to see what the future holds.

Everything we talked about is summed up nicely in this infographic that the Arctic Apple team put together.

Add captionhttp://www.arcticapples.com/want-see-how-we-made-perfect-fruit-even-better/