Star Fruit, Caramboxin, and Neurotoxins

Sliced star fruit and the chemical structure of caramboxin.

I’ll preface this with “I still ate it,” but star fruit contains a deadly neurotoxin called caramboxin. 😱*clutches pearls*

Luckily, if you have normally functioning kidneys, caramboxin gets flushed out of your system and does absolutely no harm. In fact, my friend from Taiwan says they eat star fruit daily, and they’re all doing fine so, again, totally fine for most people to eat. However, if you have kidney disease, the toxin does not get removed and it can go on to interfere with your neurons.

Neurons pass messages around your body. Molecules called neurotransmitters are released from one neuron and passed to another in order to relay that message. The neurotransmitters fit snuggly into proteins called receptors on the next nerve. This is kind of like a lock and key. Once the receptor is “unlocked” by the neurotransmitter “key,” the nerve passes the message to another nerve, and so on. Caramboxin can “unlock” and stimulate some of these nerves by snuggling up to the receptor. Normally, turning on neurons is a very controlled process, so when caramboxin gets in there, it messes things up. Symptoms include mental confusion, vomiting, and seizures, and in some cases, coma and death.

Interestingly, an early symptom of caramboxin poisoning is intractable hiccups, so if that happens to you after eating star fruit, call the doctor and ask about some kidney labs!

This was my first star fruit ever! I don’t think I let it ripen enough, but it tasted like a wet tart apple. Should I wait longer next time based on that green color? No hiccups yet!😉

Source: Garcia-Cairasco et al 2013 https://doi.org/10.1002/anie.201305382

Snippets of Science: Glowing Pumpkin Seeds (pepitas) and Protochlorophyllide

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Pepitas, the inside of pumpkin seeds, fluoresce under UV light! It is a stunning coral orange color. This photo doesn’t quite do it justice. The compound causing the fluorescence is protochlorophillide, a precursor to chlorophyll. (Chlorophyll is also fluorescent under UV light, but it glows a deep red.)

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Chlorophyll biosynthesis

The seeds themselves have a slight glow if you shine a black light on them but in my picture at the top, they are crushed with isopropanol (rubbing alcohol), which solubilizes the pigment.  We found this fluorescence by mistake actually. Several things in your pantry fluoresce under UV light (like honey, canola oil, tonic water, and peanut butter) and my daughter and I were scanning our shelves for other surprises. Sure enough we saw a faint glow on some of the hulled pumpkin seeds. I did a little research online and found out about protochlorophyllide. We also saw a similar glow from brown rice that was slightly green on the edge and I wonder if it’s the same molecule!

Sources:

Chlorophyll biosynthesis: spotlight on protochlorophyllide reduction

See Sound with Oobleck!

This is a fun, silly, and educational activity that any kid who likes to make noise will love. Using oobleck (a mix of cornstarch and water) and common household items, you will be able to visualize the sound waves made when you yell!

What we perceive as sound is a wave of pressure transmitted through air. When you yell, your vocal chords vibrate. The energy is transmitted by air molecules smacking into each other, until they they smack into your ear. There, you have cells that can convert the vibrations into electrical signals which are transmitted to and deciphered by your brain. In this activity, you will yell into a device that will transmit your sound waves from air into oobleck so you can see the waves!

Definitions

  • SOUND: Kids will probably know what sound is, but not scientifically. Sound is vibrations that travel through a medium (usually air) which are eventually heard by ears. Kids will need to understand that air, even though we can’t see it, is all around us and can be moved similarly to the way balls move, like billiards. Try waving your hand quickly so they can feel the wind it creates. You can tell them air molecules can move to carry the energy from your hand to their skin so they can feel it. Sound also travels through air in a similar way, but sounds are made when something is wiggling the air much fast than your hand can move it. Roll a ball into another ball and talk about how the energy is transferred when the first ball hits, and use this analogy for air transmitting sound.
  • VIBRATION: To young kids, I like to explain this as fast wiggles. Since you know your kid the best, to define this word, you can draw on experiences you know they have had like the vibration of an old car going down the highway. You can also put their hands on one end of a table and have them feel the vibration of you knocking at the other end of the table. They probably have experienced vibration, but just need to connect the word with the phenomenon.

Materials

  • cornstarch
  • water
  • empty paper towel or toilet paper tubes
  • tape
  • rubber bands
  • thin flexible material like plastic wrap, latex, thin rubber sheet, nitrile (I cut a square from nitrile gloves)

Method

  1. Cut the paper towel roll twice diagonally, as seen in the picture.Untitled_Artwork
  2. Flip the two end pieces up to form a U shape, then tape them together. (Or make into whatever shape you want. You basically want to be able to simultaneously yell into it and see the flexible membrane. The one below is what my daughter made from toilet paper rolls.).IMG_4134
Clearly, it doesn’t have to look pretty.
  1. Cut your thin flexible material into a square that will fit over the end of the paper towel tube.
  2. Secure the square to the tube with a rubber band, making sure the membrane is taut like a drum.
  3. To make the oobleck, mix about 2:1 cornstarch to water together (you can make a lot to play with it later, but for this activity, you only need about a teaspoon). You will know it’s the right consistency when you can smack the oobleck and it acts like a solid, but you can also slowly pour it as if it was a viscous liquid. Just add a little more cornstarch or water to get this consistency.
  4. Put about an eighth teaspoon of oobleck onto the drum end.
  5. Make all sorts of sounds into the open end of the paper towel roll and watch the oobleck dance about! Constant, steady low or high sounds work the best, but experiment to see what you can make!

Discussion

When you scream into your device, kinetic energy is being transferred from your vocal chords, through the air molecules in the tube, to the membrane, to the oobleck. Note how the oobleck is formed into different shapes depending on the pitch of your noise.

You can use this experiment to talk to your kids about eardrums (aka tympanic membrane) by comparing them to the membrane on the device. Just as the screaming-device-membrane transmits sound from air in the tube to the liquid oobleck on top, your eardrum essentially transmits sound from the air in the ear to liquid in the cochlea.

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A diagram of the anatomy of the human ear. Lars Chittka; Axel BrockmannPerception Space—The Final Frontier, A PLoS Biology Vol. 3, No. 4, e137

This project can also be done by wrapping a speaker in Saran Wrap, putting some oobleck on it, and playing your kids’ favorite songs. It’s a great visual introduction to rhythm, beat, and volume and will give them a whole new musical experience.

How to Make Bendy Bones

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If you ask most kids what bones are made of, they would quickly answer “calcium!” Though it’s not incorrect, years of us telling them to drink their milk for strong bones has hidden an amazing feature of nature, biomineralization by proteins. Calcium is only half the story of bones. Though the semi-crystalline mineral that contains calcium, oxygen, hydrogen, and phosphorus, called hydroxyapatite, provides strength and rigidity, our bones also need to be elastic to help absorb shock. This is where proteins come in. Your bones are made of living tissue that spew out networks of protein that trap and crystallize the calcium in your body. Together they form the strong, resilient biomaterial we know as bones.

You can feel the flexibility of the protein network for yourself by reacting and dissolving the hydroxyapatite from the bones in vinegar. What’s left are entertaining, wiggly bones the kids will love to play with (except my daughter, who was too grossed out and didn’t want to touch them which is why all these pictures are of my hands ¯\_(ツ)_/¯ ).

Continue reading “How to Make Bendy Bones”

Maple Syrup: a sweet, delicious teacher of science for kids

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Springtime in rural Vermont is magical. It’s not just the melting snow with rivers of mud, it’s also magical because it’s maple syrup season. For a brief period each year the sap really flows and those lucky enough to have sugar maples can harvest the sweet nectar and boil it down into the delicious breakfast treat. For our budding family, “sugaring” has become a great outdoor adventure that helps combine some of the things we love: nature, science, and eating. Read on to learn how you can make your own maple syrup at home, and for ways you can use the experience to teach some science to your kids.

Continue reading “Maple Syrup: a sweet, delicious teacher of science for kids”

Why does milk foam? The science behind your latte.

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Oh it’s fall in the Northeast again- the perfect time to switch from iced coffees to silky lattes, cappuccinos, and macchiatos. When I was younger, I remember wishing there was something warm that tasted as good and had a mouth feel as good as ice cream. Luckily, I’ve pretty much lost my sweet tooth and these coffee drinks have fulfilled that wish. Though espresso alone is one of the most delicious things on Earth, add some foamed milk and those tiny velvety bubbles transform it into perfection.

I was making a latte for myself one morning and my daughter asked if I could froth her milk, too. What a great idea, I thought! So these first few chilly mornings of the fall, we’ve been cuddling up and sharing some warm, silky drinks together. I’ve included some coffee-free recipe ideas for you to try with your little ones, too. It’s a great way to bond and also explain a little science. So, what is special about milk that allows it to foam?

Continue reading “Why does milk foam? The science behind your latte.”