In this episode of Tiny Show and Tell Us, we cover why your body feels so ‘off’ at high altitudes and how we’ve evolved not to detect low oxygen levels but high amounts of carbon dioxide. Then we unpack the confusing world of molecule chirality — what it is, why it matters, and how we evolved to only have ‘left-handed’ amino acids but ‘right-handed’ DNA and RNA.
We need your stories — they're what make these bonus episodes possible! Write in to tinymatters@acs.org with your favorite science fact or science news story for a chance to be featured in a future episode and win a Tiny Matters mug!
Transcript of this Episode
Sam Jones: Welcome to Tiny Show and Tell Us, where you write in with your favorite science story, fact, or piece of news, we read your email aloud, and then we dive deeper. I'm Sam Jones, the exec producer of Tiny Matters, and today I'm here with science communicator and video producer Alex Dainis.
Alex Dainis: Thank you for having me back. These are super fun. I love diving into some show and tells from listeners. Before we get into things, a reminder that Tiny Matters is always looking for you to write in because that's what makes future episodes possible. You can email tinymatters@acs.org or click the Google form link we put in the episode description. With that out of the way, I think it is my turn to go first.
So we have an email from listener Ning who says, "The Tiny Matters episode about how to encounter mountain sickness is super interesting as I am training and preparing for my trip to climb Mount Kilimanjaro in September." So congratulations on that training, Ning.
Sam Jones: Yeah, I was going to say, first off, amazing.
Alex Dainis: Whoa. Yeah, that is a bigger mountain than I think I will likely ever climb in my life. So I also have a sort of personal investment in this at much smaller altitudes than Mount Kilimanjaro because I do like backpacking and hiking and have gone up into the Sierras and have felt acute mountain sickness.
So acute mountain sickness is also referred to as altitude sickness or altitude illness. It's uncommon under 2,500 meters, but around 75% of travelers are affected at 3,000 meters. So the idea is that as you travel higher in altitude, the air pressure decreases. And so, the air itself, which is composed of things like oxygen and nitrogen and carbon dioxide, expands.
So this means that for every breath you're taking in, there is less oxygen available to you. This means that our lungs have to work harder to get enough oxygen into our blood, so you might feel much more out of breath. Our tissues start to experience hypoxia, which is decreased oxygen, which can lead to signs of altitude sickness. So this is what you'd actually feel at those higher altitudes. This is things like a rapid heart rate, headache, dizziness, and uncoordinated movement.
Now, the thing that I think is really fascinating about this is sort of how your body detects this because your body is actually really bad at detecting low oxygen levels. What it detects instead is high CO2 levels.
Sam Jones: That's really interesting because you always think like, "Oh my gosh, I need more air. I need more oxygen."
Alex Dainis: Yes.
Sam Jones: And you don't actually think about what your body is really detecting. Like what is the alarm system saying?
Alex Dainis: Yeah, the alarm system is too much CO2.
Sam Jones: Wow.
Alex Dainis: So what happens is that you go up to these higher altitudes, there's less oxygen in the air, and so your body does at first respond by increasing your respiration. So it says, "Okay, our CO2 is a little high. We're going to increase our respiration and get more oxygen in."
So what that does is it decreases the CO2 in your blood, so then your body thinks, "Oh, okay, we're fine, and we don't have to keep this high breathing," so then your body reduces respiration again. But that's bad because there isn't enough oxygen around, and that's why you get sick, because it's not able to detect that there's not enough oxygen. It's just detecting, "Uh-oh, we had too much CO2. Oh, well, we fixed that problem, so now we're good now."
Sam Jones: That feels like a really dumb evolutionary trait.
Alex Dainis: Yes, it does. So there are medications out there, things like acetazolamide, dexamethasone, or nifedipine, which can help treat altitude sickness and delay some of the more severe symptoms. And I know that one of the ways that acetazolamide, which also goes by the brand name Diamox, the way it does this is that it modulates the acidity of your blood, which is one of the ways that your blood reacts to having those high CO2 levels.
So, yeah, it was actually a glaucoma medication, so it's a big diuretic, but it also interferes with an enzyme in your kidneys that manages the acidity of your blood, so there's this whole big cascade of things.
So you can use some of these medications to try and treat it, but the thing we mostly tell people to do is to stop and rest when you get to higher altitudes. So if you've been to a higher altitude, even if you're not hiking, if you go to Denver, if you go to Jackson, Wyoming or something, you'll notice that you get out of breath just walking up the stairs. You don't need to be doing heavy physical exertion to feel these effects.
So one of the things is just let your body adapt. If you're going to be going on a big camping trip or hiking trip, get to this altitude a couple days beforehand. Let your body adapt and sort of all this out at a molecular level, and then go do the higher activity things you want to do.
Sometimes people use oxygen supplementation. So, again, when you're hiking or camping at these high altitudes, if you go into an outdoor store, you'll see little cans of oxygen. So you can take oxygen with you, an oxygen supplement, and that can help alleviate some of these symptoms and help you keep going and keep exerting at those higher altitudes.
If it gets really bad, you can also go into hyperbaric oxygen therapy. So this can additionally relieve symptoms by increasing the amount of oxygen in the body. But again, typically you're okay if you go and you rest, but some people with certain underlying conditions are at a higher risk for altitude sickness. So if you have something like anemia where you don't have enough red blood cells or hemoglobin to carry oxygen to your body's tissues, you could be at higher risk.
Another big one is chronic obstructive pulmonary disease, which you might've heard of referred to as just COPD. And so, this is a lung disease where the lungs and parts of the airways are damaged, which again already means that someone is getting less oxygen into their lungs and the rest of their body.
So, typically, you will be alright if you take care of yourself, you rest, you get enough liquids. But if you have some of these underlying conditions, it is something you should be totally aware of that going up to these higher altitudes can affect how your body feels.
And usually you just feel a little crummy while you're doing it, but it can be more severe. It can lead to longer sickness and something that's harder to recover from. So if you start feeling bad, take a break, take a rest, and just listen to your body. I think that's the biggest thing at these levels is listen to your body.
So, Ning, I hope that as you were climbing Mount Kilimanjaro, as you did this in September, you listened to your body, you took it easy, and you had a great time. And thank you so much for asking about this because I think the way this all works is just fascinating.
Sam Jones: Yeah. My mind is still a little bit blown by the fact that our bodies are not detecting low O2, but instead high CO2.
Alex Dainis: Right, right. That feels like an evolutionary mess up.
Sam Jones: Yeah, that's an evolutionary oopsies.
Alex Dainis: Yes, that's a big oopsies.
Sam Jones: Yes. All right, so I have a Tiny Show and Tell Us science fact from listener Quynn who wrote in saying, "We prefer the L configuration rather than D for amino acids." This is a cool one and confusing and fascinating, and there are some things we need to break down first.
Alex Dainis: I'm excited. I'm really excited for this.
Sam Jones: So first, amino acids, they make up proteins. They're often referred to as the building blocks of proteins, which of course, are what make up us and the rest of life on earth. So what is an L versus a D configuration? This is sometimes referred to as left-handedness or right-handedness as well.
And so L amino acids and D amino acids, they have the same chemical composition, but they are mirror images of each other. So for example, the chemical formula for D-alanine and L-alanine, both amino acids, it's the same. It's C3H7NO2. But when you actually look at the molecules, they're chiral, meaning they mirror each other and they cannot be superimposed.
So I like to demonstrate this with my hands. If you are not driving right now, I repeat, you cannot do this. Just come back and try this out after you stop.
Alex Dainis: Keep your hands on the wheel.
Sam Jones: Yes. So if you're able to right now, put your hands out, palms down. And so, you can see if you just look down at them that they're mirror images of each other, right? This is all making sense so far, Alex?
Alex Dainis: Yes, yes. I'm doing it with you.
Sam Jones: Okay. So now, keeping your palms facing down, try to match up your hands.
Alex Dainis: I cannot.
Sam Jones: You can't, right? So whether your right hand is on top of left or left on right, your thumbs are sticking off different sides.
Alex Dainis: Yes.
Sam Jones: And so, you might be thinking like, "So what? It's the same chemicals grouped together, who cares if one part of that is in a slightly different region than another?" Well, I'm telling you, it is important. So whether a molecule is in an L or D configuration makes a big difference in that molecule's activity.
So on earth, 19 of the 20 natural amino acids are left-handed. So let's say there's a random right-handed amino acid. Well, it can't bind to transport proteins that have evolved to only accept left-handed amino acids in your cells. So as life emerged on earth, it appears that only left-handed amino acids, almost entirely left-handed amino acids, were selected. And the question is why?
Alex Dainis: Yeah, why?
Sam Jones: It's really, really hard to say because we can't travel back four billion years.
Alex Dainis: Yeah.
Sam Jones: But some research groups are trying to find evidence of why in meteorites, space debris that can be that old that makes its way to earth. So many meteorites have been found to contain amino acids, and a lot of times we're seeing both left and right-handed versions of the amino acids in equal amounts, except there's often one type of amino acid in excess. And it's always, it seems, it's always left-handed.
Alex Dainis: Weird. That's super weird.
Sam Jones: So there's a hypothesis that meteorites may have seeded early earth with amino acids that were mostly left-handed.
Alex Dainis: Okay.
Sam Jones: There's also a hypothesis that because polarized light apparently can mess with the right-handed version of many amino acids by small but noticeable amounts, there would be more left-handed molecules around.
Alex Dainis: Okay.
Sam Jones: But that doesn't quite explain the huge difference in the amount of L versus D amino acids in nature. So still, there's just all these questions.
Interestingly, and maybe you'd heard, I mean, and by you I mean listener, I know Alex has heard this before, because Alex is a DNA person. So interestingly, DNA and RNA are right-handed, as are of course the sugars that are part of their structure. And there are some theories about handedness there.
So with DNA, there's a theory that way back billions of years ago, cosmic rays, which are fast moving particles from space that come from the sun or stars exploding or black holes, that they would knock electrons loose or an electron loose from self-replicating molecules at the time, i.e. early DNA or RNA. And because of how these cosmic rays move, which is a whole other explainer, but I will link to an article kind of showing that, but because of how they move, they would be more likely to hit and mutate right-handed molecules.
And that sounds bad, but at this stage, that was actually an opportunity for genetic variation, which may have led to organisms, and I'm talking unicellular organisms at that point, that would be better able to survive in changing environments just because they had more variety of genetic mutations like versatility. So I'm sure a lot of them died, but some of them were able to survive.
Alex Dainis: Sure.
Sam Jones: And again, it's kind of a stretch.
Alex Dainis: Yeah. So you're imagining this pool of unicellular organisms. Some have left-handed DNA, some have right-handed DNA or RNA, just nucleic acids in general. And the right-handed ones are getting mutated more by these cosmic rays, which makes them more able to evolve to their environment and just out-compete essentially?
Sam Jones: Yeah. I mean, I think the idea is it allows for random mutations to spring up, and some of them just happen to be advantageous, right?
Alex Dainis: Okay.
Sam Jones: You have these random mutations, these things just happen, and when they work well, they stick around. And now, everything has right-handed DNA and RNA, and yet at the same time, our amino acids are left-handed.
Alex Dainis: Wow.
Sam Jones: So it's just like why? There's still this huge question. I don't know if we'll ever be able to answer why there was this selectivity, but it's really interesting. The speculation is really interesting.
Alex Dainis: Yeah. I know there's also, I mean, because we can't go back those four billion years, there are so many different theories. I think you outlined a bunch of the big ones, but there's also some that talk about the fact that maybe the magnetism of early earth impacted the left or right-handedness. Yeah, and those cosmic rays.
There's all these physics things that seem to have maybe had an effect on chemistry, which then had an effect on biology, which I also think is so cool. But yeah, we can't, unfortunately go back four billion years. I do have a lingering question that I feel like our listeners might also have that we're talking about left versus right-handed, but they're called L and D.
Sam Jones: I know. D-configuration stands for dextrorotatory, which means right side.
Alex Dainis: Oh my gosh.
Sam Jones: They're just trying to make it confusing, honestly.
Alex Dainis: I know. Oh, I think it's more confusing because it says the L is from the Latin word laevis, so laevis and dexter, which are left and right. But the L being L in both languages just leads to confusion about why it's D versus R, so thank you for the reminder.
Sam Jones: Right. Yeah, that is really confusing. So all of this is confusing and fascinating. We don't have any answers as to why, why are DNA and RNA right-handed? Why are amino acids left-handed? But there's also really cool stories, really cool, fascinating stories about chirality with drugs and a lot of other things.
And maybe that's a future episode because there are some very key events that show that chirality is super-duper important. No, you cannot just swap out one form of a molecule for another. It can actually have really serious, potentially deadly consequences. So, hey, if you want to hear more about that, write in mailto:tinymatters@acs.org, and maybe we'll do an episode.
Alex Dainis: Let us know.
Sam Jones: Yes, exactly. Thank you so much, Quynn. That was a cool one.
Alex Dainis: Thank you all for tuning in to Tiny Show and Tell Us, a bonus episode from Tiny Matters, a production of the American Chemical Society.
Sam Jones: To be featured in a future episode, send us an email with your tiny show and tell at tinymatters@acs.org, or click the Google form link in this episode's description. We'll see you next time.
- Variations in altitude
- Acute Mountain Sickness
- Altitude Sickness
- Acetazolamide Oral Tablets
- Cosmic Rays and the Handedness of Life
- ‘Breakthrough’ could explain why life molecules are left- or right-handed
- Cosmic Rays May Explain Life’s Bias for Right-Handed DNA
- Must the Molecules of Life Always be Left-Handed or Right-Handed?
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