SciShow Tangents - Cells

Episode Date: December 14, 2021

We’ve talked about all sorts of living things. Bugs, for instance. And plants… elephants… the list goes on. But what we haven’t discussed is the thing that all of those animals are made of: cells! What are they? Why are they? Answers to half those questions await you!Head to https://www.patreon.com/SciShowTangents to find out how you can help support SciShow Tangents, and see all the cool perks you’ll get in return, like bonus episodes and a monthly newsletter!And go to https://store.dftba.com/collections/scishow-tangents to buy your very own, genuine SciShow Tangents sticker!A big thank you to Patreon subscriber Garth Riley for helping to make the show possible!Follow us on Twitter @SciShowTangents, where we’ll tweet out topics for upcoming episodes and you can ask the science couch questions! While you're at it, check out the Tangents crew on Twitter: Ceri: @ceriley Sam: @im_sam_schultz Hank: @hankgreen [Trivia Question]B. natans number of geneshttps://pubmed.ncbi.nlm.nih.gov/24502779/https://www.genome.gov/human-genome-project/Completion-FAQhttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC6085824/[Fact Off]Streptococcus disguises itself as red blood cellshttps://pubmed.ncbi.nlm.nih.gov/31801066/https://www.eurekalert.org/news-releases/886535https://www.smithsonianmag.com/science-nature/harmful-bacteria-masquerade-red-blood-cells-evade-immune-system-180973678/Ciliate nuclei + genetics (O. trifallax/S. histriomuscorum)https://www.wired.com/2014/09/oxytricha-encrypted-genome/http://www.marinespecies.org/aphia.php?p=taxdetails&id=427777https://www.cell.com/cell/fulltext/S0092-8674(14)00984-2https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1001473https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2647009/https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3558436/[Ask the Science Couch]Cell movement & motor proteinshttps://www.nature.com/scitable/topicpage/microtubules-and-filaments-14052932/https://www.pnas.org/content/108/51/20275https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4812444/https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1893118/https://www.cell.com/current-biology/comments/S0960-9822(98)70264-7https://www.ncbi.nlm.nih.gov/books/NBK26867/[Butt One More Thing]Buttock cellshttps://pubmed.ncbi.nlm.nih.gov/2787452/https://link.springer.com/article/10.1007/s12308-013-0175-yhttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC6888610/ 

Hello and welcome to SciShow Tangents, the lately competitive science knowledge showcase. I'm your host, Hank Green, and joining me this week as always is science expert, Sari Reilly. Hello. And our resident everyman, Sam Schultz. We just got a little preview of Sam's dream that he had last night, in which I invited him to a party so that I could murder him with my rich friends. And eat me. Oh, and eat you. Well, that's how we stay young, by drinking the blood of 33-year-olds. I think I'm 34, actually. I'm past my expiration date. You're safe now. It's finally happened. What's the last nightmare you had, Hank?

I don't know if I'm going to call this a nightmare, Sam, but this was a stressful dream that I recently had where I had to leave Oren in the car. And then I kept getting distracted and I kept being like, no, my child is in the car. I need to go. People in the car. Oh. And then I kept getting distracted and I kept being like, no, my child is in the car. I need to go. People kept like getting in my way because I was like, I'm just going to run in and come back right out.

And then like, people kept like bugging me and I was like, no. And I woke up and I was like, I have to go get Oren out of the car. That's interesting. Look, it's hard to be a parent and you're all often very, very tired.

And so this is like a thing that you have to think about all the time. It's like, did I leave my child somewhere somewhere and sometimes he will vanish in the house but i'll be like did he go out because he can go outside on his own now like even though we don't want him to he'll just like wander out can he reach the doorknobs and turn them yeah he just turns the he just walks out of the house all out sometimes he will in fact sometimes during the podcast he just walks out of the house. That's not allowed. Sometimes he will, in fact, sometimes during the podcast, he will walk out to my backyard studio and open the door and be like, Dad, and I'm like, no, man, I am making content right now.

Someday you'll be a podcaster, but for now, leave it to Dad. How have your dreams been lately, Sari? Oh, I don't really remember my dreams. I generally have stressful dreams, and I wake up in the middle of the night quite often, but I forget them promptly because they didn't make no sense unless I commit them to memory. But usually if something funny happens that I want to tell Sylvia, I'll try and remember it. And so last night in one of my dreams, she came up to me asking for a graham cracker in that voice.

And I was like, I gotta remember this. And I woke up and I just repeated to myself, Graham Cracker. Graham Cracker. So that I could tell her as soon as she woke up and was ready

to have a conversation. Every week here on SciShow Tangents, we get together to try to one-up, amaze, and delight each other with science facts

while also trying to stay on topic. Our panelists are playing for Glory and for Hank Bucks, which I will be awarding as we play. And at the end of the episode, one of them will be crowned the winner. Now, as always, we're going to introduce this week's topic with the traditional science poem, This Week from Sam. Webster's Dictionary defines cell as a mass of protoplasm with membranes and organelles.

And that, to me, is all good and well till you get to the part where they can function by themselves and then my brain begins to dwell on the fact that bodies are full of little guys we can't compel so am i a collection of little goo elves or is my brain a guest in a big blood-filled hotel all i intake and expel are handled by a staff of dedicated personnel and my role in this gooey shell is to think of other stuff while around my body they propel. So am I me or am I my cells? Neither or both. Does it matter?

Oh, well, that's just how it is till they sound my death knell. Oh, that's very good. Saving that one for the end. You put your finger on the weird thing about cells cells which is that we are made out of these individual units of life according to the normal rules of evolution should duplicate themselves infinitely and grow and grow and grow um not sustain a body that of other cells that are different from them that's not the way that it should go and when that does happen when evolution does take back over that's cancer yeah and that it should go. And when that does happen, when evolution does take back over, that's cancer.

Yeah. But the regular part where like all these cells work together to make a guy who wants a hot dog, like that's not normal. It's so freaky. That's very strange. Sari, what are cells? Well, I'm going to try something different

and start with the etymology because I thought this is interesting so cell the word comes from latin cella which means small room or a storeroom or a hut and it's related to the latin solere which means to hide or conceal so like a place where you store your stuff and that's a cell i do store my stuff in cells all the stuff that is you all stored away and like that is every meaning of cell so like the cells in your body you store stuff in them or like prison cells where you store people or electrochemical cells where you store energy or one of the small squares in your spreadsheet is a cell or a cell phone.

Wait, a cell phone isn't a cell? Cell phone comes from what I was reading, unless the internet lied to me, which it's possible. Cellular networks were because the wireless towers divided up the land into areas called cells that had cell reception. Within the cell, you had cell reception. Outside cell you had cell reception outside of the cell you didn't and so then that's where the word cell phone came from is also in like a little room but the room is outdoors and big and invisible it's defined by the the reach of some radio waves yep yep the reach of radio waves is like a cell and so all of that to say in biology, we just use the word for a little small room for our purposes, for biological purposes. And the textbook definition, kind of like Sam said

in his poem, is the smallest unit of thing that can live on its own. And it makes up all living organisms and also can take lots of different shapes generally the components are like a cell membrane so something a wall for the little room and then stuff inside the little room like cytoplasm if it's got a wall and it's got stuff inside as a cell i think there's a certain amount of we want to rule it like take some things and have them not be cells you don't want virus particles to be cells. So you start to like really refine your definition to exclude virus particles. But that doesn't matter to average people.

You're listening to SciShow Tangents. You're not going to be thinking to yourself, but you would define cell in a way that included virus particles. I'm going to write to the authorities. Why wouldn't you define it in a way that included virus particles? Because they're not cells. What are they? I don't know. Capsids?

Capsids. Oh, right. I've heard that word before. Yeah, they're like a little protein box that stores stuff inside rather than having a cell membrane. So cell membranes are also made of proteins, but the ones that encapsulate viruses are different. They're not like a phospholipid bilayer. That's the thing you learn in AP bio where it's like hydrophilic on the outside, hydrophobic on the inside, and then

you need special channels to pass through. With viruses, it's just sort of like, to my understanding, just like a little container that carries them around. But it's not as easily penetratable, like the way that they get, or at least bacteriophages get their DNA or get their RNA into other cells is through like injection. They don't like fuse with other cells or anything like that. They're the cells wario. Is that right? Sure. Yeah. Okay. Yeah. Basically, if you turn a Wario. Is that right? Sure. Yeah.

Okay. Yeah, basically, if you turn a cell upside down, that's a virus. Great. I think they're more like Waluigi because they came out of nowhere and, like,

are this mysterious entity that just showed up one day and people are like, okay, you're here now. I can get behind this. Wait, now I'm confused about the lore of Waluigi and Wario.

Yes. Okay, so Waluigi came out of nowhere so did wario so did mario everything comes out of nowhere okay maybe i can't answer that mario and luigi are canonically brothers wario and waluigi are not brothers waluigi just showed up one day to play mario tennis with everyone and they were like hey what's your name and he was like uh what's your name and then he said luigi and he was like i'm waluigi yeah that's actually the best explanation i've ever heard of it hank well you should write the mario movie or just fanfic or that i'd read it you read my Wario fanfic absolutely I promise that it will be only mildly violent and not at all any in any other way objectionable but there is going to

be a fist fight oh okay that's really mildly violent yeah I was hoping for some blood and spilling there may be a little like a bloody nose they got big noses they They do. Good for bopping them. Okay. And that means that it must be time for the quiz portion of our show. This week, we're going to be playing This or That. Are you guys ready for an episode of This or That in our episode of SciShow Tangents? Sure. Yeah. It's a sub-episode?

It's a sub-episode. Well, hello and welcome, everyone, to This or That. Cool. I don't know why we don't always do it that way. So cells can have a lot of different properties to characterize them. You've got your size. In general, it's easy to think of most cells as just small. But of course, cells can come in a really wide range of sizes.

In our bodies, cells can range from the size of lymphocytes that are around seven micrometers in diameter to neurons that can reach about a meter in length by the time you get to their axon. Different cells have different lifestyles, which means that they have different sizes to help them do their lifestyle. So today's episode of This or That, cell size edition, I'm going to be naming two cells and it's up to you to decide which one is bigger. So you have to choose the bigger cell. Okay. All right. Comparison number one. This is the bacteria edition. Which of the following is larger?

The volume of Thiomargarita nabambiensis, a bacteria that lives in marine sediments, or the volume of Epilopischium, a bacteria that is symbiotic and they live inside of the intestines of marine sturgeon fish. So we got a margarita or piss. Yeah, margarita fish. So we got a margarita or piss. Yeah, margarita or piss. You could say margarita or piss. Because you know so much about these two different things. What's the first one do?

Just lives in the ocean? It lives in marine sediments. I'm going to guess the margarita one because I feel like sediments, you have a lot more size variation if you're in an intestine you got to be pretty small oh shoot i don't know there's no rhyme or reason to this but that feels like extremely sound reasoning to me so i'm just gonna go with the same one you did oh that's good call for both of you the answer is margarita man so they live inside sturgeon fish. They're large by bacterial

standards at about 0.2 microliters of volume, still smaller than the Thymomargarita, which is one of the largest known bacteria. It was discovered in the sediments off the Namibian coast, and it's been nicknamed the sulfur pearl of Namibia. Its total volume is 22 microliters, which is around eight times larger than E. coli. And it gets its size because it has storage compartments with soluble electron donors and acceptors that allow it to store nutrients. And that trait is important for surviving in marine sediments

where nutrients are not always available. Now, comparison number two. Which is larger, the red blood cell of the Amphiuma salamander or the red blood cell of a cow? Are you going to go with a salamander or a cow? Do you want me to go first, Sam? I suppose I could go first. I'm just wondering if more blood means you have bigger or more blood means you have smaller or if there's any kind of correlation at all there. I think in general, the organism size doesn't matter a lot like it's not going to be orders of magnitude

bigger or smaller it's usually like the volume of blood that is more or less um and so my thought is because the salamander is amphibious i I think. Like they need water and land. Their blood cells might need to hold more oxygen than a cow, which is just kind of like hanging out, eating grass. So just because it feels like their red blood cells would be weirder for some reason, then I would guess salamander. I'm going to guess salamander. That sounds like extremely sound reasoning to me. So I'm going to pick exactly the same one that you just picked. Well, I mean, Sam may have hit on a new strategy for this episode and future episodes because the answer is the amphiuma salamander red blood cells.

The diameter of a cow red blood cell is about 5.83 micrometers. In comparison, the dimensions of the amphiumith salamanders cells, which are elliptical, is 66 micrometers by 37 micrometers. So 66 across 37 high, I guess. I'm not entirely clear on this. Mammalian blood cells are unique among vertebrate cells in that they do not have certain structures like organelles. And this difference, see, this is the thing. You both did not get the right answer, which is that mammals, red blood cells lack nuclei, which is a basic thing. That's one of the things about mammals that's so weird.

So we reject our nuclei in our red blood cells. The difference makes it possible for the cells to go through smaller blood vessels and hold more gas-capturing proteins. The presence of a nucleus in other vertebrate red blood cells makes them elliptical in shape, and they need to package and hold onto their DNA so those nuclei add to the overall size of the cell. So we just have little red blood cells so we can deliver more oxygen. So you were basically entirely wrong about why you were right. Well, yep.

oxygen. So you were basically entirely wrong about why you were right. Well, yep. I was going to be like, I'm like a basically a cell biologist and that's why I'm getting these right. But no, I just lucked my way into it like everything else. All right. This is our last one. Is Sam going to pick whatever Sari says again? Which of the following is larger, the diameter of an egg produced by the African clawed frog or the length of a sperm produced by a fruit fly? Both of these things are one cell. Which of them is longer? What is it? The size of an egg?

The diameter of an egg? The size of the egg, yeah. Oh, okay. So if you laid a sperm next to an egg, which one would be longer? Yeah. Aren't there weird bugs that make twice as long sperms as they are or something? Is that a thing? Yeah.

There are super long sperm out there. I guess I should be tricking you. I don't know. I've decided to collaborate this episode. Yeah, we're friends today. In December, Sari and I are friends. All the rest of the ones, we can be enemies. All right. But I'm still going to make you go first, Sam. Okay. I was going to say, I are friends. All the rest of the ones we can be enemies. All right.

But I'm still going to make you go first, Sam. Okay, I was going to say, I'll just lock in the sperm, you know? Sam's locked in on sperm. I'm also going to lock in on sperm. I feel like this fruit fry is probably one of the weird ones. You're copying me. Yeah, I'm now copying you. Well, the egg of the African clawed frog ranges from around 1 to 1.3 millimeters.

This is a big size, but also much smaller than the sperm of a fruit fly, which can reach up to 6 centimeters in length, which is about 20 times the length of its body and a thousand times bigger than a human sperm. Why don't we see them lying around? They're long, but very, very thin and small. Prior to reproduction times, the sperm is coiled up like a ball of string. After ejaculation, the sperm gets straightened out in the female's very long seminal receptacle and stored there until she is ready to have her eggs fertilized.

And longer sperm stores better in the female fruit flies' seminal receptacles, so there's pressure for them to get longer and longer, I guess. There has to be a limit at which it's like, that's actually too much. I also love the way you said sperm. Sperm. Sperms. Look, there are certain ways I was born.

I can't touch my toes. I have this face and I say sporm. Sporm. Well, congratulations, you two. You both got the maximum number of points you could have. Next, we're going to take a short break and then it will be time for the fact off. Welcome back. It is time for the fact off.

Sam and Sari have brought science facts to present to me in an attempt to blow my mind. And after they have presented their facts, I'm going to judge which one would make a better TikTok and award some points to that one. I might also award points to the other one too. It depends on how I feel. But to decide who goes first, here's a trivia question. Adult humans are made of about 37 trillion cells and about 30,000 genes. That includes 200 to 500 major cell types that have been defined so far, and it's not even counting our microbiota. So it's a lot in contrast with other organisms

that are made of maybe just a single cell. Like Bigelowilinatans, I have no idea if I said that right, a marine algae classified as Rhizaria. How many genes does this single-celled organism have? Remember, we had 30,000. Is classified as riseria. Is that a clue of some sort or just a little fun fact? Just a little fun fact if anybody wants to look it up. Am I allowed to look up riseria? I mean, as long as you don't look up riseria number of genes,

I think you'll probably be safe. I'll look it up. 30,000 genes. It's how many we have. But we are us. And it says it's a lot in contrast so the other number must be smaller.

How about one? Is that possible? Think of just like the number of things you need to make. I have to learn somehow, Sari, please. I don't know how they work maybe he just wants to get like the low end and you're gonna i guess too high and it turns out that's

right yeah hank's got it maybe he knows game theory it's more than one oh well see if you had one gene what would you make a protein yeah well. I'm sticking with it. He could win. I'm going to guess 600. Oh, Sari. Did Sam win? Yeah. Good job.

But not just to Sam when he barely wins. It's 284. It's 284. So if you had said 580, it would have been you. So are people right now who know about genes going, wow, that's not very many genes. Yes. Okay. Yes, they are.

Couldn't be me. So what I was basing it off of is I think I read about like an artificial cell that people made. And I think that had like 180 something genes and they were like okay this is like the minimal genome so i was going a little bit that's great yeah i mean you could have said two and just screwed him right over i just didn't know how genes worked so i said one and i don't know how game theory works. So, Sam, you get to decide who goes first. I'm going to go first. Okay.

Streptococcus is a nasty little group of bacteria that cause a wide variety of unpleasant conditions, from strep throat to toxic shock syndrome to a variety of infections and even skin-eating diseases. Streptococcus can be treated with antibiotics, but it's developing a resistance to that pretty rapidly, and there's no vaccine against it, and it's really good at dodging the immune system. And on top of all that, the reason that it's so good at dodging the immune system is kind of a mystery. But in 2019, scientists think they figured out

a pretty large piece of that mystery, and it has to do with the cells in your blood. So red blood cells' primary job is helping move oxygen and carbon dioxide around your body, aka respiration, and you have a whole bunch of them. Just about half of your blood is red blood cells, I think, something like that. Also in your blood are white blood cells, which zip around looking for things that should not be there, like bacteria and viruses, and then they launch antibodies to kill those things. White blood cells and red blood cells are friends, and in normal circumstances, white blood cells will

not attack red blood cells. But one of the things that streptococcus does during an infection is create proteins that rip red blood cells apart, which isn't good. But what the 2019 team discovered is that they also produce another compound called S-protein because it's only found in strep bacteria. And what S-protein seems to do is make strep bacteria stick to the cell membrane fragments of the red blood cells that it rips apart. So what the researchers proposed was that strep infections pretty much rip the skin off of red blood cells and then they glom onto it and wear the skin so that when their friends, the white blood cells, come by to see what's going on, it'll appear as though strep bacteria

are just a bunch of red blood cells minding their own business, thus dodging immune responses. So they did experiments using regular strep and strep engineered to not be able to make S-protein and they put it in mice. 90% of the mice infected with normal strep died and none of the mice infected with the strep lacking S protein died. So it seems like they were probably pretty right. And this discovery could lead to a way to develop a vaccine or at least like drugs that can treat strep bacteria better because now we know what we're looking for. Bacteria wearing the skin of its murder victims, basically. I mean, good. I'm glad we figured it out.

Bad, I'm sad they figured it out. They keep figuring things out. What do you mean? Well, the bacteria. They keep figuring out ways to evade us. Stop figuring things out. They've had a very big head start, I think. Well, not really.

I suppose not, just as long as we've been around. Just as long as antibacterial compounds have been around. But I tell you what, wearing the skin of your enemies, it's like you put on the guard's uniform, you know? Exactly. It's very clever. Yeah. I didn't know strep could do that many different things to you.

I thought you just got strep throat from it. Oh, no. You can get a lot of things. It's like Luke and Han taking the stormtrooper's armor. And they're like, aren't you a little short for a stormtrooper? Then that's how you get them. Yeah, exactly. That metaphor bears out completely.

It makes perfect sense. Strep bacteria seem to wear the skin of fallen blood cells to sneak around in the body undetected. Jerks. Sari, what do you have for us? Okay. So the sheer variety of things that are called a cell is kind of mind-boggling sometimes, especially looking at the diversity of single-celled organisms like protozoa,

which is a loose category of eukaryotes, which means they have nuclei with DNA inside them, that aren't animals, plants, or fungi. Within that taxon, but also in other branches because microscopic stuff gets weird, there's a phylum called ciliophora, which includes all of the ciliates, which are single-celled organisms that have little hair-like organelles called cilia that they use to move or eat or sense stuff. And one pretty abundant example of a ciliate is oxytrica trifallax, which is also known as several other things because, like I said, the classification gets blurry, but studying these little guys, no matter what they're called, who have been around for maybe two billion years gets very weird. Most notably, instead of just one nucleus to hold its DNA like all of our cells,

ciliates have two different nuclei. There is a macronucleus, which has most of the genetic material and acts kind of like the nucleus in a somatic cell with all the coding stuff The cell might need for regular survival And then there's a micronucleus which is much smaller and acts kind of like the nucleus in a sperm or an egg By keeping a record of the genes to be passed on during sexual reproduction and when researchers sequenced the genome in o Trifalax, they also found that the macronucleus was packed full of DNA in a totally different arrangement than ours. We have 46 chromosomes, and each chromosome has

hundreds of thousands of genes on it. Why are you laughing, Sarah? Are you laughing because of my guess of one gene? Yes. And just like how neatly this ties into this episode. And it's going to complicate your understanding of genetics.

Because this ciliate has around 16,000 nanochromosomes packed inside its macronucleus, and most of them contain only one gene. So each of these chromosomes, one gene, one chromosome, easy peas. It's just all fragmented and floating around in there and somehow stays organized enough that the cell can find and use what it needs. But that's not even the weirdest part about their genetics. In many cases, O. trifalax reproduce asexually, creating offspring clones to increase their population numbers. But when two of these protozoa have sex, it's not to produce a child. It's to do the most intense version of like an internal spring cleaning and detox, which is reconfiguring

its whole genome. So the two mating cells glom together and then share a copy of their micronuclear DNA, which is around 100 chromosomes, at which point they trash their old macronuclei because they don't need it anymore. And if I understand this process correctly, one cell takes two micronuclei, one from it and one from its partner, and break it all down into around 250,000 smaller chunks of DNA that then gets sorted into two buckets. The good stuff is macronuclear-destined sequences, which is like 5% of the chunks, but the rest is internally eliminated sequences and transposons, which are effectively garbage. So around 95% of both micronuclei just get trashed. And then, just using that 5%, somehow one cell just amplifies certain parts, rearranges the encrypted

nucleotides, and creates a working macronucleus that are a mix of new and old genes. And then they just go about their life. And in a 2014 paper, the authors wrote that this is, quote, arguably the most complex genome architecture of any known eukaryote. And it's frankly just bonkers that all this is happening inside one single cell and we don't understand why or how. It's just this weird mystery of evolution. And if it works for them, why don't we do it that way? Why don't we just trash all our DNA when we reproduce? Also, when we reproduce, why don't we just sort of rub up against each other and then

walk away with a different genome? Yeah, just become a completely different person biochemically when you have sex. Every time. But also, you get to trash all that bad stuff. Yeah. Get rid of the old you, bring in a new you that's half

someone else. And then you make clones of yourself. And you're like, okay, those children are okay. But I think I want to switch it up again. I want to be a new me, a new new me. I mean, wouldn't it be weird? Look, it's possible. Everything's possible. So there could be a world in which that actually is the case. And we get to be different people with different DNA. Wouldn't that clear up a lot of stuff if you could be a different, like actually be a different person genetically a couple of times throughout your life?

Yes, I think it'd be very interesting to see that sci-fi book. And also like the systems that people would like force each other to be other people at some point or like hold onto their DNA to be like, no one can be like me. Yeah, I mean, would it be like, would it be like kind of a unnecessary part of the

life cycle or would it be something that you're compelled to do or something that you want to do and people who don't do it are weird or whatever? Yeah. Yeah. Write a book, Hank. Well, I mean, it turns out that part's the easy part. Then you got to have a bunch of characters that care about each other and that are interesting and that the audience likes.

Write some fanfic. Write some genetic fanfic. Oh, we got them. I got them. That's how Waluigi happened. Yes. Yeah, Wario bumped into Luigi and then just like. Whoops.

Hey, Waluigi. Anyway, our two fact off facts now we've got a single-celled organism with two well i mean all these ciliates have distinct nuclei and uh they reproduce asexually but they reconfigure their genomes during this sexual process and do do the it's just a weird and wild and wonderful but difficult to explain thing or don't know, wearing your fallen foe's skin in order to evade detection. Ah, God, it's got to win. It's got to win.

Sam's is the simpler to grasp. It's easier to, the story to tell. TikToks can't be as long as you need for. Yeah. All right. Well, congratulations, Sam. I feel like that's three episodes in a row for you. I believe it is.

Oh. Sarah, you got to stop cooperating so much. Yeah. You know, tis the season. Right. And now you don't have to give Sam a birthday present because you told him all about sperm and eggs. This is your Christmas present, Sam.

One, one, Scythe's tangents win. And that means it is time to ask the science couch where we've got listener questions for our couch of finely honed scientific minds. Scythe on Discord asks, can cells move on their own? Yes and no. There are certain cells that can't, but almost all can. I guess within the human body,

there are some that can and some that can't. But certainly like all ciliates can move around. They got cilia. That's what they're for. But I guess a lot of the ones in the body are locked in place once they are mature. Kind of. I think your cells move around more than you'd expect.

Well, everything moves, Sari. The earth is spinning. They move when I go to the grocery store. They walk to the grocery store. When you open the can, when you type your little fan fiction, your cells are moving around. Type your little Waluigi conjugation fan fiction. Oh, man.

So there's the category of cells that propel themselves, whether it's through cilia or sperm or certain bacteria have flagella, which are appendages that look kind of like a tail and they move with chemical stimuli and they kind of like swirl around. That's the really long part of the fruit fly sperm. But if we're talking about within a body, then I'm pretty sure most cells have this ability because of the cytoskeleton, which is basically a bunch of interlocking proteins in every single animal, plant, or fungal cell. So, like, eukaryotic. And all cells can kind of crawl or scooch when they need to. What the heck? Kind of like a lot of the cells that need to move are, like, immune responses. are like immune responses. So like getting closer towards microorganisms or like navigating around wounds,

physically wound healing, like fibroblasts or other connective tissue stuff, reconnecting and remodeling. But then if any cell metastasizes, so like becomes cancerous, it's moving around the body. So like no matter where that originated, if a cancer is metastatic, then one of the cells that was cancerous moves in some way.

And the way they do this is with different protein filaments. And the big one is actin, which you might have heard of in muscle fibers. So like actin and myosin work together in muscles to help muscles contract and expand. But actin is much, much more prevalent across all the other cells in your body. And they can polymerize and grow longer really fast and also depolymerize and grow shorter really fast. cell scooches along it like protrudes the leading edge and then disappears the back edge like deep protrudes the back edge and then scoots itself forward like contracts a little bit so you can kind of imagine like a dog scooting around on its butt i couldn't think of a better metaphor for this but like it moves its paws forward then moves its butt forward and moves its paws forward, then moves its butt forward, and then moves its paws forward and move its butt forward.

Okay. I like that. And that's how all cells kind of scooch. Scoochers. And there are, like, other surface that like help them stick to other surfaces to like help grab them along in the way that like you couldn't just push off of nothing. A dog can't scoot on an air. It needs a little floor to put its paws on to rub its butt on the ground. I was thinking like, you know, epithelial cells, once they get mature, they're

pretty locked in place. And then red blood cells can't move because they don't have much going on. They're just little sacks full of hemoglobin. And so are sort of planktonic, where they just go where the fluid goes. But I guess, yeah. And I think during different times in formation, the cells got to get to where they need to be. And when they are maturing, like when a bone cell is maturing you know they're headed out they go to a place they're yeah they move around we are creepy little highways of cells that are constantly deciding not to kill us it's great yeah and even your epithelial cells to

some extent like as you shed old ones the new ones need to migrate up toward the surface. They don't scooch as wildly as some other ones, but they still slot in. Yeah, just getting shoved from the back, you know, kind of a conveyor belt action. Which is also weird to think about, that we're constantly losing parts of ourselves and everything's kind of held together by bonds, but we're really just kind of floating in space.

Chill bonds. Yeah. Yeah. If you want to ask your question to the Science Couch, you can follow us on Twitter at SciShow Tangents, where we will tweet out topics for upcoming episodes every week. Or you can also join the SciShow Tangents Patreon and ask us questions on our Discord. Thank you to at Rachel MyCR, at Michaela Noel, and everybody else who asked us your questions for this episode.

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I had a little special guest on it. One Stefan Chin. Oh, does it? Have we we done that yet we haven't done that yet okay good worried about myself okay second you can leave us a review wherever you listen that helps us know what you like about the show and also helps other people know what you like about the show and finally if you want to show your love for SciShow Tangents, just tell people about us. Thank you for joining us. I've been Hank Green. I've been Sari Reilly. And I've been Sam Schultz.

SciShow Tangents is created by all of us and produced by Caitlin Hoffmeister and Sam Schultz, who edits a lot of these episodes, along with Hiroko Matsushima. Our social media organizer is Paolo Garcia Prieto. Our editorial assistants are Deboki Chakravarti, Emma Douster, and Alex Billow. Our sound design is by Joseph Tuna-Medish, and we couldn't make any of this without our patrons on Patreon. Thank you, and remember, the mind is not a vessel to be filled,

but a fire to be lighted. But one more thing. Many human cells are spherical, but these spheres can morph into other shapes when something goes wrong. For example, some diseases, such as the cancer follicular lymphoma, can lead to cells that have a groove in the middle, dividing the nucleus into two main lobes. For better or for worse, even in scientific literature, these cells are called buttock cells. Cancer butt. I know, I want to laugh, but it's so sad. It's like these very serious cancer researchers being like, these so-called buttock cells proliferate. Yeah. And you're having that conversation.

You're like, so this is what we call them. We're not making light of your disease. But they look like butts. But they don't, like, they didn't name themselves. We can name them something else if we wanted to. But they look like butts.