The 5 Most Important Molecules in Your Body

The 5 Most Important Molecules in Your Body

Your body has all sorts of complicated
processes going on inside it and a lot and a lot of these processes are carried on by incredibly powerful and often incredibly large molecules. Some of these molecules that you’re using right now are so big that they challenge the definition of
what a molecule is. Technically a molecule is the smallest group of atoms that performs a function, but sometimes there are really complicated groups of
atoms that work together. They’re definitely more complex and say
molecules of water or carbon dioxide but they’re still just one unit. Many of your body’s most important
molecules fall into this category; biologists refer to these huge life-giving
arrangements of atoms as macromolecules. Some of them you’ve possibly heard of others you might never have known where that important but together they are what’s keeping you alive. And aside from water and glucose and other nutrients that you have to ingest to keep going, these are some of the most important
molecules in your body. And hey, I love and appreciate all of them equally.
No playing favorites here. But if I had to pick five of the most important
molecules that keep your body ticking I have to include these five and we’ll
start with the first one I mentioned: Deoxyribonucleic acid or DNA. It’s probably your body’s most famous
molecule and rightfully so. It’s the one that tells yourselves what proteins to
make as well as how and where. Now, you usually hear people talk about
DNA in the context of genetics like they’ll say that their hair color or
their allergy to cucumbers or whether they have wet or dry earwax is because
of their DNA and that’s true: your DNA contains your genetic blueprints; the
instructions on how to make you you, but what’s important to understand is
that your user DNA every single time your body creates a new cell and it does
this two trillion times every day. It’s made up of pairs of interlocking
molecules called nucleotides, building blocks that are arranged in a very
particular order and each of your cells is able to read these sequences of
nucleotides as a kind of code, interpreting different segments which
are your genes as instructions of how to build proteins. And when it comes to your
body, proteins are the boss! If you don’t count water they make up
seventy five percent of your body weight. There are more than 100,000 different
proteins in you right now, and your DNA knows how to make them all.
That is a lot of instructions! So it should be no surprise that DNA is by far the largest molecule you have. If you stretched out the DNA in just one
of your cells, it would be about two meters long. And this enormous code is
readable thanks to another macromolecule called messenger RNA. It
collects the recipe, from whatever segment of DNA it needs, and delivers it
to your cell’s protein assembly lines called ribosomes. So, each of your cells
has the instructions to make proteins but they still need the ingredients to
make them. Those are the amino acids and those
hundred thousand different proteins that you have all are made from different
combinations of the same 20 amino acids. In a pinch, your body can make about half
of these amino acids all by itself but nine of them, the essential amino acids, have to come
from food and that’s where another one of your body’s most important molecules
comes in: Pepsin. Pepsin is an enzyme and it’s a
really big complicated macromolecule that helps digest proteins and food
breaking them down into amino acids. It hunts down the bond between certain
amino acids and just mercilessly rips them apart and pepsin is very good at
it’s job. It’s so powerful that your stomach cells
have to produce it in a special deactivated form called pepsinogen. If it didn’t, the pepsin would set to work digesting your stomach’s own cells but
once the pepsinogen is released into the stomach it becomes activated by
hydrochloric acid in your stomach and then it’s free to wreak havoc. But just
how strong is this stuff? Well, if you’ve ever had the misfortune
of having your stomach contents come out of you, you felt it. The reason
that things like vomiting and acid reflux are so unpleasant is because they
allow pets in to come into contact with your unprotected tissues, so that burning
that you feel is basically pepsin digesting the cells in your esophagus. But normally, and thankfully, pepsin limits
it’s work to your stomach, releasing those essential amino acids that your cells
use to build the proteins that you are made of. But all this protein building takes energy. And to get energy, you first need oxygen. You breathe it in,
but that oxygen needs to get from your lungs to the rest of your body, somehow.
Enter hemoglobin. Hemoglobin is a protein found in red blood cells and it’s so big
that those red blood cells get rid of most of the other stuff inside them, like
the nucleus, to make room for just one macromolecule of hemoglobin and even
then, red blood cells can get so big that they get stuck in your capillaries which
have to dilate to let your hemoglobin-laden cells pass through. Hemoglobin’s main function is to
transport oxygen and carbon dioxide. Each molecule is made up of four groups
called hemes that have one iron atom apiece. These iron atoms have a positive charge;
they’re really good bonding with the electrons in oxygen. And when just one of the iron atoms bonds
with an oxygen molecule the whole shape of the hemoglobin changes so that three
more oxygen molecules can just pop right into the other hemes which are just
empty and waiting. Then the hemoglobin travels through your
circulatory system to unload the oxygen to the cells that need it and once the
oxygen is safely delivered the iron atoms pick up carbon dioxide. The
hemoglobin takes that to your lungs and the whole process starts all over again. Meanwhile, the cells use this oxygen to
crank out another one of your body’s most crucial molecules: ATP. ATP or
adenosine triphosphate is your body’s fuel. Your cells manufacture it in
organelles that are like power stations, the mitochondria. They usually make it with the help of
that oxygen that the hemoglobin has supplied. Of the many important molecules
that we’re talking about today, ATP is the only one that’s not considered a true
macromolecule, just because it’s smaller, but it still has plenty of moving parts.
The most useful thing about ATP is that it has three phosphorus atoms, each of
which is surrounded by oxygen atoms. Cramming these combinations of atoms,
called phosphate groups, together forces those oxygens close to one another which
serves to store a lot of energy and breaking one of the phosphates off
releases that energy. Your body is constantly going through loads of ATP to
power everything that requires energy. That includes big things, like making
your muscles contract and small things, like dilating tiny capillaries so that a
single red blood cell can get through. So, your cells get their instructions from
DNA. Some of the ingredients from the amino acids are kindly provided by
pepsin and then the cells use oxygen delivered by hemoglobin to make ATP for
energy. The digestive, respiratory, circulatory and nervous systems are all
working together here, but your body still needs to know when to do what. That
is where your endocrine system comes in and it owes a lot to cholesterol. Now hold up. If you’ve ever seen a
commercial for heart medicine or diet supplements or so-called health food
you’ve probably been subjected to some pretty negative press about cholesterol. It has a bad rap as an artery clogger
but it’s also got a really important job making hormones. Hormones are chemical
messengers that regulate processes that don’t need to happen all the time. When
the villain in a movie suddenly pops up on the screen brandishing a chainsaw, it’s your hormones that tell your blood
vessels to constrict and your heart to start pumping faster, preparing you to
fight that monster or run away. And cholesterol is the first step in making
some of these hormones. Even though you hear people talking about cholesterol in
their diet, most of the cholesterol that your body uses doesn’t come from food; your liver makes up to a gram of the
stuff every day. Some of that cholesterol stays in your liver where it’s used to
make vitamin D, but the rest is carted through your bloodstream by molecules
called lipoproteins, which are sort of like their personal chauffeurs. And it’s
these reckless drivers that have been giving cholesterol a bad name. When
lipoproteins have too much fat in them and not enough protein, they can get
stuck to the walls of arteries and form plaque that can impede the flow of blood. That’s a big problem, but it’s not caused
by the cholesterol directly. It’s the fault of its chauffeur.
Meanwhile the cholesterol molecules that have good healthier lipoproteins toting
them around have better things to do than just hang out on the side of your
arteries. These cholesterols are incorporated into cell membranes, keeping
them fluid and functioning while others are turned into steroid hormones like
cortisol, estrogen and testosterone. So cholesterol can be pretty cool. Just like you. Looking at these five
molecules gives a lot of insight into how awesome the human organism is. If you
want to learn more about what’s in you and how it works, head on over to Crash
Course where you can take your brain for a nice long soak in biology, anatomy, and
physiology and lots of other disciplines. But in the meantime, thanks for watching
this episode of SciShow. If you’d like to help us keep exploring the world just go to and find
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100 Replies to “The 5 Most Important Molecules in Your Body”

  1. Pepsin also explains the esophogeal erosion in anorexics. They develop lesions in their throat, mouth and esophagus because they vomit so often the pepsin burns their esophagus causing a chemical burn.

  2. by "one macromolecule of hemoglobin" I really REALLY hope you meant 280 million hemoglobin tetramers. hemoglobin coats the surface of RBC's, which are about the size of a mitochondrion. and though this is really small for a eukaryotic cell it's still vastly larger than even a quaternary order protein structure. so the ejection of the nucleas and the small size of RBC's is more about surface area to volume ratio than "fitting a single hemoglobin macromolecule"

    I'm sure many people have already been very angry about this so sorry :p thank you for all the great work you do 😀

  3. I should have thought that Carbon dioxide would be considered very important if not extremely so. I mean, one doesn't need their smooth muscles in spasm or constricting–that's can mean death. Not to mention it helps oxygen dissociate from hemoglobin properly. It's pretty important if a person wants to go on living. Mind, one doesn't need a lot of it by any measure, but it's very necessary.

  4. I'm curious. you mentioned lipoprotein having too much fat and too little protein causing problems with cholesterol. so, can we consume more protein to balance it out or is there another solution to this

  5. 1:07 that are 2 molecules! the left and the right one are not connected via atom bounds. only via hydrogen bounds.

  6. pepsine is indeed unpleasant to have anywhere out of your stomach :S I had acid reflux just a couple of times and I had to drink almost half a liter of milk before the burning in the esophagus subsided… wah.

  7. A molecule is not "the smallest group of atoms that performs a function". It is any number of atoms that are chemically bonded together. Where did that definition even come from? Who decides what counts as a function? Why does it have to be the smallest group? If I have a diatomic acid, like HF, and something like sulfuric acid with more atoms, they are both technically performing the same function which is to donate a proton. But looking at this comparison using your definition means that sulfuric acid is not a molecule because it is not the smallest group of atoms?!?

  8. I was taught that carbon dioxide was released into your blood stream and was converted to carbonic acid and when it reached the lungs was converted back to CO2, the red blood cells not required

  9. "and this comes to the next most inportant molicule, pepsi, and enzyme," i can see so many people thinking thats what he said

  10. Well… According with this video my DNA is the "User Manual" of my body for my cells themselves?.

  11. I'm not looking for attention but I've been off school for over 5 months and thanks to sci show I've been able to keep up on school work….well science…..some facts may be irrelevant but I've learnt soo much while off school and sci show keeps me entertained 😁😃😄 Thank you sci show! 😄😄😄

  12. 6:30 When i heard that the liver makes viatmin D i jsut realizied we have to renew the vitamine namign system. lets use numbers or the greek alphabet, but this time lets only include stuff that the bo9dy doesnt produce 😛

  13. Love these videos but is nobody gonna mention the hair? I like my information guy to look nerdy, not like a more metro bully beat down host.

  14. Speaking of DNA, if you have Lynch Syndrome like I do, your readers are intoxicated (or perhaps dyslexic) and attempt to write what they see, causing things to not be as they should. (Not exactly how it works, but you get the idea, hopefully).

  15. I love your videos, but I was baffled by the fact that you mentioned that red blood cells only have ONE molecule of haemoglobin, and that it its self takes up that much space. THIS IS UTTERLY WRONG.
    "A single red blood cell contains approximately 270 million molecules of hemoglobin protein (which is a metalloprotein). Each hemoglobin has 4 heme groups which possess hemic iron ions that impart the cell the red color. These proteins make up to 96% of the dry weight of a single cell and can carry up to 4 molecules of oxygen each. So a single red blood cell has the ability to transport roughly 1.08 billion molecular oxygen.", I took the liberty to correct the spelling.

  16. Where did you get the information on there only being 1 molecule of haemoglobin per erythrocyte? it just doesn't make sense, for only one Haemoglobin molecule, ~5nm to be the reason most of the normal cellular functions are removed from a 5000-8000nm red blood cell, secondly, you've got 4 molecules of O2 per haemoglobin, 5 trillion red blood cells per liter of blood, if there was only 1 haemoglobin per RBC, you'd be dead of hypoxia because you'd have a 33nM concentration of O2 in your blood which is a lot less than a glass of water at 2.7mM of dissolved O2. Yes Haemoglobin is huge, but as you said, DNA is bigger, and all other cells have that, Haemoglobin doesn't and the reason is so it can fit millions of molecules of Haemoglobin, not just one

  17. Great video! Just one question. I was under the impression that too much cholesterol in the cells will inhibit the production of its receptor (LDL), therefore it wont be able to be absorbed by the cell and will remain in the bloodstream. Once in the bloodstream, the extra amount and the rigidity of the molecule could lead it to become hazardous. I didn't quite understand how the lipoproteins were involved in potential artery clogging. Can someone please elaborate? Thanks!

  18. I often get amazed by how DNA works. Like DNA is simply a code but how does that code ends up making things so vastly differents like bacteria versus fungi(and even then comparing the yeast to typical mushrooms), plants and animals.

  19. When I throw up, which is rare, it just tastes really bad in the back of my tongue. So I can't relate to people who experience the burning.

  20. Nice talk about cholesterol. But the five most important molecules? 1 DNA 2 RNA 3 That carbohydrate that builds our cell walls. 4 elastin and 5 ATP.

  21. I can't say enough about how cool Micheal Aranda's hair is! The blonde part is so precise and perfectly lines up at the halfway point of the hairline. It's the most casually mathematical hairstyle I've ever seen and it's very impressive.

  22. Gonna make a guess before watching the video:

    1. Testosterone
    2. Estrogen
    3. Dopamine
    4. Serotonin (most important)
    5. Insulin (2nd most important)

    Runner ups:
    Acetyl Choline Esterase

    Edit : wow I wasnt even close LOL

  23. I checked textbooks and other sources, and an RBC contains 250,000,000 hemoglobin molecules, not just one, as stated @ 4:01.

  24. A couple minor inaccuracies:
    1) The example hormone that "tells your blood vessels to constrics and your heart to pump faster" when watching a slasher movie is probably adrenaline right? Or at least another catecholamine. Those are synthetised from modified amino-acids, not from cholesterol. I could see cortisol sooooort-of working in the example, but it's not the one most viewers will think of as the jump-scare-reaction hormone, so that's a little misleading.
    2) Even repeating the sequence several times I couldn't make out all the words, but it sounds like "then the iron atom […] carbon dioxide". The phrase could mean something else depending on what word belongs there, but I'll say anyway: carbon dioxide is carried by the protein part of hemoglobin, not by the heme part.

  25. No….technically a molecule is a combination of two or more elements held together by chemical bonds. Water is a molecule and doesn't perform a function.

  26. He makes it sound like each red blood cell only contains one molecule of hemoglobin. That’s very wrong. Each cell is packed full of many hemoglobin molecules.

  27. In college, I asked my science professor what pure ATP tasted like, and what bodily effects would happen were you to eat some.  He was practically floored by the novelty of the questions, and admitted that he didn't know, and that they were VERY good questions.  He spent the rest of the class with a bit of a dreamy, faraway gleam in his eye.

    I still don't have an answer for the questions, so if anyone has access to an organic chemistry synthesis lab, I'd love to get an answer.

  28. Something false – RBCs do get rid of most of their machinery, but it’s to fit ~300 million hemoglobin molecules, a whole lot more than 1

  29. I had hemoglobin deficiency when I was pregnant with my twins. I used to pass out randomly and whenever I would lay on my back, I'd start to pass out. Walking down the hall was hard work for me hahaha

  30. Good information but felt like he was racing to get it all out in under 8 minutes. 'Stated Clearly' does a much cleaner job in my opinion, but I still appreciate the science from both.

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