Skip to main content
Loading Explore guides…
Cell Theory Discovery · Acedra
Home
Explore
Biology
Cell Theory Discovery
Sign in to save
Chat
If YouTube asks you to sign in, open the video on YouTube.
Watch on YouTube
Reload player
Transcript
51 segments
Copy
Hide video
0:00
the stage was set but what was still lacking were the scientist with the imagination to see cells for what they really were and here in Berlin one young and ambitious man was about to break the impass Theodore schwar the two strands of biology animal and vegetable were about to come [Music] together at the time Berlin was the European Center for anatomy and the university the magnet for the most brilliant biologists [Music]
0:45
around Theodore Schwan was Keen to make a name for himself and took a position at the prestigious anatomical Museum be warned though it's not for the faint-hearted
1:03
a guide book comments boys will be admitted only in the company of their fathers or teachers and of the female sex only midwives will be granted admission the visitor's attention is called mainly to the wealth of nerve preparations a long array of monstrous births and about 500 animal skeletons [Music] the field of anatomy was in chaos nobody really knew what animals or humans were made of researchers believed that they were built of many different structures granules fibers tubes globules and
1:46
bladders and none of them seemed any more important than the others animal studies were seriously lagging behind botany and this was because the cells are so much harder to see so the scientists didn't really realize there were any cells there at all and this was fueling the notion that somehow animal tissue was fundamentally different from that of
2:14
plants but schan used innovative ways to stain his animal tissue and he had one of the new list style microscopes he kept finding the same type of globular structure in all the different samples [Music] we know that Schwan was looking at cells but at the time researchers used different terms to describe what they were seeing kin cougin and selon the penny hadn't dropped that they were looking at the same thing and without this connection they couldn't make the intellectual leap that cells
2:53
were common to all life forms this is a replica of Van Leen Hook's microscope look how simple it is it's just a piece of brass and it's got one tiny hole with a lens in it which is maybe a millimeter across yet this is the gadget that transformed the way we see the
3:13
world a tiny lens yet more powerful than any other van lean hook knew that it's the curvature of a lens that bends the light passing through it so making the object being observed here it's a flee appear larger and because van Leen Hook was a master Craftsman he could curve the lens more than anybody else almost to the point it was spherical this allowed him to magnify objects up to 500
3:50
times no one would make a more powerful microscope for over a century so he now had the techn ol but what did he look at he went from linen to fleas to the sting of a bumblebee in fact pretty much anything he could get his hands on and one of the things he looked at was water he'd noticed that in a lake near Del the water changed color with the seasons and he figured that there might be something in the water that he could discover
4:30
many of the fundamental breakthroughs of science seem so simple so absurdly simple but we shouldn't forget that until van Leen hook no one had the Curiosity to find out what might be lurking in the [Music] water he raced home to take a closer look with his
4:53
microscope the man who's going to help me study the water is Hans loner he keep the spirit of Van Leen hook Alive by making replicas of his microscopes to grind a lens Hans needs no special glass Just A Shard from an old Jam Jar will [Music]
5:18
do the only way to get enough curvature in the lens is to make it
5:27
tiny this was Van Leen hook secret and it requires Great skill and patience van lean hook built a staggering 247 microscopes a new one every couple of months for over 50 years and told nobody how he made them we've placed a drop of my Lake water onto a slide that slots into the device with a bit of luck I'll be able to see what van lean hook saw now I've looked down a fair few mic Scopes in my time and this is nothing like anything I've used before it's fishlyn see a thing so what do I
6:10
actually do where am I looking uh at the wrong side mhm you must look through this hole yep a very tiny hole and there's a lens in it yes and the lens uh through the lens you see uh the the sample that is uh put between the glass so hold it up to the light like this close to your eyes and I can see I I can see green there is a focusing knob there's a focus yes there is a focusing knob this might be made so I can move it actually away away from my eye this one this is
6:52
the it's so simple and it works so well yeah that works that really works it's now in Focus oh wow oh my God you can actually see moving creatures yes oh God that's incredible Misha's job here at the castle was to study the chemistry of white blood cells he decided to look at the large nucleus at the center of the cell and find out what it was made of to do this he needed two things a ready supply of cells and a way of getting rid of the gloop so he could study the bare nucleus
7:32
getting hold of white blood cells would normally have been tricky but tubigan was the ideal place the region had been at war with Prussia hundreds of injured Soldiers with infected wounds lay in the barracks next to the
7:50
hospital their wounds were oozing copious amounts of pus which is full of white blood cells so revolting as it sounds collected their old bandages so he could scrape off the
8:07
pus Misha needed something else his next stop was the local slaughter house to collect a pig's stomach look here it is oh disgusting he was interested in the mucus that lined the stomach this contains an enzyme called pepsin which helps break down and digest food food where where's the pepsin look here this this is the pepsin H this sort of gloopy stuff yeah there's not much of it no that's all and this is what digests helps digest the food in the stomach yeah smells like a pig stomach to me
8:44
with the pepsin Misha now had all he needed for his experiment and this is a delicacy in in tubing yes you can um fill it with uh bread or you can cut it in stripes and then you cook it and eat it with bread is it tasty yes I'm not sure about [Music] that Misha carried the bandages and the pig's Stomach back to the lab if he was right the pepsin would break down the white blood cells then for the very first time it would be possible to examine the dense nucleus at the heart of the cell
9:30
nowadays we do analysis like this using Precision equipment but of course Misha didn't have any kit like that so it wasn't easy first he had to scrape the pus from the bandages now this is mayonnaise but you get the idea then he had to wash the pepsin out of the pig's stomach using an acid and mixed it with the P after the enzyme had done its work and digested the cells only then could he analyze the nucleus on its [Music] own now the big question was what did the nucleus consist [Music]
10:23
of Misha spent months analyzing its chemistry and he found it contained a rather a strange
10:33
molecule this molecule was made up of carbon hydrogen oxygen and nitrogen he knew these elements were found in all living things but this molecule contained something extra phosphorus and that made it different very different it was an entirely new kind of Mo Ule because he found it in the nucleus Misha called it nucleon we now know it as
11:08
[Music] DNA intrigued Misha repeated his experiment on sperm cells from frogs carp bulls and [Music]
11:23
salmon every time he found exactly the same molecule [Music] incredibly some of it has survived here in this test tube is some of the first DNA ever isolated it's DNA from salmon sperm that meisha extracted in the 1870s now it may not look like much but this brown powder marks the beginning of a scientific revolution the x-rays taken here at King's College were pivotal producing them would be a painstaking job by a brilliant young scientist working with Wilkins and her name name was Rosalyn
12:01
Franklin Franklin was an expert in x-ray Imaging with her expertise the college hoped to be the first to find the structure of
12:16
DNA she worked in a new laboratory built in the basement on the rubble of the old College which had been bombed here in the lab she took strands of DNA and mounted them in inside this specially built camera the camera chamber was filled with hydrogen to get the very best image when the x-rays were switched on they Shone through the DNA and Scattered in different directions creating an image on a photographic
12:49
film Franklin took over a 100 pictures each one could take up to 90 hours of exposure at close range once the photo was processed she projected it onto the wall so she could calculate the exact distance between atoms it was picture 51 that showed the best image of the mysterious DNA
13:19
molecule this distinctive X shape was the key that would reveal how DNA is built but it was not Franklin's name that came to be a associated with the discovery of DNA's
13:34
structure Wilkins was in close touch with Scientists from Cambridge who were anxious to find the structure of DNA before American Rivals unknown to Franklin Wilkins gave photo 51 to James Watson an ambitious young scientist at cambridge's Cavendish laboratory having studied the photo Watson and his collaborator Francis Crick had a sudden ration it would transform them into scientific celebrities and put the Cell at the center of world
14:10
attention this is the eagle Pub here in Cambridge according to Watson on February the 28th 1953 Francis cric strolled into this Pub and announced to fellow drinkers we have found the secret of life now if you ask me this story is a little bit apocryphal probably embellished with some dramatic license nevertheless the sentiment is bang on and shouldn't be understated this marks one of the truly Great Moments in the history of [Music] science Crick and Watson had worked out
14:50
the structure of DNA and very soon their double helix model was announced to the world
15:01
the structure of DNA is now the most famous image in all biology what Crick and Watson showed is that it's made of two long strands intertwined into two spirals with sugar and phosphate making up the backbone but it's on the inside of the Spiral where things get really interesting on the inside are four molecules adenine thyine cytosine and guanine they're better known by their letters A T C and G they're called bases what Crick and Watson discovered is that these four basic units pair up
15:39
millions of times within the double helix and they pair up in a very specific way a always pairs with t and c always pairs with G A and T and C and G making up the rungs of the ladder within the double helix what cricken wants realized is if you split the two strands of the DNA apart you have all the information to make two new fresh pieces of DNA every time you have an A it pairs up with a t every time you have a c it pairs up with a G so when you split them apart you can
16:15
replace the missing Strand and make up a new double helix twice genius this is the Origin of Species the book in which Charles Darwin outlines the theory of evolution by natural selection but this copy is unique and totally Priceless this is the first copy of the first edition the one that the publisher sent to Darwin himself hot off the press now on page 484 there's a remarkable passage which gives an insight into what Darwin himself thought about the origins of
16:52
Life all the organic beings which have ever lived on this Earth have descended from some one primordial form into which life was first breathed now this doesn't simply say that we humans have evolved from an aplike ancestor now it goes much further than that it's suggested that all living things from insects to elephants from a higher synth to a human have evolved from one single common ancestor and it flew in the face of the Bible's account of creation [Music]
17:29
at the time Darwin didn't propose a scientific explanation for what created this original life
17:39
form his notion that life was breathed into the primordial common ancestor left room for the Creator yet Darwin's Origin of Species introduced one of the most important thoughts in science that all life on Earth sprung from one single
18:07
organism but to know what that organism would have been you have to turn to the other big idea around In Darwin's day it was the theory that cells form the basis of all living things when it was first proposed in the 1830s this was a shocking revelation
18:32
from man to flowers to frogs it showed we're all made up of the same building blocks by the time Darwin published his work on Evolution cell theory was the new Bedrock of biology and crucially scientists had shown that new cells are born only when existing cells divide all living cells are descended from other
19:02
cells so in just two decades in the 19th century scientists had come up with the two biggest ideas in biology cell theory and evolution and if you put the two together there can only be one conclusion that all life on Earth began with one single
19:24
cell Darwin himself never connected the two theories in such such a direct way but what he did do just 11 years after publishing the Origin of Species was make an Unholy attempt to explain how life may have begun he expressed this thought in a private letter to his bostonist friend Joseph Hooker and this time there was no mention of the
19:54
Creator and this is it it's incredible I've studied Darwin for many years but this is the first time I've ever seen one of his letters penned by his own hand and I've got to tell you that his handwriting is a paing but just listen to what he says if we could conceive of some warm Little Pond with all sorts of ammonia and phosphoric salts light heat electricity Etc present that a protein compound was chemically formed ready to undergo still more complex changes so
20:27
Darwin had done a complete complete U-turn no sign of the Creator he was now suggesting that life on Earth began with chemistry no wonder he stopped going to church so how did something as complex as DNA come into existence in the first place well to answer that some people turned to God believing that DNA is so Exquisite it shows the hand of some kind of intelligent design others turn to the Stars [Music]
21:05
and here at Imperial College in London a surprising discovery has provided a clue to the origins of DNA at the end of this Corridor Pioneers in a field called astrobiology have spent years analyzing rocks older than planet Earth itself these are meteorites some of which are more than 4.6 billion years old one of the lead astrobiologists is Dr Zeta Martins she looks for evidence of life beyond the confines of Earth by searching for particular molecules buried inside rocks from outer
21:49
space Hi Zito how you doing so what is it about meteorites that interesting that can tell us about the origin of life we know that uh specific uh samples of materiales like the ones I have here they're about 4.6 billion years old they're uh as old as the the formation of our early solar system this is 4.6 billion years old yes it's just it's amazing it's exciting to hold these samples in your hands and that hasn't changed no in close to 5 billion years no when you first start looking at at
22:28
this it looks like a rock but you are finding stuff in here yes we're finding organic molecules exal organic molecules that may have been important for the origin of life in our planet and that's why it's so exciting so what you're saying is that up in space which we think of as a big vacuum actually there's masses of chemistry just going on which is actually creating these the building blocks for cells exactly we think the space is an empty place but it's not it's bubbling with the chemical
22:59
reactions right with activity exactly in 2003 Zeta got hold of one particular sample whose molecules would reveal something
23:12
spectacular it was from a meteorites that had fallen to Earth in 1969 near the Australian town of meres it was dated to be nearly as old as our solar system
23:28
[Music] thanks to new technology Zeta is now able to analyze the molecules inside the Rock and she's going to show me why this particular meteorite has made such an impact now this is precious stuff it is precious so usually we only have access to milligrams of meteorite sample so you have to be really careful and not mess up what you're doing yeah I can feel a sneeze coming on you might want to hold that away I'm going to run away [Music] it's essential that I don't accidentally ruin the
24:06
[Music] evidence so the meteorite is sealed inside a glass tube to prevent contamination from DNA and other molecules on earth once dissolved in solution the sample can then be analyzed by a machine capable of detecting the molecules that make up the genetic code okay Zeta you've analyzed the meteorite sample using this pretty awesome machine show me what you find so what we find is something like this this represents one of the bases of our genetic code so this is a sort of
24:46
signature for one of the letters that makes up the genetic code for all light exactly and this comes out of a 4 and2 billion year old meteor exactly this is present in the merch and matur right it must have been mindblowing to see that for the first time exactly it was a very exciting and amazing moment actually I mean conceptually that's just out of this world well literally out of this world it is out of this world cuz what you're talking about is something
25:16
which is absolutely inherent to life to every single cell on Earth and it existed before the Earth even existed MH we finally have proven that uh components of our genetic code were in fact extraterrestrial and were present in a meteorite sample
Here to help you learn
Sign in to keep a private conversation with your course tutor.
Ask me anything about the material…
Sign in to chat