[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:00.00,0:00:03.96,Default,,0000,0000,0000,,To us modern folk, we tend to take for granted the existence of cells
Dialogue: 0,0:00:03.96,0:00:06.50,Default,,0000,0000,0000,,and the idea that all living things are made up of cells
Dialogue: 0,0:00:07.00,0:00:11.00,Default,,0000,0000,0000,,that we as human beings, as living organisms, we are made up of many, many, many cells
Dialogue: 0,0:00:11.22,0:00:19.38,Default,,0000,0000,0000,,the estimates of the cells, of the human body, are around the order of 37 trillion cells!
Dialogue: 0,0:00:19.44,0:00:23.20,Default,,0000,0000,0000,,But, if we were to rewind, even 400 years ago to the 1600's
Dialogue: 0,0:00:23.26,0:00:25.00,Default,,0000,0000,0000,,this wasn't so obvious.
Dialogue: 0,0:00:25.00,0:00:26.92,Default,,0000,0000,0000,,and that is because people really didn't have the tools
Dialogue: 0,0:00:26.92,0:00:30.96,Default,,0000,0000,0000,,to make direct observations of cells. They didn't know that these cells were around.
Dialogue: 0,0:00:30.96,0:00:34.04,Default,,0000,0000,0000,,They didn't know that things, even like unicellular organisms, even existed!
Dialogue: 0,0:00:34.54,0:00:37.34,Default,,0000,0000,0000,,But, all of that began to change, with Robert Hooke.
Dialogue: 0,0:00:38.92,0:00:43.50,Default,,0000,0000,0000,,Robert Hooke, was able to leverage a primitive microscope
Dialogue: 0,0:00:43.56,0:00:45.40,Default,,0000,0000,0000,,and this is a picture of his microscope
Dialogue: 0,0:00:45.40,0:00:46.98,Default,,0000,0000,0000,,and when you see this, you appreciate how
Dialogue: 0,0:00:47.00,0:00:48.72,Default,,0000,0000,0000,,at least relative, to what we have today, how primitive it was.
Dialogue: 0,0:00:48.72,0:00:51.66,Default,,0000,0000,0000,,He had lenses here, that would provide some magnification,
Dialogue: 0,0:00:51.66,0:00:56.28,Default,,0000,0000,0000,,but he had to use -- this right over here -- this is a flame, and he is able to channel that light
Dialogue: 0,0:00:56.28,0:00:59.42,Default,,0000,0000,0000,,so that it gets reflected over whatever he is observing.
Dialogue: 0,0:00:59.42,0:01:03.84,Default,,0000,0000,0000,,And in, 1665, he publishes the "Micrographia".
Dialogue: 0,0:01:03.84,0:01:07.34,Default,,0000,0000,0000,,I am probably not pronouncing it right.
Dialogue: 0,0:01:07.34,0:01:11.74,Default,,0000,0000,0000,,So, this is 1665, Robert Hooke publishes this
Dialogue: 0,0:01:11.78,0:01:14.76,Default,,0000,0000,0000,,and in this, he describes and he draws a lot
Dialogue: 0,0:01:14.76,0:01:18.68,Default,,0000,0000,0000,,of his observations, using his microscope.
Dialogue: 0,0:01:18.68,0:01:21.32,Default,,0000,0000,0000,,He has some fascinating drawings, he was actually quite a good artist,
Dialogue: 0,0:01:21.32,0:01:23.72,Default,,0000,0000,0000,,where he was able to draw pictures
Dialogue: 0,0:01:23.72,0:01:26.94,Default,,0000,0000,0000,,of his observations, of things like lice, and fleas.
Dialogue: 0,0:01:26.94,0:01:30.58,Default,,0000,0000,0000,,But, it's not just lice and fleas that he is able to observe.
Dialogue: 0,0:01:30.58,0:01:36.88,Default,,0000,0000,0000,,He actually takes a look at some corks or what he just sees as "cork"
Dialogue: 0,0:01:36.88,0:01:49.16,Default,,0000,0000,0000,,and when he makes that observation, he says, "Hey look, you know there are these little squares over here, and this kind of seems to be somehow kind of a basic unit of this cork. "
Dialogue: 0,0:01:49.16,0:01:56.16,Default,,0000,0000,0000,,And he says, " Well, this kinda reminds me of these little rooms that monks live in and spend their time in, which we call cells".
Dialogue: 0,0:01:56.16,0:01:58.04,Default,,0000,0000,0000,,So he calls these cells.
Dialogue: 0,0:01:58.04,0:02:00.22,Default,,0000,0000,0000,,And, that is where the word comes from.
Dialogue: 0,0:02:00.28,0:02:02.06,Default,,0000,0000,0000,,He calls them cells, in "Micrographia".
Dialogue: 0,0:02:03.10,0:02:04.02,Default,,0000,0000,0000,,That is a cell.
Dialogue: 0,0:02:04.02,0:02:07.14,Default,,0000,0000,0000,,Now unfortunately for us, he was a great artist
Dialogue: 0,0:02:07.14,0:02:09.78,Default,,0000,0000,0000,,and he was really good at drawing things
Dialogue: 0,0:02:09.78,0:02:13.58,Default,,0000,0000,0000,,and he drew a lot in his "Micrographia", but we don't have any pictures of Robert Hooke anymore.
Dialogue: 0,0:02:13.58,0:02:16.88,Default,,0000,0000,0000,,And it's a fascinating story. Most theories are that
Dialogue: 0,0:02:17.08,0:02:22.92,Default,,0000,0000,0000,,actually, it was Isaac Newton, who burned the only original painting, that we have of Robert Hooke.
Dialogue: 0,0:02:22.92,0:02:26.32,Default,,0000,0000,0000,,And, that is another intriguing story, that we can talk about, at a future date.
Dialogue: 0,0:02:26.32,0:02:31.80,Default,,0000,0000,0000,,But, what Robert Hooke — he coined these things "cells" — but he was looking at dead tissue, and actually he was
Dialogue: 0,0:02:31.80,0:02:37.04,Default,,0000,0000,0000,,looking at the remnants of cells. And what he saw was really just the cell wall remnants.
Dialogue: 0,0:02:37.04,0:02:41.92,Default,,0000,0000,0000,,He wasn't actually able to observe, directly, "living cells". And he didn't have enough to go on
Dialogue: 0,0:02:41.92,0:02:46.14,Default,,0000,0000,0000,,to think , "Hey maybe, this is a building block of all life and maybe, cells themselves reproduce."
Dialogue: 0,0:02:46.14,0:02:52.52,Default,,0000,0000,0000,,"And, all cells come from other cells. " And that doesn't start to get developed, until we get further on into history.
Dialogue: 0,0:02:52.62,0:02:57.32,Default,,0000,0000,0000,,You go a few years later, we get to Antonie von Leeuwenhoek.
Dialogue: 0,0:02:57.32,0:02:59.32,Default,,0000,0000,0000,,I know I'm not probably pronouncing it right.
Dialogue: 0,0:03:00.28,0:03:03.64,Default,,0000,0000,0000,,But he was a Dutch lense crafter, and he was inspired
Dialogue: 0,0:03:03.64,0:03:09.94,Default,,0000,0000,0000,,by Hooke's work , and he says "Hey, I can craft lenses, maybe I can use that to make better microscopes, and make better observations. "
Dialogue: 0,0:03:10.12,0:03:13.24,Default,,0000,0000,0000,,And he was able to do that, and doing that he was able to directly observe
Dialogue: 0,0:03:13.24,0:03:17.04,Default,,0000,0000,0000,,living cells and living unicellular organisms.
Dialogue: 0,0:03:17.04,0:03:19.92,Default,,0000,0000,0000,,So, he was able to directly observe sperm.
Dialogue: 0,0:03:19.92,0:03:23.34,Default,,0000,0000,0000,,He said, "Hey this thing looks like it's alive!"
Dialogue: 0,0:03:23.34,0:03:30.96,Default,,0000,0000,0000,,He was able to directly observe protists — so these unicellular, eukaryotic...
Dialogue: 0,0:03:31.06,0:03:34.78,Default,,0000,0000,0000,,... they have cell walls, these things that look like unicellular animals.
Dialogue: 0,0:03:34.78,0:03:37.78,Default,,0000,0000,0000,,And he called them, actually, "animalcules".
Dialogue: 0,0:03:41.32,0:03:47.24,Default,,0000,0000,0000,,Saying, "Hey, look, these look like these little mini-animals going on here. "
Dialogue: 0,0:03:47.30,0:03:51.06,Default,,0000,0000,0000,,And so he started to say, well maybe this is some form of a basis of life, or at least started to say,
Dialogue: 0,0:03:51.06,0:03:54.30,Default,,0000,0000,0000,,at this very small scale, you actually have life.
Dialogue: 0,0:03:55.14,0:04:03.04,Default,,0000,0000,0000,,But, a fully, modern theory of the cell, doesn't really start to emerge until we get another 100-150 years, into the future.
Dialogue: 0,0:04:03.14,0:04:05.48,Default,,0000,0000,0000,,And, we get into the early 1800's.
Dialogue: 0,0:04:05.84,0:04:13.62,Default,,0000,0000,0000,,So, if we fast-forward, to the 1830's , these two gentlemen, Matthias Schleiden and Theodor Schwann, come into the picture.
Dialogue: 0,0:04:13.62,0:04:16.36,Default,,0000,0000,0000,,And, they are the one's that start laying the foundation
Dialogue: 0,0:04:16.36,0:04:19.24,Default,,0000,0000,0000,,of what we can call, "modern cell theory".
Dialogue: 0,0:04:19.24,0:04:22.32,Default,,0000,0000,0000,,So, modern cell theory
Dialogue: 0,0:04:22.32,0:04:26.72,Default,,0000,0000,0000,,And using their observations and kind of what they are able to deduce
Dialogue: 0,0:04:26.72,0:04:30.48,Default,,0000,0000,0000,,they said, "Hey maybe, all living things
Dialogue: 0,0:04:30.48,0:04:42.36,Default,,0000,0000,0000,,all life, is composed of one or more cells."
Dialogue: 0,0:04:42.36,0:04:45.66,Default,,0000,0000,0000,,And today, we kind of take this for granted, but this wasn't obvious.
Dialogue: 0,0:04:45.66,0:04:51.60,Default,,0000,0000,0000,,It wasn't obvious that all things, that this was somehow a building block for life, one or more cells.
Dialogue: 0,0:04:51.60,0:04:54.10,Default,,0000,0000,0000,,And then, following that if all life is composed of one or more cells,
Dialogue: 0,0:04:54.10,0:04:58.74,Default,,0000,0000,0000,,you can also say, that a cell, is the basic unit of life.
Dialogue: 0,0:04:58.74,0:05:07.48,Default,,0000,0000,0000,,Cell is basic unit of life
Dialogue: 0,0:05:07.48,0:05:09.68,Default,,0000,0000,0000,,And these are strong statements, that all life, if you were to get down small enough,
Dialogue: 0,0:05:09.68,0:05:14.82,Default,,0000,0000,0000,,you are going to come to cells, living cells, that make up that life.
Dialogue: 0,0:05:15.24,0:05:20.84,Default,,0000,0000,0000,,Now, this isn't our full, complete cell theory and both of these gentlemen, they knew that cells could come from other cells.
Dialogue: 0,0:05:20.90,0:05:25.32,Default,,0000,0000,0000,,They were able to observe cells reproducing, but, it still
Dialogue: 0,0:05:25.32,0:05:30.82,Default,,0000,0000,0000,,was an open question, "Hey, maybe some cells come from other cells? While others, maybe they somehow get spontaneously created ....
Dialogue: 0,0:05:30.82,0:05:36.70,Default,,0000,0000,0000,,... if you have the right elements and the right amount of conditions. Maybe they somehow just emerge out of nothing. "
Dialogue: 0,0:05:36.78,0:05:46.58,Default,,0000,0000,0000,,And, it wasn't until this kind of third tenet of modern cell theory, it wasn't until the mid 1800's that we get our third tenet of modern cell theory that gets established.
Dialogue: 0,0:05:46.58,0:05:51.30,Default,,0000,0000,0000,,And this is this idea that all cells come from other cells.
Dialogue: 0,0:05:51.30,0:05:56.34,Default,,0000,0000,0000,,All cells from other cells
Dialogue: 0,0:05:56.34,0:05:59.96,Default,,0000,0000,0000,,And the real father of this idea, the one that really established this,
Dialogue: 0,0:05:59.96,0:06:02.80,Default,,0000,0000,0000,,is this gentleman, right here, Robert Remak.
Dialogue: 0,0:06:02.80,0:06:09.20,Default,,0000,0000,0000,,Now sometimes, the credit for this goes to, Rudolph Virchow, right over here, but it turns out that
Dialogue: 0,0:06:09.38,0:06:17.84,Default,,0000,0000,0000,,he plagiarized Remak's work, so it's really Remak who deserves the bulk of the credit
Dialogue: 0,0:06:17.84,0:06:20.06,Default,,0000,0000,0000,,for this tenant, that all cells come from other cells.
Dialogue: 0,0:06:20.06,0:06:23.98,Default,,0000,0000,0000,,And once again, he wasn't the first person to say, "Hey, maybe, we will observe that some cells..
Dialogue: 0,0:06:23.98,0:06:31.56,Default,,0000,0000,0000,,.. come from other cells." But he said, "This is a fundamental thing, all cells, this is how they actually come about they aren't just somehow, spontaneously emerged".
Dialogue: 0,0:06:31.56,0:06:34.78,Default,,0000,0000,0000,,Now whenever, even in today's world, people
Dialogue: 0,0:06:34.78,0:06:37.02,Default,,0000,0000,0000,,see this last thing, all cells come from other cells,
Dialogue: 0,0:06:37.02,0:06:42.74,Default,,0000,0000,0000,,there is a natural question, " Well, there must have been a first cell or an initial set of "proto-cells ?".
Dialogue: 0,0:06:43.10,0:06:47.10,Default,,0000,0000,0000,,And, people aren't a hundred percent sure, but when we
Dialogue: 0,0:06:47.10,0:06:53.32,Default,,0000,0000,0000,,look back, at the evolution of life on earth, we think the first cells emerged about three and a half billion years ago.
Dialogue: 0,0:06:53.32,0:06:57.48,Default,,0000,0000,0000,,And we are not a hundred percent sure about how they emerged, but there are some theories.
Dialogue: 0,0:06:57.56,0:07:00.60,Default,,0000,0000,0000,,For example, we have videos on, phospholipids,
Dialogue: 0,0:07:00.74,0:07:09.46,Default,,0000,0000,0000,,and it turns out that, phospholipids, naturally form bi-layers
Dialogue: 0,0:07:10.04,0:07:15.50,Default,,0000,0000,0000,,and they can actually form, spherical membranes, that have phospholipid bi-layers.
Dialogue: 0,0:07:15.50,0:07:19.32,Default,,0000,0000,0000,,So, that kinda gets you a start, so that can spontaneously form.
Dialogue: 0,0:07:19.32,0:07:24.70,Default,,0000,0000,0000,,And, there is also, theories that maybe in the information, the machinery of cells
Dialogue: 0,0:07:24.70,0:07:28.52,Default,,0000,0000,0000,,maybe their ancestors, if we were to go three and a half billion years or longer ago,
Dialogue: 0,0:07:28.52,0:07:34.84,Default,,0000,0000,0000,,that it might have been self-replicating RNA molecules or maybe it was somehow, self-replicating proteins
Dialogue: 0,0:07:34.84,0:07:39.82,Default,,0000,0000,0000,,that over time, over very large, large time scales,
Dialogue: 0,0:07:39.88,0:07:44.82,Default,,0000,0000,0000,,were able to, start replicating themselves, have more sophisticated machinery,
Dialogue: 0,0:07:44.96,0:07:50.50,Default,,0000,0000,0000,,the ones that had or were approaching our modern cells, were able to reproduce more,
Dialogue: 0,0:07:50.50,0:07:54.34,Default,,0000,0000,0000,,were able to take advantage of more of the energy, the resources in an environment.
Dialogue: 0,0:07:54.34,0:08:00.54,Default,,0000,0000,0000,,So, that we eventually get to our modern cells. But, this is a fascinating question, and is still an area of research.