Hi. It's Mr. Andersen and welcome to biology essentials video number five. This
is on the essential characteristics and how they're conserved. Today I am going to be
talking about life. This right here is a tree of life, a circular tree of life. And you
can see that this tree of life is going to branch over to here. These would be like the
archaea, these would be the eukaryea, we would be, humans would be right here if I can read
that right. These are going to be the bacteria that go over here. And so we have this tree
of life that tells us a few things. Number one, we're more related to Archaea then we
are to bacteria. But it also shows that there are certain characteristics that are shared
by all of life. In other words, all of life has DNA. And so that must have originated
very early in this tree of life. And so today what I'm going to talk about are essentially
characteristics, essential characteristics. In other words, things that are required for
life and how they are conserved or how they stick around through time. If we kind of plan
this out, this is what I want to talk about. I want to talk about three things and how
they're conserved. The first one would be the genetic code, and that's DNA. Next thing
is the central dogma. And that's how DNA eventually makes RNA and how RNA make proteins and then
make you. And then some metabolic pathways. Metabolism is the sum of all chemical reactions
inside life and there are some really fundamental things that you may not know that are found
within these three groups. So these would be the three domains, we call that bacteria,
archaea and eukaryea. And so all life fits into one of these three categories. And so
these three things are conserved or found in all of life. We'll also find that we move
up that tree a little bit, when we get to the eukaryotes, there are going to be characteristics
that are shared within them as well. And so as we go farther and farther and farther up
that tree of life we find more and more characteristics and we get finer and finer detail as we move
our way up. So let me quit talking about what I am going to talk about and actually do it.
Let's start with the first one and that is the genetic code. And that is DNA. So you
should be familiar with this, that double helix structure. Most people know what DNA
is but they do not necessarily know what it does. An example would be this, a jellyfish
right here. Scientists were able to take a gene out of a jellyfish that makes a glowing
protein that allows that jellyfish to do well deep in the ocean. They were able to
take that DNA and put it into a bacteria. This is a really cool picture. It's a petri
dish where scientists put different genes inside the bacteria to make them glow. In
this case it's making them glow this kind of a green color. We've also been able to
put it inside fish and make fish that glow green. And so the genetic code is found in
all of life. In other words, it's universal. We've never found anything that doesn't use
DNA as its genetic material or RNA. If we talk about viruses. And so this is found in
all of life and it is also interchangeable, which is cool. We can take the DNA back out
of here and put it in here, we can put it anywhere and DNA is going to be universal.
And so that suggests that all life comes from this one common ancestor. Next thing is the
idea of the central dogma. Central dogma, you may not be familiar with that but you
should know what it is. Watson and Crick were the people who got credit for discovering
the structure of DNA. But this guy right here, Frances Crick, spent the next then 10 years
figuring out the machinery behind the DNA. And so what it actually does. And so he summarized
it right here. And so essentially what happens is DNA can copy itself, we call that DNA replication.
It then through transcription makes RNA. RNA makes proteins and a protein eventually makes
you. And so every part of you is made up of proteins and the result of protein action.
And so all life goes through this same mechanism. In other words, in bacteria, they have the
genetic material as DNA, they make RNA out of it and they make proteins. Now the way
that they do that, the ribosomes that they use are a little bit different but the mechanism
is going to be exactly the same. And so we've never found life that doesn't utilize this
central dogma. Remember you pass your DNA on and then the cycle can begin again. And
the last one is metabolism. Metabolism, remember, is how we kind of make use of the energy that's
given to us. And so it summarizes it here. In other words, we as humans and fungi and a
lot of bacteria can take in organic material and oxygen. We then make carbon dioxide and
water, this is called cellular respiration. And then there are certain producers that
can actually make that again. Whereas plants are making sugars so they can actually break
it down. But, regardless of all of the that, there are a few things that are found in all
living organisms. And so if you know what DNA is and you know that all life has it,
you should also realize that this is the coinage, the energy coinage that all life uses as well.
And so if I ever heard that we discovered life on some other planet I would want to
know what is its hereditary material and then what is it, how is it making its energy, what's
it using for metabolism. And so the fundamental ways that we utilize energy or get energy
and make ATP is through glycolysis, Krebs Cycle and oxidative phosphorylation. So all
life uses one of those and either anaerobic or aerobic respiration. And so bacteria, fungi,
whatever, we're making ATP and we're using the same fundamental metabolic pathways. And
what does that suggest going way back to that tree of life? That it originated very early
in the life on our planet and it's been passed down through time. But we'll get more into
detail on respiration and photosynthesis a little bit later. Now, if we go to the next
group, so remember we have, if I were to sketch it out, we have the break off of bacteria
domain. We also have the branching off of archaea, these ancient life. And then finally
we have eukarya. And that's what you are. And actually everything on here from animals
all the way over to fungi, down in here to unicellular organisms and plants and all these
things are eukaryotes. Now they are a different kind of a cell. And so what do you know about
a eukaryote? It actually, if I remember right karyo comes from egg and so the best way to
think about a eukaryotic cell is that it has a nucleus. It has a nuclei on the inside where
it stores its DNA. But how did we go from these simple cells to cells that are eukaryotic
and have division of labor inside the cell itself? Well there's actually two ways that
we did that and two characteristics that I chose to talk about related to eukaryotes
tell us how we got there. So let me clear that off and get to the endomembrane system.
And so the first way that cells move from very simple cells to more complex cells, well
if you think about it let's say I have one cell, this is really simple but how can I
make that more complex? Well a really simple way to make that complex is to have it fold
in on itself. And if I have it fold in on itself, now I have an increase in surface
area and so I can do other jobs. And so we have a number of things. So you know the golgi
apparatus, endoplasmic reticulum, lysosomes, vesicles, all these things are made, we think,
from the in folding of this what's called the endomembrane system or membrane on the inside.
Now what is interesting is that we can actually look at proteins on the outside of the cell
and proteins on the inside of the cell, oops let me go back for a second, and proteins
on the inside of the cell, and we find that they'll actually be reversed. In other words
one's that on the outside of the cell will now be, let me get this right, on the outside
of this and vice versa here. So we also have some strong molecular evidence as well to
show that this in folding has occurred. And so that's a common characteristic, this endomembrane
system of all eukaryotic cells. And then another example would be organelles themselves. The
two specific ones that I would like to talk about are the mitochondria, which we use to
get energy out of our food to do oxidative phosphorolation and get as much ATP as we
can. And then the chloroplast which is used in plants and a lot of photosynthetic eukaryotes
to actually take energy from the sun and then use that to fix carbon. Now what's interesting
about these two is that they are not formed, we don't think, by an infolding of the membrane.
They are not part of that endomembrane system, so that's not them. These actually were formed
by endosymbiosis. And so what we think is that the mitochondria was a bacteria once
on its own. It was living in close proximity to these early eukaryotic cells and then eventually
started living inside. And so it's actually a cell within a cell. Now what kind of evidence
do we have, cause that seems crazy that this is actually occurring. Well if you look inside
here we actually have DNA inside a mitochondria and so they're actually reproducing by binary
fission on their own and they have a lot of properties that are very similar to bacteria.
And we think chloroplasts got into plant cells in the same exact way. And so they're kind
of hijacking or living inside of us at this time. So it is a cool way that we can get
complex eukaryotes and so those are some common characteristics of eurkaryotes and I guess
the whole general point of this video podcast is that if you come up with a solution that
solution is going to be passed up the tree of life. There is no way we can step back
and say hey let's find a new genetic information. Let's use something else. That decision was
made billions of years ago. And so I hope that's helpful.