Tip:
Highlight text to annotate it
X
hi all dr. Clark again in general biology lecture today we're going to
talk about prokaryotic and eukaryotic cells now we're going to talk about
something called endosymbiosis or the link between prokaryotic cells and
eukaryotic cells okay so I'm going to talk about the theory of endosymbiosis
which suggests that with lots of evidence clearly that prokaryotic cells
Gabe rise to eukaryotic cells through the form of symbiosis or endosymbiosis
kind of what's being depicted here okay that phagocytosis would occur and some
small prokaryote being gulped and then instead of being dissolved it is
utilized and so like a photosynthetic prokaryotic
will be then utilized inside of the cell instead of breaking it up and and you
know dissolving it instead it's utilized and the energy can be then transferred
into the cell we'll come to that come back to that in a little bit but first
we're going to talk a little bit about the two types of cells prokaryotic cells
prokaryotes main meaning no true nut or no true core refers to the lack of
nucleus guys these cell types do not have a nucleus
now just because they do not have a nucleus doesn't mean they don't have DNA
they do have DNA they have the capability of having RNA and DNA and
pretty much all the features of cells that have a nucleus it's just they have
no membrane around their DNA no separate membrane around their DNA outside of the
plasma I'll show you an example is a little bit
okay so this includes the two kingdoms are K and bacteria which as we already
discussed are also in their own domains so you have the are K domain and the
bacterial domain and probably when all said and done and everything's been
classified these are probably at least bacteria for sure there's probably the
most species-rich so they have the most species in any Kingdom that is out there
it's just we haven't even got around to naming all the bacteria per se and they
evolved really fast so I doubt we'll ever name all the bacteria but
nonetheless very species rich so lots of cells on the planet have this kind of
characteristic eukaryotic cells are the cells that most people are familiar with
okay because these are the types of cells that we have and that means they
have at ridiculous okay and also along with that true nicolas which is membrane
bound DNA you're going to have other membrane-bound internal compartments
which might have multiple different functions maybe it's the site of ATP
synthesis maybe it's the site of photosynthesis maybe it's the site of
digestive enzymes there's lots of different functions that could be around
these internal compartments and then when we're looking at this we're talking
about the other four kingdoms okay so we're talking about Protista fungi and
amilia and plant a have eukaryotic cells so first let's look at the prokaryotes
simple cellular organisms and they are the simplest okay and simplest meaning
the amount of internal compartments and things like that that they have in the
functionality is simple simple or simplistic it doesn't mean that they
don't have complex relationships because they do and so if we look at them there
there are there are a lot of similarities between prokaryotes and
eukaryotes and we'll talk about the similarities and then what are the
differences okay so first they have a plasma
membrane right and that plasma membrane is just like the plasma membrane that we
talked about before it's gonna be a phospholipid bilayer okay you know
embedded proteins might have some cholesterol you're gonna have these
proteins that are transmembrane proteins they run all the way through the
membrane which allows for things to flow in and out you might have cell surface
proteins which allow for the cell to be recognized by foreign bodies either as
being self-made or something that they can communicate with these kind of
things so organism other cells can interact with them especially in the
colonial cells you know where you might get biofilms of bacteria being made they
need to interact with each other and so they might have these outside proteins
transmembrane proteins that allow for that connection okay they have cell
walls now the construction of the cell wall what it looks like what the cell
wall is made out of okay is different and then the cell wall of say plants
okay but nonetheless it's an extra layer of protection around the plasma membrane
in some bacteria some prokaryotes while an additional layer of protection which
we call the capsule okay and this will play an important role when we start
talking about antibiotic resistance when we start talking about whether
thing is grand positive or gram-negative and these are tests to see if that
prokaryote has that capsule there's other tests like capsule tests and
acid-fast tests and other tests that can indicate whether or not a bacteria might
have a capsule or not it's just an extra layer of protection that some bacteria
will have so other than that you know the cells are pretty simple and
organization because there's no internal compartments that are membrane bound
they do have occasionally a little bit of protein work and protein fibers that
hold the structures together okay but it's not a support framework like we're
going to see when we look at eukaryotes and because all living organisms have
you know some information kind of carrying molecule either DNA or RNA
there has to be a way in which that molecule can be used to form proteins
because that's the purpose of DNA is for protein synthesis so all prokaryotes
will have ribosomes which means they have their own ribosomal RNA and this is
allowed researchers to make those connections between eukaryotes and
prokaryotes or eukaryotes and archaea and bacteria to kind of get an idea of
well when did archaea bacteria rise on the planet how many mutations have been
formed since then what's their link to eukaryotes and this can all come because
all living organisms have ribosomes which means all living organisms have
ribosomal RNA and we'll come back to this when we talk about the function of
ribosomal RNA when we talk about DNA synthesis
right now also prokaryotes also have a nucleoid region okay so they do not have
a nucleus but they have a region at which you would expect to find the DNA
and so the DNA is in chromosome form and it's in a circular chromosome so instead
of linear chromosomes like you see in eukaryotes there it's a circular
chromosome that you know the ends are connected okay we'll talk about when we
talk about how DNA is copied and and we'll talk about the benefits of having
that circular chromosome versus linear chromosomes but nonetheless the nucleoid
region is where you would expect to find the DNA it's also the region where
ribosomes are going to be constructive and synthesized okay and but again
there's no membrane except for the plasma membrane that goes around the
entire cytoplasm there are other structures that prokaryotes have that
you know can be unique to prokaryotes but lots of eukaryotes have the same
capabilities or similar functions and similar features like flagellum okay you
carry us also on flagella which are you know long protein fibers that allow for
movement okay they can be associated with moving they were gonna swim through
liquid solutions but also can be associated with feeding so they can beat
their footage element cause kind of a current and that can go into kind of a
feeding apparatus or feeding groove that allows for them to consume food with
that foot gel I'll show you a picture of footage on but if you know kind of what
a *** looks like with the long tail that that essentially is the flagellum
of the *** they also have kind of unique structures called pi light or a
pylus which allow for some prokaryotes to exchange small
chunks of DNA called plasmids and plasmids are unique circular chunks of
DNA and that that tend to mutate fairly quickly and they also tend to be very
adaptive so when bacteria are subjected to like
high temperatures or high PHS or high salinity or antibiotics or you know
these different things the plasmid region will often mutate fairly fast and
then that plasmid region can be passed from one bacteria to another bacteria
and it's easy for them to pass it between you know within species okay but
even more than that a lot of times those plasmids can be passed with in general
and sometimes even between general and so you can get antibiotic resistance in
case' where a plasmid is involved you can get
that built up and not just the species you're after but all species that are
related to it and even across some general okay we'll talk more about this
when we progress with bacteria but here you can see typical prokaryote nucleoid
region where you from the DNA and the DNA is in a circle single chromosome
okay Langella used to propel this organism through liquid solution okay it
has three layers a capsule so wall cell membrane cytoplasm cytosol same same
thing there is showing the pie or the palace's where DNA can be exchanged it's
not showing plasmids here but you would have these little circular chunks of DNA
that occur throughout kind of the cytoplasm depending on the
type of bacteria depends on you know how many there might be and the capabilities
okay and then there you can see there episomes is sites where proteins are
going to be synthesized so eukaryotes right a little bit more
large in size but again remember based on the surface to volume ratio
eukaryotic cells are not very big still they are a little bit larger than
prokaryotic cells maybe sometimes a double or triple in size but still it's
long okay and they tend to be much more complex than prokaryotic cells and so
we'll look at this complexity as we move progressed okay but again just like
prokaryotic cells they're gonna have a plasma membrane I made of phospholipids
proteins you know these kind of things that encase the cytoplasm in cytosol but
inside that cytoplasm they're also going to have membrane bound organelles or
membrane-bound compartments that we call organelles and each one of these might
have a particular function a particular job inside the cell maybe it's to make
lipids maybe it's to digest food maybe it's to you know process carbohydrates
maybe it's to make carbohydrates package things lots of different situations lots
of different organelles out there with different jobs or purposes okay again in
the cytoplasm more so than prokaryotic cells eukaryote cells are going to have
protein fibers which make a cytoskeleton these protein fibers can be utilized as
transport vessels so things can attach to the protein fiber and move from one
organelle to the nights' it can hold organelles in place and it can keep kind
of the structure of the cell from collapsing on on itself so when we look
at organelles though some of them you can see under the microscope fairly
easily okay like the nucleus and we'll you know I'll show you some
pictures of this and then if you're live lab you're going to experience seeing
Nicolas okay like I said before eukaryote is opposite of ProCare you
know you meaning true carry out meaning nut okay or core and so eukaryotes
meaning means true not prokaryotes means no or nod nut and and that's kind of
where the name comes from it's because of the nucleus and so the nucleus is
just a membrane-bound compartment that houses DNA now inside that cell again
like I said before you're going to have these internal membranes which we call
endomembrane or the endomembrane system okay and you can have all these
compartments that have different purposes provide very specific jobs to
the cell okay that are membrane bound called organelles now you know just like
all prokaryotes are not the same all eukaryotes are not the same no we didn't
really go into the differences in prokaryotes like the difference between
archaea and bacteria but we will later lectures but the differences between
some of the cells that in eukaryote are much easier to see with the naked eye
for example cell walls occur in plants and fungi and some Protista okay which
means that they have a plasma membrane and then they have a cell wall that
balance is on the outside of that plasma membrane this often is made of cellulose
a very complex carbohydrate now some protists that can have organelles called
chloroplasts which give them the ability to do photosynthesis and all plants have
chloroplasts and different amounts and different capabilities I'll talk about
this as we progress plants contain the central vacuole and
central vacuole is kind of like a storage vessel that can store water and
store nutrients can store two ions but they also can store digestive enzymes
and is utilized for digestion often and that's kind of unique to plants and then
animals can have centrioles and lysosomes and these are kind of unique
to animal cells centrioles will play a really important role when we start
talking about mitosis and meiosis these are the sites where microtubules are
originated from and and we'll come back and we'll talk about these a little bit
more okay so here you can just see the general structure of an animal cell
plasma membrane okay and remember this is a fluid mosaic so this is not rigid
okay has ability to move repressed take shape flex quite a bit but inside you
have a lot of like scaffolding proteins okay that hold these organelles often
will hold these organelles in place okay so they're not getting banged around and
moving around quite often okay there you can see the nicholas guys some other
things like the endoplasmic reticulum both rough and smooth a mitochondria
Golgi apparatus lysosomes lots of things going on here and we'll come back and
look at some of these in much greater detail then you can check out the plant
cell plant cell a lot of students don't see this but plant cell just like out
also has a plasma membrane same phospholipid bilayer okay it just
happens to be on the inside of a very rigid cell wall okay and other than that
you know there's a look at that central vacuole kind of storage vessel with
enzymes there's some chloroplasts that you don't see in animal cells okay and
then general structures that are very very similar between the two okay so
that really brings me to the how did you carry oats evolved so you
have prokaryotes which are very simplistic basically DNA storage
vesicles with the capability of you know synthesizing proteins consuming energy
and you know whatnot but they don't have individual compartments for their
organelles okay so even the bacteria that can do photosynthesis they do not
have four plus they have photosynthetic membranes but no claw clasp okay so
there's no membrane bound photosynthetic pigments so how did it come about
through endosymbiosis is where most the evidence suggests and we'll go into kind
of how this works but this you know entity this may be prokaryote is going
to consume this prokaryote and through a process that we call phagocytosis but
most of time once this occurs digestive enzymes would leak into this vesicle
here this capsule here and destroy whatever is in here and then this would
be utilized as energy or treated as a foreign body in the wasted beginning
gotten rid of but in some cases this it doesn't happen the digestive enzymes are
not utilized and instead this is encapsulated and it's maintained with
inside the organism and so this then gets incorporated into the organisms
daily life or whatnot and if this is photosynthetic then it would create
carbohydrates and then pass carbohydrates across the membrane into
this portion of the cell and it could be utilized and so the idea is that
if these are beneficial bacteria or beneficial prokaryotes that some of them
would be engulfed and not destroyed but utilized as powerhouses to the cell or
photosynthetic pigment areas and there's quite a bit of evidence for this and so
when we look at some of the evidence we see things like mitochondria and
chloroplasts that have their own DNA their DNA is separate from nuclear DNA
and in fact your as a human your mitochondria you get that from your
mother and we know that mitochondria is what really gives you kind of the
baseline of your metabolism and that really comes from your mother and your
dad has no input on that because you get your mitochondria from your mother
because you get the mitochondrial DNA from which is a circular chromosome very
similar to a prokaryotic chromosome and just like plants they would get both
their mitochondria DNA from the mother plant and the chloroplast DNA from the
mother plant and so there's a little bit there that's that's a little bit of
evidence that suggests hey look we are circular DNA this is very similar to
prokaryotes but there's a lot more than that mitochondria are about the same
size is modern bacteria the Christy that we see inside the mitochondria so these
are like finger like projections instead of mitochondria where electron transport
system proteins are going to be kind of embedded so ATP can be synthesized in
those regions um they resemble the folded membranes in modern bacteria
mitochondria have their own ribosomes and so because they have their own
ribosomes they can set the size their own ribosomes we can look at you know
structurally and genetically are the ribosomal RNA of
bacteria similar to mitochondria and they are mitochondria when they divide
they divide by binary fusion okay just like a modern bacteria does so instead
of pinching off and forming cleavage Pharaoh they just elongate until the
membranes get really thin and then they form a new membrane and disconnect and a
lot of this evidence a lot of this material came from laying marvelous okay
whoo I'm really like admire lens work and admire her scientific evidence for
endosymbiosis but not just that she being a woman who you know was
working on science when there wasn't very many women in science and then also
being ridiculed by a lot of individuals for her ideas she wrote these three
books and a lot more but the best one if you're looking at symbiosis is a
symbiotic planet excellent excellent book but then after that you know she
really talked about how organisms can acquire genomes and acquiring them from
other species talking about you know kind of the 10% of our DNA is virus DNA
and then you know what is life and she was excellent author but more than that
you know she wrote lead in endosymbiosis theory
she wrote it up in a paper and she was rejected by numerous scientific journals
until someone picked it up and now it's now it's you know thought as the piece
of work that really drove the symbiotic theory and now very few people would
ever question that this is not the evidence for how crooked pretty
prokaryotes give rise to you cares and even more than that how we got different
genomes and how we carry a lot of bacterial DNA with us and Protista DNA
and virus DNA and all kinds of things and her work was excellent great author
I suggest any of these Doron Sagan is as her son and his an excellent writer also
and so his co-author on a lot of her books but Lynn was an excellent
biologist and kind of drove the endosymbiosis theory and gets all the
credit for it I mean she she did it all right with that next time we're gonna
talk about specific organelles and we're going to talk about nucleus mitochondria
chloroplasts lysosomes central vacuole and I'm going to show you some pictures
of them and just go into a lot more detail about what's their function where
they found kind of what interacts with what and then will progress from there