Introduction to Cells: The Grand Cell Tour


Captions are on! Click “CC”at bottom right to turn off. Follow us on Twitter (@AmoebaSisters) and Facebook! If you had to think about the most exciting
day you ever had in a science classroom, which day would that be? Looking back through the years—we have a
few. The time we participated in an earthworm dissection. The time we took apart an owl pellet. The osmosis eggs. All of the fruit flies in genetic experiments. Oh, I could go on, but I will never forget
one day in my 9th grade science class. My teacher brought in pond water. And I put one drop of pond water on a microscope
slide and saw the most amazing thing ever…I saw, an amoeba. A single celled amoeba on that
microscope slide, and I was forever stuck on science from that point
on. Because I could not believe this little cell
was there, alive on this slide, still eating because that’s what amoebas do a lot. To imagine that every person is actually made
of billions of cells—of course not amoeba cells but animals cells— billions of animal
cells, is fascinating. In fact, it really makes you reflect on some
of the incredible statements of the modern cell theory. The modern cell theory includes the following:
1st that the cell is the smallest living unit in all organisms. 2nd that all living things are made of cells. One or more cells. The amoeba I observed was a single-celled
organism, so unicellular. Humans are made of many cells, so multicellular. And 3rd, all cells come from other, pre-existing
cells. Cells have their own little world inside them. They carry genetic information! They can divide! Many have functions and processes that their
organelles, structures inside them, can take care of. On our planet, we can divide cells into two
major groups. As a cell, you’re either a prokaryote or
an eukaryote. Bacteria and Arachae are prokaryotes. Everything else—plants, animals, fungi,
protists—-are eukaryotes. Both prokaryotes and eukaryotes have genetic
material. Both have cytoplasm. Both have ribosomes, which are small organelles
that make proteins. Both have cell membranes which control what
goes in and out of the cell. But what makes them different is a big deal. Prokaryote—pro rhymes with no—they have
no nucleus which holds the genetic material and controls the cell’s activities. Prokaryotes have no membrane bound organelles. Membrane bound organelles are fancy organelles
like the nucleus and mitochondria and golgi apparatus. Eukaryotes—eu rhymes with do—-they do
have membrane bound organelles. So now you may be wondering what do the organelles
do—what are their functions? Well you know our style—we love our science
with a side of comics. So we want to take you on a tour of the ride
of your life—into the inside of a cell! To start our trip, we’re first going to
have to get through this cell membrane, also called a plasma membrane. It’s selectively permeable which means that
it only lets certain select materials in and out. By doing so, it keeps things in the cell stable—also
known as keeping homeostasis. We
have an entire video on just the membrane itself—which is found in all cells, but
for now, we’re just going to have to squeeze through this protein in the membrane. Inside the cell, we find ourselves in this
jelly like material called cytoplasm. It surrounds all of these internal cell structures,
and you’ll find it inside both prokaryotes and eukaryotes. Now organelles that are just floating around
in the cytoplasm can have more support than you might think. Cells contain a cytoskeleton which is a collection
of fibers that will provide support for the cell and its organelles. The cytoskeleton can even play a major role
in movement. The cytoskeleton actually deserves its own
video though because it is very complex—and its organization varies depending on what
kind of cell you’re looking at. Moving through this cytoplasm, let’s start
with ribosomes. They are NOT membrane bound organelles and
they are going to be in both prokaryotes and eukaryotes. And they make protein. Which is really important because that’s
what so much of genetic material—DNA codes for—protein. Ribosomes can be free in the cytoplasm. They can be attached to another organelle
too, which we’ll talk about a bit later. We are now going to focus on eukaryote organelles,
which means, organelles that will be membrane bound. So this takes our travel to the big boss,
the nucleus. In eukaryotes, it holds the genetic material. Genetic material as in DNA for example. All cells have DNA but if you’re an eukaryote,
you have a nucleus to put it in. The nucleus controls the cell activities. Inside it, it has a nucleolus, which is where
ribosomes can be produced. Attached to the membrane of the nucleus, or
nuclear membrane, you can find the endoplasmic reticulum. ER for short. It does a lot of processing of molecules for
the cell—like protein folding—-and it also is highly involved in actually transporting
those molecules around. Like a highway! There is rough ER which has ribosomes attached
to it, making it—as you can imagine—rough. And them smooth ER which doesn’t have the
ribosomes. Rough ER specifically tends to be involved
with protein producing and transporting, because remember that ribosomes make protein. Molecules that leave the ER can be sent away
in vesicles that actually pinch off of the ER themselves. Smooth ER has many additional roles including
detoxification, which is one reason why your liver cells tend to have a lot of smooth ER. Another additional role of smooth ER is that
it can make some types of lipids. Next the Golgi apparatus. It’s the ultimate packaging center. It can receive items from the transport vesicles
that pinched off of the ER. It has enzymes that can modify molecules it
may receive and it sorts the materials it receives as well. It can determine where to send those molecules—including
some that may eventually be sent to the membrane so they can be secreted, which means, items
that can sent out of the cell. So with all that’s going on in here, you
might start to wonder…what’s powering this thing? The mighty mitochondria. Or mitochondrion, if just talking about 1. Like a power plant! This thing makes ATP energy in a process called
cellular respiration. It’s not a type of power plant that you
would think of…it runs on glucose, which is a sugar, and needs the presence of oxygen
to efficiently make ATP energy. Now at this point, we need to mention that
eukaryotes are not a one size fits all. Animal cells can have differences from plant cells. We have a…fork in the road here. For example, plant cells not only have mitochondria,
but they also can have these awesome organelles called chloroplasts. Chloroplasts actually make glucose by using
light energy in a process known as photosynthesis. They tend to have a green look to them because
they have a pigment that captures light energy and reflects green light. Both plant and animal cells can have vacuoles—now
vacuoles can have a lot of different functions but many types act as storage of materials. Plant cells can have one large vacuole called
a central vacuole while animal cells can have several smaller vacuoles. Remember how we already said that all cells
have membranes? Plant cells additionally have a cell wall
which is a layer that offers additional protection and shape maintenance that animal cells do
not. Hmm now how to get out of this animal cell
we’ve been in? Well…we could get out like a protein would. So if we were a protein, we would only be
made because of instructions from DNA and remember that in Eukaryotes, DNA is found
in the nucleus. We would be made by a ribosome. The ribosomes could be attached to the Rough
ER. The Rough ER highway would provide a vesicle
to send us to the Golgi apparatus where the sorting can take place. And…if we’re tagged for being secreted…we’re
sent off thru a vesicle from the Golgi to the membrane. And…out we go! Just keep in mind that in our quick tour,
there are still so many more awesome organelles found in different types of eukaryote cells
to continue exploring so to the Google for more! Well that’s it for the Amoeba Sisters and
we remind you to stay curious!

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