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If you had to think about the most exciting day you ever had in a science classroom, which

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day would that be?

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Now, looking back through the years---we have a few.

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The time we participated in an earthworm dissection.

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The time we took apart an owl pellet.

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The osmosis eggs.

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All of the fruit flies in genetic experiments.

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Oh, I could go on, but I will never forget one day in my 9th grade science class.

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My teacher brought in pond water.

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And I put one drop of pond water on a microscope slide and saw the most amazing thing ever…I

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saw, an amoeba.

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A single celled amoeba on that microscope slide, and

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I was forever stuck on science from that point on.

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Because I could not believe this little cell was there, alive on this slide, still eating

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because that’s what amoebas do a lot.

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To imagine that every person is actually made of billions of cells---of course not amoeba

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cells but animals cells--- billions of animal cells, that's fascinating.

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In fact, it really makes you reflect on some of the incredible statements of the modern

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cell theory.

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The modern cell theory includes the following: First that the cell is the smallest living unit

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in all organisms.

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Second that all living things are made of cells.

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One or more cells.

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The amoeba I observed was a single-celled organism, so unicellular.

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Humans are made of many cells, so multicellular.

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And third, all cells come from other pre-existing cells.

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Cells have their own little world inside them.

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They carry genetic information!

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They can divide!

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Many have functions and processes that their organelles, structures inside them, can take

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care of.

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On our planet, we can divide cells into two major groups.

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As a cell, you’re either a prokaryote or an eukaryote.

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Bacteria and arachae are prokaryotes.

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But everything else---plants, animals, fungi, protists----are eukaryotes.

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Both prokaryotes and eukaryotes have genetic material.

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Both have cytoplasm.

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Both have ribosomes, which are small organelles that make proteins.

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Both have cell membranes which control what goes in and out of the cell.

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But what makes them different is a big deal.

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Prokaryote---the "pro" rhymes with "no"---they have no nucleus which holds the genetic material

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and controls the cell’s activities.

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Prokaryotes have no membrane-bound organelles.

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Membrane-bound organelles are fancy organelles like the nucleus and mitochondria and Golgi

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apparatus.

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Eukaryotes---the "eu" rhymes with "Do"----they do have membrane bound organelles.

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So, now you may be wondering what do the organelles do---what are their functions?

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Well you know our style---we love our science with a side of comics.

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So, we want to take you on a tour of the ride of your life---into the inside of a cell!

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To start our trip, we’re first going to have to get through this cell membrane, also

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called a plasma membrane.

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It’s selectively permeable which means that it only lets certain select materials in and

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out.

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By doing so, it keeps things in the cell stable---also known as keeping homeostasis.

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We have an entire video on just the membrane

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itself---which is found in all cells, but for now, we’re just going to have to squeeze

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through this protein in the membrane.

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Now, inside the cell, we find ourselves in this jelly-like material called cytoplasm.

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It surrounds all of these internal cell structures, and you’ll find it inside both prokaryotes

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and eukaryotes.

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Now organelles that are floating around in the cytoplasm can have more support than

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you might think.

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Cells contain a cytoskeleton which is a collection of fibers that can provide support for the

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cell and its organelles.

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The cytoskeleton can even play a major role in cell movement.

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The cytoskeleton actually deserves its own video because it is very complex---and

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its organization can vary depending on what kind of cell you’re looking at.

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Moving through this cytoplasm, let’s start with ribosomes.

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They are NOT membrane-bound organelles and they are going to be in both prokaryotes and

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eukaryotes.

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They make protein,

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which is really important because that’s what so much of genetic material---DNA codes

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for---protein.

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Ribosomes can be free in the cytoplasm,

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but they can be attached to another organelle too, which we’ll talk about a bit later.

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We are now going to focus on organelles, the membrane bound. So, we are going to be focussing on organelles that you would find in an

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eukaryote cell. 

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This takes our travel to the big boss, the nucleus.

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Now in eukaryotes, it holds the genetic material.

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Genetic material as in DNA for example.

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Both prokaryotes and eukaryotes have DNA but if you’re an eukaryote, you have a nucleus to put it in.

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The nucleus controls the cell's activities and

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inside it, it has a nucleolus, which is where ribosomes can be produced.

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Attached to the membrane of the nucleus or nuclear membrane, you can find the endoplasmic

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reticulum.

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ER for short.

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It does a lot of processing of molecules for the cell---like protein folding----and it

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also is highly involved in actually transporting those molecules around.

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Like a highway!

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There is rough ER which has ribosomes attached to it, making it---as you can imagine---rough.

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And them smooth ER which doesn’t have the ribosomes.

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Rough ER specifically tends to be involved with protein producing and transporting, because

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remember that ribosomes make protein.

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Molecules that leave the ER can be sent away in vesicles that actually pinch off of the

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ER themselves.

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Now, smooth ER has many additional roles including detoxification, which is one reason why your

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liver cells tend to have a lot of smooth ER.

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Another additional role of smooth ER is that it can make some types of lipids.

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Next, the Golgi apparatus.

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It’s the ultimate packaging center.

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It can receive items from the transport vesicles that pinched off the ER.

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It has enzymes that can modify molecules it may receive and it sorts the materials it

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receives as well.

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It can determine where to send those molecules---including some that may eventually be sent to the membrane

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so they can be secreted, which means, items that can sent out of the cell.

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So, with all that’s going on in here, you might start to wonder…what’s powering

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this thing?

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The mighty mitochondria

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or mitochondrion, if just talking about one.

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They are like power plants!

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The mitochondria make ATP energy in a process called cellular respiration.

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It’s not a type of power plant that you might think of…it runs on glucose, which

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is a sugar, and needs the presence of oxygen to efficiently make ATP energy.

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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.

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We have a…fork in the road here.

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For example, plant cells not only have mitochondria, but they also can have these awesome organelles

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called chloroplasts.

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Chloroplasts actually make glucose by using light energy in a process known as photosynthesis.

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They tend to have a green look to them because they have a pigment that captures light energy

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and reflects green light.

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Now, both plant and animal cells can have vacuoles---now vacuoles can have a lot of different functions

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but many types act as storage of materials.

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Plant cells can have one large vacuole called a central vacuole while animal cells can have

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several smaller vacuoles.

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Remember how we already said that all cells have membranes? They do.

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But plant cells additionally have a cell wall which is a layer that offers additional protection

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and shape maintenance that animal cells do not.

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Hmm now how do we get out of this animal cell that we’ve been in?

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Well, we could get out like a protein would.

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So, if we were a protein, we would only be made because of instructions from DNA and

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remember that in eukaryotes, DNA is found in the nucleus.

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We would be made by a ribosome.

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The ribosomes could be attached to the rough ER.

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And the rough ER highway would provide a vesicle to send us to the Golgi apparatus where 

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sorting can take place.

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And…if we’re tagged for being secreted...we’re sent off through a vesicle from the Golgi to

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the membrane.

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And…out we go!

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Just keep in mind that in our quick tour, there are still so many more awesome organelles

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found in lots of different types of eukaryote cells to continue exploring, so to the Google for

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more!

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Well that’s it for the Amoeba Sisters and we remind you to stay curious!