Lesson video

Hi, I'm Mrs. Hudson, and today I'm going to be teaching you a lesson called Eukaryotic and Prokaryotic Organisms. This is a biology lesson, and it comes under the unit titled Eukaryotic and Prokaryotic Cells.

Let's get going.

The outcome of today's lesson is: I can describe differences in the cell structures of eukaryotic and prokaryotic organisms. So we're going to be asking ourselves, what are eukaryotic and prokaryotic organisms, and what are the differences between them? There will be some key words in today's lesson that will help us to understand the content.

Those key words are eukaryotic, multicellular, prokaryotic, and unicellular.

Let's look at what those mean.

So eukaryotic are cells that contain a membrane-bound nucleus, and this contains the DNA.

Humans are examples of eukaryotic organisms, because our cells contain a nucleus.

Multicellular are organisms that are made up of more than one cell.

Again, humans are examples of multicellular organisms. Prokaryotic are cells with no membrane-bound nucleus.

DNA is free-floating in the cytoplasm.

The prokaryotic organisms do not have cells that contain a nucleus.

And unicellular is an organism that consists of only one cell.

So today's lesson will be split up into three different parts.

First of all, we're going to define eukaryotic and prokaryotic, then we're going to move on to identifying eukaryotic and prokaryotic cells, and then finally, we will be comparing eukaryotic and prokaryotic cells.

Let's get going with the first part of the lesson, to define eukaryotic and prokaryotic.

So on this slide here, you can see there's an image of a bacterial cell on the left hand side and an animal cell on the right hand side.

First thing I want you to think about is, do both of these cells contain a nucleus? Now, hopefully for this, we recognised that the bacterial cell does not have a nucleus, but the animal cell does have a nucleus.

So it's this subcellular structure, which on the animal model cell is shaded in a slightly grey colour here, and the DNA will be held inside the nucleus in an animal cell, but in our bacterial cell, we've got this kind of squiggly, long, stringy loop, and that is the DNA, and the DNA here is just free-floating in the cytoplasm.

So looking at our definitions of eukaryotic and prokaryotic, in our bacterial cell, we can see there no nucleus with free-floating DNA, which helps us to give our definition.

So prokaryotic cells do not contain a membrane-bound nucleus.

DNA is free-floating in the cytoplasm.

So the main thing here is that prokaryotic cells have no membrane-bound nucleus, which just means they've got no nucleus.

Membrane-bound just means that there's a membrane around the outside of the nucleus, whereas an animal cell is a eukaryotic cell.

Eukaryotic cells do contain an membrane-bound nucleus, and DNA is usually contained within the nucleus.

So in summary, prokaryotic cells do not contain a membrane-bound nucleus; eukaryotic cells do contain a membrane-bound nucleus.

Let's quickly check our understanding of that.

The first question, what is the definition of a eukaryotic cell? A, a cell with no membrane-bound nucleus; B, a cell with no cell wall; or C, a cell with a membrane-bound nucleus.

Hopefully here, we got C, eukaryotic cells are cells with a membrane-bound nucleus.

Next question is true or false.

So prokaryotic cells have DNA free-floating in the cytoplasm.

Is that true or false? And then justify your answer.

A, prokaryotic cells have no membrane-bound nucleus, or B prokaryotic cells have a membrane-bound nucleus.

Okay, so for the first part, so this is true, prokaryotic cells do have free-floating DNA, and the reason for this is A, prokaryotic cells have no membrane-bound nucleus.

Really great job if you've got both of those questions right.

Moving on to our third and final question.

Which of these images show a prokaryotic cell A, B, or C? This is A.

A is showing you a bacterium which has no nucleus, and you can see that the DNA is just free-floating in the cytoplasm, whereas B, which is an animal cell, and C, which is a plant cell, both do have a nucleus.

We're ready now to move on to our first task of the lesson.

So question one, label each cell as prokaryotic or eukaryotic, and then secondly, describe the difference between eukaryotic and prokaryotic cells.

And for question two, a bit of a hint here, you want to be talking about the membrane-bound nucleus, but also the DNA.

Pause the video now, I'm sure you're gonna do a great job, and then press play ready for me to go through the answers.

Okay, so hopefully we found that nice and simple.

So looking at these two cells here, the first cell is prokaryotic.

It's a bacterial cell, and you can see that it has no membrane-bound nucleus.

The second cell is an animal cell, which is eukaryotic, and on that diagram, you can see the membrane-bound nucleus.

In the second part of this question, describe the difference between eukaryotic and prokaryotic cells.

Prokaryotic cells do not have a membrane-bound nucleus.

Their DNA is free-floating in the cytoplasm, and eukaryotic cells do have a membrane-bound nucleus.

This usually contains DNA.

You might not have that exactly the same word-for-word, but if you need to pause the video now to check your answer or add anything in, please do.

And then we're gonna move on to the second part of today's lesson.

Brilliant job! So now we know the definitions of eukaryotic and prokaryotic, we can move on to the second part of the lesson, which is identifying eukaryotic and prokaryotic cells.

So here are some images of different cells.

Can you name any of these cells? Now, we've already mentioned three of these in today's lesson already.

The first two in particular we should remember.

So the first cell is a bacterium cell, the second cell is an animal cell, the third cell is a plant cell, and the fourth one is probably the one that may be least familiar to us.

This is a fungus, and specifically, it's a yeast cell.

Now, these are the four cells that we are gonna use as examples today.

One of these cells is the only example of a prokaryotic organism, which, remember, means it doesn't contain a membrane-bound nucleus.

And the prokaryotic cell is the bacterium cell.

And we can look at that diagram and see that there is no membrane-bound nucleus.

The DNA is free-floating in the cytoplasm, whereas the animal, plant, and fungus cell, they all have a nucleus which will contain the DNA inside, and therefore, those three are examples of eukaryotic organisms. So the bacterium is prokaryotic, the animal, plant, and fungus are eukaryotic organisms. Now, if you look at bacteria a little bit more closely, bacteria are prokaryotic cells and they're also some of the simplest organisms that exist.

Bacteria are usually unicellular organisms. Bacteria are often thought to be some of the first organisms that evolved on Earth.

They're very simple structures, and they're just made up of one cell, which means they're unicellular.

So if we look at the word unicellular, the prefix uni- means one and cellular means made of cells.

So therefore, unicellular means made up of one cell, and bacteria are just made up of one cell.

They are unicellular organisms. Prokaryotic cells are bacteria.

And we can see in this diagram here, we've got some E.

coli bacteria.

Now this diagram is showing you lots of different E.

coli bacteria, but each individual rod shape on that diagram is showing you one E.

coli bacteria, and they are unicellular.

Animal, plant, and fungi are eukaryotic organisms. Their cell structures are usually complex.

Most eukaryotic organisms are multicellular, but some are unicellular.

So if we remember, unicellular means made up of one cell.

Multicellular, if we look at that word, multi- means many and cellular means made of cells, so therefore, multicellular means made up of many cells.

And just like we said, eukaryotic organisms can be unicellular or they can be multicellular.

So this is a unicellular protist, which is called an amoeba.

And that organism is just made up of one cell, it is unicellular, whereas lots of different eukaryotic organisms are multicellular.

This is just one example, it's a catfish, and it's made up of many cells, so therefore, it is multicellular.

Let's check our understanding so far.

So true or false: prokaryotes are usually unicellular organisms. True or false? Justify your answer.

A, bacteria are prokaryotes and they are usually unicellular organisms, or B, bacteria are prokaryotes and they are multicellular organisms. Okay, so prokaryotes are usually unicellular organisms. This is true.

And the reason for it is that bacteria are prokaryotes and they are usually unicellular organisms. Well done if you got that right.

Next question.

So match the cell to its names.

So we've got three pictures of cells, A, B, and C, and then three names, bacterial cell, plant cell, and animal cell.

Can you match them up? Hopefully we got this.

So A is a plant cell, B is an animal cell, and C is a bacterial cell.

Remember, plant and animal cells are eukaryotic, whereas a bacterial cell is prokaryotic.

Almost all living cells contain genetic material, cytoplasm, a cell membrane, and ribosomes.

So here, we've got an animal cell and a bacterial cell.

An animal cell is eukaryotic, whereas a bacterial cell is prokaryotic.

And they do share some common similarities.

So almost all living cells contain cytoplasm, cell membrane, and ribosomes.

Let's look at what they are labelled on these diagrams. So the genetic material, the DNA, in the animal cell is found inside the nucleus, whereas the genetic material is free-floating within the cytoplasm of the bacterial cell, but they do both still contain genetic material.

Both of the cells have a cell membrane.

It's the outermost layer of the animal cell, whereas a bacterial cell also has a cell wall, so the cell membrane is not quite the outermost layer.

Both cells contain ribosomes.

Now, ribosomes are the subcellular structure where protein synthesis takes place.

They're the smallest subcellular structure, and they are not membrane-bound subcellular structures.

So both animal and bacterial cells contain ribosomes.

And then finally you've got the cytoplasm.

The cytoplasm is a jelly-like liquid that surrounds all the subcellular structures, and both animal and bacterial cells, so eukaryotic and prokaryotic cells, will contain cytoplasm.

On this slide, we've got the animal cell, fungal cell, which is a yeast, and a plant cell.

These are all eukaryotic organisms. Eukaryotic cells contain membrane-bound structures such as the nucleus, mitochondria, and chloroplasts.

So all of these cells contain the three substances we mentioned in the previous slide.

They contain cell membrane, cytoplasm, and ribosomes, but they also contain a nucleus, which we can see labelled here, and that will contain the DNA within it.

They contain mitochondria, which is where aerobic respiration takes place and releases energy.

Plant cells also contain a subcellular structure which is membrane-bound called a chloroplast.

Photosynthesis takes place inside the chloroplast, which is why plant cells have them but animal and fungal cells do not.

So let's just quickly check our understanding of this.

Which of these cells is a fungus: A, B, or C? This is C.

A is a plant cell, B is an animal cell, and C is a fungus, specifically a yeast cell.

Well done if you got that right.

Which of the following is not a membrane-bound subcellular structure? A, ribosomes, B, mitochondria, or C, nucleus? This is A, the ribosomes.

Remember, ribosomes are not membrane-bound, but mitochondria and nucleus are membrane-bound subcellular structures.

Therefore, eukaryotic organisms will have all three of these subcellular structures, but a prokaryotic cell will not contain mitochondria or nucleus.

We're ready now to move on to task B.

The first part of this task is to complete the table below.

So you've got four images of different cells and you need to write the name of that cell in and then write whether they are eukaryotic or prokaryotic.

Then in the second part of the task, you're going to tick the features that are true for or can be found in each type of cell.

So there's four different types of cell: plant, animal, fungus, and bacterium, and then there are certain features.

So you need to tick if they are unicellular or multicellular or potentially they could be both, and then you need to tick if there is that subcellular structure found inside of that cell, I'm sure you're gonna do a fantastic job.

Pause the video now and then press Play when you're ready for me to go through the answers.

Let's have a look at how we did.

So the first cell is an animal cell, and this is eukaryotic.

Second cell is a plant cell, and this is eukaryotic.

The third cell is a fungal cell, but you may have also written it specifically as a yeast cell, and this is also eukaryotic.

All three of those cells have got a membrane-bound nucleus.

The final cell is a bacterial cell, and this is prokaryotic.

It's prokaryotic because it doesn't have a membrane-bound nucleus.

Moving on to the second part, so plant, animal, fungus, and bacterium can all be unicellular organisms, whereas plant, animal, and fungus can be multicellular, but not a bacterium.

Plant animal and fungus all contain a nucleus, but remember, bacterium is prokaryotic, so it does not contain a membrane-bound nucleus.

Plant, animal, and fungus contain mitochondria, whereas bacterium doesn't.

This is because mitochondria is a membrane-bound subcellular structure, and therefore, eukaryotic organisms do contain mitochondria, but prokaryotics such as bacterium do not.

The plant cell is the only example of a cell that contains chloroplasts, but all four of our cells contain ribosomes and all four of our cells contain DNA.

It's just that in the eukaryotic organisms, plant, animal, and fungus, that DNA is found within the nucleus, whereas in a bacterium, the DNA is free-floating in the cytoplasm.

Great job if you managed to get all of those right.

We're ready now to move on to the last part of our lesson.

In the final part of today's lesson, we're going to be comparing eukaryotic and prokaryotic cells.

So let's have a look.

We're going to look at an individual feature of each of the prokaryotic and eukaryotic cells.

So the first thing we're going to look at, and we have mentioned this before, is whether there's membrane-bound subcellular structures within the cells.

The prokaryotic cells do not contain membrane-bound structures.

There's no nucleus, and therefore, the DNA is free-floating in the cytoplasm.

So you can see on this bacterial cell here, there's no nucleus, but you can see that DNA just free-floating in the cytoplasm.

In contrast to this, eukaryotic cells do contain a membrane-bound structure such as nucleus, but also mitochondria and chloroplasts.

And we can see here we've got three eukaryotic cells, animal cell, fungal cell, which is a yeast, and plant cell.

Now, animal and fungal and plant cells all contain a nucleus, but you can see the nucleus is labelled here on the animal cell.

And similarly, all three cells contain mitochondria, but it's labelled here.

One single mitochondria has been labelled on the fungal cell.

Now, plant cells do also contain a different subcellular structure, which is the chloroplast.

This is where photosynthesis takes place, and therefore, animal cells and fungal cells don't have chloroplasts, but plant cells do.

So in summary, prokaryotic cells do not contain membrane-bound structures, but eukaryotic cells do.

Next, we're going to look at the DNA.

So in prokaryotic cells, there's no membrane-bound nucleus, so the DNA is free-floating in the cytoplasm, which we can see in this diagram here of a bacterial cell.

Bacteria also can have a ring of DNA, which is called a plasmid.

And you can see that labelled on this diagram here, it's just a circular loop, and that is a ring of DNA called a plasmid.

Eukaryotic cells contain a membrane-bound nucleus with the DNA inside of it.

And you can see here on our three eukaryotic cells that you've got the nucleus labelled, and the DNA will be inside that nucleus.

We just can't see it on this diagram.

Now let's look at the size difference between prokaryotic and eukaryotic cells.

Prokaryotic cells are usually much smaller and their length is between one to five micrometres, so that funny little U there with a little line down it, that's the symbol for micrometres.

And there are 1,000 micrometres in one millimetre, just to give you a reference.

And we can see here if we look at that bacterial cell, in general, most bacterial cells will be between one to five micrometres.

Whereas eukaryotic cells are generally larger and their lengths are between five to 100 micrometres in length.

So there's the animal cell, which is eukaryotic, and in general, most eukaryotic cells will fall between five to 100 micrometres in length, which is larger than prokaryotic cells.

Now looking at cell division, so this is how cells make a copy of themselves.

And in prokaryotic cells, bacteria divide by a process called binary fission.

So we can see we've got one bacterial cell here, and it is replicating itself to make two identical bacterial cells, and that process is called binary fission.

Whereas eukaryotic cells, they can also divide, but the process by which they divide is called mitosis.

So here we've got our fungi yeast cell, and this is replicating itself to form two identical yeast cells, and this process is called mitosis.

Now looking at cell walls, prokaryotic cells, like bacteria, they do have a cell wall and it's made from a substance called peptidoglycan.

So we can see labelled on this bacterial cell, the very outermost layer is the cell wall, and that's made from peptidoglycan.

Bacteria cells do still have a cell membrane, it's just not the outermost layer of that prokaryotic cell.

Now, eukaryotic organisms is a little bit different.

Plant cells have a cell wall, and it's made from a substance called cellulose.

Also, yeast cells have a cell wall, too.

However, animal cells do not have a cell wall.

So we can see here we've got two pictures, we've got a fungal yeast cell and a plant cell, and both of those have a cell wall, but an animal cell does not have a cell wall.

Let's check our understanding of that.

So how so prokaryotic cells divide? A, mitosis, B, myosis, or C, binary fission.

Prokaryotic cells divide by C, binary fission.

Well done.

If you wanted to find out what eukaryotic cells divide by, that would've been A, that's mitosis.

Which of these would you not find in a prokaryotic cell? A, ribosome, B, mitochondria, or C, cell membrane? This is B, mitochondria, because mitochondria are membrane-bound subcellular structures.

True or false? All eukaryotic cells contain a cell wall.

And then justify your answer.

A, animal, plant, and yeast cells contain a cell wall, or B, plant and yeast cells contain a cell wall, but animal cells do not.

This is false.

The reason that it's false is because B, plant and yeast cells contain a cell wall, but animal cells do not.

Well done if you got that right.

And then finally, prokaryotic cells are usually smaller than eukaryotic cells.

True or false? Justify your answer.

A, prokaryotic cells are one to five micrometres, or B, prokaryotic cells are usually five to 100 micrometres.

This is true, and the justification is A, prokaryotic cells are one to five micrometres.

Great job! We're ready now to move on to our final task of the lesson.

So the first part is to complete the table and compare the features of prokaryotic and eukaryotic cells.

You've got a table here with a column for the feature, prokaryotic cells, and eukaryotic cells.

And the features that you're going to be describing are: membrane-bound subcellular structures, so whether they're present or not and what they might be called, DNA, so if it's present and where it's found, size, so the size, smaller or larger, and then try to be specific.

Can you remember how big those organisms are? And then cell divisions are the type of cell division that takes place.

And then finally, if those types of organisms have a cell wall.

So that's the first part of the task.

And the second part, you're going to use these diagrams to answer the following questions.

So we've got two cells there and then the lengths along them.

So in A, you've got identify three similarities between the prokaryotic and eukaryotic cells in the diagram, and B, identify three differences between the prokaryotic and eukaryotic cells in the diagram.

I'm sure you're gonna do an amazing job.

Press Pause and then have a go, and Play when you're ready for me to go through the answers.

Let's have a look at how we did.

So starting off with membrane-bound subcellular structures, prokaryotic cells do not contain membrane-bound subcellular structures.

Eukaryotic cells do contain membrane-bound subcellular structures such as nucleus, mitochondria, and then plants contain chloroplasts.

DNA, in prokaryotic cells, DNA is free-floating within the cytoplasm and they can also contain a ring of DNA, which is called a plasmid.

Well done if you remember that little bit about plasmid.

And in eukaryotic cells, DNA is usually contained within the nucleus.

Moving on to the next bit, size, prokaryotic cells are smaller usually and between one to five micrometres in size, whereas eukaryotic cells are larger and between five to 100 micrometres.

Prokaryotic cells divide by binary fission and eukaryotic cells divide by mitosis.

Prokaryotic cells do have cell walls, and they're made of a substance called peptidoglycan.

Eukaryotic cells, animal cells have no cell wall, plant and yeast cells do have cell walls, and the plant cell wall is made from cellulose.

If you need to pause the video and check your answers, then please do before I move on to the second part of this task.

So looking at the second part, three similarities between the prokaryotic and eukaryotic cell.

Well, they both have cytoplasm, they both have a cell membrane, they both have DNA, and both have got ribosomes.

So any three of those four is excellent.

Well done.

Three differences between the prokaryotic and eukaryotic cells, the prokaryotic cell has no nucleus, DNA is free-floating in the cytoplasm, whereas the DNA in the eukaryotic cell is held within the nucleus.

In this, the prokaryotic cell is smaller than the eukaryotic cell by nine micrometres.

The prokaryotic cell has a plasmid, whereas the eukaryotic cell does not.

And finally, the prokaryotic cell has no membrane-bound subcellular structures, whereas the eukaryotic cell has mitochondria and chloroplasts.

It does also have a nucleus, but we've already mentioned that.

What a brilliant job if you managed to get all of those right! If you need to pause the video to add any extra detail and feedback into your own answer, please do.

But I think we're ready to summarise everything that we've learned this lesson.

So in summary, we learned that bacteria are prokaryotic cells and that they're unicellular, which means they're made up of only one cell.

Prokaryotic cells contain no membrane-bound subcellular structures such as a nucleus, and therefore, their DNA is free-floating in the cytoplasm.

We did, however, say though that there are some subcellular structures common to both prokaryotic and eukaryotic cells.

Prokaryotic cells are usually smaller in size.

They have cell walls made from peptidoglycan and they divide by binary fission.

Animals, plants, and fungi are eukaryotic organisms. They can be unicellular or they can be multicellular.

Eukaryotic cells contain membrane-bound subcellular structures, and their DNA is usually held within the nucleus.

We specifically said there that the membrane membrane-bound subcellular structures were mitochondria and the nucleus, which were in all three examples of eukaryotic organisms we talked about, but plant cells also contained a third, which was the chloroplasts.

Eukaryotic cells are usually larger in size and they divide by mitosis.

And then finally, plant and yeast cells have cell walls, but animal cells do not.

You've done amazingly well this lesson! Well done.

I'm really looking forward to seeing you next time.