Lesson video

Hello, today's lesson is from the unit classification in modern biology.

The title is Classified Organisms as Eukaryotic or Prokaryotic.

Hello, my name's Dr.

Pugh and I'll be taking you through today's lesson.

Today's lesson outcome is by the end of today's lesson, you should be able to describe the common features of the cells of eukaryotic and prokaryotic organisms. Now, the key words you're gonna require for today's lesson are nucleus, genome, eukaryotes, plasmid, and prokaryotes.

And I'm gonna share those definitions with you now.

I'm not gonna read through those, but if you'd like to pause the video now and make notes or copy them into your notes, do so now.

Okay, today's lesson outline, the lesson's gonna come in three parts.

The first part is gonna do with the common features of animal and plant cells.

Second part is going to be describing eukaryotic cells.

And the third part is gonna be describing prokaryotic cells.

Okay, so let's look at common features of animal and plant cells.

So the cell is the basic building block of life, and all organisms are made of cells.

Different type of living organisms, they've got different cells.

So the cells of plants, animals, and bacteria have some similar features, but we also have some different features and we're gonna expand and describe the similarities and features as the lesson goes on.

So let's look at some of these common features if we look at cells using a light microscope.

So we have animal cells on the left, we have plant cells on the right, and the animal cells look like cheek cells.

You may have done this practical at school, you take cheek cells and then stain them with with a dye.

And here, you can see that the nucleus is stained with a red dye and the cytoplasm is stained with a blue dye.

And therefore we can see some of those features that some cells possessed.

The nucleus, cytoplasm, and cell membrane.

If you look at the light micrograph on the right hand side, the plant cells, we can't make out some of those internal subcellular structures like a nucleus, but we can see where the cytoplasm is located.

We can see a cell wall membrane very close together, and we can see those small green structures inside the cell, which are the chloroplasts.

So let's look at the cell, the features of animal cells.

So most animal cells have the following subcellular structures.

So subcellular structures, they're the little structures inside cells which perform particular tasks.

So we have a cell membrane, and the cell membrane will control what goes in and what goes out of the cell, such as water, glucose, amino acids, carbon dioxide.

The cytoplasm, this is the site where chemical reactions take place.

We have a nucleus containing genetic material of this particular organism.

We have a mitochondria, and this is a site of anaerobic respiration, which is the release of energy from glucose using oxygen.

And we have ribosomes, which are the sites of protein synthesis.

Now, let's compare that with a plant cell.

So the plant cell is gonna share some common features and you can see those already, but let's go through them again.

We've got the cell membrane, does exactly the same job as it does in animal cells, cytoplasm, mitochondrion, ribosome, and the nucleus.

So all of these subcellular structures perform the same role as they do in animal cells, but plant cells have got some additional features that are unique to those.

So we have a cell wall, which is made from cellulose and it gives the cell strength and shape.

We have chloroplasts.

They are little green objects we saw on the the previous slide from the light microscope.

They're green because they contain chlorophyll and they absorb light energy for photosynthesis.

And they have a large permanent vacuole, which contains a solution of salts and sugars.

So let's do our first knowledge check.

So which of these following subcellular structures do both plant and animal cells contain? So pause the video now, make your selection, and I'll give you the correct answers in a moment.

Okay, let's go through the answers.

So which of the following subcellular structures to both animal and plant cells contain the nucleus and cytoplasm? So well done if you've got those correct.

Cell wall is not correct because that is a feature of plant cells only as is D, the chloroplasts.

Okay, let's have a go at practise question now.

So there's a table here.

We have subcellular structures on the left hand side.

We have a column, animal cells and plant cells.

And I'd like you to tick to show the subcellular structures that are found in animal and/or plant cells.

So pause the video, make your selections, and I'll feedback in a moment.

Okay, let's go through the answers.

So cytoplasm is shared by both animal and plant cells.

That's a site where chemical reactions take place.

Cell wall is only possessed by plant cells.

Nucleus is possessed by both animal and plant cells.

Chloroplasts are found in plant cells only.

Plasmids are not found in either animal or plant cells.

They're unique to bacteria.

And we'll look at the structure of bacteria or prokaryotes a little later.

Cell membrane found in animal and plant cells, and a mitochondrion or mitochondria, plural of mitochondrion, are found in both animal and plant cells.

So maybe corrections or well done if you've got all of those correct.

So let's do another practise question.

So we've got Sam and Jacob here and they're discussing common features of animal and plant cells.

We have made some mistakes, so have a look at what they are saying and can you correct those mistakes? I'll pause the video or we'll feedback in a moment.

Okay, so let's take Sam's comment.

First of all, "Animal and plant cells have a nucleus, a cell wall, and a permanent vacuole." What was incorrect there? And if he corrected that he should have something like this.

"Animal and plant cells have a nucleus, a cell membrane, cytoplasm, mitochondria, and ribosomes." Let's look at Jacob's original statements.

"Animal cells have subcellular structures that plant cells don't contain such as chloroplasts." Well, what was incorrect about that? Plant cells have parts that animal cells don't have such as chloroplasts.

So again, well done if you've got those correct.

Okay, moving on to second part.

Today's lesson, we have the eukaryotes.

So animals and plants are classified into a group of organisms called eukaryotes.

Eukaryotes include the following animals, plants, fungi and small unicellular organisms called protists.

In each of these organisms, the cells contain membrane-bound subcellular structures.

That's quite a mouthful.

What you mean is that there are small structures contained within them that have a membrane surrounding them.

An example would be a nucleus or a mitochondria or a chloroplast.

Many eukaryotes are multicellular.

That means they're made up of many cells that are stuck together and organised to do different roles.

But there are unicellular animals, plants, fungi, and protists.

And by unicellular, I mean they exist as individual single cells.

Let's look at some examples now.

So zooplankton are unicellular animals, and these are found in water environments such as lakes, streams, rivers, and the ocean.

Phytoplankton, these are unicellular, plant-like organisms, which can photosynthesize particularly found in the upper waters of the oceans where you can obtain light for photosynthesis.

And we have the protists, an example of which is an ameba here, which are also found in lakes, rivers, and streams. So let's look at the membrane bound subcellular structures that are contained within eukaryotic cells.

So firstly, the nucleus.

This is a membrane bound subcellular structure, which contains the genetic information, the DNA of the cell.

The mitochondria, notice it's plural this time.

Previous slide, it was mitochondrion, which is the singular name.

So mitochondria are membrane-bound organelles that carry out aerobic respiration, the release of energy from glucose using oxygen.

Chloroplast, these are membrane-bound structures that carry out photosynthesis, they contain the green pigment, chlorophyll.

So we have nucleus, mitochondria, and chloroplast all as examples of membrane-bound subcellular structures.

Quite a mouthful.

All right, let's do knowledge check.

Which of the following are eukaryotes? And your choices are A, animals, B, viruses, C, bacteria, and, D, fungi.

So pause the video, make your choice, and I'll give you the correct answers in a moment.

Okay, let's check your answers.

So the correct answers are, A, animals and, D, fungi.

Viruses are not eukaryotes and bacteria are prokaryotes.

They're not eukaryotes.

Okay, let's look at amoeba, right? Amoeba are protists and the subcellular structures in an amoeba include the following, cytoplasm, site of chemical reactions; nucleus contain the genetic material; cell membrane controls the exit and entry of substances; ribosomes, site of protein synthesis; chloroplasts, site of photosynthesis, and they possess small temporary vacuole.

So not like the permanent vacuoles we see in plant cells.

These are small and temporary.

So what evidence is there that amoeba are eukaryotes? So looking at that, looking at these subcellular structures that we have, we have some that are membrane bound.

Let's go through them.

So the nucleus is a membrane-bound organelle, and we have chloroplasts which are membrane-bound organelles.

And you should know by now that eukaryotes, one of the definitions of eukaryotes, is that they contain membrane-bound subcellular structures.

So that is the evidence that this amoeba is eukaryotes.

Let's look at the other class of eukaryotes.

Now, the yeast are fungi, they are unicellular fungi, and the subcellular structures in a yeast cell include the following, cytoplasm, nucleus, cell membrane, cell wall, ribosomes, mitochondria, and a temporary vacuole.

So if I were to ask you the question now, what evidence is there that you see eukaryotes? Hopefully, you would say, "Well, yeast contains membrane-bound subcellular structures, the nucleus, the mitochondria." Okay, so let's do a knowledge check based on this part of the lesson.

What is the evidence that yeast are eukaryotes? Is it A, they possess a cell wall, B, they possess a nucleus, C, they possess a cell membrane, or D, they possess mitochondria.

So pause the video, make your selections, and I'll give you the correct answers when you come back.

Okay? So what is the evidence that yeast are eukaryotes? Hopefully, you've selected the following.

They possess a nucleus and a mitochondria, which are both membrane-bound subcellular structures.

Okay, let's have a go at this practise question now.

So look at the cells below.

We have cell A and we have cell B.

So what I'd like you to do now is on the diagram, can you label the following? Can you label the nucleus, chloroplasts, ribosomes, cell wall, cell membrane, large permanent vacuole and the cytoplasm? So pause the video, label the cells, and I'll give you the right answers in a moment.

Okay, so let's check your labels now.

So let's go through cell A, first of all.

So hopefully, you've identified a chloroplast, cell membrane, innermost layer; cell wall, outermost layer; ribosome; nucleus; cytoplasm, and a large permanent vacuole.

Now, cell B, which features can we identify here? Cell wall, cell membrane, and ribosome.

Okay, let's check your answer.

So cell A is eukaryotic because it has membrane-bound subcellular structures such as nucleus and chloroplasts.

Cell B is not a eukaryote.

It doesn't contain any membrane-bound subcellular structures, and therefore it's a prokaryotic cell.

It is a bacterial cell.

Okay, so let's move on to the third part of today's lesson.

So, so far we've looked at common features of animal and plant cells.

We've looked at eukaryotes.

Let's look at the prokaryotes now.

Right, bacteria are classified into a group of organisms called prokaryotes.

And you can see here, it's an electron micrograph showing you bacteria.

They are single cell and unicellular organisms and they do not possess a nucleus.

Now, let's look at the common features of bacterial cells, which are prokaryotes.

They possess a cell wall, and this cell wall gives the bacterial cells strength and shape just like plant cells.

Cell membrane regulates the entry and exit of substances.

We have a single DNA loop.

It's a circular bacterial chromosome.

There is no nucleus.

Bacteria also possess small circular DNA molecules, which are referred to as plasmid.

And plasmid is a very important human health because they often contain antibiotic resistance genes.

So just to reiterate, prokaryotic cells do not have a nucleus.

They do not have any membrane bound.

Common features include the following, the cell wall, which gives strength and shape just like plant cells, cell membrane, a single DNA loop, and small DNA molecules, small circular DNA molecules called plasmids.

Prokaryotic cells do not have a nucleus.

They do not possess any membrane-bound subcellular structures.

So let's look at the bacterial genome in a little bit more details.

We've got a prokaryotic bacterial cell on the left hand side and a eukaryotic yeast cell on the right hand side, both unicellular organisms. And we can see in the bacterial cell that the genetic material exists as a single loop of DNA, it's not contained within a nucleus node.

They also possess small, circular DNA molecules called plasmids.

And plasmids have quite an important role in human health because some disease-causing bacteria possess plasmids, which have antibiotic resistance genes.

If we look at the eukaryotic cell, the genetic material, the DNA is contained within the nucleus, which is a membrane-bound subcellular structure.

Let's look at the relative sizes of prokaryotic cells versus eukaryotic cells.

So the prokaryotic bacterial cell on the left and bacterial cells range from about 0.

1 to 5 micrometres in diameter.

And to put that into context, one micrometre is 1000th of a millimetre.

So bacterial cells are very small.

Eukaryotic cells are small, but not as small as bacterial cells, and this size ranges from 10 to around 100 micrometres in diameter.

So let's do another knowledge check.

Which of the following statements are true? Any prokaryotic cells range from 10 to 100 micrometres in diameter.

Prokaryotic cells are much smaller than eukaryotic cells.

Prokaryotic cells have DNA stored in a nucleus.

Prokaryotic cells contain mitochondria.

So pause the video, make your choices, and I will go through the correct answer in a while.

Okay, so which statements are true? Prokaryotic cells are much smaller than eukaryotic cells.

Hopefully, you got the correct answer.

It's certainly not A because they're small than 10 to 100 micrometres in diameter.

It's not C because prokaryotic cells have a bacterial chromosome, a loop of bacteria, which is not stored within a nucleus, and prokaryotic cells do not contain mitochondria, and nor do they contain any membrane-bound subcellular structures.

Right, another practise question.

So what I'd like you to do now is fill in the gaps to complete the sentences, but you can only use the words eukaryotic and prokaryotic to fill the gap.

So pause the video, you know the score, and we'll feedback in a moment.

Okay, so let's fill in the blank.

So, A, prokaryotic cells are usually much smaller than eukaryotic cells.

B, the DNA of eukaryotic cells is enclosed in a nucleus.

C, bacteria are made up of prokaryotic cells.

Protists are made up of eukaryotic cells.

E, the genetic material of prokaryotic cells is in a single thin DNA loop, and there may be one or more small rings of DNA called plasmids.

F, prokaryotic cells do not have a nucleus.

And G, the cells of eukaryotic organisms have a nucleus, but the cells of prokaryotic organisms do not.

Some more practise questions.

Can you identify whether the following statements are correct or incorrect? If the statement is incorrect, can you rewrite it to correct it? So pause the video and we'll make your selections answer the questions and we'll feedback in a moment.

Okay, let's look at all unicellular organisms are prokaryotes.

Is that correct or incorrect? It is incorrect.

Some unicellular organisms such as bacteria are prokaryotes, but some such as amoeba and other protists are eukaryotes.

B, all prokaryotes are unicellular.

This statement is correct and we don't need to change it because all bacterial cells are unicellular, do not exist as multicellular organisms. Second feedback question, can you identify whether the following statements are correct or incorrect? Again, and if the statement is incorrect, can you rewrite it to correct it? The two statements are, C, all eukaryotes are multicellular, D, all eukaryotes have a cell wall.

Pause the video, answer the questions.

I'll give you the correct answer in a moment.

Okay, let's look at statement C, all eukaryotes are multicellular, incorrect.

Some eukaryotes such as plants are multicellular, but others such as the protists are unicellular.

D, all eukaryotes have a cell wall.

Is that correct or incorrect? It is incorrect.

Some eukaryotes such as plants and yeast do have a cell wall, but animal cells do not possess a cell wall.

So well done if you've got those and all of those feedback questions correct.

So let's summarise today's lesson, which has been on classifying organisms as eukaryotic or prokaryotic.

So eukaryotes and prokaryotes are made of cells that have a cell membrane, cytoplasm, and genetic material enclosed in nucleus.

Animals, plants, fungi, and protists are therefore eukaryotes.

All eukaryotes have membrane-bound subcellular structures, for example, mitochondria and chloroplasts.

However, bacterial cells are prokaryotic.

They're much smaller than eukaryotic cells and they have cytoplasm and cell membrane surrounded by a cell wall.

The genetic material in prokaryotes is a single DNA loop, and they may possess one or more small rings of DNA called plasmids.

In prokaryotes, the DNA is not enclosed in a nucleus.

So I hope you've enjoyed today's lesson and hope to see you again soon.

Goodbye.