Lesson video

Welcome to this lesson from the unit, "Cells".

The lesson title is, "Specialised cells are adapted for their functions".

This lesson follows on from previous lessons on animal and plant cells.

And in those lessons, you learned about the structures of those cells and what they had in common.

You also learned about the differences between animal and plant cells.

In today's lesson, we're gonna look at how even though cells can be of the same type, such as animal cells, they can be different shapes and sizes and have different structures.

And these are related to their function, which is their job.

My name's Mrs. Barnard, and I'm going to be taking you through today's lesson.

And by the end of today's lesson, you should be able to describe how animal and plant cells are specialised for their job.

So we need to have a look at our keywords in today's lesson.

Now there's gonna be a lot of scientific keywords, lots of them that you will have come across before in animals and plant cells, but these are three new ones.

So we've got adaptation, specialised, and function.

These are the definitions for those words.

Now we will be going through them later in the lesson, but if you want to pause the video in order to write them down or refer back to them, then please do so.

Our lesson today is going to be in two parts.

Part one is that cells are different shapes and sizes, and part two is that cells are adapted for their job or function.

So let's get started with our first part of today's lesson, cells are different shapes and sizes.

So here's two images of an animal and plant cell.

Now hopefully, you've seen images that look like this before.

So animal and plant cells share some common structures.

So, here we go.

First off, we're gonna start with a question.

So what are the cell structures that these two share? Now you might want to have a moment to discuss this with somebody, see how many you can come up with.

So pause the video while you do that.

Okay, how did you do? Did you remember them all? So first of all, we've got the nucleus, and the nucleus is where the genetic information of the cell is stored.

All living organisms need information in order to carry out the cell's activities.

But in animal and plant cells, it's stored in the nucleus.

Next we've got the cytoplasm, and the cytoplasm is where the cell's activities take place.

And then we've got the cell membrane.

The cell membrane's got a really important job because it controls what enters and leaves the cell.

And finally, in these cells, we've got the mitochondria, and the mitochondria use food as fuel to release energy for all of the cell's activities.

And we call that process respiration, and it's one of the common processes of all living organisms. So the plant you can see in this picture got some additional structure that animal cells don't have, and you should have learnt about those in previous lessons.

These are pictures of animal and plant cells.

Now, they are models.

Models, remember, are a way of explaining complex ideas in a more simple way.

So this is not what all animal and plant cells look like.

They are just simplified versions, so you tend to see them looking like this because it's quite easy for you to see all of the parts and label them easily.

So animals, even though they share common structures, some have additional structures, and some animal cells have different shapes.

So let's have a little look at some examples.

So our first one here is a cell that lines the airway.

It's got these little hairs on the surface, they're called cilia, but they help to move mucus and dust and microorganisms that might go into your airway and it stops them from going down into your lungs and it sort of wafts them back and out of your lungs and up towards your throat and down into your stomach.

Now other cells don't need to have those special hairs on the surface because that's not their job.

They're not in the airway.

So those are particular, or they're specialised adaptations of that cell.

Now this one, sperm cell, the sperm cell's got a tail that allows it to swim to get to the egg and in order for its genetic information to be fused with the genetic information of the egg.

So that tail's really important.

And then this nerve cell, this is another version of an animal cell and it's got this long section that comes out the back.

It's not a tail like the sperm cell, so it doesn't move and swim.

But what it does is it carries messages through your body and it's part of the nervous system.

And finally we've got the egg cell, which has these extra layers around the outside to give it protection and also to make it sticky so it can join to the inside of the uterus.

So you can see they're all animal cells, but they all look slightly different.

So it's time for a quick check now.

So from your knowledge of animal and plant cells, which cell here, A, B, or C, is not an animal cell? Pause the video and then we'll come back.

Okay, did you get it right? It is B.

And it's B because you can see that that cell there has got a cell wall, it's got chloroplast, and it's got a vacuole.

And all of those are features which are a plant cell.

So it's not an animal cell.

Okay.

So animal cells can also be different sizes.

The egg cell is 24 times bigger than the sperm cell.

So here we go, there's an egg cell and then let's have a look at how small the sperm cell would be.

There it is.

Not completely to scale, but it's just about there.

So you can see it's really, really small.

So when you look at them comparably, like we did on that first slide, you can see that they contain the same structures but the size is so different.

And then let's look at this next one.

So this is the nerve cell that we looked at.

And you can see this long bit that comes out the back, it's called the axon.

Now, the axon can vary in size from less than a millimetre.

So on your ruler, the smallest division is a millimetre.

So this is 0.

025 of a millimetre, so that's how small it can be.

But then it can go all the way up to 1000 millimetres, which is a metre, so like a metre stick that you would have in your classrooms. So you can see there's a really, really big difference, just in one type of cell.

So again, time for another quick check.

All animal cells contain the same structures and are the same size.

Now is that true or false? And once you decided, I want you to see which of those explanations below you think justifies your answer.

Is it that animal cells can be different shapes and sizes? Or is it animal cells can be different shapes but are all the same size? So pause the video and then we'll come back and have a look at your answer.

Okay, let's see how you did them.

So all animal cells contain the same structures and of the same size.

That is false.

And we would justify that answer by saying because animal cells can be different shapes and sizes.

So if you've got that one right, well done.

And let's move on to a practise.

So in each of these cells, I'd like you to identify the nucleus, the mitochondria, and the cell membrane.

So you may wish to draw these cells and label them as part of this task.

So if you're drawing them, make sure that you use scientific line drawing so that your drawings are large and they are clear and they are labelled.

So that's gonna take you a little bit of time.

So pause the video and we'll come back and we'll check that you've labelled them correctly afterwards.

Okay then, shall we see how you got on? So first of all, we've got the sperm cell there, and your sperm cell, the nucleus is that big section there.

Now it takes up quite a large part of the cell, but if you think about how small the nucleus is as we saw, sorry, how small the sperm cell is as we saw in the previous slide, you can see that the nucleus would take up quite a big proportion of it.

And then we've got the mitochondria, which are providing the energy for the sperm to move.

And then we've got the cell membrane around the outside.

So even though it's got a funny shape, the cell membrane still goes around the outside of all of the cell.

Next one, we've got this cell from the airway and we've got the nucleus there.

And then we've got the cell membrane around the outside of the cell.

And then again, we've got the mitochondria, providing the energy that the cell needs for its activities.

Okay, let's look at the next one, which is our nerve cell.

Again, you've got the nucleus there in the cell body and then you've got this cell membrane, which even though it's a funny shape, it goes all the way around the outside of the cell.

And then finally, we've got the mitochondria, again providing the energy for the cell's activities.

And finally, we've got our egg cell here and its nucleus, and then it's got its cell membrane around the outside.

It's got some other layers around the outside of that, but it's got its cell membrane that goes around the cytoplasm.

And finally, we've got the mitochondria to provide energy.

So if you've got all of those cells drawn and labelled correctly, then that's really good.

Well done.

So now it's time to move on to the second part of our lesson today, which is that cells are adapted for their function.

So all animals share common features, but their cells can vary in shape, their number of internal structures, and the type of internal structures that they have.

So here's a couple of examples for you.

So we've got an egg cell here.

So as well as having its cell membrane and nucleus and cytoplasm, it's also got these nutrient stores for cell growth because egg cells are involved in reproduction and it's important that any growing embryo has the nutrients that it requires.

It's got a jelly layer around the outside for protection.

Then we've got another cell here, which is an intestine cell, and your intestines are part of your digestive system.

You can see it's got this folded membrane.

So this is unlike the cell that we looked at before, which had the little hairs on the surface.

In this example, the actual membrane is folded around and that gives it a large surface area.

And because it's in your digestive system, this allows it to absorb the nutrients that the cell needs for its activities and also to move those nutrients into the blood and pass them around the body.

Differences between cells are called adaptations.

And below are two animal cells, and you can see that they have different adaptations.

These adaptations make them specialised for their functions.

And those are the three key words for today's lesson.

So cells have adaptations which make them specialise for their functions, their jobs.

So you can see here that both of these cells have mitochondria, as well as cell membrane, cytoplasm, and nucleus.

And the fat cell also has a fat store.

Let's have a little look at these two in detail.

So our muscle cell here has lots of mitochondria because the job of mitochondria is to use food as fuel to release energy.

And muscle cells need a lot of energy for movement, either the movement of our bones or the movement of our digestive systems or our hearts.

Either way, muscles require lots of mitochondria.

Fat cells don't require as much mitochondria, but they do have a fat store, and that means that when organisms require extra energy, there is fat stored somewhere that they can use.

Also, it can be stored there for insulation to keep them warm.

And you can see as well fewer mitochondria because these cells do not require as much energy.

Red blood cells, now this is an image of a red blood cell at a very powerful microscope and you can see it's in 3D and it's had colour added to it.

If you look at that and draw a scientific diagram of it, a model of it, and you cut it through, you can see it's got a shape a bit like a donut, but without the hole in the middle completely cut through.

So it's actually got quite a large surface area in order to be able to absorb oxygen.

It also has a cell membrane around the outside and its cytoplasm contains a substance called haemoglobin.

Now, haemoglobin carries oxygen.

So as well as that cell membrane having a large surface area for the oxygen to move into the cell, it also does not have a nucleus.

So there's more space for the haemoglobin to carry the oxygen and then for those blood cells to move around the body and deliver the oxygen to all the cells.

Now, here are some examples of plant cells.

Plant cells also have adaptations that make them specialised for their functions.

So first of all, I want you to look really closely and I want you to decide what structures are missing.

So pause the video while you have a think.

Okay, did you notice what was missing? So in this first cell, which is a phloem cell, it's part of the tubes that move up through a plant and move sugars through the plant.

You can see it doesn't have a nucleus or chloroplasts.

And if you look at this other cell, which is from the surface of a leaf, it also doesn't have chloroplasts.

Okay.

So these cells don't contain any chloroplasts as their job is not involved in taking light in order to make food for the plant.

So they don't need chloroplasts.

So a phloem cell also has no nucleus, and that means it's got extra space in order for sugars to move through it.

You can also see that it's got these gaps in the cell wall, so that allows the sugars to move from one cell to the other.

And in actual fact, in a plant, these cells are stacked up on top of one another so that sugars can move through it like a tube.

And you can see that this epidermis cell, which is on the surface of a leaf, has a waxy layer on the surface for protection that helps to protect it from pests that might want to eat the plant, but also against the elements in the weather as well.

You can also see it has no chloroplast, and that's because even though it's on the surface of a leaf, this particular cell is not involved in absorbing sunlight to make food, which means it has to be able to let the light through so that the cells underneath absorb the sunlight to make food.

So it's very thin so that light can pass through, and it has no chloroplast because it doesn't take in the sunlight to make the food.

It's time to have a little go at writing explanation of the adaptations of a specialised cell to its function.

So here's an example that we're going to do together.

So we're gonna suggest how this airway cell is specialised for its function.

And the information that we've got is all the things we already know about a cell.

So it's got nucleus, mitochondria, cytoplasm, cell membrane, and it's also got these hairs which move back and forth.

We also need to know what its function is.

So its function is to clear the airways.

So let's see what we would write.

We would write that the hairs trap particles that are breathed in.

That the hairs brush the particles back up the airways away from the lungs, and that the mitochondria would provide the energy for these hairs to move.

So it's your turn to have a go at one now.

So suggest how a sperm cell is specialised for its function.

There's a picture of the sperm cell there with all the information you need on the diagram, and then its function is reproduction.

So pause the video while you have a go at writing your own explanation.

Okay, let's have a look at how you got on then.

So we should have that the sperm cell has a tail to move to the egg, that it has lots of mitochondria to provide energy to move that tail, and then it has a nucleus in order to pass on its genetic information or DNA.

So if you've got those right, then well done.

You've been able to explain the adaptations of the specialised cell for its function.

Now we're gonna do it a different way around this time.

And for this one, we've got four pictures of specialised cells, and then we've got four functions of specialised cells.

Now, with your knowledge of cells and these pictures, these diagrams, I want you to match the correct picture to the cell function.

And the cell functions are: to absorb water from the soil for a plant, number one.

Number two, to pass messages from the brain to all parts of the body.

Number three, to transport oxygen in the blood.

And number four, to lengthen and shorten to move muscles.

So decide which one matches which, and then come back and we'll have a look at if you've got them correct.

Okay, let's see how you did them.

So A is to absorb water from the soil for the plant.

So that's a root hair cell.

B, that's a muscle cell, and it's number four, which is lengthen and shorten to move muscles.

C is number two because that's a nerve cell and it passes messages from the brain to all parts of the body.

And D is number three.

It transports oxygen in the blood because that's a red blood cell.

Okay, there's going to be a second part to this task now.

So the second part is to explain one way each cell is adapted to help carry out its function.

Now, the way that you're going to work that out is by looking at them, looking at their structures and looking at their shapes, and suggesting how one of those features allows it to be adapted for its function.

Okay, so pause the video while you write those and then we'll come back and we'll see how you got on.

Okay, let's see what you got then.

So for the first one, we've got that it has got a large surface area, so its shape gives it more surface area to absorb water.

Okay, so that's our root hair cell there.

And then B, it's got lots of mitochondria to provide energy because the job of muscles is movement.

And then we've got C.

So it's got a long shape.

You might remember from the previous slide that that long bit is called an axon and that allows it to transmit messages.

And then we've got our red blood cells.

Its got no nucleus, so you might have also said a large surface area, so there's more space to carry oxygen or to absorb oxygen.

So if you manage to write those explanations, then that's really good job.

Well done.

So it comes to the summary of today's lesson.

So we are summarising specialised cells are adapted for their function.

So animal and plant cells share some common structures.

Plant cells have some additional structures.

Cells can be different shapes and sizes and can contain fewer or more structures.

These differences between cells are adaptations.

Specialised cells have adaptations to carry out their functions.

Well done for your work in today's lesson.