Lesson video

Hello, and welcome to this lesson in the unit Cells.

The title of today's lesson is Animal Cell Structures and Their Functions.

Cells are the living building blocks of all organisms on earth, but animals share lots of similarities in their cells, and the structures that they contain all have different jobs, and that's what we're going to be learning about today.

My name's Mrs. Barnard, and I'm gonna be taking you through your learning today, and by the end of today's lesson, you should be able to identify the common structures of animal cells, and you should be able to describe what the jobs of these structures are.

Now, first of all, we're gonna have a little look at what our keywords are for today's lesson.

Now, there are some complex keywords in today's lesson, so we'll try to repeat them quite a few times during the lesson, so that hopefully, by the end, you'll have a good understanding of what they are.

So the keywords we're gonna be looking at today are: cell membrane, cytoplasm, nucleus, mitochondria, and finally, model.

Now, model is a word you probably have come across before, but we definitely need a scientific definition of it for today's learning.

So let's have a look at what our agreed definitions for these words are going to be today.

So, a cell membrane.

So a cell membrane surrounds the cell, and it controls what substances enter and leave the cell.

The cytoplasm, that's the jelly-like substance that's inside the cell, where the chemical reactions of the cell take place.

And the nucleus, that contains the DNA, and DNA is the information that controls the activities of the cell.

And then we have mitochondria.

They use food and oxygen as a fuel to provide energy for a cell in a process called cellular respiration.

Now, you may remember respiration from a previous lesson as one of the common processes of living things.

It was one of those Rs.

And finally, a model.

So scientists use models as simpler representations of complex things and ideas.

Now, you don't need to remember all that now, because we're gonna be going back over it, but those are just for you to look at through your learning today.

So, our lesson is in four sections today.

The first one is that cells are 3D.

Now, you may have heard of the word 3D before, or three dimensional, but we're gonna go into a little bit more detail on that one in that first section of the lesson.

Then we're gonna look at what the common structures of animal cells are, and then in the third part of the lesson, what the jobs of those different structures are within animal cells.

And then finally, we're gonna be looking at how we model animal cells, so we're talking about scientific modelling of cells in section four of the lesson.

So let's get on with cells are 3D.

So, cells are the living building blocks that all living organisms are made of, but they're often drawn in 2D, or two dimensions.

So this is how you may see them drawn in a textbook, or you may have drawn pictures in your notes of an animal cell, and it would look like this.

2D is a flat image.

So it does allow us to see the structures that are inside the cell, so it is an important way of drawing cells, but it's not a completely clear representation of what an animal cell looks like, because cells are actually 3D, or three dimensional, and they come in lots of different shapes and sizes.

So this is a drawing of a ball that's in 2D, so it's a flat image.

So if we were to have a look at the same picture of a ball, but in 3D, this is what it would look like.

So you can see the use of shading there allows you to see that it's in three dimensions, rather than a flat image that's in two dimensions.

So let's have a look at how this relates to cells.

So this is a drawing of an animal cell in 2D.

Now, I'm sure that you've seen pictures of animal cells in 2D, I mean, there was one on the previous slide, but let's have a look at what the animal cell looks like in 3D.

Here it is.

Now, there's a few extra structures in there that you don't need to worry about in today's lesson, but you can see you've got lots of similar structures in the 2D image and in the 3D image, and you can see the difference between those two images.

Let's have a look at what that same thing would look like with a plant cell.

So you've got a 2D image of a plant cell there.

You can see that it's quite a flat image, but it's got everything that we need to know, but then if we were to see that in 3D, you can see all of the parts there with a few extra ones there inside that 3D image of a plant cell.

And then a bacteria cell, can't forget about bacteria.

They're tiny, but they're still there and they're still living.

So this is a drawing of a bacteria cell in 2D, and then this is a drawing of a bacterial cell in 3D.

Again, you can see the difference between the flat image and the image that looks three dimensional.

So time for a quick check.

Which of these is the best drawing of a 3D shape? Is it A, B, C? Which one do you think? Okay, let's see if you got it right.

It's A, so we've got a cube, so that's the best drawing of a 3D shape.

Okay, what about this one? So this is about cells.

So our blood contains red blood cells.

Which of these images shows the red blood cells in 3D? Is it A, B, or C? Which one do you think? Okay, it is B.

So B shows the 3D image.

Well done.

Okay, let's have a little practise of this 2D, 3D concept now.

So this is the photograph, and it shows a simple 2D animal cell that's been made out of plasticine, and you can see that you've got the cell, that's the flat orange section, and then you've got a structure inside the cell, that's that sort of circular blue section there.

Now, if you've got some plasticine or Blu Tack or Play-Doh or something similar, that would be useful for the activity, but if not, don't worry, because you can just describe what you would do for this task.

And the task is as follows.

I'd like you to use some plasticine or similar material to make a 3D version of that cell that's been made there in 2D.

Or if you don't have any of those materials to hand, you can just describe how you would've made it 3D if you did.

So you want to pause the video while you do that, and then we'll come back and we'll check in.

Okay, so how did you do with making your 3D model or describing your 3D model? So if you've made one, it should look something like this, and then the description of that would be that the plasticine or Play-Doh has been rolled into a ball to make the cell 3D, and the structure in the middle is a little ball that's inside the cell.

Okay, so you can see that that structure is now a 3D version of the model on the slide before.

So if you got that right, then well done.

Okay, so it's time now to move on to the second part of our lesson, and that is the common structures of animal cells.

So, most cells are too small to see with your naked eye, so that means without a microscope.

So we've got an image here of a leopard, and underneath all that fur, it's got some skin, and if you could get close enough in, you would be able to see that the animal skin is made of cells, animal cells.

Now, in order for us to be able to see them, we'd have to really, really magnify them for our eyes to be able to visualise those cells, and we can do that using a light microscope, and you may have had the chance to use a light microscope in previous lessons.

However, there are more structures inside the cell, and you can see one of them there that's stained in that purpley colour that's in the middle, 'cause that's quite a big structure, but there are other smaller structures that are inside those cells, and we really need a more powerful microscope to be able to see those structures that are within the cell.

So they're very, very small.

So, another quick check now, so it's a true or false.

Animal cells can be seen with the naked eye.

Is that true, or is it false? And once you've decided, you need to choose one of the statements below to justify your answer.

And would it be, animal cells are big enough to see with just our eyes, or, animal cells are too small to be seen without a microscope? So I'll check back in a second.

Okay, so let's see what we got.

So, animal cells can be seen with the naked eye, that is false, they're too small, and the reason is, animal cells are too small to be seen without a microscope.

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

So, humans and all other animals are made up of cells.

Here are some examples of some different animals.

Often when people think about animals, they think about mammals, like humans or cats in the first two images, but actually, animals come in all sorts of different shapes and sizes, including invertebrates like beetles or ladybirds, as in this picture, or sea creatures like jellyfish.

They're all animals, and they're all therefore made up of cells.

Specifically, they're all made up of animal cells, and because they're all made up of animal cells, that means that the cells share lots of common structures.

So let's have a look at what these common structures in the animal cells are.

So here's an image of an animal cell, it's a 2D image, and the structures that we need to know by the end of today's lesson are the cell membrane there that goes around the outside, and then we've got the cytoplasm, that's in the middle of the cell, the jelly stuff that's in the middle of the cell, and then we've got the nucleus, and then finally, we've got the mitochondria.

Now, those are some tricky scientific words, and it's gonna take you a while of repeating them to get those into your brains, so it might be worth just taking a few minutes to have a look at this slide before we move on to the next activity.

So feel free to pause the video if you'd like to do that, but otherwise, we're gonna move on to a check.

And here is our check.

Which of these structures is not part of an animal cell? Is it, A, the nucleus; B, the cell membrane; C, the brain; or D, the mitochondria? Which is not part of an animal cell? Okay, let's see if you got it right.

So the answer is brain.

Brain is the one that is not part of an animal cell, so well done if you got that right.

So a little practise test for you now.

So starting with the basic structure below, or something similar, it just has to be a smooth line, okay, that joins together, draw a diagram to show the common structures of animal cells.

So you need to include everything that we've just discussed, and you need to label those structures inside the cell.

So you'll want to pause the video now so that you can do your drawing, and then we'll come back and we will check in in a bit.

Good luck.

Okay, let's see how you got on with that one.

So with the basic structure, you should have drawn in there a nucleus, so that's sort of like a circle, and then these mitochondria that are like sausage shaped, and then the cytoplasm is all of the jelly stuff that's around the outside of those structures, and then the cell membrane that goes all the way around the outside of the cell.

Now, it's important with a scientific diagram that you use continuous lines and no sketching.

It just makes the image really nice and clear, and it's a model of whatever it is in science that we are actually looking at.

So let's move on to the next section of our lesson, which is the function of those animal cell structures.

So again, here is an image of a cell.

You can see it's a slightly different shape, and each of the structures of animal cells have specific jobs.

So our first one here is our cell membrane.

So cell membranes, that's one of our keywords, and its job is that it surrounds the cytoplasm and it controls what substances can enter, so come into the cell, and to leave the cell.

So it protects the cell, because it doesn't let things in that the cell doesn't need, it will let things out that the cell needs to get rid of, like waste products, it'll also allow in the things that the cell needs for food, so its nutrients.

So the cell membrane's got a really important job in controlling what enters and leaves the cell for the survival of that living organism.

And then we've got here the cytoplasm, and the cytoplasm is the jelly-like substance that fills the cell, so that's most of the mass of the cell, and that's where all of the chemical reactions in the cell take place.

Now, you may have a very different understanding of what a chemical reaction is.

It isn't all explosions and heat and sound.

Chemical reactions can be quite quiet and slow.

Things like building proteins, for example, or breaking down substances that you need, or, as in respiration, releasing energy from oxygen and food.

So chemical reactions are what happens in that jelly substance that fills most of the cell, the cytoplasm.

So let's move on to a couple more structures.

So then we have the nucleus.

So the nucleus is like the busy part of the cell.

It's where all of the instructions are, and the instructions are in the form of DNA.

So DNA is the instructions for our cell for all of its activities.

It gives information that allows other substances to be made in order for the cell to function.

You've probably heard of the word DNA before.

So DNA is just the instructions that living organisms have.

And then we've got these funny sausage-shaped things.

These are our mitochondria.

It's important to realise that mitochondria, if you cut them one way, look like sausages, but if you cut them the other way, they might look like circles in a 2D image.

So you've got your mitochondria there, and their job is to provide energy for the cell, so in the process called respiration.

Now, remember that's one of the common processes of all living organisms, respiration, it's one of the Rs in that MRS GREN code that we used in one of our earlier lessons, and that energy is released so the cell can carry out all of its functions, including those chemical reactions that we just talked about that happen in the cytoplasm.

Okay, so time for a quick check now.

So what I would like you to do is match the structure, or the part of the cell, to its function.

So we've got cytoplasm, cell membrane, nucleus and mitochondria, and then our descriptions are, where the chemical reactions of the cell take place, it contains DNA and controls the activities in the cell, it provides energy for the cell's activities by respiration, and it controls which substances enter and leave the cell.

So we need you to match those up.

Okay, on you go.

Okay, let's see how we got on, then.

So the cytoplasm is where the chemical reactions of the cell take place, the cell membrane, that controls what substances enter and leave the cell, then we've got the nucleus that contains DNA and controls the activities in the cell, and then we have mitochondria, which provide the energy for the cell's activities by respiration.

Okay, well done.

Okay, so let's do a practise task now.

So Izzy is trying to help her friends understand what a cell is and what the structures inside do.

So she explains the cell with an analogy.

So, this is how she explains it.

So if your body was a town, a cell is like one house in the town, and it contains smaller structures that have their own jobs.

So what I would like you to do is write an analogy like Izzy that compares the jobs of each cell structure to something in your house.

So if the cell is your house, what different parts of the house would be those structures that we've already described? What are they similar to? This is like this, because.

Those are the kind of phrases that you'd be looking to use in your answers.

So you're gonna have to pause the video, 'cause you've got some longer sentences to write now, and we'll come back and check in soon.

Okay, let's see how you got on.

So, we're looking at an analogy, so it's a comparison.

So here are some examples.

Now, these don't have to be exactly the same, because your comparisons might be different, but it's just to give you an idea of what an analogy would be for the parts of the cell.

So the cell membrane is like the walls and the windows and the doors of your house.

They control what things come in and out of the house.

And then the cell cytoplasm is like all the rooms in your house where all of the activities take place.

They take place inside your house, within the walls and the windows and the doors, and there's lots of different activities that take place in your house.

And then the nucleus is like the computer or the bookcase or where all of the information is stored.

And finally, the mitochondria are like the batteries or the plug sockets in your house that provide energy for all the activities that take place inside your house.

Okay, so now finally, we move on to the last part of our lesson today, which is modelling animal cells.

So models are used in science to explain things that are difficult to see or to understand, and the analogy that you just did in the previous activity, that was a form of model.

You were trying to explain a difficult idea with something that's easier to understand, something that you come across every day.

So, animal cells can be modelled in 2D, so we talked about that at the very start of the lesson, and they can be modelled in 3D.

Both of these are models, because they're not the real cell, so they're representations of what that cell looked like in 2D and 3D in order to make it easier to understand.

And as we said before, an analogy is also a model.

So a model represents something in the real world.

It's a simpler representation of the real thing, a simpler version.

So here's an example, so we've got a real car here.

It's quite an old car, but it's a real car, okay? And let's have a look at a simple model of that.

So that would be a simple model of that car.

You can see it is 3D, and it would move, okay? But let's have a look at this one.

This is a more detailed model of a car.

Can you see how it's much more similar to that first picture? It looks like it's got doors that open and close, it's got wheels that move, it's got a similar shape, a similar colour, so it's a much more detailed model of the car.

Now, the second model, the simple model, still gives us a good understanding of a car, it still would represent a car, and we would understand that that's what it was, but a more detailed model would be better.

So different models of the same thing can include different amounts of detail.

So, time for a quick check.

So I'd like you to choose the correct answer, the correct description of what a model is.

So, a model.

Is it, A, includes every part and detail of the real thing? Is it, B, a simpler version of the real thing? Or is it, C, the real thing? Which one do you think? Okay, it's B.

So hopefully you got that one right.

It's a simpler version of the real thing, 'cause the real thing is quite complicated, so we want a simpler version in order to explain it.

So a model can be a physical model, like with that car example there, and you can touch it and you can feel it and you can turn it over and you can look at it closely, or it could be a description, and our description might be in words, or it might be in diagrams like this one above, or it could be a mathematical model.

So you might have had this shown to you in lessons previously, or you might have seen it in maths, okay, where you show measurements and how things are related to other things.

So how about modelling an animal cell? So here we go, we've got a model here, made out of some things found around the house.

I'm sure you've all made models before.

And what we've got here is we've got a box, it's like an open box, and we've got a nucleus there represented by a ping pong ball, a cell membrane around the outside of the box, and then we've got some pasta there to represent the mitochondria.

So this is a 3D model of an animal cell.

It's quite a simple model, but it is a 3D model.

So some models are better than others, and we can use our understanding of science to say whether this model is a good model or whether it can be improved, and what we call that is evaluation.

To evaluate a model is to be able to say the ways that the model is similar to the cell and the ways that the model is different to the cell.

So it shows our scientific understanding of cells, because we're able to say whether the model is a good representation or whether it's a representation that can be improved.

So we're gonna have a go at evaluating a model of an animal cell.

So here is a model of an animal cell that, again, has been made using things that you could find around the house.

So I'm gonna do one first with you, and then you're gonna have a go at doing it in a similar way.

So let's have a look at this one.

So it has a bag like a cell membrane, so that is a way that it is similar to an animal cell.

It's filled with a fluid like the cytoplasm.

So the cytoplasm is a jelly-like substance, and this is filled with a fluid like that, so that makes it a good model.

It has a 3D nucleus in there, and it has 3D mitochondria, and they're all surrounded by the cytoplasm, so that makes it a good model.

However, the bag does not let substances in and out like the cell membrane does.

So in that way, this model can be improved, because it doesn't show exactly what the cell membrane would do.

So I'd like you to have a go now at evaluating this model of an animal cell in a similar way.

I'm gonna leave the first one up, so you've got it to refer to.

So we want some sentences that are similar to those ones in this model answer.

Okay, on you go.

Okay, let's see how you got on.

So here are some examples of things you might have said.

You may not have used exactly the same words, and that's okay, as long as you found some ways in which the model is the same and some ways in which the model is different.

So it has a 3D nucleus, similar to the other model that's on there.

It has a sponge to show the 3D cytoplasm.

But the mitochondria are not in 3D in this model, so that's something that can be improved.

And finally, there isn't a cell membrane in this one.

So if you managed to find some ways where the model was the same or different to an animal cell, then you have evaluated a scientific model.

Well done.

Okay, so let's carry on practise with this modelling activity.

So Sofia here says, I can improve this cell model by adding a cover over the top.

What we would like you to do is write an evaluation of this cell model by describing how you could improve it.

So, you could state the materials that you would use, it could be anything that you could find around the house, and explain why your improvements would make it a better scientific model.

So what could you use, and how would it make it a better scientific model? Okay, I hope you came up with some really creative ideas.

So let's have a look.

Remember, these are just examples, so you may have come up with something slightly different, but that's okay.

So, there is no cytoplasm in this cell model.

This is where the chemical reactions take place.

So you could improve that by pouring jelly into the box and letting it cool.

That's one thing that you could do, or any other liquid, you might have said, to pour into the box.

There's no cell membrane that controls what substances enter and leave, okay, 'cause it's quite a solid box there with no holes.

So you could improve that by putting cling film over the top, and then you could put little small holes in the cling film to show that things can pass in and out of the cell.

And you can see here that the mitochondria and nucleus are already shown in 3D, so you'd probably keep those the same.

So if you put some information there that's similar to that, well done, and hopefully you used some longer sentences that included some descriptions of the functions of those cell parts in your answer as well.

So, we come to the summary of today's lesson.

So, cells are 3D, and they are the living building blocks of all living organisms. The cell membrane surrounds the cell and controls what substances enter and leave the cell.

The cytoplasm is the jelly-like substance inside the cell where the chemical reactions of the cell take place.

And the cell nucleus contains DNA, which stores information that controls the activities in the cell.

Mitochondria provide energy for the cell from cellular respiration.

And finally, a model is a simpler representation of something.

Scientific models can be evaluated for their strengths and their weaknesses.

Well done for your work today.

There was a lot of information and a lot of new scientific words.