Lesson video

Hi, I'm Mrs. Hudson, and today, I'm going to be teaching you a lesson called "Animal cells: common structures and specialised cells." 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 identify common structures of animal cells and describe how some specialised cells in animals are adapted for the jobs the cells do.

So we're going to be asking ourselves, what do most animal cells look like? And then, what is a specialised animal cell, and how are they adapted to the job they do? As part of today's lesson, there will be some words that will really help us to understand the content.

These are the keywords.

And the keywords for today's lesson are cytoplasm, cell membrane, nucleus, DNA, and mitochondria.

Let's have a look at what those words actually mean.

The cytoplasm is a jelly-like substance containing dissolved nutrients and salts where many chemical reactions happen.

The cell membrane is a partially permeable structure that surrounds the cell; it controls the movement of substances into and out of the cell.

Partially permeable just means that it allows some substances through but not others.

The nucleus is a sub-cellular structure that contains genetic material, and it controls cellular activities.

DNA is a molecule found in the nucleus of cells and contains the genetic code for making proteins.

Mitochondria are sub-cellular structures that contain the enzymes for respiration, and it is where most energy is released in respiration.

Today's lesson is going to be split up into three different parts.

First of all, we're going to be looking at sub-cellular structures.

Then we're going to move on to look at what specialised cells are.

And then finally, we're gonna look in greater detail at some specialised animal cells.

Let's get going with the first part of the lesson, though, the sub-cellular structures.

We use models of cells to help simplify their complex structures.

In reality, all cells are three-dimensional, and they're quite complicated to understand.

So in science, we use models of cells, and this is a model of an animal cell.

Not all animal cells look like this model.

They don't have this specific shape, but they do contain similar sub-cellular structures.

You need to know the model animal cell.

The parts that make up the model animal cell are called the sub-cellular structures.

How many of the sub-cellular structures can you name? Let's see how many of them we got right.

So these are the sub-cellular structures found in an animal cell.

There are five of them that we need to know about.

So first of all, we've got the nucleus, which is labelled here.

Remember, the nucleus contains the genetic material.

Then the smallest sub-cellular structure are the ribosomes.

These are very small circles in this diagram.

Then you've got the mitochondrion.

Mitochondrion is singular, which means you've got one of them.

And if you are talking of plural, about more than one, it would be mitochondria.

And then the cytoplasm on the diagram just looks like empty space, but in reality, it's a jelly-like liquid that surrounds all of the other sub-cellular structures.

And then the very outside of the cell is called the cell membrane.

Now, this is important because it controls what can enter and exit the cell.

So the five sub-cellular structures found in an animal cell are the nucleus, the ribosomes, the mitochondria, cytoplasm, and cell membrane.

Let's just quickly check our understanding so far.

Which of the images represents the model for the animal cell? A, B, or C? Now, hopefully here we all recognise that it was B.

Well done if you did.

For those of you wondering, A is a plant cell, and C is a bacterium.

Which sub-cellular structure is the line pointing towards in this image? A, cell membrane, B, mitochondrion, or C, nucleus? This is B, the mitochondrion.

Remember, mitochondrion is singular, and mitochondria is plural.

Which sub-cellular structure is the line pointing towards in this image? A, nucleus, B, ribosome, or C, cytoplasm? This one is A, the nucleus.

Well done if you managed to get those right.

Now we know what the different sub-cellular structures are in animal cells, let's have a look at what their functions are.

So this is their role in the cell.

We're going to start with the cell membrane.

Now, the cell membrane controls what enters and exits the cell.

The cell membrane is partially permeable, which means that it allows some substances to diffuse through but not others.

Usually, cell membranes are partially permeable and allow liquids and small solutes to enter the cell, but not large solutes.

This is really important because it keeps the internal conditions in the cell relatively constant and allows a cell membrane to control what can enter and exit.

Now we're going to look at the cytoplasm.

Remember, on our animal cell model, the cytoplasm just looks like empty space, but in reality, the cytoplasm is a jelly-like substance that surrounds the sub-cellular structures.

And the cytoplasm, importantly, contains nutrients and dissolved salts.

And this is where many of the chemical reactions take place in a cell.

The nucleus controls the activities of the cell.

The nucleus contains something called DNA, and DNA contains the genetic code to make new proteins.

Now we're going to have a look at the mitochondrion.

On the diagram, we've got one mitochondrion labelled, but plural is mitochondria, and there are usually many mitochondria in a cell.

Aerobic respiration takes place inside the mitochondria.

The mitochondria contain enzymes for respiration, and it is where most of the energy is released in respiration.

Our respiration is an extremely important process in all living things.

And aerobic respiration takes place inside the mitochondria, and then the energy that's released is transferred for other cellular processes, which effectively is what is keeping us alive.

So the mitochondria are very important.

And finally, we've got the ribosomes.

The ribosomes, remember, are very small sub-cellular structures, and this is where protein synthesis takes place.

Synthesis means to make.

So effectively, we're saying that proteins are made in the ribosomes.

But it's really good practise to use the word synthesis, so we'll say protein synthesis takes place in the ribosomes.

Now let's check our understanding of the function of some of our sub-cellular structures.

So first of all, which of these statements is true for the cytoplasm? A, it is where protein synthesis takes place, B, it contains DNA, the molecule of inheritance, or C, it is where many chemical reactions take place? Hopefully here we wrote C.

It's where many chemical reactions take place, in the cytoplasm.

Next question, where are proteins synthesised in animal cells? A, mitochondria, B, ribosomes, or C, the nucleus? This is B, the ribosomes.

Well done if you got that right.

We're now ready to move on to our first task on sub-cellular structures.

Your job is to annotate the diagram to show the sub-cellular structures and their function.

One has been completed for you as an example.

So we can see on this animal cell model here, on the top label, that is the cell membrane.

So we've written the name of the sub-cellular structure first and then followed it up with the function.

So the function of the cell membrane is that it controls what enters and exits the cell as it is partially permeable.

So try to remember as much about that function as you possibly can.

So have a go at this task.

Pause the video.

I'm sure you're gonna do a great job, and then press play when you're ready for me to feed back.

Okay, great job.

Let's see how we did.

So the first label which sits underneath the cell membrane is the nucleus, and the nucleus controls the activities of the cell.

It contains DNA, which is the molecule of inheritance.

Then underneath the nucleus, we've got the ribosome.

Ribosomes are where protein synthesis takes place.

You may have written proteins are made here, but remember, synthesis is a great word to use.

Then on the other side of the diagram at the bottom, we've got the cytoplasm, which looks like empty space, but actually, it's a jelly-like liquid that contains nutrients and salts, and many of the chemical reactions take place here.

And then finally at the top, we've got a mitochondrion.

Aerobic respiration occurs here, and it contains the enzymes for respiration.

There's quite a lot of information on this slide, so if you need to pause the video to add anything into your answers, then please do.

And then we can press play and carry on with the rest of the lesson.

But great job so far.

Well done.

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

We know about sub-cellular structures, so let's have a look at some specialised cells.

Specialised cells are cells that have a specific structure and function.

Structure is the shape of the cell, structures that it has, which includes the sub-cellular structures.

Function is the job of that cell.

Here are some examples of some specialised animal cells that you need to know about.

Nerve cell, red blood cell, sperm cell, egg cell, ciliated cell, and muscle cells.

Notice that in this diagram here, the muscle cells contain multiple individual muscle cells.

There are four muscle cells there.

Each one is an individual muscle cell.

Why do you think that we need specialised cells? Have a think about that.

Well, specialised cells look very different due to their specific shapes and sub-cellular structures.

So we can see that we've got three different specialised cells here, and none of them look like that animal cell model that we were just looking at.

They have a very different shape.

They contain different sub-cellular structures.

And this is really important because they each carry out a specific role.

So specialised cells are adapted to be able to carry out their specific function.

If we take humans, for example, humans are very complex organisms. There are lots of different systems taking place and different chemical reactions taking place all at one time.

And we need cells to be able to do very specific jobs.

And specialised cells are cells that have adapted to look a certain way and have certain structures so that they are excellent at doing the job that they need to do.

Let's just quickly check our understanding so far.

So which of these images below shows an egg cell? A, B, or C? Hopefully here we've gone with C.

That is the egg cell.

A is a red blood cell, and B is a sperm cell.

What is this specialised cell? A, nerve cell, B, muscle cell, or C, ciliated cell? This one is C.

It is a ciliated cell.

Well done if you got that right.

And finally, what is this specialised cell? A, sperm cell, B, egg cell, or C, a red blood cell? This is A, a sperm cell.

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

So your job here is first of all to write the name of each specialised cell below the picture.

And then secondly, can you answer the question, what are specialised cells? You're gonna do a great job of this.

Pause the video now, and then press play when you're ready for me to feed back.

Right, well done.

Let's go through the answers.

So first of all, we've got a nerve cell, then a red blood cell, a sperm cell, egg cell, a ciliated cell, and finally, muscle cells.

Now for question two, what are specialised cells? Specialised cells are adapted to have a specific function.

They have different shapes and sub-cellular structures.

Now, you might have written that in a slightly different way, but it's the key idea that they are adapted to have a specific function or a specific job and that they are different shapes and contain different sub-cellular structures.

We're now ready to move on to the final part of our lesson, which is specialised animal cells.

So we're going to look in a little bit more detail about those specialised animal cells and how they are adapted to do their job.

So first of all, can you remember what this specialised cell is? This is a nerve cell.

The job of nerve cells is to transmit electrical impulses throughout the body, and this is because they form part of the nervous system.

So that nerve cell there, its job is to transmit electrical impulses and connect to other nerve cells so that those electrical impulses can be passed quickly throughout the body.

So on this diagram here, the blue lines are representing the electrical impulse.

So in this nerve cell here, the impulse arrives in the first nerve cell, and then the impulse travels down the nerve cell axon.

Then we've got branched ends between the nerve cells, and they connect those nerve cells together so that the electrical impulse can be passed between the two of them.

And then the electrical impulse travels to the connecting nerve cell and passes down it.

Now, nerve cells are adapted to their function in the following ways.

And remember, the main function of the nerve cell is to transmit electrical impulses.

So the first thing is that they have a very long and thin axon, which is the part of the nerve cell that's labelled there, and that is so they can carry impulses over long distances very quickly.

Then they have a myelin sheath that surrounds the nerve cells so that the impulse can travel faster.

Now, on the diagram, the myelin sheath covers the axon, and it's those little rectangles that you can see travelling down the axon.

Again, they surround the nerve so that that impulse can travel faster.

And finally, you've got something called dendrites.

Branched connections, which are called dendrites, are at each end of the nerve cell, and this is so that they can connect to other nerve cells and transmit impulses quickly.

So the adaptations of the nerve cell are all about trying to make sure impulses travel quickly.

You have a long, thin axon, a myelin sheath, and then branched connections called dendrites.

Let's move on to another specialised cell.

Can you remember what this specialised cell is? This is a red blood cell.

And the function of red blood cells is to carry oxygen around the body for aerobic respiration.

Now, in the lungs, oxygen diffuses through the alveoli into the red blood cells.

And then the oxygen, once it's diffused into the red blood cells, binds to something called haemoglobin, which is inside of the red blood cells, and then it's delivered to most body cells for respiration.

So how are red blood cells adapted to their function? Now remember, the function of red blood cells is to transport oxygen around the body.

So the first adaptation is that red blood cells have no nucleus so that there is more space inside the cell to carry oxygen.

Now, red blood cells are still eukaryotic cells even though they don't have a nucleus; it's just that they're specialised.

This is one of the ways that they are a specialised eukaryotic cell.

If there's no nucleus inside of the red blood cell, more oxygen can be carried inside of it.

And then the second adaptation is that they have a biconcave shape.

Biconcave means it's a bit like a disc, there's a dip in the middle, and this increases the surface area of the red blood cell so that more oxygen can be absorbed in the lungs.

So both of these adaptations increase the amount of oxygen that the red blood cell can carry.

So can you remember what this specialised cell is? This is a sperm cell.

Now, sperm cells are the male sex cells.

They have to swim to meet the egg cell before fertilisation can occur.

So in reproduction, you will have a sperm cell and an egg cell, and they need to join together for fertilisation to occur so that a zygote and then an embryo can be formed.

Now, the sperm cell needs to be adapted to be able to be mobile.

It needs to be able to swim.

The sperm cells have to swim through the cervix and the uterus to find that egg cell.

So millions of sperm are released, but usually only one of them will fertilise the egg.

It's very important that they are able to move and swim through the cervix and uterus.

The sperm cells are adapted to their function in the following ways.

Remember, they need to be able to move and swim.

So first of all, they've got a tail so that they can swim towards the egg.

They've also got many mitochondria so that lots of energy is released for movement.

And remember, if we go back to the beginning of this lesson, that mitochondria is where aerobic respiration occurs, and that releases energy.

So the sperm has got lots of mitochondria so that energy can be released, which is then used for movement.

In the head of the sperm, there's something called an acrosome which contains enzymes, and those enzymes are there to break down the egg cell membrane.

This is really important because it ensures that the sperm is able to fertilise the egg.

And finally, the nucleus, which is what's labelled on this diagram now, the nucleus contains half the number of chromosomes.

Now, the word that we use for this in science is haploid.

So the nucleus is haploid in the sperm cell.

Now, this has to be the case because the sperm and the egg cell are going to fuse together to create a new cell, and that new cell has to have the full amount of genetic information.

So therefore, the sperm and the egg both contain half the amount of genetic information.

So when they combine, you've got a full set of chromosomes.

So let's have a look at our next specialised cell.

Can you remember what this one is here? This is the egg cell.

So again, similar to the sperm cell, the egg cell is involved in reproduction.

The egg cell is the female sex cell, and it is fertilised by the sperm cell, forming a zygote.

A zygote is the first cell that is formed after the sperm and egg fertilise together to form one individual cell with the full set of genetic information.

So on the picture here, we can see we've got the sperm cell, which is mobile and is able to swim towards the egg cell, and then fertilisation will occur.

Once that happens, you form the zygote.

And you can see that on this image here, you've got multiple cells that are being viewed underneath the microscope, and the zygote is labelling the one individual cell that's formed after fertilisation.

And then that cell will then replicate to form two, and then they will replicate again to form four, et cetera, and it will continue to go on.

And we can see there that we've got a diagram where we've got some dividing cells labelled.

So the egg cell is adapted to its function in the following ways.

Remember, its job is to be fertilised by the sperm and support a developing embryo.

So the first thing is that the cell membrane changes after fertilisation with one sperm.

This usually means that no more sperm can enter.

So once one sperm has fertilised that egg, the cell membrane changes so that no more sperm can fertilise the egg.

We've also got the nucleus again containing half the number of chromosomes, which is haploid, for the same reason that the sperm has.

We need to make sure that when the sperm and the egg fertilise together, that we have a full set of DNA.

We've also got the cytoplasm, which contains lots of nutrients to sustain the early growing embryo.

Moving on to a different type of specialised cell now, can you remember what this cell is? This is a ciliated cell.

Ciliated cells line the airways, and their job is to move mucus up and out of the lungs.

So you can see on this diagram here, we've got multiple ciliated cells.

And they've got these little tiny hair-like structures on the top of them, and they're labelled above that.

You've got some little bits that, they look a little bit like clouds, but they're just representing mucus.

Mucus is what you get if you're poorly and you're coughing and you've got phlegmy type stuff.

That is mucus.

And effectively, your ciliated cells work together to try and move that mucus up and out of the airways.

The ciliated cells line the bronchi and the trachea, which form part of the respiratory system.

So ciliated cells are adapted to their function in the following way.

Now remember, their job is to move mucus up and out of the airways.

So again, we've got these ciliated cells with the tiny hair-like structures called cilia.

So ciliated cells, their surfaces are covered in tiny hair-like structures called cilia that move together to sweep the mucus up and out of the lungs.

So here, if these were some ciliated cells, a slightly simplified version, as you can see, the cilia, the tiny hair-like structures on the top of the ciliated cells, and they're all pointing in the same direction.

They're all pointing upright like that.

But then what will happen is they will all move together.

So in the next image, they've all moved to be more flat.

And then eventually, they will move back up again.

So they have this motion where they work together to waft that mucus and move it along, up and out of the lungs.

Finally, we're going to look at the muscle cells.

So muscle cells contract in order to allow the body to move.

If we didn't have muscles attached to our skeleton, then we wouldn't be able to move our skeleton.

So muscle cells contract in order to make our body be able to move.

Muscle cells are adapted to their function in the following ways.

So they contain filaments of protein that can slide and cause muscle contraction.

So muscle cells contain filaments of protein, and they slide over each other to cause that muscle contraction.

Also, muscle cells contain many mitochondria.

And remember, mitochondria are the site of aerobic respiration.

So they're gonna release lots of energy, and then that is used for muscle contraction.

So muscle cells are adapted in two ways.

They contain filaments of protein that can slide to cause muscle contraction, and they have lots of mitochondria, which releases energy for that muscle contraction.

Let's quickly check our understanding.

So which of the following is true for ciliated cells? A, they have a tail so that they can swim, B, have tiny hair-like structures called cilia to sweep mucus, or C, have branched ends to send impulses quickly? Hopefully here we remembered that it was B, ciliated cells have those tiny hair-like structures called cilia which sweep the mucus up and out of the lungs.

Well done if you got that right.

Next question.

Which of the following is true for muscle cells? A, contain nutrients to sustain muscle contraction, B, have a biconcave shape to increase their surface area, or C, have lots of mitochondria to release energy? This is C, muscle cells contain lots of mitochondria to release energy, which allows that muscle contraction to happen.

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

So the first part of the task is to match the specialised cell to its function.

So you are just going to write the letter that is representing that cell in the box below.

Then you're going to answer the following questions.

So number two, how are ciliated cells adapted to help move mucus out of the airways? Three, what structures do muscle cells contain that enable them to carry out muscle contraction? Four, describe how each specialised cell is adapted to its function.

So you need to recognise what the cell is, and then the labels are given to you as a guidance for what you might need to talk about.

And there are two more cells there for you to also do the same thing for.

So pause the video now.

Spend a really good amount of time trying to put as much information down as you possibly can.

You're gonna do a fantastic job.

And then press play, and I will go through the answers.

Well done for managing to do all of that.

Let's go through the answers.

So in the first box, this is C because this is a sperm cell.

Then we've got B, which is a red blood cell.

The third one is E, which is a ciliated cell.

The fourth one is A, which is a nerve cell.

Then we've got F, which is a muscle cell, or muscle cells 'cause there's four of them.

And then finally, we've got D, which is the egg cell.

Well done if you got all of those right.

Great job.

Let's move on now to the written questions.

So how are ciliated cells adapted to help move mucus up and out of the airways? Ciliated cells have tiny hair-like structures called cilia that move together to move mucus up and out of the bronchi and trachea, which collectively are called the airways.

Question three, what structures do muscle cells contain that enable them to carry out muscle contraction? Muscle cells contain filaments of protein that can slide over each other to cause muscle contraction.

And muscle cells also contain lots of mitochondria to release energy for muscle contraction.

So describe how each specialised cell is adapted to its function.

Let's start with the nerve cell.

So the nerve cell's got a long and thin axon to carry nerve impulses over long distances quickly.

You've got the myelin sheath so that impulses can travel faster, and then branched connections called dendrites to connect to other nerve cells.

Then the red blood cell.

Got no nucleus to increase the space inside the cell to carry more oxygen, and also this biconcave shape so that the cell has a large surface area to absorb more oxygen in the lungs.

Then we've got the sperm cell.

So the sperm cell has a tail so that it can swim towards the egg.

It's got many mitochondria to release energy for movement.

In the head, there's the acrosome, which contains enzymes to break down the cell membrane.

And then finally, the nucleus contains half the number of chromosomes, which is called haploid.

And then the other cell here is the egg cell.

Again, the egg cell has half the number of chromosomes, it's haploid.

The cytoplasm contains lots of nutrients to support the growing embryo.

And then finally, the cell membrane changes once one sperm fertilises.

And you might have then written that this stops any other sperms from fertilising the egg.

There's a lot of information that you've learned, so that is amazing if you managed to fill lots of those diagrams in with the information.

If you need to pause the video to make sure that you've got all of the feedback that you need, please do.

But you've done a fantastic job this lesson.

Well done.

Let's just summarise everything that we have learned.

So in summary, we have learned today that animal cells have common features called sub-cellular structures, and each of them have a function.

The common sub-cellular structures found in animal cells are the cell membrane, cytoplasm, nucleus, mitochondria, and ribosomes.

And you need to know what each of their functions are.

We then looked at specialised cells and how they are adapted to carry out a specific function.

And we said that specialised cells have different shapes, and they also contain different sub-cellular structures that enable them to carry out those functions.

So they look very, very different.

Some examples of specialised cells that you need to know about are nerve cells, sperm cells, egg cells, red blood cells, muscle cell, and ciliated cells.

And then we looked in more detail about the specific structures of those specialised cells that enable them to carry out their very specific function.

So a lot of information in today's lesson.

You've done an absolutely fantastic job.

Well done.

And I look forward to seeing you next time.