Lesson video

Hello, I'm Mrs. Hudson, and today I'm really looking forward to teaching you a lesson, which is called cells.

This is the first lesson in a new biology topic, which is called eukaryotic and prokaryotic cells.

Now, your outcome for today's lesson is that I can identify that all cells have some structures in common, and I can explain that all organisms are unicellular or multicellular.

So we are going to be looking at cells and identifying what unicellular and multicellular means and give some examples.

And then we're going to have a look at a little bit more detail about the structures that make up cells.

Now, here are some keywords that are going to be really important for today's lesson.

An organism is a living thing made of one or more cells.

A cell is the basic unit of all forms of life.

Multicellular is an organism made of many cells.

A microorganism is an organism that can only be viewed through a microscope.

And unicellular is an organism that consists of a single cell.

Now, you might want to pause the video now to jot or make a note of these keywords so that you can refer back to them later on in the lesson.

And this is the structure of today's lesson.

So the first thing we're going to be looking at is all living organisms are made of one or more cells.

Then we're going to identify some subcellular structures.

And finally, we're going to look at the functions of subcellular structures.

So let's get started by looking at all living organisms are made of one or more cells.

So all organisms, including animals, plants, fungi, and microorganisms are made up of one or more living cells.

Effectively, everything alive is made up of cells.

So we've got an animal, we've got an orca there, you've got a plant and you've got fungi.

Some living organisms are multicellular.

And these are some examples of multicellular organisms, animals, plants, and fungi.

However, some organisms are unicellular and protists, there's a picture there of a protist, that's an example of a unicellular organism.

So what does that mean, multicellular and unicellular, Many animals and plants are multicellular.

Most things that we encounter in everyday life are multicellular.

If you can see something without a microscope, it's going to be multicellular.

So if we break down this word multi, the prefix means many and cellular means made of cells.

So therefore, multicellular means made up of many cells.

Anything with more than one cell is multicellular.

Microorganisms, such as bacteria are unicellular.

So if we break down this word, the prefix uni means one.

So if you think of a unicycle, that's a bike that only has one wheel.

Unicellular, the uni means one, cellular means made of cells.

So unicellular organisms are made up of only one cell.

So many plants and animals are multicellular, which means they're made up of many cells and they are organised to form tissues, organs, and organ systems. So there's a hierarchy in the way that organisms are structured.

And the smallest part of an organism is always the cells.

So lots of similar cells will work together and then they will form a tissue, and then you'll have lots of different tissues that work together to form an organ.

And that organ has a specific job.

And then within an organism, you will usually have multiple organs that will all work together to form an organ system.

And then again, different organ systems will all work together collectively to form the whole organism.

So the smallest part of an organism are the cells, then it's the tissues, organs, organ systems, and organism.

I think sometimes what students misunderstand can be that only animals are made up of different tissues, organs, and organ systems, but plants also are as well.

So for example, in a plant, there's lots of different types of cells, and then you have tissues.

So you have different tissues that make up the leaf, for example.

And then the organ itself is the leaf.

And the organ system can be the root system or the shoot system.

And then the whole organism will be the plant.

Microorganisms, such as bacteria, are unicellular.

So that means that they're made up of just one cell.

And this picture here is a picture of an E.

coli bacteria.

And you can see in the picture that there's lots of little rod-shaped organisms, and each one of those rod-shaped organisms is an E.

coli.

And you can see on the picture as well that it says one micrometre.

What this is showing is that the organism is extremely small.

We would need a microscope to be able to see it, and that's because they're each just made of one cell.

They are unicellular organisms. You can also get unicellular animal, plant, fungi and protist organisms as well.

It's not just bacteria.

So here are some examples.

This is zooplankton and they are unicellular animals.

Phytoplankton are unicellular plant-like organisms. And amoeba are unicellular protists.

So there are some examples of unicellular animal, plant, fungi, and protists.

Time to check our understanding.

I'm sure we're gonna do a great job.

The first question is what is the smallest unit of living organisms? A, organs, B, tissues, C, cells or D, organ system? This is C, cells.

Great if you got that right.

Next question.

Which of the following are examples of multicellular organisms? A, bacterium, B, human, C, rose bush, or D, amoeba? So hopefully for this you got B and C.

Humans we know are multicellular, but also a rose bush, which is a type of plant, is multicellular.

Bacterium we know our unicellular and amoeba was an example of a unicellular protist.

Next question, true or false this time.

All organisms are made up from organ systems. True or false? Now, this is false.

Now I would like you to justify that answer.

So A, not all organisms have the same organ systems, or B, only multicellular organisms are made from organ systems. This is B.

Remember, only an organism that is multicellular can contain organ systems. Right, time for us to have a go at our first task.

So what we would like you to do here is to identify if the statements are true or false by placing a tick in the column.

Then secondly, explain why the false statements are incorrect.

So if you have ticked false in the table, you are then going to say why the statement is false.

So let's see which one of these statements are true and false.

So cells work together to carry out functions is true.

All unicellular organisms are bacteria is false.

All multicellular organisms are animals is also false.

Each tissue is made of multiple cells is true.

Tissues are only found in animals is false.

And an organ system is composed of several types of cells is true.

So now let's have a look at those false statements, which hopefully you got right.

And let's talk about why they are indeed false.

So the first one, all unicellular organisms are bacteria is false because bacteria are unicellular but there are unicellular animals, plants and fungi too, for example, zooplankton, phytoplankton and amoeba.

Those are the examples we talked about.

All multicellular organisms are animals.

Many animals are multicellular, but there are other multicellular organisms, such as plants and also some fungi too.

Tissues are only found in animals.

This is false because many multicellular organisms have tissues, not just animals.

For example, mesophyll tissues in plants, which you find in the leaves, they are tissues.

Now, you might want to pause the video now to give yourself a little bit of time to correct any work or give yourself any feedback.

You've done an absolutely fantastic job of the first outcome for today's lesson.

Now we're going to move on to our second one, which is identifying subcellular structures.

So cells are three-dimensional and have different shapes and subcellular structures depending on their functions.

So every single cell will have a slightly different function, a slightly different shape, and they will contain slightly different subcellular structures.

Now, these three images here are 3D representations of animal cell, a plant cell, and a bacterium.

And you can see inside them they've got slightly different structures and they're different shapes.

Now, sometimes this can be a little bit complicated for us to understand.

Therefore, we use 2D diagrams to represent cells.

It can be difficult to draw cells 3D.

So instead, cells are often drawn as these 2D diagrams below.

So we've got an animal cell model, and next to it, we've got a plant cell model.

Can you name any of the subcellular structures inside this animal and plant cell model? Let's have a look.

So these are the subcellular structures in a typical animal cell.

So there's that animal cell model, and we're going to look now at the subcellular structures contained within it.

So the first thing is the cell membrane, and this is the line that surrounds the animal cell and gives it the shape that it has on this picture.

And then inside, you've got that grey circle, which is called the nucleus.

The cytoplasm is the space that's inside of the cell membrane.

It's just it looks like empty space on the diagram, but in reality, it's a jelly-like substance that surrounds all of the subcellular structures.

Then that structure there is the mitochondrion, And then the smaller circles are called ribosomes.

So these are the subcellular structures found in a typical animal cell: the cell membrane, the nucleus, the cytoplasm, the mitochondrion, and the ribosome.

These are the subcellular structures that are found in a typical plant cell.

So some of these are the same as an animal cell and there are some that are different.

So the cell membrane we did see in the animal cell, but this time, it's the inner membrane because there is also another line that is outside of the cell membrane in a plant cell.

So we've got the cell membrane, the ribosomes are in plant cells, those much smaller circles.

The cytoplasm is in a plant cell, which is that jelly-like substance that surrounds all of the subcellular structures.

The nucleus is also inside of a plant cell model.

However, we also have a cell wall.

This is the very outer layer of the cell.

And this is not found in animals, but it is found in plants.

The mitochondrion, again, we found those in animal cells.

They are also in plant cells.

Then you've got the structure, which is called the large permanent vacuole.

And again, we find that inside plant cells but not animals.

And then chloroplasts, this structure that's labelled here, again, found in plant cells but not in animal cells.

This is where photosynthesis happens, which is why it's only found in plant cells.

So plant and animal cells have the following structures in common: the nucleus, the cytoplasm, the ribosomes, the cell membrane, and the mitochondria.

However, the plant cell also has these three structures: the chloroplast, the permanent vacuole, and the cell wall.

Time for us to check our understanding.

So which subcellular structure is the arrow pointing towards? A, cell wall, B cell membrane, or C, nucleus? This is the cell membrane.

Remember, this is an animal cell.

The outer layer was the cell membrane.

Which subcellular structure is the arrow pointing towards here? A, cytoplasm, B, chloroplast or C, mitochondrion.

This is the cytoplasm.

Brilliant if you got that right.

Next question, which subcellular structure is the arrow pointing towards here? The chloroplast, A, the mitochondria, B or the vacuole, C.

This is the mitochondrion, B.

Well done.

This one, which subcellular structure is the arrow pointing towards? A, the vacuole, B, the ribosome, or C, the nucleus.

Now, this is a plant cell and this structure is the vacuole.

So well done if you noticed that and got that right.

Let's move on to our second task.

So in this task, I would like you, please to label this model animal cell using the label lines and then label this model plant cell using the label lines again.

Okay, let's check that we got this right and you mark your work and feedback to yourself.

So that label is the mitochondrion.

Make sure you check your spelling, make sure you've spelled it right.

Then you've got the ribosome.

The black circle there is just specifically pointing out that it's the little circle that is the ribosome.

You've got the cell membrane, the nucleus, and the cytoplasm.

Really well done if you managed to get all of those right and spelt correctly.

That's brilliant.

Now let's look at the plant cell.

So first of all, we've got the chloroplast, which is unique to the plant, the large permanent vacuole, also unique to the plant.

And then we've got the mitochondrion, the cell wall, which again is unique to the plant, cell membrane, ribosome, cytoplasm, and the nucleus.

So you might want to pause the video just to check that you've got all of those spelled correctly before we move on to the next part of the lesson.

But well done.

So brilliant job.

We're onto the final part Of our lesson now where we're going to look at the functions of those subcellular structures that we've just identified.

So let's get going.

So why do you think that cells are made up of different subcellular structures? For example, why does the plant cell need to have three different subcellular structures to the animal cell? Well, the reason is because each subcellular structure has a specific function within the cell.

And plants are obviously different to animals; plants photosynthesize, but animals don't.

So plants need to have a subcellular structure where photosynthesis occurs, but animal cells don't need that.

And there's lots of other different examples, which mean that they have different subcellular structures.

Well, first, we're gonna look at the cell membrane.

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

And remember that is the cell membrane pointed out on the diagram.

The cell membrane is also partially permeable.

And what that means is it allows some substances to diffuse through but not others.

And this helps to regulate the cell's internal environment.

So for example, if you've got a partially permeable membrane, water and also small solutes are able to diffuse through that membrane, but larger solutes are unable to.

What that means is that the cell is able to control what can go into the cell and what can come out of the cell and that helps to make sure that the inside environment inside the cell is monitored and remains relatively constant.

The nucleus contains the genetic information, which is known as the DNA, and the nucleus controls the activities of the cell.

The cytoplasm, which remember, we said is a jelly-like substance, and it contains dissolved nutrients and salts.

And the jelly-like substance surrounds all of the subcellular structures within that cell.

And it is where many of the chemical reactions essential for life take place.

So the cytoplasm is a jelly-like substance that contains dissolved nutrients and salts.

And it's where many of the chemical reactions take place.

The ribosomes are very small subcellular structures, but they are still very important.

This is where protein synthesis occurs.

Now, synthesis means to make, so ribosomes are where proteins are made in the cell.

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

Aerobic respiration occurs in the mitochondria and remember that respiration releases a lot of energy, so therefore, that released energy can be used for lots of cellular processes, and this is really important.

So mitochondria are where aerobic respiration occurs, which releases lots of energy.

Now let's look at the functions of the subcellular structures that are just found in the plant cells.

So first of all, we've got the chloroplasts.

Now, chloroplasts are the site of photosynthesis and they contain a green pigment called chlorophyll that absorbs sunlight.

Now, photosynthesis is a really important process that makes glucose in plants.

Animals get their glucose from food and drink, so therefore, they don't need to have chloroplasts in their cells because they don't photosynthesize.

So therefore, chloroplasts are very, very important for plants because they allow photosynthesis to occur.

The second structure is the large, permanent vacuole.

This contains sap, which helps keep the cell turgid.

Now, again, this is very important for plants because unlike lots of animals, which have skeletons to keep them upright, plants do not, but they do still grow upright.

And part of this is because they have this vacuole, which can fill up with water and it can store nutrients, but also, it causes the plant cell to swell up, and that is what turgid means, and it provides a structure and support to the plant.

The third subcellular structure is the cell wall, and this contains a substance called cellulose, which provides strength and support to the cell.

Excellent.

Let's check our understanding now.

So what is the function of the cell membrane? A, it is where most of the cell reactions take place.

B, it contains DNA, which controls the cell's activities.

Or C, it controls what enters and exits the cell.

This is C, it controls what enters and exits the cell.

Well done.

What is the function of the nucleus? A, it is where protein synthesis occurs.

B, it contains DNA, which controls the cell's activities.

Or C, it is the site of aerobic respiration.

This is B.

Well done if you got that right.

Next question.

Where are proteins made in a cell? A, ribosomes, B, nucleus or C, cytoplasm.

This is A, the ribosomes.

Where does aerobic respiration occur? A, ribosomes, B, mitochondrion or C, the cytoplasm.

This is B.

Well done if you wrote mitochondrion.

Now let's apply that knowledge to our final task.

There are a few parts to this task.

So the first thing you have to do is complete the table.

So you've got the structure on the left and the function on the right, and you either have to name the structure or write what the function of that structure is.

And secondly, you're going to complete a table by adding the correct subcellular structures to each column.

So in the left-hand column, you've got the subcellular structures in both plant and animal cells.

And then in the right column, you have the subcellular structures just found in plant cells.

And then question three, explain why animals do not need chloroplasts.

And then finally, you've got Izzy is talking to her teacher about plant and animal cells.

What has Izzy said correctly and what has she got incorrect? Write the correct sentences for Izzy to improve.

So this is what Izzy has said.

"Animal cells contain chloroplasts because that is where respiration takes place.

Only plant cells contain a cell membrane and a vacuole, but both plant and animal cells contain ribosomes and mitochondria." So what has Izzy said that's correct.

What has she said that's incorrect? And can you write the correct sentences for Izzy to improve? Pause the video now and have a go at those tasks.

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

Let's go through the answers.

So hopefully we didn't find that too difficult.

Make sure that you pause the video if you need a little bit of extra time to correct any of your answers or write anything extra into your answer but let's go through it.

So the first structure was the cytoplasm.

The function of the nucleus is that it contains DNA, which controls the cell activities.

Ribosomes is where photosynthesis takes place.

Mitochondria is where the energy is released through aerobic respiration.

The function of the cell membrane is that it controls what enters and exits the cell.

The cell wall is the structure.

The vacuole contains sap, which helps keep the cell turgid.

And then the function of the chloroplast is that it contains chlorophyll and this is where photosynthesis occurs.

Well done if you got those correct.

The second task, the subcellular structures in both plant and animal cells are the cell membrane, cytoplasm, ribosomes, nucleus, and mitochondria.

Doesn't matter what order you've got those in, as long as they are in the correct column.

And then the subcellular structures just found in plants are the cell wall, the vacuole and the chloroplasts.

And then why do animal cells not need chloroplasts? Well, this is because plants make glucose through photosynthesis and this process occurs in the chloroplasts whereas animals get their glucose through food and drink and therefore, we don't need chloroplasts because we don't photosynthesize.

Now, you might have written something that doesn't look exactly like that, but as long as you've got the point that photosynthesis only occurs in plants because that's how they make their glucose, whereas animals do not Photosynthesize.

We get our glucose through food and drink.

And then the final task.

So what has Izzy said that's correct, and what has Izzy said that's incorrect? How could you prove the incorrect statements? So Izzy has correctly said that only plant cells contain a vacuole and that both plant and animal cells contain ribosomes and mitochondria.

Izzy has incorrectly said that animal cells contain chloroplasts, and she also said that respiration takes place inside of them.

Photosynthesis takes place in the chloroplasts and respiration takes place in the mitochondria.

Izzy also said only plant cells contain a cell membrane, whereas both plant and animal cells do.

Only plant cells contain a cell wall.

Again, if you need to pause the video here to write anything down and correct your answers, please do.

But I hope that you did a really fantastic job with that.

You've done extremely well today.

Let's summarise everything that we have learned.

So summary.

All organisms are made up of one or more living cells.

All cells have some structures in common and have a three-dimensional shape.

Chemical reactions essential to life appear in the cytoplasm and the cell membrane regulates the cell's internal environment.

Many animals and plants are multicellular.

They are made up of many cells, organised to form tissues and organs.

Microorganisms, such as bacteria, are unicellular.

They are made of just one cell.

What a brilliant lesson you've had.

Thank you so much.

I really look forward to seeing you next time.