Lesson video

Hi, I'm Mrs. Hudson, and today, I'm going to be teaching you a lesson called Plant Cells, Common Structures and Specialised Cells.

This is a biology lesson, and it comes under the unit titled Eukaryotic and Prokaryotic Cells.

The outcome of today's lesson is I can identify common structures of plant cells and relate each structure to its function.

There will be some key words in today's lesson, and those words are cell wall, chloroplast, permanent vacuole, photosynthesis and active transport.

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

A cell wall is a subcellular structure that is made from cellulose fibres and strengthens the cell and supports the plant.

A chloroplast is a subcellular structure that contains the green pigment chlorophyll, which absorbs light energy for photosynthesis.

The permanent vacuole is a subcellular structure that is filled with cell sap to help keep the cell turgid.

Photosynthesis is a chemical reaction that plants use to make glucose, which takes place in the chloroplasts.

And finally, active transport is a process where particles move from low to high concentration against a concentration gradient.

This requires energy.

If you need to pause the video to make a note of these keywords, please do, and then press play when you're ready for me to keep going.

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

In the first part of the lesson, we're going to be looking at plant cells, subcellular structures, and then we're going to move on to specialised plant cells.

And then finally in the lesson, we're going to look at features of specialised plant cells.

Let's get going with the first part of the lesson, plant subcellular structures.

To start with, let's have a look at this picture.

What is this picture showing? Now, this is a 2D model of a plant cell.

The image shows the common subcellular structures you find inside a plant cell.

Can you identify any of the subcellular structures in this diagram? You might have been able to remember some of them.

Animal and plant cells have certain subcellular structures that are in common.

So here are some of those subcellular structures.

We've got the nucleus, the cell membrane, which in the plant cell is not the very outermost layer, it's the second layer in.

You've got ribosomes, which are the smallest subcellular structure, mitochondria, the cytoplasm, which on this diagram just looks like empty space, but it's actually a jelly-like liquid that surrounds all of the other subcellular structures.

Animal and plant cells have these subcellular structures in common.

Plant cells also have three additional subcellular structures, and these are a cell wall, chloroplasts and a large permanent vacuole.

So the three that we're going to put on now, you would not find in an animal cell.

So those are the cell wall, which is the outermost layer, the chloroplasts, which is where photosynthesis takes place, and the large permanent vacuole.

Let's quickly check our understanding so far.

So here, we've got an image of a plant cell.

Which subcellular structure is the line pointing to? A, cytoplasm, B, chloroplast, or C, large permanent vacuole.

This is C, the large permanent vacuole.

Great job if you got that right.

Next question, which subcellular structure is the line pointing to here? A, mitochondrion, B, chloroplast, or C, ribosome.

This one is B, the chloroplast.

Remember, the chloroplasts, you don't find in animal cells, but you do find in plant cells.

Great job if you got that right.

Next one, which subcellular structure is the line pointing to here? A, cell membrane, B, cytoplasm, or C, cell wall.

Hopefully, you didn't get caught out here.

This one is C, the cell wall.

Remember, the outermost layer of a plant cell is the cell wall, and then the next layer in is the cell membrane.

Great job if you managed to get that right.

Which of the following is not found in an animal cell? A, chloroplasts, B, ribosomes, or C, mitochondria? This one is A, the chloroplasts.

Fantastic job if you managed to get all of those right.

Now that we know all of the different subcellular structures, let's have a look at their specific functions.

Each subcellular structure has a specific function, so this means that they've all got a different role in the cell.

Let's have a look at what those roles are.

The cell membrane is partially permeable.

That means it lets some substances through, but not others, and it controls what enters and exits the cell.

This is really important because it makes sure that the internal conditions of the cell remain relatively constant.

The ribosomes are where protein synthesis takes place.

So the ribosomes are where proteins are made.

The cytoplasm is that jelly-like liquid containing salts and nutrients, and this is where many chemical reactions occur.

The mitochondrion is where aerobic respiration occurs, and they contain the enzymes for respiration.

And the nucleus controls the cell activities, and it contains the DNA, which is the genetic material.

Let's have a look now at the functions of the three subcellular structures that we only found in the plant cells and not animal cells.

First of all, we've got the chloroplasts.

This is where photosynthesis takes place, and it contains the green pigment chlorophyll, which absorbs light energy for photosynthesis.

Cell wall is on the very outside of the plant cell, and this is made from cellulose fibres, and the job of it is to strengthen the cell and supports the plant.

And then finally, the large permanent vacuole is filled with cell sap to help keep the cell turgid.

Let's see how much of that we have remembered.

So what is the function of the cell wall? A, it is the site where most chemical reactions occur.

B, to provide strength to the cell and support the plant.

Or C, it is where photosynthesis takes place.

The cell wall is B, it provides strength to the cell and supports the plant.

Next question, match the subcellular structure to the correct function.

So we've got cell wall, large permanent vacuole and chloroplasts.

And then the function A contains cell sap, where most chemical reactions occur.

B, made from cellulose, provides strength to the cell and supports the plant.

And C, contains chlorophyll, where photosynthesis takes place.

So match those up.

So what we should have here is the cell wall goes to B, the large permanent vacuole goes to A and the chloroplast goes to C.

Great job if you managed to get all three of those right.

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

So the first part of the task A is to label this plant cell with the subcellular structures.

And then in the second part of the task, you're going to complete the table.

And on that table, you've got the structure and then the function, and different parts have been filled in for you.

So if the structure's missing, you put the correct structure in.

And if the function's missing, you write the function for that structure in there.

I'm sure you're gonna do a fantastic job of this.

Pause the video, and press play when you're ready for me to go through the answers.

Right, let's see how we did.

So this cell, let's start labelling it.

We've got the cell membrane.

So this is the second layer in.

The ribosomes are the smallest subcellular structure.

We've got the mitochondrion.

Then we've got the cytoplasm, which looks like empty space.

The cell wall is the outermost layer.

The chloroplasts are there, and the large permanent vacuole.

And finally, we've got the nucleus.

Fantastic job if you managed to get all of those right.

Now moving on to our table, the function of the cytoplasm is that it's a jelly-like liquid where many chemical reactions occur.

And the structure that controls the cell activities and contains DNA is the nucleus.

Protein synthesis occurs in the ribosome.

Mitochondrion is where aerobic respiration occurs, and has enzymes for respiration.

Partially permeable and controls what enters and exits the cell, that is the cell membrane.

And the function of the cell wall is it's made from cellulose, provides strength and support.

And then filled with cell sap to help keep the cell turgid is a permanent vacuole.

And finally, the function of the chloroplast, contains chlorophyll and where photosynthesis takes place.

Brilliant job if you managed to recognise lots of those.

If you need to pause the video to correct any of your answers, please do, and then press play, and we'll carry on with the rest of the lesson.

Fantastic job.

So now we know plant subcellular structures, let's look at some specialised plant cells.

Specialised cells in plants are adapted to carry out specific functions.

So what we mean by that is they have specific shapes and specific structures, including subcellular structures, that help them to carry out a specific job.

Now, here are some examples of plant specialised cells.

Can you name any of them? Now, you might be able to recognise some of them.

So the first example is a palisade cell.

Now, you might notice that that cell is the same as the 2D model that we use to represent a plant cell.

But actually that type of cell is representing specifically is a palisade cell that you find in leaves.

Then we've got a guard cell, which are found on the bottom of leaves.

This one we might have recognised is a root hair cell, which we find in the roots.

And then the two at the end, we've got the xylem, which transports water, and the phloem that transports glucose and minerals.

Well done if you managed to recognise some of those.

Let's look in a little bit more detail at some of those specialised cells and what their jobs are.

So we're starting with palisade cells.

Palisade cells are found at the top of leaves so that they can absorb as much energy as possible.

So if you look at that diagram we've got there, this is a cross section of a leaf.

So if you chopped a leaf in 1/2 and you were looking at all the different layers from top to bottom, that is what this picture is showing you.

And you can see there the top and the bottom are labelled.

Now, one of those cells towards the top is a palisade cell.

And the reason those palisade cells are at the very top layer of the leaf is because their job is to absorb as much energy from the sun as possible.

So palisade cells are found at the top of leaves so they can absorb as much energy as possible.

If we look now at guard cells, guard cells are found on the underside, which means the bottom of leaves, and they open and close the stomata.

So the stomata are little holes that are found on the bottom of leaves.

And the guard cells work to keep these holes either open or to keep the stomata closed.

So again, if we look at the cross section of a leaf, you can see on that diagram there on the bottom of the leaves, so now we're at the underside of the leaf, you've got those guard cells, and they open and close the stomata.

When the stomata are open, carbon dioxide diffuses into the leaf, and water vapour and oxygen diffuse out.

So here through those stomata, carbon dioxide will diffuse into the leaf.

Remember, that's needed for photosynthesis.

And then water vapour and oxygen will diffuse out of the leaf.

Now, if we look at root hair cells, the outside surface of roots are covered in root hair cells, and their job is to absorb water and minerals from the soil.

So we can see on this diagram here, you've got a section of roots from a plant, and then you've zoomed in, which has created this diagram where you've got the root hair cells.

So we've got the roots of plants, and then you've got many root hair cells covering all of the roots of plants.

Now, if we look at one individual root hair cell, the job of the root hair cell is to absorb water by osmosis, and mineral ions are absorbed by active transport.

And finally, we're going to look at the xylem and the phloem.

The xylem and the phloem run up the stem of plants.

And this is the diagram here of the xylem on the left and the phloem on the right.

The xylem transports water upwards from roots to leaves in one direction.

So we can see here that you've got the xylem, and water is being transported, but notice that the arrow is only pointing upwards.

So water travels in one direction in a plant, from roots to leaves, whereas the phloem transports glucose and amino acids up and down the plant.

So the difference here is what is being transported and in what direction.

The xylem transports water up the plant from roots to leaves.

The phloem transports glucose and amino acids up and down the plant.

You can see here how the xylem and phloem are distributed in the stem.

So this here is showing you a stem or a vascular bundle in the plant, and you've got the xylem, which is the vessel that's transporting water up from root to leaves.

And then the phloem is a different vessel which transports glucose and amino acids up and down the plant.

Let's see how much of that we can remember.

So starting with a true or false question.

The xylem transports water in all directions in a plant, true or false? And justify your answer.

A, water travels from the roots to the leaves in one direction, or B, water is needed for respiration, and travels in all directions to every cell of the plant.

Well, this is false.

The xylem doesn't transport water in all directions.

And the justification is A, water travels from roots to the leaves in one direction.

The reason why B is wrong is because water is not needed for respiration.

Water is a product of respiration.

Well done if you managed to get that right.

And the next question, what is the function of the guard cells? A, control if the chloroplasts are open or closed.

B, control if the stomata are open or closed.

And C, absorb energy for photosynthesis.

This is B, it controls if the stomata are open or closed.

Great job if you got that right.

And now a true or false question.

Root hair cells do not contain chloroplasts, true or false? Justify your answer.

A, photosynthesis can take place in the roots to make glucose, or B, photosynthesis cannot take place without sunlight, and so there are no chloroplasts in the root hair cells.

Now, this is true.

Root hair cells do not contain chloroplasts, and the justification is B, photosynthesis cannot take place without sunlight, and so there are no chloroplasts in root hair cells.

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

In the first part, you need to name the specialised plant cells in the diagrams. And then question two, what is the function of the root hair cells? Number three, explain where palisade cells are located in a leaf.

So you have to say where they're located and why.

And then four, what is the function of the guard cells.

And five, which two specialised cells are located in the plant stem, and what do they transport? I'm sure you're gonna do a great job.

Pause the video now, and press play, ready for me to go through the answers.

Let's see how we did.

So naming these specialised cells.

The first one is a palisade cell, then a guard cell, then a root hair cell.

Then we've got the xylem and the phloem last.

Number two, what is the function of root hair cells? The outside surface of roots are covered in root hair cells.

Their job is to absorb water and minerals from the soil.

Now, you might have added in there as well that water's absorbed through osmosis, and minerals are absorbed through active transport.

Well done if you managed to get those right.

Then question three, explain where palisade cells are located.

Palisade cells are found at the top of leaves.

This is so they can absorb as much energy as possible for photosynthesis.

Question four, what is the function of guard cells? Guard cells control the opening and closing of the stomata.

Carbon dioxide diffuses into the stomata, and water vapour and oxygen diffuse out.

And number five, which two specialised cells are located in the plant stem, and what do they transport? The xylem and the phloem are found inside the stem.

The xylem transports water up the plant from roots to shoots.

The phloem transports glucose and amino acids up and down.

Now, you might not have exactly word for word the same answers there.

If you need to pause the video and check you've got all of the right points, then please do.

And then press play when you're ready for me to carry on with the rest of the lesson.

Great job.

So we've looked at the plant cell subcellular structures, and then we've looked at specialised plant cells.

Now let's have a look at the features of those specialised plant cells.

First, we're going to look at the palisade cell again.

So remember, the function of the palisade cell is to absorb as much light as possible for photosynthesis.

Palisade cells are adapted to their function in the following ways, so they have got many chloroplasts to absorb as much light as possible for photosynthesis.

The chloroplasts contain this green pigment called chlorophyll, and the chlorophyll absorbs the sunlight.

So the more chloroplasts there are, the more sunlight that can be absorbed.

Palisade cells also have this column shape, and this means that they're kind of a rectangular shape, and this is so that they can be packed really close together at the top of the leaf.

That means that there are more palisade cells.

The more palisade cells that there are, the more light that can be absorbed.

And again, if we look at the cross section of the leaf, we can see our palisade cells there, and they're packed really closely together.

But the third feature is that they're found at the top of the leaf to absorb as much light as possible.

So the three features of the palisade cell, many chloroplasts, they've got a column shape, and they're found at the top of the leaf.

Now we're going to look at the guard cells.

The function of the guard cells was to open and close the stomata.

And the guard cells are adapted to their function in the following ways.

So we've got a stomata here during the day, and then we've got a stomata at night.

Now, notice that the stomata is the part of this diagram in the middle.

So stomata during the day, you can see that that stomata is open.

Whereas at nighttime, the stomata is closed.

So let's start by looking at the stomata during the day.

So in bright light, which is the day, the guard cells absorb water by osmosis and they become turgid.

This keeps the stomata open.

So during the day, the guard cells absorb water by osmosis, and they become turgid.

What this means is they swell up.

And this makes sure that the stomata stays open.

So we can see there in the middle, you've got open stomata, and water is able to evaporate through that stomata.

Whereas at nighttime, in low level light, the guard cells lose water and become flacid.

This causes the stomata to close.

And then we can see there on the diagram, there's a closed stomata, and water cannot leave.

Now, the reason why this is quite important is because carbon dioxide diffuses into the plant through the stomata.

And remember, carbon dioxide is needed for photosynthesis.

During the day, there's plenty of light available for photosynthesis to occur.

So that means that the stomata needs to be open so that carbon dioxide can diffuse into the plant.

Whereas at nighttime, there isn't any light available for photosynthesis.

So the rate of photosynthesis is very, very low.

What this means is that the plant doesn't need as much carbon dioxide during this time, so therefore the stomata can close, and that means that no water is going to escape the plant.

Stomata are located on the underside of leaves to limit the amount of water lost through evaporation.

So if there's lots of sunlight shining onto that leaf, which there will be, imagine if those stomata are at the top, water would constantly be evaporated from the top of the leaves.

But because the stomata are located at the bottom, water evaporates through the bottom, but there isn't as much direct sunlight, so it limits the amount of water that is lost through evaporation.

Now we're going to have a look at root hair cells.

Remember, the function of root hair cells was to absorb water and minerals from the soil.

And root hair cells have adapted to this function in the following ways.

So the first thing is they've got this really long, thin hair-like projection to increase the surface area for absorption of water and mineral ions.

So you can see the shape of the root hair cell is it's sort of got this rectangular shape, but then it's a really long projection that comes out.

This increases the surface area so more water and more mineral ions can be absorbed.

It's also got a large permanent vacuole to store as much water as possible.

And then, you can see that it's got many mitochondria to release energy needed for active transport of minerals from the soil.

So mitochondria is where aerobic respiration takes place, and that means that energy can be released.

That energy is then transferred for the active transport of those minimal ions from the soil.

Now let's look at the xylem cells.

Remember, xylem cells transport water up the plant in one direction.

And they're adapted to their function in the following ways.

So xylem cells are effectively dead.

They contain no subcellular structures.

And what this means is it gives more space, which means that more water can pass through the xylem freely.

The ends of the xylem cells have also broken down, which forms long hollow tubes, which allows water to move through really easily.

And then the cell walls are thickened with a substance called lignin to strengthen the hollow tubes providing support.

Remember, if water's travelling through the plant, the cell walls need to be able to withstand the pressure of the water.

And to do this, they're thickened with the substance called lignin.

Now let's look at the phloem cells.

Remember, their job was to move glucose and amino acids up and down in the plant.

They're adapted to be able to do this in the following ways.

So the first thing is that the cells have few subcellular structures.

So that's similar to the xylem.

And this is to allow more glucose and amino acids to flow through.

And then on the diagram, you can see they've got these plates with little holes in.

They are called sieve plates, and they join the phloem themselves together, and they've got little holes in which allow glucose and amino acids to flow through.

And this is called translocation.

So the movement of glucose and amino acids through the plant is called translocation.

And then you'll notice that this diagram's slightly different to the one we've been looking at previously in the lesson.

And it's because there are cells attached to the phloem, which are called companion cells.

And they contain lots of mitochondria, which release energy to help transport glucose and amino acids through the plant.

So you've got these companion cells attached, with lots of mitochondria to transfer that energy needed to move glucose and amino acids through the plant.

Let's check our understanding.

Which is not true for a xylem cell? A, contains lignin to strengthen.

B, contains companion cells to transfer energy.

And C, cells contain no ends to create hollow tubes.

This is B, xylem cells do not contain companion cells.

That is the phloem.

Great job if you got that right.

Next question, why do root hair cells have long hair-like projections? A, to store as much water as possible.

B, increase surface area to absorb more light energy.

Or C, increase surface area to absorb more water and minerals.

This is C, it increases the surface area to absorb more water and minerals.

And then true or false question.

At night, guard cells become turgid and stay open, true or false? and then justify your answer.

A, guard cells are open at night to allow water to leave, or B, guard cells are closed at night to stop water loss.

This is false.

The justification is that guard cells are closed at night to stop water loss.

Guard cells become turgid in the day, not at night.

Fantastic if you remembered that.

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

And in the first part of the task, you need to add labels and annotations to the diagram to describe three ways palisade cells are adapted to their function.

Then in the second part, you are going to explain how guard cells help control the amount of water that is lost from plant leaves.

And you've got the day there, and the night diagram to help you explain that.

And then number three, describe three adaptations of root hair cells.

Then moving on to four, Andeep has been asked to describe the difference between xylem and phloem cells.

What is correct about what Andeep has said, and what is incorrect? Make corrections to the incorrect statements.

So Andeep has said, "Xylem cells are practically dead.

"Their ends have broken down to form long hollow tubes "for glucose to travel through.

"Xylem cells are connected to companion cells, "which provide energy to move glucose.

"Phloem cells have few subcellular structures "to allow more water to move through.

"They also have sieve plates with small holes "to allow water to move through easily." I'm sure you're gonna do a fantastic job of this.

Pause the video, and press play, ready for me to feedback on the answers.

So for the question one, we should have had many chloroplasts to absorb as much light as possible for photosynthesis.

Then we've got a column shape so that they can be packed close together at the top of the leaf.

And then finally, they're found at the top of the leaf to absorb as much energy as possible.

Great job if you got that right.

For number two, in the day, guard cells absorb water by osmosis and become turgid.

This keeps the stomata open, and water is evaporated.

And then at night, guard cells lose water at night and become flacid.

This closes the stomata and water cannot evaporate.

For number three, the three adaptations of root hair cells, their long, thin-like hair projection to increase the surface area for absorption of water and mineral ions.

They've got a large permanent vacuole to store as much water as possible.

Many mitochondria to release energy needed for active transport of minerals from the soil.

And then finally, for number four, xylem the cells do contain essentially dead cells, which form hollow tubes for water to pass through, not glucose.

Xylem cells are not connected to companion cells.

Phloem cells are connected to companion cells.

Companion cells do provide energy to help move glucose, but this is through the phloem, not the xylem.

Phloem cells do have few subcellular structures to allow more glucose to move through, not water.

And finally, phloem cells do have sieve plates with small holes.

These allow glucose to move through, not water.

That's quite a lot of information in the feedback.

If you need to go back and have a look at any of the other answers, please do, and then press play because we're going to summarise what we've learned today.

So in summary today, we have said plants and animal cells do have some common subcellular structures.

Plant cells usually have three additional structures, which are the cell wall, chloroplasts and a large permanent vacuole.

Each subcellular structure has a specific function within the cell.

Specialised cells are adapted for their function.

They each have specific features that enable them to carry out their functions.

And we looked specifically at these five specialised cells, the palisade cell, the guard cell, the root hair cell, the xylem and the phloem.

You've done a fantastic job this lesson, well done.

I really look forward to seeing you next time.