Welcome to today's lesson from the Oak National Academy.

This lesson is taken from the unit Breathing and Respiration, and it's all about anaerobic cellular respiration and fermentation in microorganisms. So we're getting very small today.

So far, we've talked about respiration happening in human beings, and now we're getting microscopic, thinking about how it happens in microorganisms, those small living things.

Hi there, I'm Mrs. Wheat and I'll be taking you for today's lesson.

By the end of today's lesson, you'll be able to describe the reactants and products of anaerobic cellular respiration in microorganisms, and ways in which the process is useful to us.

Let's have a look at our keywords.

We've got five keywords for today's lesson.

We have microorganism, anaerobic cellular respiration, ethanol, alcohol, and fermentation.

I'll show you our definitions for our keywords now.

They're gonna come up now, but don't feel like you have to rush and try and memorise them.

If you want to pause the video and read through them or copy 'em down, that's totally fine, but I will be explaining each of these in tonnes of detail as they come up in the lesson.

So here they are.

Today's lesson is in two parts.

First of all, we'll talk about anaerobic respiration in microorganisms, and then we'll move on to talking about this process called fermentation.

But first of all, anaerobic respiration in microorganisms. All living organisms carry out cellular respiration to provide energy for life processes.

So I've got two different types of microorganisms here shown in my pictures.

These are taken with an electron microscope.

Take five seconds or pause the video to think about what are these two microorganisms? Click play when you're ready to hear the answer.

So these rod shaped microorganisms are bacteria, and these other ones, these are yeast.

We'll be talking particularly about yeast a lot today.

So even really tiny living microorganisms need energy for life processes.

They still move, they still reproduce.

So the energy for those processes needs to come from somewhere.

Microorganisms can carry out anaerobic cellular respiration.

It's similar to anaerobic cellular respiration in humans, but with some key differences.

Before we start directly comparing those key differences, I want you to have a look at this diagram of a cell.

First of all, I want you to try and name the different parts of the cell, and then once you've done that, I want you to have a think about what type of cell might it be.

So you'll probably need to pause the video now to think about what are the different parts of the cell, and then identify what type of cell this might be.

Let's look at the different parts.

So we have this kidney bean safe structure is mitochondria, we've got this jelly-like substance, which all the parts of the cell are suspended in, that's called the cytoplasm.

We've got the cell membrane, which controls what goes in and outta the cell.

It's got a cell wall, which gives it structure.

It's got a nucleus where DNA is stored.

So what type of cell might this be then? It's got a cell wall, it's got a cell membrane, but it doesn't have any chloroplast and it doesn't have a permanent vacuole.

What might this be? This is a yeast cell, the microorganism we'll be primarily talking about today.

So anaerobic cellular respiration in microorganisms and humans forms different products.

So in humans, we have glucose, the only reactant reacting to make lactic acid.

In microorganisms, again, the only reaction is glucose, anaerobic, an means without, aero means air.

So anaerobic respiration, whatever organism this is happening in, means that there's no oxygen involved.

So glucose, that's something they've got in common, the only reacting.

But in microorganisms like yeast, the products are carbon dioxide and ethanol.

The similarities between anaerobic respiration in microorganisms and humans are, it occurs when oxygen is not available, glucose is the only reactant, occurs in the cytoplasm of cells.

So the mitochondria is not involved at all, like it is anaerobic respiration, and it releases less energy than aerobic respiration.

Let's see if you understood that.

Which answer shows the correct reactants and products for anaerobic respiration in microorganisms? Is it A, glucose and oxygen react to make lactic acid, is it B, glucose reacts to make lactic acid or C, glucose reacts to make carbon dioxide and ethanol? You'll have five seconds or you can pause the video to take some more time to think about your response.

Click play when you're ready to see the answer.

Okay, the answer is C.

Glucose reacts to make carbon dioxide and ethanol.

So the first equation has oxygen in it.

So that can't be to do with anaerobic respiration at all.

The next equation, glucose reacts to make lactic acid, that's anaerobic respiration in humans, not in microorganisms like yeast.

So the only correct answer could possibly be C.

Well done if you figured that out.

Now we're gonna look at the equation for anaerobic cellular respiration in microorganisms. So we'll start off with the reactant glucose.

Anaerobic respiration is a form of cellular respiration that occurs without oxygen.

Remember, anaerobic, anaero, that means without air.

The only reactant of anaerobic respiration in microorganisms is glucose.

Glucose is a type of sugar that cells can use as a fuel.

So for all of the types of respiration that you'll learn about, glucose is always a reactant because that's what our cells can use as fuel for the process.

Okay, let's take a look at one of the products, carbon dioxide.

One of the products of anaerobic cellular respiration in microorganisms is carbon dioxide.

This carbon dioxide gas is a waste product, so it's poisonous, it's harmful.

The cells need to get rid of it.

The cell removes this carbon dioxide using diffusion.

Let's take a look at the other products of anaerobic respiration in microorganisms. The other product of anaerobic cellular respiration in microorganisms is ethanol.

Ethanol is a type of alcohol.

It's also a waste product.

So if it builds up, it damages the cell, it's toxic to the cell, and it's also removed from the cell via diffusion.

Okay, let's check you understood that.

Which of these words on the list are reactants or reactants and product or products of anaerobic cellular respiration in microorganisms, lactic acid, oxygen, water, cytoplasm, carbon dioxide, energy, glucose or ethanol? You can take five seconds or you can pause the video here to think about which are the products or product or which are the reactants or reactant, good luck.

Okay, let's check those answers.

So the reactants, only glucose, the products, ethanol and carbon dioxide.

Well done if you got that right.

So what about those other answers, why were those wrong? Well, lactic acid is a product of anaerobic cellular respiration, but in humans, not microorganisms. Oxygen is a reactant in aerobic cellular respiration, water is a product in aerobic cellular respiration.

Cytoplasm is not an element, it's not a compound, it's not a molecule, it's a part of the cell.

So it can't be in our word summary.

Energy, again, it's not a physical thing, it's not matter.

It's not an element, it's not a compound, it's not a molecule, so it can't be in our chemical reaction here.

Anaerobic cellular respiration provides energy, but that's transferred from one energy store to another.

It's not a physical product or reactant.

So we're gonna have a go now at our first practise task of today's lesson, place each statement into the correct section of a Venn diagram to show whether it refers to anaerobic respiration in microorganisms, anaerobic respiration in humans, whether it's to do with both of those processes, so that would go in the section of the Venn diagram where the circles are overlapping, or whether it's neither.

It's not got anything to do with either of those processes.

It doesn't belong anywhere, neither.

So that would be outside the circles completely.

Okay, so put these statements into the Venn diagram.

Producers lactic acid, oxygen's a reactant, carbon dioxide is produced, happens in mitochondria, occurs in cytoplasm, glucose is a reactant, can cause muscle cramps, ethanol is produced, water is produced, oxygen when, oh, occurs when oxygen is unavailable, provides a small amount of energy for life processes.

So you'll need to pause now, give yourself as much time as you need to put those statements into the Venn diagram, good luck.

Okay, let's have a look at those answers.

Produces lactic acid, where does that go? That's anaerobic respiration in humans.

Oxygen is a reactant, that is neither process.

Oxygen is a reactant in aerobic cellular respiration, not in anaerobic cellular respiration.

Carbon dioxide is produced.

That's anaerobic respiration in microorganisms like yeast.

Happens in mitochondria.

That is neither, aerobic respiration, part of it happens in the mitochondria, but not for anaerobic respiration.

Mitochondria is not involved.

Occurs in the cytoplasm, that is both processes.

So both types of anaerobic respiration happen in the cytoplasm.

Glucose is a reactant, that's both processes.

Can cause muscle cramps.

That's anaerobic respiration in humans.

Ethanol is produced, that's anaerobic respiration in microorganisms, like yeast.

Water is produced, that is neither.

That is a reactant of aerobic cellular respiration.

Occurs when oxygen is unavailable.

That's both processes.

And provides a small amount of energy for life processes.

That's also both processes.

Well done if you got those right, really good job.

Okay, we've looked at anaerobic respiration in microorganisms, had a look at the word equation and seeing how it's similar to anaerobic respiration in humans and how it's different to aerobic cellular respiration.

Now we're gonna look at this keyword fermentation.

So anaerobic cellular respiration in microorganisms is also known as fermentation.

Humans have been using fermentation to make food or drink for thousands of years.

So take some time here.

Take the five seconds that there is in the video or pause, have a think about can you think of any food and drink that's associated with the word fermentation? So play when you're ready to hear some answers.

Let's look at some answers.

So this isn't every single fermented product that exists, but it's some of the more common ones.

So first we have bread.

So leavened bread is risen, leavened by yeast.

We add yeast to bread in order to make it rise.

So otherwise, we just have this hard, flat lump of dough.

So I'm pretty happy for that.

So fermentation is really important for bread.

We've also got alcoholic drinks like wine or beer, the microorganisms in that make ethanol, which is what makes it alcoholic.

We've also got things like yoghourt.

So those, again, are fermented by bacteria in order to make that sour taste that yoghourt has.

So fermentation is really, really important to lots of different human food products.

Even chocolate is a fermented food.

So it's really, really important.

We've been doing it for a super, super long time in order to improve the taste of food or just create that food in general.

So what is fermentation? Is it A, aerobic respiration in humans, B, anaerobic respiration in humans, C, aerobic respiration in microorganisms or D, anaerobic respiration in microorganisms? Take five seconds or pause the video.

Click play when you're ready to see the answer.

It is D, anaerobic respiration in microorganisms. Great work if you got that right.

Okay, now we're gonna talk about dough, we're gonna talk about bread, and we're gonna talk about that really important organism again, yeast.

So yeast is a microorganism added to dough in order to make it rise.

Let's think about what dough is.

Dough is a mixture of flour and water, and so flour is a source of carbohydrate.

So the yeast breaks down the carbohydrates in the flour into glucose.

So now this yeast that's been mixed into the dough has a source of glucose in order to respire with.

So why is it anaerobic respiration that's happening? Why can't the yeast do aerobic respiration? Take five seconds or pause the video and click play when you're ready to hear the answer.

So the yeast has been mixed inside this dough, a mixture of flour and water.

There's not very much air inside dough, so there's not enough oxygen for the yeast to respire aerobically.

So it has to anaerobically respire instead.

As a yeast anaerobically respires, carbon dioxide gas is produced, causing the bread to rise.

A tiny amount of ethanol is also produced, but that's completely evaporated off during the cooking process.

So bread goes in the oven at like 200 degrees Celsius.

The boiling point of ethanol is like 78 degrees Celsius.

So you don't need to worry about bread being alcoholic.

There's definitely no alcohol in there.

But let's focus on the carbon dioxide gas.

So if you look at my picture of the bread there, you'll see some air holes in it, and those air holes were caused by the carbon dioxide gas that was produced by the yeast when it anaerobically respired.

Bubbles of carbon dioxide rise up in the bread and cause the bread to be leavened, which is super useful because otherwise again, we'd just have this hard, dense disc of dough, which wouldn't be very tasty.

And remember that the yeast producing this carbon dioxide is a waste product.

The yeast doesn't want it.

This just diffuses out of the cells, the yeast cells.

So fermentation is really interesting because we're harnessing what is essentially a waste product for the yeast and turning it into something really, really useful for human beings to use.

Now we're gonna look at how important yeast is in order for making alcoholic drinks.

So yeast can be added to fruit or other plants to make alcoholic beverages.

So with wine, the fruit is grapes.

For things like beer, it's wheat and barley and grains like that.

One of the first stages in making alcohol is crushing whatever plant material you're using in order to release some of those carbohydrates.

So if we take wine making as our example, the yeast breaks down the carbohydrates in the grapes to glucose.

And again, the yeast is now inside this kind of liquid mush of grapes and the juice that's been released from the grapes.

So there's not very much air in this liquid.

So the yeast respires anaerobically instead of aerobically.

As the yeast anaerobically respires, ethanol is produce, making the drink alcoholic.

Carbon dioxide's also released as well.

And that's why some alcoholic drinks like beer are fizzy.

It's those carbon dioxide bubbles inside it that give it the fizz.

Let's have a look and see if we understood that.

Complete the sentences about fermentation.

Use some of the words from the list.

Lactic acid, respire, water, ethanol, yeast, fermentation, and carbon dioxide.

So put some of those words into the sentence below.

So we have blank is a microorganism which undergoes blank in the production of some food or drink.

As it anaerobic respires, it produces blank blank, which causes bread to rise.

When added to fruit like grapes, it produces blank, which makes drinks alcoholic.

So you'll need to pause a video now, take some time to think about it and put those words or some of those words into the right spaces.

Click play when you're ready to see the answers.

Okay, let's go through the answers.

So yeast is a microorganism which undergoes fermentation in the production of some food and drinks.

As it anaerobically respires, it produces carbon dioxide, which causes bread to rise.

When added to fruit like grapes, it produces ethanol, which makes drinks alcoholic.

Great work if you got that right.

Now let's have a go at our final practise task for today's lesson.

So a student is conducting an experiment into yeast.

They fill two measuring cylinders with flour, sugar, and water.

They add yeast to one cylinder only.

So I've got cylinder A and I've got cylinder B.

So cylinder A is gonna have flour, water, and only sugar.

Cylinder B has got flour, water, sugar, but it's also got yeast.

Explain as fully as you can why the dough in cylinder B rose.

So that's what I'm trying to share with my little diagram.

So you can see the yellow stuff, that's the dough.

It's risen a lot higher than it has an A.

Nothing's really happened in A, and those little circles, those are some bubbles in there.

Okay, so that's what I'm trying to show with my diagram.

So explain as fully as you can why the dough cylinder B rose, but the dough in cylinder A did not rise.

So think about everything we've learned this lesson, thinking about anaerobic cellular respiration in microorganisms, try and explain what happened in this diagram.

Pause the video, take as much time as you need.

Think about your answer, write it down, and then click play when you're ready to see the answer.

Okay, let's look at the answers.

So cylinder B contained yeast, but so A did not.

Yeast is a microorganism which carries out anaerobic cellular respiration, also known fermentation, when it's in dough.

The yeast in cylinder B broke down the sugar into glucose.

It used this glucose to carry out fermentation, or you could have also written anaerobic cellular respiration or just anaerobic respiration.

This caused carbon dioxide to be produced, this carbon dioxide gas bubbles in the dough, causing it to rise.

Really, really great work if you got that right.

Well done on all your hard work in today's lesson, let's summarise it to make sure it sticks in our brains.

Anaerobic cellular respiration in microorganisms can be summarised as glucose reacts to make carbon dioxide and ethanol.

When microorganisms carry out anaerobic cellular respiration, it is called fermentation.

Humans use fermentation in microorganisms to make products such as bread, yoghourt, and alcoholic drinks.

Amazing work today, well done on all your hard work.

Hopefully you know a lot more now about anaerobic cellular respiration in microorganisms. Take a break now and come back when you're ready for the next lesson.