Lesson video

Hello and welcome to this lesson from the Oak National Academy.

Today's lesson is called Anaerobic Cellular Respiration in Humans and Other Organisms. It is taken from the unit aerobic and anaerobic cellular respiration.

Hi, I'm Mrs. Wheate, and I'm gonna be your teacher 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 humans, plants, and microorganisms, and explain where, why, and when it takes place.

Let's have a look at our keywords.

Today's lesson has five keywords, so I'm gonna read them through all now, but if you want a bit more time, I'll be quiet for about five seconds, so you can read them through all to yourself.

But if you want even longer than that, you can pause the video and click play when you're ready to continue with the lesson.

So here are our keywords.

Cellular respiration, an exothermic chemical process that transfers energy for life processes using glucose as a fuel.

Anaerobic, a process that does not require oxygen.

Lactic acid, a product of anaerobic cellular respiration in humans that causes muscle cramps.

Oxygen debt, the amount of oxygen necessary to remove lactic acid from the body after exercise.

And fermentation, anaerobic cellular respiration in yeast that produces ethanol, which is a type of alcohol, and carbon dioxide gas.

Today's lesson is in two parts.

In the first part of today's lesson, we'll talk about anaerobic cellular respiration in humans.

And then in the second part of today's lesson, we'll talk about anaerobic cellular respiration in other organisms such as plants and microorganisms like yeast and bacteria.

But first, let's talk about anaerobic cellular respiration in humans.

Our muscles work really hard when we exercise, and so they need energy in order to do that work.

The mitochondria in contracting muscle cells need a lot of oxygen for aerobic cellular respiration, that cellular respiration that requires oxygen to occur, and this transfers energy for muscular contraction.

So here we've got some muscles, some muscle tissue, bicep and a tricep.

If we magnify in there, we can see an individual muscle cell.

And inside those muscle cells are mitochondria, and that's the site of aerobic cellular respiration.

Sometimes during exercise, oxygen cannot be transported to the muscle cells fast enough for aerobic cellular respiration to recur, so a different process happens instead.

This is called anaerobic cellular respiration.

So anaerobic cellular respiration is another type of cellular respiration.

It takes place when there is no oxygen available or not enough oxygen available for aerobic cellular respiration to occur.

So if we look at that word anaerobic and we break it down into its original meaning, we've got the aerobic part, which means requires oxygen.

So aerobic cellular respiration, respiration that requires oxygen to occur.

If we look at that an, we look at the prefix there, that means without.

So anaerobic cellular respiration means a form of respiration that occurs without oxygen.

So like aerobic cellular respiration, it's an exothermic chemical process.

So that means it transfers energy to the surroundings.

It transfers energy for life processes and uses glucose as a fuel.

It transfers less energy than aerobic cellular respiration, but it transfers energy more quickly.

Let's check to see if you understood that.

True or false, anaerobic cellular respiration occurs without oxygen.

Is that true or is that false? Take five seconds, or if you want some more time to think about it, click pause, and click play, when you're ready to see the answer.

It is true.

Okay, why is it true? So how do you know that anaerobic cellular respiration is the type of respiration that occurs without oxygen? Again, take five seconds, or if you want some more thinking time, click pause, click play, when you're ready to the answer.

Let's look at the answer.

Aerobic means requires oxygen, and an, the prefix an, A-N, before aerobic means without.

Anaerobic cellular respiration takes place when there is no oxygen available for aerobic cellular respiration.

Great job if you got that right.

Aerobic cellular respiration occurs in the mitochondria of cells, but anaerobic cellular respiration takes place only in the cytoplasm of cells, and the mitochondria are not involved at all.

Okay, so what we're gonna look at now is a summary of the reactants and products of anaerobic cellular respiration.

We're gonna put them into equations.

Just like aerobic cellular respiration, anaerobic cellular respiration isn't just one chemical reaction, it's a series of different chemical reactions.

Well, kind of my definition at the start, I called it a chemical process.

However, it is really, because it is such a long process, it's useful to summarise it in equation.

So having the back of your mind that this equation is telling you the full story, but it is a useful summary.

So we're gonna look at the word equation and the balanced symbol equation.

And so there is only one reactant, and that is glucose.

And this is how you represent that as a balanced symbol formula.

So the glucose reacts to make lactic acid, and this is how you represent that, balanced symbol formula.

Let's check to see how you're doing.

Which of the following is a reactant of anaerobic respiration in humans? Is it A, oxygen.

B, glucose.

C, carbon dioxide.

Or D, lactic acid.

Take five seconds or click pause, if you want a bit more thinking time, click play, when you're ready to see the answer.

The answer is B, glucose.

Great job if you got that right.

Let's do another one.

Which of the following is a product of anaerobic cellular respiration in humans? Again, take five seconds or click pause, if you want a bit more thinking time, click play, when you're ready to see the answer.

It is D, lactic acid.

But let's look at the other answers.

A, oxygen.

Oxygen isn't a product, nor is it a reactant of anaerobic cellular respiration.

Anaerobic means without requiring oxygen.

So oxygen's nothing to do with this.

B, glucose.

Well, that was the reactant, so it can't also be the product.

C, carbon dioxide.

Carbon dioxide gas not involved in anaerobic respiration in humans at all.

Well done if you got that right.

In this part of the lesson, we're gonna talk about that product, lactic acid, in more detail.

The lactic acid produced by anaerobic cellular respiration in humans is a waste product that can cause muscle cramps.

So our body has a lot of mechanisms that get rid of this lactic acid.

It is transported to the liver by the blood where it reacts with oxygen, and it's either broken down into carbon dioxide and water, which are then excreted.

Or converted to glucose, and then glycogen, which is stored in the liver and the muscles.

And that glycogen can then at later date be broken down back into glucose, ready to be used in either aerobic or anaerobic cellular respiration.

It's normal to rest and breathe deeply after you finish exercise.

I'm sure you've noticed before, maybe you did 100 metre sprint in PE, you even after, you know, it's only what, like 12, 13, depending on how fast you are, 15 seconds of physical exercise.

But afterwards, you might be breathing really deeply for a long time.

It's like, "Well, what's going on? Why is that happening?" So this is because your body needs as much oxygen as possible to remove the lactic acid from your cells.

Breathing rate and heart rate.

So breathing rate obviously increases, because you're trying to get as much oxygen, while breathing in air, and then that oxygen diffusing into your blood vessels.

That makes sense.

Your heart rate remains high after exercise as well, because your heart is what moves that oxygenated blood around your body to the muscle cells that need it.

So I'll read that again.

Breathing rate and heart rate remain high after exercise to facilitate this getting as much oxygen to all of your muscle cells as possible.

And the amount of oxygen we need to remove lactic acid from our bodies is called oxygen debt.

So it's got a specific time, it's called oxygen debt.

And it's, well, that's all to do with the fact that after you finish strenuous exercise, you're still breathing in deeply, your heart rate is still elevated.

Okay, let's check to see if that made sense.

Complete the sentences about cellular respiration.

Use the words on the list.

Anaerobic, aerobic, debt, respiration, oxygen, quotient, heart, water.

After exercise, blank, is needed to remove the lactic acid produced by, blank, cellular respiration.

Breathing rate and, blank, rate remain high after exercise in order to take in as much oxygen as is needed.

The amount of oxygen needed to remove lactic acid for the body is known as oxygen, blank.

So take five seconds or if you want some more time, click pause, click play, when you ready to see the answer.

Okay, let's look at the answers.

After exercise, oxygen is needed to remove the lactic acid produced by anaerobic cellular respiration.

Breathing rate and heart rate remain high after exercise in order to take in as much oxygen as is needed.

The amount of oxygen needed to remove lactic acid from the body is known as oxygen debt.

Well done if you got that right.

This is our first practise task of today's lesson.

Number one, write the word equation for anaerobic cellular respiration in humans.

Number two, write the balanced symbol equation for anaerobic cell respiration in humans.

Number three, where does anaerobic respiration occur? Number four, state two differences between anaerobic cellular respiration in humans and aerobic cellular respiration.

Number five, describe what happens to the lactic acid produced by anaerobic respiration.

Number six, explain why breathing rate and heart rate remain high after exercising.

And finally, number seven, explain what is meant by oxygen debt.

You need to pause your video now in order to give yourself enough time to think through your answers to write them down, click play, when you're ready to continue with the lesson and to see the answers.

Good luck.

Let's check your answers.

Number one, write the word equation for anaerobic cellular respiration in humans.

So glucose reacts to make lactic acid.

And number two, we wanted that in a balanced symbol equation.

So this is what it looks like as a balanced symbol equation.

I'll give you a few seconds to just double check that what you've written on your page is the same as what is on the screen here.

Number three, where does anaerobic respiration occur? It occurs in the cells cytoplasm.

Number four, state two differences between anaerobic cellular respiration in humans and aerobic cellular respiration.

So anaerobic cell respiration in humans.

It occurs in the cytoplasm only.

It transfers less energy.

And it's a shorter process, so it transfers energy more quickly.

Or you could have written that the other way around.

Aerobic cellular respiration in humans occurs in the mitochondria and the cytoplasm.

Transfers more energy.

And it's a longer process, so it transfers energy more slowly.

Number five, describe what happens to the lactic acid produced by anaerobic respiration.

It is transported to the liver by the blood, reacts with oxygen and is either broken down into carbon dioxide and water then excreted.

Or converted to glucose, and then glycogen and stored in the liver and muscles.

Number six, explain why breathing rate and heart rate remain high after exercising.

To gain as much oxygen as possible in order to remove the lactic acid.

And number seven, explain what is meant by oxygen debt.

The amount of oxygen necessary to remove lactic acid from the body after exercise.

Great job if you got those right.

We've completed the first part of today's lesson.

We've talked about anaerobic cellular respiration in humans.

Now we're gonna talk about anaerobic cellular respiration in other organisms such as plants and microorganisms like yeast and bacteria.

Anaerobic cellular respiration also occurs in plants and in microorganisms like yeast.

There are similarities between anaerobic cellular respiration in plants and yeast, and anaerobic respiration in humans.

So they both occur when oxygen is not available.

Glucose is the only reactant.

It occurs only in the cell cytoplasm.

It transfers less energy than aerobic cellular respiration.

It transfers energy more quickly than aerobic cellular respiration, 'cause it's a shorter process.

However, the products are different and that's the main difference between them.

Anaerobic cellular respiration in plants and yeast is a chemical process, a series of chemical reactions.

But again, just like anaerobic cellular respiration in humans, because it's such a long process, we can summarise the reactants and products, and put it into an equation.

Have it in the back of your mind, when you see these equations, they're not telling you the whole story, but they are a very useful summary of what's going on.

So we're gonna do it as a word equation and a balanced symbol equation.

The reactant is glucose.

This is how we represent glucose in balanced symbol formula.

So glucose reacts to make.

We've got two products, ethanol and carbon dioxide.

And this is how you represent those as part of a balanced symbol equation.

Let's check to see if you understood that.

Which of the following is a product of anaerobic respiration in plants and microorganisms? Is it A, carbon dioxide.

B, glucose.

C, water.

Or D, ethanol.

Take five seconds or if you want some more time, click pause, click play, when you're ready to see the answer.

Let's look at the answers.

So A, carbon dioxide is correct.

And D, ethanol is correct.

Great job if you got that right.

Let's look at the other answers.

So B, glucose.

That's incorrect, because it's a reactant of anaerobic respiration.

C, water.

That's incorrect as well.

That's not involved in anaerobic respiration in plants, in microorganisms, or in humans.

True or false.

Anaerobic cellular respiration in humans and plants are similar processes.

Is that true or is that false? Take five seconds, if want some more time, click pause, click play, when you ready to see the answer.

Yeah, it is true.

Okay, why is that true? Take another five seconds, or click pause, if you want more time, click play, when you ready to see the answer.

They both are forms of respiration that occur when oxygen isn't available, but they are not identical.

For example, they have different products.

Great job if you got that right.

In plants and microorganisms, anaerobic cellular respiration happens in particular conditions.

For example, some plants and bacteria live in wetlands where the soil is waterlogged with a low oxygen concentration.

So my photo here is of a wetland and it's a semi-aquatic area or ecosystem.

And so we've got a lot of it is grassy, and other like small short plants.

But then we also have large areas of very waterlogged, completely water saturated soil.

And so you might not have heard the word wetland, but you probably have heard the term marsh or swamp, or peat bog or just bog.

Those are all types of wetland.

So the plants that grow in these areas, the roots grow into the waterlogged soil, and they can't absorb oxygen from the water.

So some plants can absorb oxygen from water, for example, pondweed, which you might have come across in your science lessons.

But these plants specifically, they can't, not all plants, because you can't just put any plants under these water and expect it to thrive.

So these plants, they can't aerobically respire underneath the water.

They can't absorb oxygen from the water, so the roots carry out anaerobic cellular respiration.

So because the roots can't absorb the oxygen that's in the water, they don't carry out aerobic respiration, they carry out anaerobic cellular respiration.

And the bacteria growing in the waterlogged soil, they do the same.

They also carry out anaerobic cellular respiration in order to transfer the energy they need for life processes.

When anaerobic cellular respiration happens in microorganisms, it has a special name, it is also called fermentation.

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

Anaerobic cellular respiration in yeast produces ethanol, which is a type of alcohol, and this enables us to make alcoholic drinks by fermenting the sugar that's inside crops.

Yeast is also added to bread dough to make it rise during baking.

It breaks down the carbohydrates in the flour into glucose.

Because there is little oxygen in dough, the yeast cells use the glucose to respire anaerobically.

The ethanol produced evaporates due to the heat of the oven.

The boiling point of ethanol is only around 80 degrees, so the breads in the oven are around 200 degrees, so there's definitely no ethanol left in the bread.

The carbon dioxide gases produced by anaerobic respiration that causes the bread to rise or swell up.

And you can see that in the picture here.

You can see the holes in the bread, which are caused by bubbles of carbon dioxide gas, which causes the bread to rise.

Let's check C, if you understood that.

Fermentation is a type of anaerobic cellular respiration that occurs in A, animals.

B, plant.

Or C, microorganisms. Take five seconds, or if you want a bit more time, click pause, click play, when you're ready to see the answer.

The answer is C, microorganisms. Great job if you got that right.

This is the final practise task of today's lesson.

Great job so far.

Number one, write the word equation for anaerobic cellular respiration in plants and microorganisms. Number two, write the balanced symbol equation for anaerobic cellular respiration in plants and microorganisms. Number three, state one similarity and one difference between anaerobic cellular respiration in plants and anaerobic cellular respiration in humans.

Number four, what is fermentation? And number five, describe two ways in which humans use fermentation to make food or drink products.

You'll need to pause the video now to give yourself enough time to think about your answers and to write them down, click play, when you're ready to move on the lesson and see the answers.

Good luck.

Let's have a look at the answers.

Number one, write the word equation for anaerobic cellular respiration in plants and microorganisms. So glucose reacts to make ethanol and carbon dioxide.

And number two, I wanted that as a balanced symbol equation.

This is how you represent that as a balanced symbol equation.

I'll give you a few seconds, so you can look through it, and just really make sure that what you've written on the page is the same as what I've got here on the slide.

Number three, state one similarity and one difference between anaerobic cellular respiration in plants and anaerobic cellular respiration in humans.

So the similarities occurs when oxygen is not available.

Glucose is the only reactant.

Occurs only in the cell cytoplasm.

Transfers less energy than aerobic cellular respiration.

Transfers energy more quickly than aerobic cellular respiration.

And the difference, this got different products, ethanol and carbon dioxide in plants, and lactic acid in humans.

Number four, what is fermentation? Fermentation is a process of anaerobic cellular respiration in microorganisms such as yeast and bacteria.

And finally, number five, describe two ways in which humans use fermentation to make food or drink products.

Fermentation in yeast produces ethanol, which is used to make alcoholic drinks, including wine and beer.

Fermentation in yeast also produces carbon dioxide gas, which is used to make dough rise when baking bread.

Great job if you got those right.

Great job on all your hard work today.

Let's summarise the lesson to help us remember it.

Anaerobic cellular respiration is a type of cellular respiration that takes place in the cell cytoplasm without oxygen.

Equations for anaerobic cellular respiration in humans.

Glucose reacts to make lactic acid.

And here's the balanced symbol equation, I'll give you a few seconds to make sure you copy that down correctly.

Lactic acid can cause muscle cramps and lead to oxygen debt.

Anaerobic cellular respiration transfers less energy more quickly.

Equations for anaerobic cellular respiration in plants and microorganisms, also called fermentation when anaerobic cellular respiration occurs in microorganisms. So glucose react to make ethanol and carbon dioxide.

Here it is as a balanced symbol equation.

I'll give you a few seconds to make sure that you've copied it done correctly.

And finally, the products of fermentation are useful in food and drink making.

Again, really great job on our lesson today, and I hope to see you again soon for our next lesson.