Lesson video

This lesson is called Bacteria in the Human Digestive System and is part of the unit, the Human Digestive System.

Hi there, welcome to today's lesson.

My name's Mrs. McCready and I'm here to guide you through today's lesson, so let's see what we're going to learn today.

In today's lesson, we're going to learn the important roles of bacteria in the human digestive system and as part of our lesson today, we're going to come across a number of key words.

Now I'll introduce them to you as we go, but if you'd like to note them down now or with their definitions, just pause the video and make a note.

So in our lesson today on bacteria in the human digestive system, we're going to firstly look at what bacteria are before we look at how bacteria are used in the digestive system, are you ready to get started? I know I am, so let's go.

So bacteria are living organisms, that means they are alive just like you and I are.

They are found pretty much everywhere, they are found on most surfaces.

They're found in the water, in soil and in the air.

They're found on our skin and they're also found inside of us, so bacteria are almost everywhere.

Pretty much everywhere we go, everything we touch, we'll come across bacteria.

Now, bacteria are tiny.

They are so small that they can only be seen using a microscope.

So if we take a sample of bacteria, which we've grown on a plate and put it onto a microscope and zoom in, we'll see these really tiny microscopic creatures, so let's just check.

Bacteria are unicellular microorganisms, that means they are made of a single cell, let's just check our words.

Unicellular means that cellular, they are made of cells and uni, they are made of one, uni meaning one.

They are unicellular microorganisms, micro meaning very small and organism meaning a living thing.

So bacteria are unicellular microorganisms, they are very small living things made of one cell.

Now bacteria have a number of components that we would expect to see in a cell.

For instance, bacteria have a cell wall and they also have DNA, but that DNA free floats in the cytoplasm.

So bacteria are living things and they have these key components to their body, to their cell, so let's just quickly check our understanding.

What I'd like you to do is join the two correct boxes to describe bacteria, I'll give you five seconds to think about it.

So hopefully you have selected unicellular and joined it to microorganisms, well done if you did.

Now, some bacteria are pathogens and that means that they can cause disease, now you've probably come across some of those diseases before.

For instance, E.

coli, you might have heard of that bacterium causes food poisoning, pretty unpleasant.

C.

difficile can infect wounds and be really, really painful and very unpleasant as well.

And streptococcus pneumoniae causes pneumonia, which is a condition of the lungs, which makes it really hard to breathe, can be very nasty and even fatal.

We can see in the picture there an example of E.

Coli, which causes food poisoning and food poisoning makes you sick and gives you diarrhoea as well, very unpleasant.

So some bacteria are pathogenic, they cause disease, but other bacteria do not harm us and some bacteria are very helpful indeed.

So some bacteria we use to make medicines, other bacteria we use to make yoghourts and cheese.

If it weren't for bacteria, we wouldn't have yoghourts and cheese and other bacteria are used for other processes like making tea and coffee, actually preparing tea and coffee so that we can then go and make our cups of tea and coffee afterwards.

So some bacteria are unpleasant and nasty, but most of them are either harmless or very helpful indeed.

So let's just check our understanding.

Is this statement true or false? All bacteria are pathogens? Don't forget to justify your answer, I'll give you five seconds to think about it.

Okay, hopefully you have said that this statement that all bacteria are pathogens is false and hopefully you have justified your answer by saying that some bacteria are useful and not harmful to humans, well done if you did.

What I'd like you to do now is to firstly label the bacterium diagram with the labels listed, and then I'd like you to give an example of how bacteria can be helpful and unhelpful to us.

So pause the video, take your time and come back to me when you are ready.

Okay, let's check our work.

So you should have labelled the bacterium with the cell wall around the outside.

The DNA is that single loop in the centre and the cytoplasm that substance everywhere else inside the cell.

So your label should be roughly where or at least pointing to the parts of the cell as I have.

So next, I asked you to give an example of how bacteria can be helpful and unhelpful to us.

So you might have included unhelpful examples such as those causing disease, E.

coli causing food poisoning, C.

difficile infecting wounds and streptococcus pneumoniae causing pneumonia or you might have included helpful examples such as making medicines, yoghourts and cheese, tea and coffee, or perhaps you've included other examples that you know of.

Okay, let's move on to the second part of our lesson, which is about bacteria and its role in digestion.

So we know that food contains carbohydrates, proteins, and fats, and we also understand that these are large molecules which must be broken down into smaller molecules, so that they can be absorbed into the blood and used for energy growth and repair.

Now, in order to break those foods down into their smaller nutrients which can be absorbed, we have to use bacteria.

There are millions of bacteria which live within our digestive system, and collectively these are called our gut flora, so bacteria are present in the stomach and in the small and the large intestines, and they are importantly involved indigestion of our food.

Bacteria are really important in the human digestive system, because they help to digest food that we are unable to digest ourselves, remembering that digestion is breaking large molecules down into small ones, some of this happens with the help of bacteria.

So bacteria produce some enzymes that digest our food that we just cannot make.

So we do make some enzymes, but we cannot make them all and instead bacteria make those enzymes and release them into our digestive system to help digest some of our food.

So if it weren't for bacteria, some of our food would remain undigested.

Enzymes are involved in chemical digestion and enzymes speed up the reactions that they help to facilitate.

In the case of digestion, enzymes, speed up reactions involved in digesting or breaking down food from large molecules into smaller ones, so that they can be absorbed and those large molecules are broken down by the enzyme.

So the large molecule changes from a large molecule into a smaller one, but the enzyme that is doing that reaction processing that reaction remains unchanged.

And we can see that in the diagram here, that the carbohydrate has been broken down into two small sugar molecules, but the enzyme has remained unchanged and can be reused again for another reaction.

So bacteria are important in producing a range of enzymes that we cannot make that are directly involved in digesting our food into nutrients.

Bacteria also make vitamins that we need to keep ourselves healthy for instance, vitamin K.

Now these vitamins we cannot make ourselves, but we need them to maintain our health and bacteria are really useful because they make them for us instead.

Bacteria have a third function as well within our digestive system, and that is to compete with pathogenic bacteria in the gut to prevent them from making us ill.

So pathogenic bacteria are bacteria that causes disease and the gut flora bacteria in our gut compete with these pathogenic bacteria for food and for space to live.

So by being present within our gut, they are taking up space, stopping pathogenic bacteria from growing there instead and they are also competing for food and so preventing bacteria from getting the nutrients that they need in order to survive and to make us ill.

And so bacteria, the gut flora bacteria, the good bacteria in our gut is helping us to stay healthy by competing for food and space to live and out competing the pathogenic bacteria as a result, so these are really useful functions that bacteria offer us.

Let's just check our understanding on that then.

Which of these roles in digestion do gut bacteria provide? Do they produce minerals? Do they make enzymes or do they compete with other nutrients? What do you think? I'll give you five seconds to decide.

So well done, if you spotted that they make enzymes.

Now there are a number of things that can kill our gut flora, the bacteria living inside our digestive system, and these include taking antibiotics for another infection that we have, being unwell or having a poor diet, all of these things can kill our gut flora.

And if our gut flora get killed off, then some of our food will not be able to be digested and will remain undigested.

So some of that digestion by bacteria simply won't happen and therefore some of the nutrients that we need and would have got from that process of digestion by bacteria are not made and that means that we will suffer as a result.

So it's really important to keep our gut flora living and well, because if we don't, it can lead to pain and diarrhoea.

And if it happens for a very long time, it can cause other diseases and eventually can cause death as well.

So it's really important that we look after our gut bacteria and we can do that in a number of different ways.

For instance, we can eat a range of fruit and vegetables, which will help to nourish our gut bacteria, we can also consume probiotic drinks and yoghourts, we can also eat fermented food like kimchi and kombucha.

All of these things will help to keep our gut bacteria healthy and alive and therefore keep us healthy and alive, so a quick check of understanding.

What I'd like you to do is choose one option for each statement, is the statement right? Are you sure it's right? Do you think it's right? Do you think it's wrong or are you sure it's wrong? So the statements are eating fruit and vegetables is helpful to our gut bacteria, taking antibiotics is harmful to our gut bacteria.

We can digest all of our food without gut bacteria and the bacteria that live in our gut are pathogens.

I'll give you a few seconds to decide and then we'll go through each statement.

Okay, so statement A is right, statement B is also right.

Statement C is wrong and statement D is also wrong.

Well done if you got all of those right.

So what I'd like you to do now is to have a look at this conversation that these students are having about bacteria and how they are useful in the digestive system.

Now, unfortunately, they've made a few mistakes, so what I would like you to do is to read their ideas and rewrite them to correct their mistakes.

Now, take your time.

Really consider what they've said and work out where they're wrong, pause the video and come back to me when you are ready.

Okay, let's check our work.

So Aisha, you should have corrected her to say, enzymes are really important in digestion, they are made by bacteria to digest some of our food.

For Sam, you should have said bacteria make enzymes to digest our food.

There are millions of bacteria in our digestive system, and for Lucas, you could have corrected him to say that bacteria compete with each other for food and space, pathogenic bacteria can make us ill.

So just review your work, make sure you've made the correct amendments and well done.

Okay, let's summarise our lesson now then.

So in today's lesson on bacteria in the human digestive system, we have seen that bacteria are unicellular microorganisms and some of those bacteria are pathogens, which means that they can cause disease, but many of them are helpful and can be used to make food and medicines.

Bacteria live in our digestive system and produce enzymes which digest food that we cannot digest ourselves.

Bacteria also compete with pathogenic bacteria to stop them making us unwell.

So I hope you've enjoyed today's lesson, thank you very much for joining me and I hope to see you again soon, bye.