Lesson video

Hi there, I'm Mrs. Kemp, and welcome to today's lesson all about food is a source of building materials and energy.

It fits really nicely into our diet and exercise unit, but you might also recognise some of the information from where you've looked at healthy diets back in primary school.

So today's lesson has a main outcome and that is I can explain how food is used for growth and repair and to provide energy, and interpret information on food labels about the amounts of nutrients and energy provided by different foods.

These are some of the key terms that we're going to be using today, and if you want to have a little look at those in a little bit more detail, please do pause the video.

Otherwise, don't worry, I will be explaining them as we go.

Okay, I'm excited to get started, so let's move on to our first learning cycle.

So we've got three altogether today, why we need food, different individuals have different requirements and food labels.

So of course we're going to be starting with why we need food.

So a little thing for us to do, first of all, can you remember drawing food chains back in year seven at some point? What I would like you to do is draw me a really quick one.

If you need more time, you can pause the video at this point.

Okay, I'm gonna show you an example one so you can kind of check against it.

So you should have something that is a producer at the beginning okay? So typically that would be a plant, but you could also have algae, you could also have some bacteria.

We've then got our primary consumer.

I've got a caterpillar here that eats the leaves of that grass.

And then you should have a secondary consumer, which I've got a bird.

The bird, of course, would eat the caterpillar.

The food in this food chain is always made by the producer, and that's why we need that at the start of our food chain.

The food is then passed along that food chain every time the next consumer eats it, okay? So our primary consumer, our caterpillar is eating the plant and it's passing that food along the chain.

They all use that food in order to build something called biomass.

Now, biomass might be a new word to you.

So let's break that down and really have a think about it.

So we've got bio and we've got mass.

Whenever you have bio on the front of a word, so the prefix, then that means that it's related to living things.

It means life, such as biology, the study of living things.

That bio means life.

The mass then is the amount of matter that is in that object.

So biomass is the amount of matter that makes up a living thing.

Now, actually, biomass is not just the mass, but it is in fact the dry mass, okay? And we need to do a special thing to that organism before we can actually find out its dry mass, okay? So first of all, we need to obtain it, okay? And then we need to put it into an oven, all right? What it does is it dries that organism out and removes all of the water.

Now, because that process will obviously mean that that organism would die, then we need a really good reason to do this, to work out their biomass.

Normally, we would probably just look in a book and see what other people have found for this.

We wouldn't necessarily do it every time.

Once it's been dried out then, and we are sure that there's no water left, we would put it back into the oven, take it out, weigh it again, put it back into the oven, take it out and weigh it again.

Once it had reached a completely stable weight, we know that that is just the biomass left and not any water.

So the food that is the source of building materials for this biomass, then we use for growth and repair, okay? Children such as yourselves, you will be growing all of the time and you'll require lots of different foods in order for that to happen.

So your carbohydrates, your proteins, your lipids, your vitamins and minerals are all really important.

Everybody, of course, they will also need to not just grow, but also repair any damaged tissues.

We can see in that little image there where that person's got the cut on the back of their head and their body is sealed that up essentially.

And that's what you can see the scar there.

Our bodies are amazing things, they can seal up when we have some sort of damage.

So moving onto then our first check.

Which method best describes how to find the biomass of an organism? Is it A: weigh the living organism on an electronic balance, B: first dry out the organism in an oven and then weigh on a balance, or is it C: first weigh the organism on an electric balance and then dry out in the oven? I'll give you a little moment to think about that.

But if you do need more time, please do pause the video.

Okay, did you think B: first dry out the organism in an oven and then weigh on a balance? Excellent, really well done.

So as well as growth and repair, we also use our food for other things.

And in particular, we use it as a fuel to provide us with energy.

We use energy for lots of different life processes.

You probably remember those life processes from the cells topic back in year seven.

So we need to carry out chemical reactions in our cells.

So we build up molecules such as proteins, and that does require energy.

Also, do you remember those muscles from the muscle and skeleton system back in year seven as well? That actually in order for those muscle cells to work to contract, they do need energy.

There are other types of movement as well that require energy.

But essentially all living things require energy in order to stay alive.

So what happens to our food is that once we've taken it in, okay, it needs to be broken down in our digestive system, and that will then provide all the nutrients that we need in our cells, including that all important glucose.

Glucose is that fuel then that along with oxygen, provides energy for our cells in a process that we call cellular respiration.

Hopefully you'll remember our animal cells and we remember that one of the parts of the animal cell is called the mitochondria.

Here we can see it on the diagram there.

And the mitochondria is where cellular respiration takes place.

And both animal and plant cells contain those mitochondria.

The energy that is provided for them by respiration is used in all of those life processes and all of the things like muscle contraction, like creating longer chains of molecules such as proteins.

Onto our next check then, which processes use food as a fuel to provide energy, A: cellular respiration, B: digestion, C: movement, or D: photosynthesis.

You have a little thing for a moment.

If you need more time, please do pause the video.

Did you think A: cellular respiration? Brilliant.

Well done.

Okay, onto our first task of the day then.

So this is task A.

Please do get your worksheet out to record your answers on it.

Number one, write a definition for biomass.

Number two, draw an example of a food chain and describe how the consumers get energy from the food that we eat.

Number three, suggest some ways the organism may use the energy provided by their food.

I'll give you a little moment to think about it, but if you do need more time, please do pause that video.

Okay, so number one, the definition for biomass.

Biomass is the dry mass of a living organism.

Number two, remember you should start with a producer.

You've probably drawn something like a plant or maybe some algae.

Number two, a primary consumer.

This is something that will eat the plant.

And number three is a secondary consumer that will eat the primary consumer.

Consumers digest the food they eat to provide glucose, which is used as a fuel for cellular respiration to provide energy.

Finally, number three, some examples would be chemical reactions in cells, muscle contraction and movement.

I hope you've got all those down.

If not, please do add to your answer.

Okay, brilliant.

We're gonna move on to our second learning cycle of today.

Different individuals have different requirements.

Okay, first of all, let's have a little think.

How do you get to school? How much energy do you think it requires? So do you ride a bike, do you walk or maybe you travel by car? Which of those do you do? So when we think about the amount of energy, we need to think about what the units would be for that energy.

So we've got a joule here.

A joule is a unit of energy.

We often see it written as a kilojoule.

A kilojoule is a thousand joules.

And that the amount of activity a person does each day will affect the amount of energy that they require from their food.

So thinking back to how you get into school.

If you were riding your bike, then you will have used about 2.

5 kilojoules per hour.

If you were walking, then you will have used 1.

3 kilojoules per hour.

And if you were just sitting down, so sitting in that car on the way to school, you would've only used about 0.

6 kilojoules.

These are only average amounts though, so other people might use slightly more, they might use slightly less, but it gives us an idea that actually, if you're riding a bike for an hour, you are going to use a lot more energy than if you were sitting in a car.

So scientists have actually looked into this and they've thought about how can we classify people by how active they are? And what they've said is, is that if you are a very active person, okay, then you will be doing all of these things.

You'll be moving around the house, school or work.

So getting up, moving around all the time, you'll be doing at least 60 minutes of gentle exercise, such as walking, leisurely cycling or gardening.

But then importantly, for someone who's very active, you'll also be doing 60 minutes of vigorous exercise, such as running, fast cycling or football or swimming during the day or during the week.

If you're active, then you will be doing those things, okay? But actually you probably won't be doing quite as much vigorous exercise.

And then if you are sedentary, then actually you won't be doing as many of these things at all.

You might just be moving quite slowly around your workplace or around your home.

I wonder where you feel that you would maybe fit into these categories.

Would you put yourself as active? Would you put yourself as very active? Something to consider as the lesson goes on.

So from those categories, what these scientists did is they worked out how much on average that person needed, how much energy that person needed during a day, okay? And we're gonna have a go at reading this graph to see what kind of information we can pick up on it.

So first of all, let's consider this question.

How much energy is needed for a sedentary female in their forties? Now what we'll need to look at is we'll need to look at that slightly a yellowy orange colour there.

We can see that that's going to tell us that they are female.

And then we need to look on that X axis to find where the people are in their forties and also that they are sedentary.

So they are not very active at all.

We then find the bar that is the yellowy colour 'cause that tells us it's the female, and we go along to the axis to find the amount of energy.

And we can see from that that they need on average about 8,000 kilojoules of energy.

So now we know how to read the graph.

We also want to think about what patterns we can see in that data, okay? So overall, looking at it.

And actually what we can see is that no matter which age or sex, as activity increases, so does the amount of energy needed.

So in all of those categories, in the teenager and in the 40 year olds, the sedentary people, they need less energy than the very active people.

We can also see that in both of the age groups, the males actually do require more energy than the females if they have a similar activity level.

Okay, so where you've got your very active teenager there, then we can see that there, that blue line is much higher than that yellowy orange line.

So that tells us that when they've got the same level of activity, actually the males do need more energy.

So you are going to have a little go at this yourself, then onto our next check.

Again, we've got that same graph to show the amount of energy needed per day by different types of people.

How much energy is needed for an active male teenager? I'll give you a little bit of time to think about it, but if you do need more time, please do pause the video.

Okay, let's have a look at what we're looking for then.

We're looking for male.

So of course it's time, we're looking for that blue purple line, and we are looking for our very active teenager.

If we draw a liner on the top of that bar to the Y axis, then we find it's 12,000 kilojoules.

I'm sure you've got that right.

Well done.

Onto our next task of today then, task B.

Again, please do find your worksheet out so you can record your answers.

This time we've got a slightly different graph.

This graph is to show the amount of energy needed per day by different types of people.

Please do make sure that you look very carefully at the key to see which one is the teenager, which one is the over 60.

Also make sure that you read what we've got on the different axis.

So number one, how much energy is required by a sedentary teenager? Number two, how much energy is required by a very active over 60? And number three, what patterns can you see in the data? I'll give you a little bit of time to think about it, but if you do need more time, please pause the video.

Okay, so number one, we should have got 10,000 kilojoules.

Number two, similar answer, 10,000 kilojoules.

Finally, number three, the patterns that we could see are in both age groups.

As the level of activity increases, so does the need for energy per day.

In all levels of activity, the teenagers require more energy, And a sedentary teenager would require the same amount of energy as a very active over 60.

I'm sure you've done really well on those.

Excellent.

Onto our final learning cycle of today: food labels.

So when food is packaged, it should always have a food label that shows nutritional information.

Here's an example of one from some orange juice.

By law, the label actually has to give you certain information on it, and you can see that there is that information on this one.

So the amount of energy, the amount of fat, the amount of saturated fat, carbohydrate, sugars, proteins, and salt.

Now often we do get some other information on there as well.

We can see that on here it's also telling us vitamin C and potassium, but actually those things are not on there by law.

That is chosen by the manufacturer.

Essentially, they are there to help us try and make healthier choices with our food.

So if we can see the amount of fat and we can see the amount of sugar that is in there, then we can make sensible choices from the types of food that we are eating.

It's important to note though, if you think about certain types of foods, like whole foods such as an apple or a banana, they do not have these type of nutritional information on them.

And actually whole foods do tend to be healthier and they're a better decision to make if we are choosing types of food.

Onto our first check then, so this one's a true or false.

By law, a food label must contain information about fat, salt, and vitamin content.

Do you think that's true or false? Can you justify your answer? So by law, salt is not required on a food label.

B: by bylaw vitamin content is not required on a food label.

I'll give you a moment to think about it, but if you do need more time, pause the video.

Okay, of course that is false and our reasoning is that by law, vitamin content is not required on a food label.

Excellent, really well done.

So let's have a go at comparing two our types of food using their food labels, okay.

We're going to be having a look at the energy content in particular, and these are from two different types of breakfast cereal.

So first of all, let's just have a look at what sort of levels they give us.

They give us, first of all, the values that are per a hundred grammes.

If you took that cereal and you weighed out a hundred grammes, this is the amount of energy that you would find in them.

So for A, we've got 1,604 kilojoules of energy, whereas in B, we've got 1,540.

They also mentioned the kilocalories there.

So there's 378 kilocalories in A and 358 kilocalories in B.

So actually per hundred gramme, we can see that A has got more energy in it.

More importantly for us, those individuals, we might actually want to look at the portion size.

And often the portion size for cereal is 30 grammes.

We can see that in B because they are biscuit sized and so they're not a free pouring cereal that actually it's slightly more, it's 38 grammes.

And so in a normal portion of A, there's a 481 kilojoules or 113 kilocalories, whereas in B, there's 575 kilojoules or 136 calories.

So what does that mean for us then? Well, cereal A is actually providing more energy per hundred gramme than cereal B.

Cereal A actually provides 90 kilojoules more than cereal B.

However, the recommended portion size of A, so it's always important to check is eight grammes smaller than in B.

And so that actually means that a recommended portion of A provides 94 kilojoules less energy than B.

Alright, so actually because of that portion size, it does mean that B is going to give us more energy when we look at those portion sizes.

So if a person did follow those manufacturer's recommendation, which of the cereals do you think would be good to recommend to a highly active teenager? So somebody who's doing all of that activity that we mentioned earlier on.

I think that we would go for B, wouldn't we? Because as an active teenager, they're going to require a lot of energy from their food.

They are growing, they are moving, so contracting their muscles all the time.

So therefore they will be using a lot of energy that needs to be provided with their food.

If a person is more sedentary then, yes, they still require energy for movement 'cause they will be moving and also growth, but actually they're going to need a little bit less.

So maybe we would recommend A instead that's got a smaller amount of energy.

We can move on to our final check of today then.

So what are the two units of energy shown on food labels? Have a little look at those.

Do you think it's A, B, C, or D? I will give you a moment to think about it, but if you do need more time, please do pause the video.

Okay, did you come up with A: kilocalories and C: kilojoules? Excellent, well done.

Nicely in time now for our task C, our final task of the day, and again, we can find this on our worksheet, so please do get that out.

So here we've got some food labels and we're going to need those in order to answer these following questions.

So number one, how many kilojoules of energy is provided by a hundred gramme of cereal A? Number two, what is the recommended serving size for each type of cereal? Number three, what is the difference in the amount of calories per serving for A and B? Number four, which cereal would you recommend to an active teenager and why? I'll give you a moment to think about it, but if you do need more time, please do pause that video.

Okay, so if we used our food labels correctly, for number one, we should have one 1,635 kilojoules.

Number two should be 30 grammes.

Number three, A should be 116 takeaway 113, which gives us three kilocalories.

And finally, number four, the cereals provided a similar amount of energy.

Cereal A is slightly higher by three calories, kilocalories, sorry.

So will be provided more energy for an active teenager, but it's very, very minimal.

So if you said both of them are very similar, actually that's pretty good.

So thank you very much for today.

I've really enjoyed it.

Let's just go over that core content in a summary to finish off.

So food is used to make biomass, which can be passed from organism to organism through a food chain.

Food is also used in cellular respiration as a fuel to provide energy for life processes.

Different people will require different amounts of energy in their diet, depending on their lifestyle.

Food labels show information about the nutritional value of the food, and must by law include information about the amount of energy, fat, saturated fat, carbohydrate, sugar, protein, and salt.

People can use the information on food labels to help them make choices about the food they eat.

So again, thank you so much for learning with me today.

I do hope that you'll watch one of my videos again.

And thank you very much.

Bye.