Lesson video

This lesson is called "Obtaining the elements needed to make biological molecules" and is from the unit "Biological molecules and enzymes." Hi there, my name's Ms McCready and I'm here to guide you through today's lesson, so thank you very much for joining me.

In our lesson today, we're going to describe which chemical elements make up carbohydrates, proteins, and lipids, and where producers and consumers get these elements from.

Now we're going to cover quite a number of keywords in today's lesson and they're listed on the screen there for you now.

You may wish to pause the video and make a note of them, but I will introduce these words to you as we come across them.

So in our lesson today we're going to start off by looking at the elements that are obtained from the atmosphere.

Then we're going to have a look at the elements which are obtained from water, then the elements that are obtained from soil, before looking at the fact that consumers rely upon producers.

So I hope you're ready to start.

I certainly am, let's go.

So we know that all organisms require carbohydrates, proteins and lipids to survive and thrive.

That is because carbohydrates, proteins, and lipids form the vast majority of a cell and therefore all of the functions that an organism can carry out.

Now, carbohydrates, proteins, and lipids are really important biological molecules because they help to build up the cells and tissues and they also provide a source of energy as well.

And without those two things, the structure of the organism and the energy in order to make the organism work, an organism cannot survive.

So you can see how important and vital carbohydrates, proteins, and lipids are to an organism's health and survival.

Now, carbohydrates, as you can see from the screen there, this molecule of carbohydrate presented there, they are made from three elements.

Carbon, shown in black in the diagram.

Hydrogen, shown in white in the diagram.

And oxygen, shown in red in the diagram.

And you can see that putting them together in a particular way forms this relatively complicated molecule.

This is called a carbohydrate.

Where the word carbohydrate stands for carbon, hydrogen, and the ate meaning oxygen.

Now, proteins and lipids are also made from carbon, hydrogen, and oxygen, but proteins are made from these small monomers called amino acids.

And amino acids all contain another compound called nitrogen.

And if we have a look at the diagram there on the screen, you can see the carbon, the hydrogen, and the oxygen, but you can also see the nitrogen there present.

Now that's a general structure of an amino acid and there are about 20 different types of amino acids present within living organisms. And there's that big red block called the R group.

And the R group it varies depending on which amino acid it is.

So that's the different bit, but the rest of the amino acid is the same regardless.

And you can see how important carbon, hydrogen, oxygen, and nitrogen are to amino acids.

It's also worth noting that some lipids also contain nitrogen as well.

So let's quickly check.

Which elements are used to build carbohydrates, lipids, and proteins? What do you think? I'll give you five seconds to decide.

Okay, so hopefully you've remembered that carbohydrates, lipids, and proteins share carbon, hydrogen, and oxygen as the elements used to make them.

Now, when we consider how living organisms get those elements, we have to start by looking at plants.

Now, plants are what we call autotrophic producers.

That means that they can make their own food.

So let's just look at that word in a bit more detail.

Auto means self, and trophic means feeding.

So you can see that plants are autotrophic, self-feeding, therefore they can make their own food.

And the word producers is simply a reference to the fact that they are making stuff, they are making their own food, and they are making their own bodies as well, actually.

So they are producing things.

A bit like a factory produces things as well, so does a plant.

So plants are autotrophic producers.

Now let's have a look at the atmosphere.

So what does the atmosphere contain? Well, one of the most important things that it contains is carbon and oxygen, and they are bound together as carbon dioxide in this molecule form.

Now plants are able to absorb, that means take into themselves, carbon dioxide from the atmosphere in through their leaves and then use carbon dioxide in this process of photosynthesis in order to make glucose.

So plants are able to take carbon out of the atmosphere in the version of carbon dioxide and turn it into their body and energy that they need for their body to function, and we have to rely on plants doing that in order for us to obtain carbon for our body.

So let's quickly check our understanding.

What can an autotroph do that a consumer cannot do? Can it make its own food, excrete carbon dioxide, or use glucose as an energy source? What do you think? I'll give you five seconds to decide.

Okay, well hopefully you've remembered what autotroph means and related that to answer A, that an autotroph can make its own food, well done.

So the atmosphere is what we would consider to be an abiotic part of the ecosystem.

So abiotic means non-living because the word A means non and biotic means living.

So abiotic parts of the environment such as the atmosphere are not themselves living.

I know things live within the atmosphere, but that is not the atmosphere itself.

So the atmosphere is a non-living part of the ecosystem, and that is where the carbon dioxide is stored.

Now, plants can use this process of photosynthesis to convert carbon dioxide from the atmosphere, the abiotic part, into carbohydrates that are stored within their cells and tissues, which is the biotic part of the ecosystem.

So plants take carbon dioxide from the atmosphere, the abiotic part.

Using photosynthesis, they convert them into carbohydrates, which is the biotic, the living part of the environment because they're combined within the living organism, the plant in this case.

So photosynthesis is turning abiotic carbon into biotic carbon, from carbon dioxide into carbohydrates.

Now, animals and fungi cannot do that.

We rely entirely upon photosynthetic organisms such as plants in order to harvest carbon dioxide from the atmosphere and convert it into carbohydrates so that we can then consume those and incorporate them into our body.

So it's only producers that can convert carbon from the abiotic environment into the biotic environment.

So let's quickly check our understanding then.

Which living organisms can harvest carbon from the atmosphere? Is it animals, fungi, or plants? I'll give you five seconds to think about it.

Okay, well, hopefully you've remembered that it's only plants that can harvest carbon from the atmosphere.

Well done if you got that right.

I'd also like you to have a think about this.

So here's a couple of sentences about plants and what they can do, and I'd like you to use the words listed on the screen there to complete the gaps in the sentences.

I'll give you a few moments to think about it.

Come back to me when you're ready.

Okay, so let's have a review of this.

So plants are producers because they make their own food, and plants use photosynthesis to convert abiotic carbon dioxide into biotic carbohydrates in their body.

Did you get all of those right? Well done if you did, excellent job.

So what I'd like you to do now is two things.

Firstly, throughout this lesson we're going to create a map, a kind of picture diagram, really, of various different molecules, how they are absorbed and converted within different organisms. So what I'd like you to do is start by drawing a large plant like a tree.

Doesn't have to be fancy, doesn't have to be artistic.

Just a bog standard outline of a tree will be fine somewhere in the middle of your page, I suggest you put it in the middle.

And then what I want you to do is add some labels to the atmosphere, to carbon dioxide, to photosynthesis, and then add an arrow to show how carbon and oxygen move from the atmosphere into the plant.

So have a think about how you're gonna lay that out, what you're gonna include.

Make sure you include all those different bits of it and put that neatly onto your page.

You're going to add to this diagram throughout the whole of this lesson, so make sure you've got plenty of space around it and you do it nice and neatly.

Then once you've done that, I'd like you to use the terms abiotic and biotic to describe how plants convert carbon dioxide into carbohydrates and include as much detail as you possibly can within that description.

So pause the video and come back to me when you're ready, and have fun.

Okay, so let's see what your map might start looking like now.

So hopefully you've added a tree, something very basic like this.

You've added the term photosynthesis within the branches and the leaves of the tree.

You've added atmosphere into the space in the air.

Carbon dioxide within the atmosphere space as well.

And then an arrow to show that carbon dioxide is moving into the plant and it's associated with this process of photosynthesis.

So that's our starter, we're gonna keep coming back to that throughout today's lesson.

Then in response to question two, which was about using the terms abiotic and biotic to describe how plants convert carbon dioxide into carbohydrates, you could have included things such as that carbon is found in the atmosphere as carbon dioxide, that plants use this process of photosynthesis to convert carbon dioxide into carbohydrates, and that photosynthesis moves carbon and oxygen from carbon dioxide from the abiotic atmosphere into biotic living organisms. Hopefully you've used all of those words, including abiotic and biotic, as I asked you to within the question.

So just review your answer, make sure you have used abiotic and biotic and that you've talked about how CO2, carbon dioxide, is moved into carbohydrates by plants.

And well done.

That required a bit of thinking about, so that was good work.

Okay, so let's move on to our next section of our lesson.

So this is about elements from water.

So water is a compound made of hydrogen and oxygen.

You can see the diagram there.

We've got a large oxygen molecule and then two hydrogen molecules on either side.

And all organisms are able to take in water for use within their bodies.

You can see in the picture there is a gazelle on its knees drinking from a lake, and of course we all drink water as well.

Now plants use water to sustain themselves, but they also obtain hydrogen from the water that they take into their body as well.

So you can see that water is made of oxygen and hydrogen, H2O, so it's two hydrogen molecules and an oxygen.

Through photosynthesis, plants are able to split that water into hydrogen and oxygen, so they're able to split water into the two hydrogen molecules and the one oxygen molecule.

Plants have already taken carbon dioxide into themselves via their leaves from the atmosphere, and with the hydrogen, they're able to combine those together, the hydrogen from water plus the carbon and the oxygen from carbon dioxide, into carbohydrates, and you can see how carbon, hydrogen, and oxygen are all recombined into a different shape, into a different configuration to form glucose.

And the oxygen that the plants have split off from the hydrogen from water is actually a waste product in this process, so this is what's happening in the process of photosynthesis, this is what plants are doing to the water and the carbon dioxide that they require as part of photosynthesis.

So oxygen's a waste product.

So let's have a quick look at this.

Which compounds are represented by X and Y in the diagrams? We've got water leading to X and carbon dioxide leading to glucose, with Y as a waste product.

I'll give you five seconds to think about it.

Okay, so what is X? So X is hydrogen because hydrogen, carbon, and oxygen are all combined together to form glucose.

And Y is oxygen.

Remember, oxygen is a waste product to plants.

So what I'd like you to do now is to carry on with that map that we've already started.

So you've got your tree and the atmosphere and photosynthesis already listed.

What I'd like you to do this time is to add a raining cloud to your diagram, which is raining into a lake which is filling up.

I want you to add the label water and I want you to add arrows to show how water is moving from the lake into the plant where it is ultimately used for photosynthesis.

So have a think about that.

Add this raining cloud into a lake and then the water moving from the lake into the plant ready for use in photosynthesis.

Once you've added to your map, I would then like you to describe how water is used by plants in photosynthesis.

You may want to draw a different diagram or you might want to use a flow chart if you wish to.

We've already seen how that looks in our lesson so far today.

So how is water used by plants in photosynthesis? How is it split up and what's it used for? So pause the video, come back to me when you're ready.

Okay, so let's see what your map might be looking like now.

So you've already got your atmosphere and photosynthesis and your tree.

Hopefully you've added your raining cloud and it's raining into a lake.

And from the water in the lake, it's moving via the ground into the plant.

I've added root hair cells on, you might not necessarily have included that bit of detail.

And then up the trunk of the tree to photosynthesis, which is happening in the leaves of the plants.

So the water is having to move through the whole tree up to the leaves so that it can be then used there.

So make sure you've got all that detail and your map is ready to go for the next stage.

Then let's have a look at the next question, which was about describing how water is used by plants in photosynthesis, and you could have drawn a diagram if you wanted to.

So you might have included commentary along the lines that photosynthesis splits water into hydrogen and oxygen, and that oxygen is ultimately a waste product in this process.

The hydrogen is combined with carbon dioxide to form a carbohydrate called glucose.

And you might have included a diagram such as this one where water is being split into hydrogen and oxygen and then combined with carbon dioxide to form glucose.

Check over your work, make sure you've got all the salient important details before we move on.

And well done, again that was quite tricky to do.

So let's move on to the next part of our lesson about elements that are obtained from the soil.

So many structural and functional molecules, including all enzymes, are proteins, and we know that proteins are made from amino acids.

So these are the monomers which are joined together in a very long chain to form the protein, and then that protein is folded up into its final shape so that it can do its job.

Now, the order that those amino acids are joined together in is coded for within DNA, and that DNA is stored within the nucleus of the cells.

So DNA is really important.

It stores the instructions for how to build a protein using the right amino acids in the correct order.

And putting DNA and turning it into a protein chain of amino acids is called protein synthesis.

This process is called protein synthesis and ultimately results in the protein itself.

So this is a really important fundamental process that's going on within all living organisms. Now, proteins are made using carbon, hydrogen, and oxygen and also using nitrogen.

So remember that plants have made carbohydrates using photosynthesis and they're able to use the carbon, the hydrogen, and the oxygen within those carbohydrates, join it with nitrogen, and turn it into amino acids.

So we take our carbohydrate, or rather, a plant takes its carbohydrate, it adds nitrogen to it and turns it into an amino acid.

And from there it can then join lots and lots of amino acids together to form a protein.

So let's quickly check that.

How do plant cells make carbohydrates? Do they make carbohydrates through respiration, through amino acids, through photosynthesis, or through protein synthesis? I'll give you five seconds to decide.

Okay, so have you decided that plant cells make carbohydrates through photosynthesis? I hope so, well done.

Now, nitrogen, where's this coming from? Well, nitrogen is phenomenally abundant within the atmosphere.

About 78% of the atmosphere is made of nitrogen, so it's a really, really common element.

The problem is that getting it out of the atmosphere is really, really tricky, and actually only a very small minority of organisms are able to extract nitrogen from the atmosphere, and this specifically includes bacteria.

So it's bacteria who are able to move nitrogen from the atmosphere into a living organism, into a biotic form from the abiotic atmosphere.

Now, some plants use bacteria within their own structures to do that harvesting of nitrogen.

So green beans and peas are good examples of plants which have adapted themselves to incorporate bacteria into their roots so that they can harvest nitrogen from the atmosphere and turn it into their bodies.

These are real favourites of gardeners as well, gardeners and farmers, because they help to keep the soil nice and fresh because they're adding nitrogen into the soil.

Now all plants are able to absorb nitrogen from the soil, but only a very small minority of them are able to absorb nitrogen from the atmosphere using the help of bacteria.

Now, getting nitrogen from the soil is reasonably straightforward for a plant because dead organisms, including plants, plus animals and fungi, when they die and they decompose release nitrogen and compounds containing nitrogen into the soil.

So these dead organisms get turned into nitrogen-based compounds called nitrates and nitrites.

Nitrates is the NO3 version.

Nitrites is the NO2 version.

So you can see that this is nitrogen combined with oxygen.

And these nitrogen compounds, nitrates and nitrites, are then stored within the soil and then can be harvested by the plants via their roots into their body.

So the plant is able to absorb the nitrates and the nitrites into their body via their root system.

Now, all plants are able to do this.

It's only a very few plants which are able to use bacteria to harvest the nitrogen from the atmosphere itself.

So let's just double check that you've got that.

So which organisms are able to absorb nitrogen through their roots? Is it bacteria, consumers, or all plants? I'll give you five seconds to think about it.

Okay, so hopefully remembering that it's through their roots that I've mentioned here that you've chosen therefore all plants, well done.

So going back to your map that you've been creating of these various different molecules and how they're being absorbed, what I'd like you this time to do is to continue adding to your map but this time add some dead leaves to your picture and some labels indicating the soil, the fact that nitrates and nitrites are present within there.

Remember NO3 and NO2.

And how those nitrogen-containing compounds, nitrates and nitrites, move from the soil into the plant.

So add that detail into your map.

Remember, I'm not looking for artistic prowess and fantastic artistic qualities.

I'm just looking for a very straightforward diagram showing this process.

And then once you've done that, I'd like you to describe what nitrogen is used for in a cell by outlining what it is combined with and what it is used to make.

So pause the video and come back to me when you've finished being creative.

Okay, so let's see what your map might be looking like now.

So you've got the bits that you've already drawn and then you should have added some soil, so I've depicted some dead leaves here.

And with that you should have added the labels of nitrates and nitrites, so I've listed the chemical compounds there NO3 and NO2, but you might have written nitrates and nitrites instead.

And then hopefully you've joined them into the plant via an arrow showing how they're moving via the root system up through the plant and into the plant proper itself.

As far as your other question is concerned about describing what nitrogen is used for and what's combined with to make other things, you should have written something along the lines of that nitrogen is used to produce amino acids and it is combined with carbon, hydrogen, and oxygen in order to do that, in order to make those amino acids.

Those amino acids are then joined together into a long chain to create proteins, and that the instructions for creating those proteins, for synthesising those proteins, is stored within DNA.

So check your work over, make sure you've got all the right bits in your map and you've got the right bits in your answer to question two as well, and then we'll move on.

So we're now in our final bit of our lesson, and this is looking at how consumers rely upon producers.

So let's draw this all together then.

We've seen how producers use photosynthesis and other processes to bring essential elements into the food chain.

So we've seen that there's carbon dioxide in the atmosphere, there's water around us, and there's nitrogen in the soil.

And plants absorb carbon, oxygen, hydrogen, and nitrogen from those various places, from the atmosphere, from the soil.

They use a variety of different processes then to turn those elements into carbohydrates, proteins, and lipids.

And it is a variety of processes that enable those basic abiotic elements to be turned into biotic components of the living plant.

Consumers can only get carbon, hydrogen, and nitrogen that they require for their body by eating other organisms. So consumers can absorb oxygen from the atmosphere, for instance, but they can't harvest carbon or nitrogen from the atmosphere even though they are also present there.

So carbon, hydrogen, and nitrogen have to be obtained through other ways, and those other ways involve eating other organisms. And only once a consumer has eaten another organism can they then use those elements to make the biological molecules that they require in order for them to grow, for them to repair themselves, and also for the energy that they require in order to survive.

So these consumers include all sorts of different organisms such as lions, which are meat eaters, hedgehogs, which are meat and plant eaters, and beetles, which are plant eaters.

And you can see that all of these organisms are ultimately eating something that has eaten a plant.

Not necessarily themselves eating the plant, so the lion isn't eating plants, but they'll be eating an organism like a gazelle or an antelope which has itself eaten plants.

So consumers are consuming producers, plants, in order to get carbon, hydrogen, and nitrogen.

Now, I've already said that consumers can absorb oxygen from the atmosphere, and oxygen's really important 'cause it's used during aerobic respiration to release energy from the food that has been consumed and to produce carbon dioxide.

So we've got this chemical reaction going on of glucose with oxygen leading to carbon dioxide and water and the release of energy.

This is aerobic respiration.

And this is what consumers are using oxygen for.

But they're not able to use oxygen to build carbohydrates, they have to get that oxygen required for carbohydrates from producers.

So the oxygen that consumers are using is specifically for aerobic respiration and not for anything else.

And therefore, life on Earth exists only because producers convert carbon, oxygen, hydrogen, and nitrogen from the abiotic parts of the environment, such as the atmosphere and the soil, into their biotic living bodies.

This is entirely dependent upon producers.

If it weren't for producers, consumers would not exist.

So let's just double check that then.

Consumers can exist without producers such as plants.

True or false? I'll give you a few seconds to decide.

Okay, well, hopefully you've remembered what I've just said and you've said false, but why? Can you justify your answer with one of those two statements? I'll give you a few more seconds to think about it.

Okay, so hopefully you've chosen answer B, that consumers can only get the carbon and nitrogen they need to survive by eating producers, well done.

So our last major task of today, I'd like you to continue your map and this time I'd like you to add a consumer to your diagram and an arrow to show how carbon, oxygen, hydrogen, and nitrogen are moving from the plant to the consumer.

So choose a consumer of your choice.

It could be a cow or a sheep, it could be a cat or a dog, it could be a human, it could be a mushroom, it could be all sorts of different animals or fungi, up to you.

Something that you can draw relatively easily and fairly quickly, though, please.

And then add those extra details on.

Then once you've done that, what I'd like you to do is to explain using details from across the whole lesson how plants are essential to life on Earth.

So give yourself enough time, be super creative, and come back to me when you're ready.

Okay, let's look at the last little bit of our map from today's lesson.

So hopefully you've added a consumer.

I've chosen a cow, but you might have chosen any animal or maybe a mushroom.

And then you've added an arrow showing how carbon, hydrogen, oxygen, and nitrogen are all moving from the plant into the consumer.

And then in answer to our second question, what I hope you've included are things such as the fact that plants are autotrophic producers, they can make their own food, and that they absorb elements from the abiotic parts of the ecosystem and use them to make biological molecules, including carbohydrates, proteins, and lipids.

And this is bringing carbon, hydrogen, and nitrogen into the food chain.

And consumers rely upon eating producers to get these elements in forms that they can use for growth, repair, and for energy.

Again, check your work over before you carry on, make sure you've got all of the really important details there, and well done indeed again.

So in our lesson today we have seen that actually it's producers which are doing all of the work.

They are absorbing carbon and oxygen from the air, hydrogen from water, and nitrogen from the soil.

And they are using these elements to make carbohydrates, proteins, and lipids.

And only when those processes have happened can consumers then use producers to bring those elements into the food chain.

So it is producers that are providing a vital link between the abiotic environment and the biotic parts of the ecosystem.

I hope you've enjoyed that lesson and learnt plenty today as well.

Thank you so much for joining me and I'll hopefully see you again soon, bye.