This content introduces the four major classes of biomolecules – carbohydrates, lipids, proteins, and nucleic acids – explaining their fundamental building blocks (monomers) and their crucial roles in the structure and function of cells and organisms.
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I want you to think for a moment about your very favorite food. What
is it? We all have different food preferences,
but food is a source of large molecules that are needed for life called biomolecules. Also
known as macromolecules. Carbohydrates, Lipids, Proteins, and Nucleic Acids.
In different types of food, you might find higher amounts of these biomolecules. For example,
peanut butter can be high in both proteins and lipids. And while we’ll mention examples of
foods that contain different biomolecules in this video, this is not a video on nutrition – this is
a video on the classes of biomolecules and their importance to the structure and function of cells.
And, therefore, also to the entire organism because organisms consist of these cells.
Before we get into details about the 4 biomolecules,
we need to talk about one very important vocab word. The word monomer. A monomer is a building
block – if I had some large substance, the parts that make up that substance are called
monomers. With each biomolecule class, we will mention its monomer if it applies.
We’ll start with the biomolecule class of carbohydrates. Generally,
food sources such as bread, pasta, fruit, and vegetables tend to be high in carbohydrates.
The monomer of a carbohydrate, remember: that means the building block, is the
monosaccharide. One example of a monosaccharide is the sugar glucose. Glucose is a pretty
big deal considering it’s used in cellular respiration to make ATP, an energy currency.
If two monosaccharides – such as glucose - are combined, you can get a disaccharide. For example,
put these two glucose sugars together,and you get the disaccharide maltose. By the way,
a lot of sugars have that -ose ending. Glucose, maltose, lactose, sucrose,
fructose – I could go on. The ending -ose can be a carbohydrate clue. If you join a lot of
monosaccharides together, that can combine to make a polysaccharide. A big carbohydrate.
So how are carbohydrates important to an organism and the structure and function of its cells? Well,
plants have cell walls of carbohydrates, specifically a large one known as cellulose.
Fungi have cell walls of carbohydrates too, specifically one known as chitin. Fun Fact:
that carbohydrate chitin is also what makes up the exoskeleton of insects.
We mentioned glucose is used to make ATP, that makes carbohydrates a fast
source of energy for cells. So that’s a big function for carbs: a major energy source
that cells can access. That energy can also be stored in a polysaccharide form ---remember,
polysaccharide is a big carbohydrate---such as starch for plants or glycogen for animals.
Next up: lipids. Lipids include fats and oils; examples of food sources could include butter
or olive oil. This is a seriously diverse group. Meaning there are a lot of types of
lipids. There are triglycerides. There are phospholipids. There are steroids.
These are just some examples. Most – but not all - lipids have building blocks of
glycerol and fatty acids. One thing though that lipids generally share? Generally,
they’re hydrophobic or at least contain a significant hydrophobic component. That
means- lipids or at least a major component of them- don’t like water. Lipids generally won’t
dissolve in water. And that’s interesting as generally, the other biomolecules will.
So how are lipids important to an organism and the structure and function of its cells? Remember how
we said all cells – plant cells, animal cells, all cells- have membranes? Well thank you,
phospholipids, for that phospholipid bilayer – because that’s right,
lipids make up cell membrane structure. Lipids have a major function of being a
source of long-term energy storage – you remember how we said carbohydrates were a
fast source of energy but when those carbs are used up, lipids have a function as long-term
energy storage that an organism can use. Lipids also are very important for different types of
insulation. The insulation may involve helping a cell carry an electrical impulse: for example,
this myelin sheath made of lipids that can be found on many neurons. Or the insulation may
involve temperature regulation so thermal insulation: for example, the blubber on
this adult harp seal is made of lipids, helping it conserve heat. Another cool function about lipids:
many lipids act as hormones which are chemical messengers for many different processes.
Next: proteins! Protein food sources include beans, meat, nuts, and eggs. The monomer of
a protein is an amino acid. Usually, proteins consist of many amino acids bonded together.
There are different types of amino acids. So how are proteins important to an organism and
the structure and function of its cells? Structure wise, tissue like muscle tissue,
consists heavily of proteins. Proteins can make up all kinds of other structures – hair
or collagen - for example. Proteins can also be found embedded in cell membranes as protein
channels and channels are important to that cell membrane structure with functions of letting
certain substances pass through. Proteins can also be receptors which are critical in
cell signaling so cells can coordinate actions together. Most enzymes are made of proteins.
Remember enzymes can build up or break down substances in all kinds of metabolic processes.
Antibodies – which are made by immune cells in your body - are proteins and they are involved
in protecting your body. And some critical hormones such as insulin are proteins. And when
we start talking about genes – genes are made of DNA – but many genes do code for proteins.
And that brings us to our last one that includes DNA: nucleic acids. Nucleic acids include DNA and
RNA, which we'll get to in more depth when we get to genetics. Nucleic acids have a monomer
called a nucleotide. That's going to be an easy one for you to remember because nucleotide sounds
like nucleic acid. By the way, you might wonder: are nucleic acids like DNA and RNA found in my
food? And the answer would be yes! Whenever you eat something that came from something living,
it actually could still have DNA inside it. For example, when you eat a strawberry,
you're actually crunching all the cells that made up that strawberry. In the nucleus of
all of those strawberry cells is DNA. Any type of life -like plants or animals or fungi or
bacteria- they must contain nucleic acids like DNA to direct the cells' activities.
How are nucleic acids important for your cells? Well, most of your cells contain
all of your genetic information in the form of nucleic acids -DNA and RNA- and this is
needed for the coding of your traits. Traits involved in structure and various functions.
Ok so we just did a very general tour of 4 biomolecules. Before we go,
I just have to marvel at biomolecule structure. Because it’s absolutely
beautiful. So if I arrange them in the order we did: carbs, lipids, proteins, and nucleic acids:
how might we remember the major and most common elements in them? There’s a popular
mnemonic known as CHO, CHO, CHON, CHONP – although it’s “chomp” with an “n” - to
help remember the C – carbon, H-hydrogen, O-oxygen, N-nitrogen, and P-phosphorous.
Does that mean you won’t find other elements in the biomolecules? Of course not! But it’s
important to understand the arrangement of these elements in biomolecules,
because the structure of the arrangement greatly impacts their function. You can
learn more in our further reading suggestions in the description. Well,
that’s it for the Amoeba Sisters, and we remind you to stay curious.
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