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molecules make you think of chemistry
right
well they're also very important in
biology
in this video we're going to look at
carbohydrates proteins and lipids when i
say lipids i'm talking about fats and
oils
life processes depend on biological
molecules
whose structure is related to their
function
did you know that living organisms are
actually made from quite a small group
of molecules what do you think the most
common molecule in you is
it's actually water
about 55 to 60 percent of an adult
human's body weight comes from water
and in some organisms this can be up to
90 percent
your muscles and kidneys are
particularly watery at about 79
but even your bones are made up of 31
water bet you didn't expect that
okay enough of water for now
imagine we removed all the water in your
body
what would be left
well it would pretty much be just
proteins lipids carbohydrates and
nucleic acids such as dna
so what are these all made of
well carbohydrates and lipids are really
simple
they just contain three elements
carbon hydrogen and oxygen
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proteins are a little more complex with
four or five elements
carbon hydrogen oxygen nitrogen and
sometimes sulfur
let's start by looking at carbohydrates
there are three main types of
carbohydrate
monosaccharides disaccharides and
polysaccharides
simple sugars like glucose and fructose
are monosaccharides
sucrose which is made up of two simple
sugars joined together is a disaccharide
and some carbohydrates are polymers that
are made up of lots of sugars joined
together and so are called
polysaccharides
starch glycogen and cellulose are three
important polysaccharides
cellulose is found in plant walls and
starch is the storage unit for surplus
glucose made in photosynthesis
glycogen is the storage unit used by
animals for surplus glucose
and is found in the liver and muscle
tissues
starch is tested for using an iodine
solution
if the solution turns blue black then
starch is present
now on to proteins
proteins are also polymers
but whereas in carbohydrates the monomer
or repeating unit was glucose
for proteins it's amino acids
the protein then folds up into a complex
3d shape which is held together by weak
bonds the function of each protein
depends on its shape because enzymes are
proteins and the bonds holding proteins
together are weak this is why enzymes
denature above certain temperatures the
bonds are broken and the structure of
the protein is changed
there are 20 different amino acids that
make up proteins
the order of amino acids varies in
different proteins and so 20 different
amino acids means an almost infinite
number of different proteins can be made
it is estimated there are about 50 000
different proteins in the human body
alone
you will come across proteins nearly
everywhere for example
in cell membranes where they control the
movement of substances during active
transport
as enzymes so in photosynthesis
respiration dna copying and digestion
as hormones such as insulin estrogen and
testosterone
and as antibodies for fighting infection
so that's proteins and carbohydrates
let's end with lipids many lipids are
triglycerides
these have a single glycerol molecule
with three fatty acid tails attached
different lipids contain different fatty
acids
triglycerides are a form of dietary fat
found in meats dairy and cooking oils
the liver also makes triglycerides
they are used by cells and tissue for
energy or otherwise stored as fat
some examples of lipids are steroid
hormones cholesterol vitamin a and
vitamin d
so there you have it the three key
biological molecules that are essential
to living processes carbohydrates
proteins and lipids if you liked the
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