hello and welcome to the kitchen I
wanted to invite you here today because
last week we started off in my bathroom
and I kind of feel bad about that and
also because as I'm making lunch today I
want to do you know sort of use it as a
lab during this time in my kitchen I'm
going to talk to you about three
different things one the three most
important molecules on the earth -
possibly the grossest sandwich I'm ever
going to eat and three an obscure
scientist who taught us everything that
we know about urine
so far we've talked about carbon and
we've talked about water and now we're
going to talk about the molecules that
make up every living thing and every
living thing in every living thing I
don't care if you're a bacterium or if
you're a blue whale or if you're Lady
Gaga or if you're a mite living on the
queen of England's eyelashes they're
called biological molecules these aren't
just building blocks these are the
molecules necessary for every living
thing on earth to survive they are
essential sources of energy they are the
means of storing that energy they are
also the instructions that all organisms
used to be born to grow and ultimately
pass those same instructions on to their
future generation they are the
ingredients for life and we call them
the carbohydrates the lipids the
proteins and the nucleic acids and today
we're just going to be talking about the
first three it's no coincidence that we
classify them in the same way that we
classify food because they're food and
for this classification we have to thank
a little-known English physician who
hundreds of years ago dedicated his life
to the study of human pee oh my goodness
I'm back and that that must mean that
it's time for the most awkwardly named
segment here on crash course the viola
graphene his name was William Prout and
in the early 1800s he became fascinated
with human digestion especially our
urine and that's because he thought that
the best way to understand the human
body was through chemistry and the best
way to understand the body's chemistry
was to understand what it does to food
by day he was a practicing physician but
every morning before breakfast he did
research in his home laboratory in
London and there he did many great
things like being the first to discover
that our stomachs contained hydrochloric
acid and writing a breakthrough book
about kidney stones called an inquiry
into the nature and treatment of gravel
calculus and other diseases connected
with a deranged operation of urinary
organs and he was of course the first
person to discover the chemical
composition of pure urea the main
component of urine for the record here
it is and in the presence of water urea
gives off ammonia which is why your pee
smells through his years of studying
urine
route came to the conclusion that all
foodstuffs fell into three categories
the saccharine us carbohydrates the Oleg
honest the fat and the albumin Asst the
proteins he went so far as to say that
in order to be healthy you needed to eat
all three of these things not just you
know sheep kidneys in gin which is
probably what most of London was living
on at the time but like many great minds
Pratt was overlooked in his own lifetime
because while he was studying actual
science everybody else was walking
around believing that the color of your
urine was determined by your personality
this guy looks like a total jerk to me
and if you can tell that much by color I
wonder what you could tell by taste now
he didn't understand that there were
biological molecules he didn't
understand what these things were but he
did understand that there were three
ingredients necessary for life and it
turns out that all organisms either need
to synthesize or ingest those
ingredients in order to live we're gonna
start out with the most basic of these
ingredients for life and that is the
carbohydrate you've no doubt heard of
them you may in fact be avoiding them
like the plague but the fact is that
nothing and no one can avoid
carbohydrates because they are the
source of all energy that we have
available to us carbohydrates are made
up of sugars and the simplest of them
are called monosaccharides mono for one
saccharides for the actual root of the
word sugar the star of the show here is
glucose because it's truly fundamental
by which I mean like number one on the
global food chain because it comes from
the Sun all biological energy is
originally captured from the Sun by
plants as glucose through photosynthesis
and every cell that needs energy uses
glucose to get that energy through a
process called respiration in addition
to glucose there are other
monosaccharides like fructose which has
the same molecular formula c6h12o6
but arranged differently these subtle
chemical differences do matter fructose
for example is significantly sweeter
than glucose it's also processed by our
bodies in different ways and then there
are disaccharides which like the name
says are just two monosaccharides put
together and the most famous of these is
sucrose which is simply a glucose
molecule and a fructose molecule joined
by a covalent bond mono and
disaccharides are pretty much little
niblets of energy that are really easy
for our body
to process but when these carbohydrates
start to form into longer and longer
chains their function and their roles
change as well instead of being sources
for instant energy to become storehouses
of energy or structural compounds these
are polysaccharides instead of being
just two or three monosaccharides put
together polysaccharides can contain
thousands of simple sugar units and
because they're so big and burly they're
great for building with implants
cellulose is the most common structural
compound it's just a bunch of glucose
molecules bound together and it is the
most common organic compound on the
planet unfortunately it's very difficult
to digest cows can do it
but humans certainly cannot which is why
you don't enjoy eating grass
polysaccharides are also really good for
storing energy and not just structurally
but just as an energy store and that's
where we get bread now really
interesting thing here bread made up of
starch the most simple of which is
called an ELO's amylose and cellulose
look almost exactly identical but one is
grass and the other is bread like
chemistry plants store glucose in the
form of starch and it comes in lots and
lots of different forms from roots and
tubers to the sweet flesh of fruits to
the starchy seeds of the wheat plant
that end up being milled into flour
ground up grain is the main ingredient
in the bread of course and most of
calories or the energy content comes
from carbohydrates what I eat this and
I'm gonna eat the hell out of it I'm
gonna be eating all of the chemical
energy that this wheat plant got from
the Sun in order to feed its next
generation of seeds that we then stole
for our own use all for me now we as
human beings can't grow fruits or tubers
so we have to store our energy in a
couple of different ways the way that we
tend to store carbohydrate energy is in
glycogen which is very similar to
amylose or starch but has more branches
and is more complicated it's basically
made up of the glucose that we have left
over after we eat and it sits and our
muscles really really ready to use and
it's also stored in our liver it's
generally a pretty short term store if
we don't eat for like a day pretty much
all of our glycogen gets depleted but
over the longer term the way that we
store our energy is through fat all of
our moms worst enemies the fat which
turn out to be actually really important
and are the most familiar sort of a very
important biological molecule
the lipid lipids are smaller in simpler
than complex carbohydrates and the group
together because they share an inability
to dissolve in water this is because
their chemical bonds are mostly nonpolar
and since water as we learned in
previous episode despises nonpolar
molecules the two do not mix it's like
oil and water in fact it's exactly like
oil and water and if you've ever read a
nutrition label or seen this thing
called the television you probably
pretty conversant in the way that we
classify fats but then you know 99% of
us have no idea what those
classifications actually mean fats are
made up mainly of two chemical
ingredients glycerol which is a kind of
alcohol and fatty acids which are long
carbon hydrogen chains that end in a
carboxyl group when you get three fatty
acid molecules together and connect them
to a glycerol that's a triglyceride
these feature prominently in things like
butter and peanut butter and oils and
white parts of meat these triglycerides
can either be saturated or unsaturated
and I know that when we put the word fat
and saturated into the same sentence it
sounds like an evening at KFC but here
we're talking about being saturated with
hydrogen as you hopefully remember from
our first lesson carbon is very nimble
and how it uses its four electrons it
can form single or double or even
sometimes triple bonds this means that
if the carbon atoms in a fatty acid are
connected to each other with single
bonds all of the carbon atoms end up
connected to at least two hydrogen atoms
and one of them picks up a third so the
fatty acid is saturated with hydrogen
but when some of the carbon atoms are
connected to each other with double
bonds all of those carbons electrons are
spoken for and so they're not able to
pick up those hydrogen atoms this means
that they're not saturated with hydrogen
and they are unsaturated fatty acids to
demonstrate may I direct your attention
to this jar of peanut butter here you
can kind of see both kinds of fat the
liquid stuff you see at the top here
that is the unsaturated fat which we
generally think of as oils the pasty
stuff down here also contains lots of
unsaturated fat but also contains
saturated fat which doesn't have any
double bonds and so could pack more
tightly and form solids at room
temperature and there are also other fat
classifications that you've heard of
trans fats which everyone tells you
never to eat there right don't eat them
they don't exist in nature and are
basically unsaturated fatty acids that
instead of kinking go straight across
and so they're extra super bad for you
don't eat them omega-3 5
sour fatty acids that are unsaturated at
the three position which is like right
there then that's the only difference
but that the reason why these are
important is because we can't synthesize
them ourselves they're essential fatty
acids meaning that we need to eat them
in order to get them all this is
starting to make me pretty hungry but
before we get to more food stuff there
are some unappetizing sort of lipids
that we also need to talk about so
remember that triglycerides are three
fatty acids connected to a glycerol Swap
one of those fatty acids out for a
phosphate group and you have a
phospholipid and these make up cell
membrane walls since that phosphate
group gives that end a polarity it's
attracted to water the other end is
nonpolar and it avoids water so if you
were to scatter a bunch of phospholipids
into some water they would automatically
arrange themselves like this with the
hydrophobic ends facing each other and
the hydrophilic ends sticking out to
face the water every cell in your body
uses this natural structure to form its
cell wall in order to keep the bad stuff
out and the good stuff in another class
of lipids is the steroids steroids have
a backbone of four interconnected carbon
rings which can be used to form hundreds
of variation the most fundamental of
them is cholesterol which binds with
phospholipids to help form cell walls
but these can also be activated to turn
into different lipid hormones and so now
we approach the most complicated
powerful polymorphously awesome
chemicals in our body the protein and by
complicated I mean that they are
probably the most complicated chemical
compounds on the planet in fact they're
so amazing that we're gonna do a
separate episode on them and how they
are created by DNA but right now and you
there are tens of thousands of proteins
doing everything they can to keep you
alive there are enzymes regulating
chemical processes helping you digest
food there are antibodies connecting
themselves to invaders like bacteria and
viruses so that your immune system can
get them their protein endorphins that
like mess around with your brain and
make you like feel emotions are they're
everywhere they do everything and
proteins do all of the stuff using just
20 different ingredients and these are
the amino acids just like fatty acids
amino acids have a carboxyl group at one
end and on the other end they have an
amino group amino acid ah now hey I
don't know if you notice this but
is the first time that nitrogen has
shown up in our food this is super
important because despite the fact that
nitrogen is like everywhere it's like
80% of the air we can't just pull it out
of the air and put it into our bodies we
have to get nitrogen from food and so we
have to eat foods that are high in
protein like this egg which by its very
virtue because is all the white part is
protein it contains a goodly amount of
nitrogen now in the middle of the amino
and the acid group is a carbon and it
shares one of its electrons with a good
ol hydrogen and the other electron is
free to be shared with R which is just a
kind of fill in the blank we call it the
R group it could also be called a side
chain and there are 20 different kinds
of side chains whatever fits in that
blank will determine the shape and the
function of that amino acid so if you
put this in there you get valine which
is an amino acid that does a lot of
stuff like protecting and building
muscle tissue and if you put this in
there you get tryptophan which may be
best known for its role in helping you
regulate mood and energy levels amino
acids form long chains called
polypeptides proteins are formed when
these polypeptides not only connect but
elaborate and frankly really elegant
structures they fold
they coil they twist if they were
sculptures I would go to the museum
every day just to look at them and I'd
walk straight past the nudes without
even looking but protein synthesis is
only possible if you have all of the
amino acids necessary and there are nine
of them that we can't make ourselves
histidine isoleucine leucine lysine
methionine phenylalanine threonine
tryptophan and valine by eating foods
that are high in protein we can digest
them down into their base particles and
then use these essential amino acids and
building up our own proteins some foods
especially ones that contain animal
protein have all of the essential amino
acids including this egg and that
concludes this triple decker sandwich of
biological awesomeness which is all we
need to be happy healthy people and I'm
sure because of that it's going to be
delicious
nope thank you for watching this episode
of crash course we'll be discussing
something else very interesting next
week I don't know I don't even know what
it is don't forget go back reinforce
what you have learned today by going
back and watching bits that you may not
feel like you got completely also of
course
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