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Biology library
Course: Biology library > Unit 36
Lesson 1: Crash Course: Biology- Why carbon is everywhere
- Water - Liquid awesome
- Biological molecules - You are what you eat
- Eukaryopolis - The city of animal cells
- In da club - Membranes & transport
- Plant cells
- ATP & respiration
- Photosynthesis
- Heredity
- DNA, hot pockets, & the longest word ever
- Mitosis: Splitting up is complicated
- Meiosis: Where the sex starts
- Natural Selection
- Speciation: Of ligers & men
- Animal development: We're just tubes
- Evolutionary development: Chicken teeth
- Population genetics: When Darwin met Mendel
- Taxonomy: Life's filing system
- Evolution: It's a Thing
- Comparative anatomy: What makes us animals
- Simple animals: Sponges, jellies, & octopuses
- Complex animals: Annelids & arthropods
- Chordates
- Animal behavior
- The nervous system
- Circulatory & respiratory systems
- The digestive system
- The excretory system: From your heart to the toilet
- The skeletal system: It's ALIVE!
- Big Guns: The Muscular System
- Your immune system: Natural born killer
- Great glands - Your endocrine system
- The reproductive system: How gonads go
- Old & Odd: Archaea, Bacteria & Protists
- The sex lives of nonvascular plants
- Vascular plants = Winning!
- The plants & the bees: Plant reproduction
- Fungi: Death Becomes Them
- Ecology - Rules for living on earth
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Biological molecules - You are what you eat
Hank talks about the molecules that make up every living thing - carbohydrates, lipids, and proteins - and how we find them in our environment and in the food that we eat. Created by EcoGeek.
Want to join the conversation?
- Is there a way to convert cellulose to starch? Could I use some enzyme or chemical to turn my lawn into starch?(15 votes)
- There is no way to directly convert cellulose to starch (like simple mutarotation). However, there are a few multi-step chemical processes that could be utilized to turn cellulose into starch, and, of course, enzymes that catalyze each reaction step. First cellulose's glycosidic linkages need to be broken down; the most ubiquitous enzyme capable of this is cellulase, which can be harvested from bacteria. So throw that on some cellulose in an ionic solution, and cellulose will break down into its components, i.e. D-glucose. From there you now have the building blocks to synthesize starch. With the correct enzymes under the correct conditions (which plants have, as they make starch for energy storage), you could then also make starch.(24 votes)
- why can't we eat trans fat(11 votes)
- You can, except it isn't good for you that's all.(2 votes)
- How come we can easily digest starch but not cellulose (since Hank says they are pretty much the same chemically)? What are the chemical reasons?(10 votes)
- Cellulose is structured in a different way; some of the carbon rings are flipped, making them harder to take apart, but easier to stack.(16 votes)
- Do cell walls have a bi-layer too?(10 votes)
- Plant cells have cell membranes made of phospholipids, to regulate osmosis and cell function. Outside the cell membrane, plant cells have a cell wall, which keeps the plant's overall structure in tact.(5 votes)
- How is fat supposed to be good for us? Doesn't it make us obese and give us diseases?(3 votes)
- Macronutrients are nutrients that provide energy; proteins, fat and carbohydrates.
Fat does not just provide us with energy, it's used in vitamin absorption, your brain, your cells, hormones, hair, skin, etc. They are important for your body to function.
Fat does not make you fat by itself. An excess amount of anything that provides you with energy, will be stored as fat, so you can use the energy later. Fat can be stored as fat, just like carbohydrates and protein can.(20 votes)
- I would like to know what are nucleic acids.(7 votes)
- DNA is deoxyribonucleic acid. RNA is ribonucleic acid. So therefore DNA and RNA are both different types of nucleic acid.
Hope this helps!(5 votes)
- What is polarity? And how is this related to solubility?(3 votes)
- Polarity means one end is positive and the other is negative. For example in phospholipids, the phosphate is positive and the other side is negative. The negative side avoids water, so the molecule doesn't mix well. Solubility is how well something mixes, so there is your answer.(11 votes)
- Why can't we get nitrogen from the air? We get oxygen from it . . .(4 votes)
- We cannot assimilate nitrogen gas because is a very stable molecule. Oxygen gas is nowhere near that stable.
There are very few organisms that are capable of assimilating nitrogen gas. The cyanobacteria can. Beyond that, the only thing that I know of that can do this is a type of bacteria called rhizobia, which lives in symbiosis with legumes and a small number of other plants -- that is how legumes can fix nitrogen (it is actually the bacteria).
Oh, yes, there is also a group of plants that live in symbiosis with a type of bacteria called Frankia, they're called the "Actinorhizal" plants, but I don't know much about them.
Other than that, I don't know of any organism that can metabolize nitrogen gas -- it is just too inert.(5 votes)
- Why do we eat things we can't digest?(5 votes)
- Like cows, we also have bacteria in our stomach that can indeed digest some things. And because sometimes bark kinda looks like those brownies....(1 vote)
- What are lipids?(3 votes)
- Lipids are one of the four major groups of organic molecules; the other three being proteins, nucleic acids (DNA), and carbohydrates (sugars). Lipids are made up of the same elements as carbohydrates: carbon, hydrogen, and oxygen. However, lipids tend to contain many more hydrogen atoms than oxygen atoms.
Lipids include fats, steroids, phospholipids, and waxes. One main characteristic of lipids is that they do not dissolve in water.
What do they do?
Lipids play an important role in living organisms. Some of their main functions include energy storage, hormones, and cell membranes.(2 votes)
Video transcript
- Hello, and welcome, to the kitchen. I wanted to invite you here
today because last week we started off in my bathroom, and I kinda feel bad about that, and also because as
I'm making lunch today, I wanted to 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. Two, possibly the grossest
sandwich I'm ever going to eat. And three, an obscure scientist
who taught us everything that we know about urine. (upbeat music) So far we've talked about carbon and we've talked about water. And now we're gonna
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 use to be born, to grow and
to ultimately pass those same instructions on the
the 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 gonna 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. (upbeat music) Wow, my goodness, I'm back
in the den so that must mean that it's time for the most
awkwardly named segment here on crash course, Biolography. His name was William Prout. And in the early 1800's
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 the 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, Prout came to the conclusion that
all foods stuff fell into three categories. The Saccharinous, carbohydrates. The Oleaginous, the fats and the Albuminous, 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, sheep, kidneys
and gin which is probably what most of London was
living on at the time. But like many great minds,
Prout was overlooked in his own lifetime, because while
he was study 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 could 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 synthesis or ingest those ingredients
in order to live. We're gonna start off 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 of 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 C-6-H-12-O-6 but arranged differently. These subtle chemical
differences do matter. Fructose for example, is
significantly sweeter that 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 just little niblets of energy that are really easy for our bodies to process. But when these carbohydrates
start to form into longer and longer chains their functions and their roles change as well. Instead of being sources
for instant energy they become store houses 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 burley, they're great for building with. In plants, cellulose is
the most common structural compound, it's just 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 Amylose. Amylose and cellulose looked
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 tuberose, 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 the calories, or the energy content
comes from carbohydrates. When 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 it's
next generation of seeds that we then stole for
our own use, all for me. Now we have 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 in our muscles really ready to use and it's
also stored in our livers. 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 in the longer
term, the way that we store our energy is through fat. All of our mom's worst energy, the fat which turns out to be
actually really important. And are the most familiar
sort of a very important biological molecule, the lipid. Lipids are smaller and simpler
than complex carbohydrates and they're grouped together
because they share an inability to dissolve in water. This is because their chemical
bonds are mostly non-polar. As since water, as we learnt
in the previous episode despises non-polar 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 a
television, you're 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 a 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 in how
it uses it's four electrons, it can form single, or double or even sometimes triple bonds. This means that if a carbon
atom and a fatty acid are connected by single
bonds all of the carbon atoms end up connected to at
least two hydrogen atoms, and one of them picks the 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 those carbon's 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 done here also contains lots of unsaturated fat but
also contains saturated fat. Which doesn't have any
double bonds so it can pack more tightly and form
solids at room temperature. And there are also other
fat classifications you've heard of. Trans fats, which everyone
tells you never to eat. They're 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 three fats are fatty
acids that are unsaturated at the three position,
which is like right there, then that's the only difference. But the reason why these are important is because we can't
synthesis 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. And the other end is
non-polar 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 variations. 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
compound 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, in 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 bacterium and viruses so that your immune system can get 'em! There are protein endorphins
that like mess around with your brain and make
you like feel emotions. So they're everywhere, they do everything! And proteins do all of this
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. Now hey I don't know if
you noticed this but this 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 it is, all the white part is protein, it contains
a goodly amount of nitrogen. Now on the middle of the
amino and the acid group is a carbon and it shares
one of its electrons with a group of hydrogen
and the other electron is free to be shared with R. Which is just to kind
of fill in the blank. We call it the R group. It can also be called a side chain and there are 20 different
kinds of side chains. Whatever fits in the blank
will determine the shape and the function of that amino acid. So if we put this in there we get Valine, which is an amino acid
that does a lot of stuff like protecting and
building muscle tissue. And if we put this in there
you get Tryptophan which may be best known for it's role
in helping you regulate mood and energy level. Amino acids form long
chains called polypeptides. Proteins are formed
when these polypeptides not only connect, but elaborate into 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 passed
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!