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  • Hi. It's Mr. Andersen and in this podcast I'm going to talk about the Molecules

  • of Life. The first time I learned this I was pretty amazed. But basically the way the world

  • works is that we eat food. And then the building blocks of that food we weave together to make

  • living things. And so this right here is called a Dave Thomas. Dave Thomas is the founder

  • of Wendy's. But Dave Thomas and his body was made up of building blocks that came from

  • the food that he created. In other words the proteins in the burger are broken down into

  • amino acids. And those make the proteins in him. Or the sugars in the carbohydrates of

  • the bun are broken down to make sugars that are used in cellular respiration to make ATP

  • to move the materials inside him. Or the fat inside the burger is used to make the lipids

  • inside the cell membranes of a Dave Thomas. He's actually really fascinating guy when

  • I read about him a little bit. I didn't know this be he worked for Colonel Sanders in the

  • KFC. So it's worth studying the wikipedia a little bit on Dave Thomas. Also a war hero.

  • So cool. But basically life is built on carbon. And the reason life is built on carbon is

  • that carbon has four valence electrons. In other words it has six protons. That means

  • it has six electrons. And two electrons in the first level, but it has one electron in

  • each of these, if we were to draw a Lewis Dot Diagram. One of these in each of those

  • outer valence shells. And so basically it's really good at bonding. And so the reason

  • life is made up of carbon is because it makes fairly stable large carbon based molecules.

  • And that's what we are. If it weren't carbon then maybe it would be silicon, which sits

  • right below this. I remember watching a Star Trek episode way back in the day where there

  • are these giant rock animals called the Horta. And basically this right here is Spock mind-melding

  • with a Horta. But based in silicon. And so if we were to find life somewhere out there

  • in the universe maybe silica would be an example of that. And my computer is made up of silica

  • which is about as close to life as we have on our planet. So the first thing you should

  • understand is the idea of what a functional group is. So life is made up of carbon. These

  • huge carbon chains. That's what DNA is pretty much made up of, carbon and hydrogen. But

  • there are things around the outside that are called functional groups. And those give functionality.

  • They give behavior to the chemicals. And so if we go through these, starting with the

  • first one. This would be a carboxyl group. There's going to be a carbon right here at

  • the middle. And so we could abbreviate a carboxyl group by just writing COOH. By basically a

  • carboxyl group is going to donate this hydrogen ion. And so it will make things that are carboxylic

  • acid. This carboxyl group and the amino group actually form amino acids. Next one would

  • be the carbonyl group. Carbonyl group has a carbon right here. If it's in the middle

  • we call it a keytone. At the end it's called an aldehyde. So formaldehyde would be an example

  • of that. This would be a methyl group. An methyl group is going to be a carbon with

  • three hydrogens around the outside of it. Methyl groups would be important in methylation.

  • So basically what they can do, DNA would be a great example of that, is they can methylate

  • these big carbon compounds. Make them non-functional. Amino group would be another one. Amino group

  • is going to have a NH2. So it's got nitrogen. And we need nitrogen to survive. And the reason

  • we need nitrogen is to make amino acids. And basically an amino acid, which is the building

  • block of proteins are made up of carboxyl group and amino group. Next one would be the

  • phosphate. Phosphate, you may know this, it's actually what's on the end of ATP. It's what

  • we use for energy transfer. Also it's used to build DNA for example. So transfer of energy

  • would be a phosphate group. And then finally we have the hydroxyl group. Hydroxyl group

  • is going to be an OH. What that does is make it polar. And so it makes it readily dissolvable.

  • And so if you learn these six in biology, just what they are, you're going to see, even

  • in this presentation, that they're going to start showing up. And you can predict some

  • of the properties. So amino groups will grab onto a hydrogen ion. Become bases. And so

  • there's a lot of things you can learn from functional groups. But the first thing you

  • want to do is simply memorize them. Now we get to the actual molecules of life which

  • are mostly polymers. Now know this, that polymers are made up of monomers. And so monomers are

  • the building blocks. And polymers are these large macromolecules. And there's only four

  • in biology that you have to learn. So it's pretty easy. But those polymers are built

  • through a process called dehydration. So if we look right here, this is one amino acid.

  • And this is another amino acid. You could see right here again that there's an amino

  • group on this side. There's a carboxyl group on that side. But basically if we look right

  • here in the middle. If we have two amino acids right next to each other, if I were to remove

  • just this section right here, it's an oxygen and two hydrogens, what am I removing? I'm

  • removing H2O. And that's called water. And so we call that a dehydration reaction because

  • you're removing water. Just like when you're dehydrated, you don't have enough water. So

  • you remove that water and we form a covalent bond in the middle. That would be a peptide

  • bond. And so the proteins inside my hair and my nails and my skin and all of that is made

  • up of amino acids that are attached together. Each time we attach two amino acids, we've

  • got to lose a water. Likewise if we want to break it apart, so let's say I eat a burger.

  • One of those Wendy's burgers, and I want to breakdown the proteins and make amino acids

  • out of it, that I can use inside my body, what would be the reaction there? That's called

  • hydrolysis. So hydrolysis now is hydro, water, lysis means to break, and so we're adding

  • a water here in the middle and we're breaking that bond apart. And so now we have two amino

  • acids. And so how do you build proteins? Through dehydration reaction. How do you break them

  • down? Hydrolysis. How do you build nucleic acids, like DNA? Dehydration reaction. How

  • do you break it down? You can do that through hydrolysis. And so even carbohydrates, the

  • same way. And so let's get to those four major macromolecules. The first one is going to

  • be called nucleic acids. Nucleic acids, the two big ones you should understand are RNA

  • and DNA. DNA stores information inside the cell. RNA is kind of a slave to the DNA, but

  • it does work. So these right here would be polymers, large macromolecules. What are the

  • building blocks? It's going to be these nucleotides. And so this would be a nucleotide that builds,

  • this would be one that builds DNA. So it's got a base a sugar and a phosphate. And so

  • we simply attach these over and over and over again. And so it would fit right in here.

  • And that would be one nucleotide. So we attach them over and over and over again. Again we

  • do that through a dehydration reaction. And eventually you have DNA. So where do we get

  • our DNA? We eat our food and we break it down into monomers and then we can weave that back

  • into the stuff of life. If we go to proteins, proteins again are made up of amino acids.

  • Again, here's that amino group. Right here would be the carboxyl group. Right here in

  • the middle of an amino acid we have a carbon and a hydrogen. And then on the side we have

  • an R or side chain. And so basically this is going to be different in every amino acid.

  • And so just like we have 26 letters that make all of the words in our alphabet, there are

  • only 20 amino acids that humans need to survive. And these are all 20 amino acids. And if you

  • look at them, don't memorize them. That would be silly, but if you look at them what you'll

  • see is, here it is. Here is our carboxyl group, our amino group. And all of them have carboxyl,

  • amino, carboxyl, amino. But if you look on the side, this R or side chain is going to

  • be different in every amino acid. So this would be one side chain. That would be another

  • side chain. That would be another side chain. And we have a few properties. So like these

  • ones would all be positive. These ones would be negative. These ones right here would be

  • uncharged so, excuse me charged. And you can see like here's a hydroxyl group, here's a

  • hydroxyl group. Here's an amino, an amino group and so that's why they're charged. And

  • so basically what is a protein? A protein is this huge three dimensional structure that's

  • made up of sometimes thousands of amino acids attached together. And so why do they look

  • the way they do? Well the order of them is important. And DNA holds that. But once you

  • have all those amino acids attached together, it will basically look like this where you

  • have all the backbone. But on the side you're going to have all your R or side chains. And

  • so basically once you build a polypeptide or protein, it's then going to fold into a

  • characteristic shape like this. Why is it going to do that? Well first of all they're

  • all going to be all of these alpha helices. And basically those are built on hydrogen

  • bonds. Then all the polar side chains will fold to the outside of the protein. And all

  • the non-polar hide in the middle. You'll have positive attached to negative. And sometimes

  • we refer to this all as the tertiary structure. And then the quaternary structure would be,

  • you know, having more then one polypeptide attached together. But when you look at me

  • you're looking at proteins. And that proteins are all built of these monomers which are

  • amino acids. Next one then would be the lipids. Lipids basically, there's one thing that ties

  • those all together. They're a carbon, a carbon, a carbon, a carbon, a carbon, a carbon, a

  • carbon, a carbon, a carbon, a carbon and then hydrogen around the outside. So we call these

  • things hydrocarbons. And so this would be a fatty acid. But this would be like a triglyceride.

  • It makes that burger. That fatness of the burger really good. This would be a phospholipid.

  • And that would be inside the membranes of all living material. Or cholesterol. You can

  • see that hydrocarbon chain right here. These things are used for energy. But they also

  • build up membranes. One more important thing about them is that they come in two different

  • types, saturated and unsaturated. Basically if you're saturated it means you're straight

  • because you have hydrogen around the whole thing. If you're unsaturated you have a double

  • bond in the middle. And so things like fat, like butter, animal fat, are going to be saturated.

  • Unsaturated would be things like an olive oil. Because if they're bent they can't quite

  • get next to each other and so they form a liquid at room temperature. We can make them

  • saturated by bubbling hydrogen through it. And transforming that fat. So you maybe heard

  • of transfats. And then the last one is going to be carbohydrates. Carbohydrates actually

  • come in three different types. We have monosaccharides. The quintessential example is glucose. We

  • have disaccharides. And example of that would be sucrose. And then we have these huge polysaccharides,

  • which are hundreds and hundreds and hundred of glucose molecules attached together. Or

  • saccharide sugar molecules attached together. So basically when you're eating a potato or

  • when you're eating bread or when you're eating anything that has starch, it is a bunch of

  • sugar molecules. So there's one, another, another, another. And so they're all attached

  • together using covalent bonds. And so if I want to breakdown carbohydrates what do I

  • do? Well I have to snip that off. Hydrolysis. Break those into sugars and then I can use

  • them in cellular respiration. And so those are the molecules of life. Again, there's

  • only four of them. But if you think back to that burger and how that burger eventually

  • becomes you, it's a pretty cool process. And I hope that's helpful.

Hi. It's Mr. Andersen and in this podcast I'm going to talk about the Molecules

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B2 中高級

生命的分子 (The Molecules of Life)

  • 63 14
    Cheng-Hong Liu 發佈於 2021 年 01 月 14 日
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