All right folks, welcome back. We are in the second lecture on Chapter 2 on body chemistry or the chemistry of life. I've titled it a couple different ways, but it's an overview of chemistry. applies to the human body.
Last time, last lecture, we ended up here talking about water. So let's just review where we've been so far. This is the things that we've talked about already in this... chapter.
We talked about matter and energy. We talked about atoms and the way that they form bonds using those electrons. The bond formation, making bonds and breaking bonds, that is called a reaction.
There's different types of reactions we talked about. Those reactions have a speed or a rate and they require energy exchange. And then we talked about molecules. When we begin to form many, many bonds into a much larger structure, than just a single atom, we form molecules.
And molecules fall into two categories, okay? Inorganic and organic, okay? Inorganic and organic. Inorganic is defined by lacking hydrocarbons, okay?
Hydrocarbons define something that is organic. And so we started talking about water and the properties of water, okay? So back a couple of slides here. We went through the... four or six properties, depending on if you're in the notes or in the PowerPoint or the note sheet.
Some of these properties of water that make it so valuable and important as a medium in which biology exists. So we're going to finish off talking about water, and then we're going to talk about ions and electrolytes, salts, acids and bases, pH and buffers. That will close out our discussion about inorganic molecules.
Thank you. And then we'll close off by talking about organic. And this looks like just a tiny little section here of the whole chapter, but in fact this is almost half of the material because what we're covering here is really a condensed version of a biochemistry course.
Now this is not a biochemistry course, so we will not be learning it in the detail that you would learn in a biochemistry course. However, these are the, this is an overview of a biochemistry course. of a good biochemistry course.
Now, there's a lot more that goes into that about enzyme kinetics and pathways and such. But this is kind of approaching biochemistry. All right, so we've already addressed these things about water.
We talked about how water is a polar molecule. The electronegativity difference between the oxygen and the hydrogen pull on the electrons more strongly with the oxygen, and therefore it gives it a partial negative. charge.
So, that's what we see here. Here's the oxygen, here are these two hydrogens, and due to this difference in electronegativity, which we remember looking at that heat map table that showed the different electronegativities of different chemicals, it produces this partial negative charge here on the oxygen side, and this partial positive charge on the hydrogen side. That property drives all of the other things that we just learned about for water. This dipole moment is sometimes called a dipole, just means it has polarity.
One side is negative and the other side is positive. Now, it's not a full charge, it's a partial charge, and that's kind of hard to understand, but that's what this little delta symbol means. It means partial. And due to these properties, therefore, water has certain behavior in a container.
It gives it surface tension, it's attractiveness, it's... ability to dissolve other molecules. And in fact, we can dissolve things like table salt. Here we can see a molecule of chloride is being hydrated by water molecules.
If you look closely, you'll see that this negative charged chloride, all of the blue hydrogen molecules are kind of facing towards the chloride because that is in fact where the partial positive charge is. And then the sodium, you'll notice that the water molecules are kind of flipped around. That is, all of the oxygen. molecules are facing that positively charge sodium. Okay, so that's this hydration bubble or hydration layer that is kind of surrounding the chloride and surrounding the sodium is due to what is favorable for the polarity of the water molecule.
Okay, so that's the ability of water to dissolve, okay, ions and electrolytes, which we'll get to a little bit later. Okay, glucose also has the ability to dissolve in water because it does share some polarity, okay? Chloride and sodium have full negative and a full positive charge, so its solubility is very high.
Sugar just has partial charges around it, so it's not quite as soluble as sugar. Although if you dump table sugar into a glass of water, as we all probably have experienced, you'll see that it dissolves quite readily. All right, so properties of aqueous solutions.
Remember when we see this word aqueous, it means water, in water. So electrolytes, we have to learn about electrolytes and body fluids. So what the heck is an electrolyte? It is something... is a solution that has ions in it that can carry an electrical charge.
So it usually means that there's solutes in there that have full charge or even partial charge. The most common ones that we'll talk about are... elements like sodium, potassium, calcium, amongst others, chloride.
Those are all electrolytes. And we'll talk about that in the context of nutrition and the body's body fluid balance. Body fluid balance in these electrolytes is super critical. These levels in the blood and in the lymph and other bodily fluids is very, very impactful for health.
So here is a table listing several common electrolytes. that we see in the human body. Sodium chloride, just good old table salt we're probably the most familiar with, it dissociates in water into a sodium ion and a chloride ion. That's carrying a full positive charge for sodium and a full negative charge for chloride.
In a very similar manner, all these other electrolytes dissociate or dissolve in water. Okay, potassium here, potassium chloride, calcium phosphate, sodium bicarbonate. okay magnesium chloride etc these are very very important electrolytes because when you add these molecules into water they dissociate and become ions okay an ion is a molecule that has a full charge plus one minus one even a plus two or minus two some of these have more than one unit of charge associated with them and calcium because of its place on the periodic table carries a plus two charge.
It will always be plus two. Again, we'll come back to this when we talk about the cardiovascular system and especially the urinary system. We will be talking about these ion levels in much more detail.
Okay, we will also talk about these in the context of the nerve. system because the way that neurons send and receive signals, the electrical impulse, is really a movement of ions and the movement is of sodium and chloride and calcium in some cases. All right, so another major theme or major concept that is true in the human body. The first part of the lecture, we talked about how matter and energy, the exchange between matter and energy is a major concept.
We talked about metabolism and all the biochemical transformations that are exchanging matter and energy. That's a key concept. The next key concept is the concept of water versus oil.
Okay. If you've had your favorite salad dressing, and if it's like a vinaigrette, not so much ranch. But water and oil don't mix. And the basis of that rests in their chemistry.
That is, the hydrophobic and hydrophilic nature of any solution or any molecule is based on its ability to be attracted to water or more fearful of water and attracted to lipids. So water versus oil. Okay, or the hydrophobicity or the hydrophilicity. Okay, hydrophilic means you're attracted to.
If you're an audiophile, you love music. Audiophile, philic, means attraction. Okay, phobia means fear of. Okay, so hydrophobia, hydrophobic means a fear of water.
And so there are two terms here that are interchangeable. You could say hydrophilic or you could say lipophobic. Okay.
Okay, lipophilic, lipid means fats or lipids. And then we're at either philic or phobic. Okay, so if you hear those two terms, hydrophilic and lipophobic are synonymous.
And hydrophobic and lipophilic are synonymous. All right, anyways, major concept here. Something that is hydrophilic means that it is attracted to water.
Philos means loving. Hydrophobic, water-fearing. This precept governs all of biochemistry. The way that a cell membrane is formed or different vacuoles, and actually how proteins fold is dependent on this relationship. So it's a very, very critical thing.
As we talk about molecules in solution, you have different types of molecules that go in solution. You can have a colloid. A colloid is a solid solution of very large organic molecules, for example, blood and plasma.
So a colloid really has big molecules that don't dissolve. A red blood cell will never dissolve because it's a large molecule. Proteins don't dissolve.
But you could have a table salt. Well, that would dissolve into ions. So a colloid...
A suspension is something that will, the molecules are so big that they tend to settle out given enough time. So again, a salad dressing is a good example of this. An Italian salad dressing where you have the vinegar part, you have the oil part, and you can shake it up and give it some mixture before you add it to your salad.
But if you just set it on the counter, over time it will slowly separate. Because it's water and oil, that vinegar is aqueous. So that's really a suspension. There's all the herbs and goodies that are in that saldress, and we'll separate out because they won't dissolve. Concentration is merely a way of measuring the amount of solute in the solvent.
Moles per liter or milligrams per mil, these are common units of measure for concentration. All right, pH. As we're working our way down through these inorganic molecules, we talked about water. And we're going to do that. We talked a little bit about ions and electrolytes.
And now we need to talk about acids and bases. Acids and bases, which is the basis of this concept called pH. pH is a measure of the concentration of hydrogen ion. That's what pH means.
It's actually kind of percentage hydrogen. It's not really percentage, but it's parts. And so hydrogen ion is really just... a proton. So if you hear something as protonated or deprotonated, that's kind of biochemistry lingo, but protonation means that an acid, it was acidified, okay?
That was a free proton is the same as a hydrogen ion. Same thing, they're synonyms, okay? Proton and hydrogen ion.
Because it's just missing its electron, okay? So if you take the electron away from hydrogen, all you're left with is a proton. It's a proton. And that's really the role of an acid is to add protons to the solution, and therefore, in turn, they get added to other molecules.
We know water, okay? Water, drinking water, and our typical water that we interact with is of a neutral pH. That is, the amount of hydrogen versus the amount of hydroxide is balanced. Okay, there's not more. hydrogen ion than hydroxide ion. They are balanced.
And so we call that neutral pH, which we call a pH level of 7. So pH is a measure of hydrogen ions. But when pH gets very low, this concentration gets very high. When the opposite ion here, hydroxide, gets high, then our pH will get high.
We'll talk about that in a subsequent slide. here. So things that are defined as acidic are the pH is lower than 7. This means that there's a high hydrogen ion concentration and a low hydroxide ion concentration.
Things that are basic have a pH that is higher than 7. And then the reverse is true here. Our blood is buffered in a very tight window of pH. And it very rarely moves because of the buffers that are inherent in our blood. our blood. Between 7.35 to 7.45 is the normal physiological pH of blood. All right, we measure pH on a pH scale, and that scale is logarithmic, okay?
It is log 10. That is, for each unit, one unit, okay, let's say we go from 7 to 6, that's actually a tenfold jump in the hydrogen ion concentration. Okay, so if you go from 7 to... 6, that's tenfold.
From 6 to 5, that's another tenfold. So from 7 to 5 is 10 times 10 is a hundredfold. So it's logarithmic. Here's that scale. So here's neutral pH, pH of 7. And the easy thing, kind of the trick, without learning all the mathematics that are really at the basis of this, is to look at the negative exponent here below it.
So this is 10 raised to 5. to the minus seventh. That's 10 to the minus seventh concentration of hydrogen ions in water. Okay. So there's an equal amount, um, 10 to the minus seventh of hydrogen ions as there is hydroxide ions.
They are equal. They're both at 10 to the minus seventh. As we move into a more acidic pH, okay, the pH number goes down. Well, we see, um, that number increasing when we have a lower exponent. That means the number is is higher.
That's the confusing thing about exponents, but if you just look at the negative exponent 4, pH of 4 means 10 to the minus 4th. pH of 3, 10 to the minus 3rd. pH of 2, 10 to the minus 2nd or 2. So in that sense, it's very easy when you're looking at concentrations of hydrogen ion.
As I said here, this is kind of physiological pH or neutral pH. Their blood is just slightly alkaline, 7.4 on a daily basis. average. There's some other substances here that we need to note. Saliva and milk is slightly acidic. Tomatoes and grapes and other acidic fruits and vegetables like citrus have some acidity.
Stomach acid, notably here, extremely acidic. Right now your stomach is full of acid. Now that acidity increases as you begin thinking about food or eating food because you're getting gastric juices begin to be secreted in higher concentration.
But normally, you have a very acidic stomach environment. And you're thinking to yourself, how does that even work? How does my stomach maintain such a dangerous pH?
Well, there's built-in protection in the lining of the stomach. There's a layer of mucus that is protective. And the sphincters at the bottom and the top of the stomach are closed very tightly, and it does not allow those juices outward.
unless you have acid reflux and you get heartburn one of your sphincters might open up a little bit you have some acid reflux and it starts going up into your esophagus and you get that burning sensation that's because the acidity is escaping the stomach and entering up into your esophagus and you get all the burps and belches and a little bit of that acid is going up it does not feel very good because the acidity is burning and aligning up the esophagus the stomach can handle it no problem The esophagus cannot handle it, and that's why it's painful. Anyway, stomach acid. That is very important for the job of the stomach, which is digestion. A key thing that acidity does is to influence the enzymes that are active in the stomach. So you have all kinds of digestive enzymes that require a very low pH for optimum activity.
They only exist in the stomach. They would be not active. in other parts of the body, okay, which would be a pH approximately 7, okay, 7.4.
Okay, so that's acidity, okay, low pH. Now we go into alkaline or basic, okay, alkalinity or basic, that is, those are synonyms. And again, we're going into a higher pH, talk about ocean water, slightly basic, household bleach, okay, about a pH of 9, household ammonia, about a pH of 11 to 12, okay, oven cleaner, very, very caustic. It's basically straight up sodium hydroxide.
Potassium hydroxide, sodium hydroxide, those are very, very strong bases. They're adding lots and lots of hydroxide ion to the environment. All right. So, what is the definition of an acid? An acid is a solute that adds hydrogen ions to the solution.
It's a proton donor. So every acid, you think about some of the most powerful acids like hydrogen. and chloride, okay? Hydrochloric acid. Hydrochloric acid is a very strong acid.
It completely dissociates. Chloride leaves, grabs the electron from the hydrogen, and now that hydrogen is just, the hydrogen ion is just floating around its solution. And likely, if another molecule is present in that solution, like a protein, some innocent bystander protein is just sitting there and it gets...
Protonated, that is the hydrogen ion gets added to one of its functional groups. It didn't want that, but because the acid is there, that occurs. That can mess up your proteins. So strong acids dissociate completely.
like hydrochloric acid. A base, okay, what's the definition of a base? It's a solute that removes hydrogen ions from a solution. Or the flip side of that you can think about is adding hydroxide ions to solution.
So strong acids and strong bases are something that you learn about in a chemistry course, but in fact in the physiological context in the human body, we don't often talk about strong acids and strong bases. We talk about weak acids and weak bases. And they have the same properties, but their tendency to dissociate in an inqueous environment is lower. So they're more of a weak acid, just like the name implies. and that means that they don't fully dissociate.
There is some balance to where that hydroxide ion or the hydrogen ion goes. So salts, so when you add a strong acid and a strong base to each other like sodium hydroxide and hydrogen chloride or hydrochloric acid, when you add those together ironically you get water and salt. salt because the sodium chloride from the acid and base combine into table salt.
Now you'd have to dehydrate this and evaporate all the water to form the salt again, but this is salt. Salt is a solute that is associated to cations and anions. Remember a cation, the T there is to remember that as a positive charge, that would be sodium, and the anion is the negative charge, that would be chloride in this example. All right, so we've We've learned a little bit about what pH and acid bases are. That leads us into this next topic, which is so vital for the physiological context, which is a buffer.
What is a buffer? A buffer is a weak acid and salt combination that resists rapid change in pH. It's a weak acid-salt combination that resists large changes. in pH. It's something that resists change in pH. So if you accidentally spill a bunch of acid into a system, and that system is not buffered, you've just spilled acidity, well, the pH is going to plummet.
The pH is going to go down very rapidly because it's not buffered. Instead of spilling into an unbuffered system, let's say you spill it into a buffered system. In this case, because you have molecules that can serve to soak up that acid, it will change pH, but not drastically.
It will only change pH a little bit, and that's the benefit of a buffer. pH will still change, but on a much slower... in a much slower manner. Okay, so buffers are very important.
They can resist strong acids or they can resist strong bases. It just depends on the type of buffer and you have different buffers, lots and lots of different buffers. There are two really important ones that are in our blood that we will learn about. The presence of antacids are really buffers that are kind of counteracting the acidity of your stomach.
If you've heard of Alka-Seltzer... Tums or Rolaids. These are basic compounds that are attempting, they're essentially a weak base that's attempting to buffer out or tamp down or settle down an overactive stomach acid.
So when you eat something and your stomach is kind of going crazy, you take an antacid, anti acid to mitigate that acidity. Because of its chemistry it works and it's very very useful. Alright, so this is the only kind of scary graph that you'll see me present.
And this is a buffer curve. So on the x-axis here, we see the amount of hydrogen ion. And then on the y-axis, we have the pH level.
And so the red line here represents the activity of a buffer. Every buffering system. has a pKa.
Imagine that is the middle of this S-curve. If you imagine this is kind of like an S-curve, there's a steep portion and then a flat portion and then another steep portion. In the very center of that S curve is the pKa. It's the middle pH where that buffer has equal potential to buffer against acids or to buffer against bases. We're not going to get into a lot of these the mathematics about pKa because that's just not this course.
But in a chemistry course you'll have to know that. If you go into biochem you will be memorizing pKa's for lots of stuff. All right, so we have just kind of brought ourselves through inorganic chemistry, okay? There's a whole other section here that has to do with metals that we're not going to touch on because it's really irrelevant. But we've talked about water, some electrolytes or ions or salts.
We've talked about acid-base chemistry and buffers, okay? Now we're going to finish off this chapter by talking about organic molecules, okay? Organic molecules are characterized by having hydrocarbons, okay? Hydrocarbons, that is a C covalently bonded to an H.
If you have one of these, it's an organic molecule. If you do not have this, it is not. So you could have CO2, carbon dioxide, right? You've probably seen this before. CO2.
And people say, oh, look, there's a carbon. It must be organic. No.
Okay? There is definitely a carbon there, but there are no bonds to a hydrogen. And therefore, it is considered an inorganic.
molecule. It's actually a waste product of our metabolic processes. So you need hydrocarbon bonds for it to be considered. There are four classes of organic molecules.
As you see here, carbohydrates, lipids, proteins, and nucleic acids. You're going to have to just memorize those four classes. We're going to go into each of them in a little detail, not a lot of detail, not as much as you would get in a biochemistry course.
Um, they, uh, all of these organic molecules, um, serve, uh, they function as polymers. Okay. Polymer is a long chain of covalently bounded, bonded, uh, molecules. Okay.
So think about pearls on a string that works for you. Um, you have a monomer, which is a single subunit and a polymer means multiple of those subunits covalently bonded to each other. Okay.
So proteins act that way. Um, sugars act that way. nucleic acids went back that way. Lipids are the odd man out.
Lipids do not form polymers, strictly speaking, okay? They do form bilayers. They form membranes and they form micelles.
That is, lipids like to also kind of group together in a very unique way, but they don't form polymers, okay? So only, let's say, carbs, proteins. and nucleic acids. These are the ones that form polymers.
Lipids do not. And that's because of the unique hydrophobic nature of lipids. Now, I wrote on the board, so I've got to wipe it off here. Just give me a second. All right, now you might have noticed here I've kind of listed some of these major top major concepts.
We talked about matter and energy, we talked about oil and water, hydrophilics versus hydrophobic, and this the last major concept that is underlying all of the things that we're going to go on to talk about with carbohydrates, proteins, and lipids and such is redox reactions, okay? Reduction, oxidation. And that's a whole other core.
You know, you need to go to a chemistry class. to really appreciate that. But that's the chemical transformations that are underlying the exchange of matter and energy. Redox reactions are the reason why we get energy out of matter, out of fuels.
Our ability to transfer electrons. Remember, Leo goes Ger. Leo is loss of electrons, that's oxidation.
And Ger, G-E-R, is gain of electrons. that's reduction. Glucose and oxygen are these two important components that we need to take into our body.
We eat food, which is a source of glucose or sugar, and we breathe oxygen. And during... After respiration, there is an exchange of electrons between oxygen and glucose.
That's at the basis of all metabolism. An exchange of electrons, something's being oxidized and the other thing is being reduced. We're not going to go into the reasons for that, but if you can remember, redox runs all of metabolism.
That will help you understand stuff. All right, so let's start talking about our first category. Remember, there's four classes of organic molecules.
Carbohydrates, proteins, lipids, and nucleic acids. We might not go in that precise order. mix them up, but those are the four classes.
Firstly, carbohydrates, okay? And the name here is pretty descriptive, okay? You have carbon that is hydrated.
And so just as I said before, definition of an organic molecule is hydrated, okay, not hydrated as in water, but a carbon that has a hydrogen attached to it, okay, so it's a hydrocarbon, so carbohydrate, and in fact, it is somewhat of a hydrated carbon because it follows the, so if you look at glucose, C6H12O6, this is the chemical equation for glucose. If you break that down, you actually have one carbon and you have water. If you follow the ratios 6-12-6, it's the same as 1-2-1. So it's actually a hydrate of carbon.
Carbohydrate. Isn't that wonderful? So organic molecules that contain H and C and usually oxygen, not always, but usually, they're covalently bonded. important.
They are associated to each other by covalent bonds and that's the way the polymers are bound to each other. They can contain functional groups that determine chemistry and we'll go into those. First of all carbohydrates.
Alright so these are important functional groups that you'll have to memorize. As I reference them you'll just have to know what I'm talking about. These are the four that you need to know.
An amine group has a nitrogen in there. There's usually two, sometimes three. H is attached to it, and then it can be attached to the rest of the molecule. That's an amine. Our carboxyl group, or our carboxylic acid, has a double-bonded C to an O, and then another OH.
That's a carboxyl group, or a carboxylic acid. If we remove this H, it's a carboxylic. It's been dissociated. A hydroxyl group, just an OH, is a hydroxyl group. If that were to...
be a free ion, it would be a hydroxide. This is a hydroxyl. If you had an ion, it would be a hydroxide. Hydroxyl, just OH, the basis of making an alcohol if you're into organic chemistry. And then a phosphate.
A phosphate has a P in the middle, a phosphorus. Something that makes a phosphate is they're surrounded by oxygens. One, two, three, four oxygens. Usually two of them are having a full negative charge.
charge, and therefore, phosphates are a source of negative charge, and this is the basis of why DNA has a negatively charged background, backbone, because of the phosphates. We'll get into that later, okay? Functional groups that you need to know. All right, so carbohydrates, okay? Sugar, okay?
Some of the sugars that you're probably familiar with is like table sugars, sucrose, okay? Sucrose is the table sugar that we're familiar with. That's not glucose, okay? Glucose has very little... sweetness to it, okay?
If you took a bunch of glucose and put it in your mouth, it would be very mildly sweet, okay? Sucrose is quite sweet, so we put sucrose in our coffee or whatever, okay? Monosaccharides, so those sugars like galactose and glucose and ribose, those are monosaccharides because there is one sugar, okay? Saccharide in the Latin means sweet, okay?
So one sweet thing, okay? They typically contain three to seven carbons, okay? So if you're looking at a sugar and you're trying to figure out what type of sugar it is, you'd have to count the number of carbons, okay? And there's anywhere from three to seven in a typical sugar, okay?
The one that we know the most about, we talk about, is glucose. It has six carbons, okay? But these are the popular ones, glucose, fructose, galactose.
If we take two of these and we join them with a covalent bond, Okay, we have a disaccharide, meaning two. Sucrose, table sugar, is really joining of glucose and two glucoses. and galactose make lactose.
So if you're lactose intolerant, there's a special bond there that is not easy to break for some part of the population. So alpha versus the beta. a glycosidic bond.
We're not going to get into all that detail. Okay. Maltose is two glucoses.
Sucrose is glucose plus fructose. Okay. Glucose plus fructose equals sucrose.
Polysaccharides. Poly means many. Many saccharides means you have a long chain of sugars.
Okay. This is really a storage form. Okay. So when you have a long polymer of sugars, that's in its storage form.
It means it's not accessible. because they're now involved in these covalent bonds, and you really need them in their single form for them to be biochemically active or available. So if we have lots of sugar that's entered our body, our body will naturally start pushing some of it away into a warehouse as a polysaccharide.
The one that we use the most is called glycogen. Glycogen is a polysaccharide. It is a storage form of sugar.
When you carb load, if you're an athlete and you play on the football team, and like Thursday night you have a big spaghetti dinner, all that pasta, you're carb loading. You're actually shoving away glucose in the form of glycogen into your muscles and into your liver in the hopes that the next day when you play football or whatever sport, you're going to be breaking up that sugar and utilizing it. One sugar at a time, you're going to break down that polysaccharide into monosaccharides, and those will go through glycolysis and...
cycle and oxidative phosphorylation and you'll get some ATP. Your muscles can go. All right. So in animals, the storage form is glycogen. In plants, the storage form is starch.
So if you eat potatoes or other starchy foods, the storage molecule there is very similar to glycogen, starch. Cellulose is another storage form. But it is largely indigestible.
That is, our bodies do not contain the enzymes to effectively break the bonds here. These here contain a certain type of bond, an alpha glycosidic bond, and these contain beta bonds, which is ironically the same as lactose. So the reason why we have problems with lactose and we have problems with cellulose is because of the type of bond, and our body sometimes does not contain those enzymes. Here's what the sugar looks like. Here is a straight-chain sugar, and straight chains can actually cyclize.
That is, this does a nucleophilic attack of this carbon, and he forms a cyclic form. So if you see either of these, they're both sugars. One is just in a cyclized form, one is in a linear form.
But both count as, in this case, glucose. We would count how many carbons, 1, 2, 3, 4, 5, 6. We count the ox. We can count the hydrogens, and we could figure out what's the pattern here of OHs, and we can learn that this is, in fact, glucose and not galactose.
I'm not going to ask you that, so don't worry about identifying sugars. This is a space-filling model of the same molecule. And so, as I said before, in these organic molecules we have monomers, like monosaccharides, and if we go through a reaction to form a covalent linkage, now we have a polymer, or in this case a diacetyl. saccharide. Okay, so here's a molecule of glucose, and here's a molecule of fructose.
Okay, now fructose has two extra ring carbons, and that's why it looks a little bit different as a five ringed. cycle, a cyclic form, but there's still six carbons on there, okay? One, two, three, four, five, six, okay? So if we join glucose and fructose, you can see that there is an OH on the glucose and an H here on the fructose, and we call this a dehydration synthesis, because what are we doing to the water? We're removing water, and when you remove water, you get dehydrated, okay?
So dehydration... Synthesis, the product of removing the water is to synthesize a bond. So you're forming what's called a glycolytic bond.
glycosidic bond. And so that's the way that you have now joined the two monomers, okay, monosaccharides into a disaccharide. And this is table sugar, okay? So when you would eat this, it binds to the right receptor and your taste buds and it tastes sweet.
The reverse reaction here, if we have the bond, we add water and maybe an enzyme to speed that up, you can break them down, and you can do individual things with glucose and fructose. So disaccharides and monosaccharides will have different properties, especially with respect to taste, but also with respect to biochemical reactions. This is a picture of the storage form.
These are examples of glycogen. Each of these little round balls is a single sugar. And there are straight chain bonds and there are side chain bonds.
alpha-1,4 versus the alpha-1,6 glycosidic bond. Again, you'll learn about those later. What's important for us in the human body is that when we need energy, okay, let's say we've eaten some food, but it's been now a couple of days, we've eaten some food, we've couple hours since our last meal. There's no new food coming into the GI tract and therefore spilling into the bloodstream.
So what are we going to do? All of the rest of the food has been, let's say, pooped out. Well, we still have a storage form in the liver or in the muscle, and it's in this form. To really get access to this storage form, we need to alert some special enzymes that can break off individual glucose. molecules from these long chains.
And so if you wake up, wake up or activate the right types of enzymes, well suddenly they will start breaking off and cleaving these bonds and that free glucose will spill into the bloodstream. And now you have this storage form being utilized and those individual glucose molecules will then get pushed into the bloodstream and now you have plenty of sugar for the brain or the muscle or whatever. Okay so an important outworking of this is how metabolism is regulated, okay? And our endocrine hormones can either speed up or slow down these enzymes, the liver enzymes. Again, that's kind of downstream application.
I'm kind of jumping ahead of the... And this is just a table we talked about monodye and polysaccharides already. Alright, lipids.
Lipids are a second category of macromolecules, or organic molecules. And as I said before, lipids are kind of the odd man out. That is, they have very different properties as compared to carbs, proteins, and nucleic acids.
They are the only ones that have a slightly different chemistry. They're hydrophobic. They do not play well with water or an aqueous environment.
So they're mainly hydrophobic molecules such as... fats, oils, and waxes. Mostly made of carbon and hydrogen atoms and they include these molecules here. Fatty acids, eicosanoids, glycerides, steroids, phospholipids, and glycolipids.
Those are all examples. They're all qualified as lipids. We're going to go through a couple of these very quickly and we will come back and refer to these concepts in subsequent chapters, especially in... and AMP2.
So fatty acids, okay, fatty acids are long chains of hydrocarbons. Let's look at a picture because it's easier to show, okay? So here's a long chain hydrocarbon, okay? All you see is gray and blue, gray and blue, gray and blue, okay? And the zigzag is just covalently bound carbons, okay?
These are the same things. One is a space-filling model, one is a line model, okay? So you can see there's a long chain of... carbons and all the other available bonding sites, because carbon has four available valence electrons, therefore it can form four bonds. Well, two of them are always involved in a straight chain, and then two of them are available for hydrogen bonding, okay?
I mean, that's not, I just said something that's wrong, okay? Not hydrogen bonding, but bonding to hydrogen. Hydrogen bonding is something different, okay?
Intramolecular versus intramolecular, inter molecular. Anyway, so this is a fatty acid chain, okay? It's basically carbon and every single other spot, okay, is saturated with hydrogen, okay?
I'm going to say that again. Every other spot here is saturated with hydrogen. There are no double bonds and there are no other molecules. So that's actually a definition. that you will hear about, which is a saturated fatty acid, okay?
And the result of this is to create a linear molecule, okay? It looks zigzaggy, but we call this a linear molecule because it's straight. It's called... acid, it has 12 carbons, and on this side we have a carboxylic acid. Here's a double bond to oxygen and an OH, and then this H, because of the conjugation of electrons here, can go into solution.
So this is an acid. It's a fatty acid. So if we introduce a double bond, notice these are all single carbon-carbon double bonds, it's a covalent bond. If we introduce a double bond, well, we've desaturated, okay?
We were saturated with oxygen. Now, those available... electrons are not saturated with oxygen, with hydrogen, excuse me, but now we're forming a double bond, okay? So we call this a monounsaturated fatty acid, okay? Mono meaning there's only one.
It's forming this double bond. The result of this double bond is to create a kink or a bend in this otherwise straight molecule. Because we've placed a double bond here, now it's bent. It forms a bend in the molecule, and that bend actually has some important consequences.
So here is a straight chain saturated fatty acid. Here is another straight chain fatty acid. But here we have a double bond.
Now, as you learn in chemistry, you could have either a cis double bond or a trans double bond. And we're going into the weeds here a little bit. But this is the trans conformation, and this is the cis. So the cis has this bent conformation here.
And the trans does not. So if you've heard about trans fats, trans fats are double bonds that have been forced to become in the trans conformation, so they're straight. So they actually function, even though they're a monounsaturated fatty acid, they function like a saturated.
So trans fats are not good for us. They're pretty much as bad for us as saturated fats. So, here is just to kind of exaggerate the point that when we introduce a double bond, we introduce this bend in the molecule. Now, who cares?
The reason that this is meaningful is if you think about these molecules... molecules as bricks, okay? And what you need when you have bricks is that they stack on top of each other very flatly and uniformly, and therefore you get this nice tight packing that occurs, okay? So this can form tight packing. this cannot.
It's all jumbled and twisted and bent. It just does not form as tight of a packing molecule as this. So saturated fats and actually trans fats have this straight or linear conformation.
They pack tightly and therefore they build up in your arteries. So that's why these are bad because they pack tightly together and their physical characteristics The characteristics reveal that. So if you look at butter at room temperature, what form is it in? Solid, semi-solid, okay?
Or lard or Crisco or any other hard fat, okay? Animal fats are hard, okay? Or they have some type of semi-solid at room temperature. Plant oils, they are usually mono or polyunsaturated.
They're more oils. They're more liquidy, okay? So olive oil and vegetable oil. vegetable oil and lots of oils have more of this conformation and therefore because they can't pack tightly they have a more liquid form at room temperature. So those are technically speaking slightly more healthy than the animal fats.
Now coconut oil is unique, right? If any of you have worked with coconut oil it is also solid at room temperature. If you melt it just a little bit it goes into, it melts. But surprisingly it's still healthy. has better properties than animal fats.
All right. So this is what I just talked about here. The way it looks on the tabletop at room temperature could give you a good indication of whether it is saturated fatty acids or it is unsaturated.
Okay. Vegetable oils, lots of unsaturated. Okay.
Shortening, Crisco, lard. Those are highly saturated. Okay. And they're solid like butter.
Okay. Or margarine. at room temperature.
And therefore, because they have this tendency to form these tightly packed clumps, it builds up in our arteries, okay, and it can accumulate, and that causes all kinds of problems in the cardiovascular system. All right. So those are fatty acids and things like triglycerides.
Ecosanoids are derived from the fatty acid called arachidonic acid. We have two groups here, leukotrienes and prostaglandins. We will briefly... mention prostaglandins when it comes to the nervous system and our sensation of pain and inflammation. This is really involved in an inflammatory response and the way that we mitigate pain and inflammation is through NSAIDs, non-steroidal anti-inflammatory drugs.
NSAIDs target prostaglandins, actually the prostaglandins pathway. So prostaglandin disease lipid that's involved in pain and inflammation. Okay.
This is arachidonic acid. Okay. So it is important for the formation of other lipids.
I'm not going to ask you about this. I'm going to skip over it for now. Okay.
Glycerides are where we take our fatty acids and we attach them to a glycerol. Let's look at a picture. So here is our fatty acids. We've just looked at a bunch of those.
If we form a covalent bond with a glycerol molecule, here shown in purple, form a triglycerol, sorry, triglyceride. So triglycerides are a three-carbon backbone, one, two, three, and attached to them are three fatty acids. This is called a triglyceride. So this is the storage form of most of our fats. If you have adipose tissue or fat tissue around our body, visceral fat or subcutaneous fat, this is the form.
that you will see in those fat vacuoles. I hear adipose. So again, there's some chemistry here to form the bond or break the bond, but this is the storage form for most of our fats.
We also have steroids in the form of cholesterol. Cholesterol is the precursor. And from cholesterol, we can make important things like sex steroids, as well as other sex hormones. I'm just going to reference them.
This is another class of lipids. Here's cholesterol. Steroids, cholesterols, have this classic four-ring presentation, four-ring structure, one, two, three, four. There's four rings, and they typically have this similar arrangement.
Here on the left is estrogen, 17-beta-estradiol, and testosterone. These are the molecules that play a role in the metabolism of the body. play huge roles in puberty and sexual differentiation.
Both of these molecules are derivative of cholesterol. So this is the starting place. There's a couple steps that lead you in this direction or a couple steps that lead you in this direction. Phospholipids, okay, very, very important class, subclass within lipids, okay? Phospholipids and glycolipids, very important for membranes, okay?
So here's our glycerol backbone, okay? talked about triglycerides, the glycerol is always the same as three carbons, one, two, three. And instead of having three fatty acids, the third position, instead of another fatty acid, now we have this special head group. Okay, and so it's a phosphate with usually some other modification at the top.
Okay, so this is a glycerol phospholipid, or just called a phospholipid. So this tail portion here is hydrophobic, water-fearing, and this top portion, because of this phosphate, remember that phosphates have negative charge, and therefore it's attracting other polar molecules like water. So this top portion is water-loving, hydrophilic, and this bottom portion is hydrophobic.
water theory. Therefore, this molecule is key in establishing the lipid bilayer, which is the membranes in our cells. There's other ways of forming a similar type of molecule. This is a glycolipid. So instead of having a phosphate group here, we just have a sugar or a carbohydrate.
That's the same background, backbone of glycerol, one, two, three carbons, two fatty acid chains, which could have any number of carbons in there. But the third position has some other functional group. Okay, so here's phospholipids.
And when we look at... Then in diagram, we'll just make that whole top portion a ball, and we'll have the two chains hanging down into this tail, okay, the tail-like appearance. They can form my cells, or they can form...
phospholipid bilayers or membranes. I'm going to skip over this for now. This is basically how you make soap.
You take glycerol, you add strong base, and you can make soap. If you've ever done a crafty Etsy thing and you made... like fancy soap.
This is the chemistry here. I'm not going to ask you about it. It's just kind of an interesting thing.
The basis of soap, just the point that I want to make here is we have a sodium associated with this carboxylic acid and a long fatty acid chain. And that's really the function of soap is to have one portion here that is hydrophobic and one portion here which is hydrophilic. That is critical for soap because when you want to have water release dirt and grime and soil from your clothing or even from your hands, we need to interface with the oils and the dirt and the grime. And soap turns out to have both of these properties.
It has the property of being aliphatic or amphipathic or amphiphilic. Amphi means a little of both. It has some hydrophobicity and some hydrophilicity. So soap can form these micelles, and so this oil particle or piece of dirt or piece of grime that needs to be removed from your clothing or removed from your skin gets surrounded by these fatty acid chains.
Notice the balls here are facing outward, so it's interacting with water, but the inward tails are pointing towards the oily or the dirt molecule, which tends to be hydrophobic. So we've now added soap to our dirty laundry or dishes or our hands and it helps us to remove them from from our skin or our laundry. Alright I'm over time by a couple minutes I apologize for that.
Next up is protein. That will be the next next video will be the last video in this chapter. See you guys in class.