Introduction to Biological Macromolecules: Carbohydrates, Proteins, and Lipids Explained

Hi everybody, I want to cover with you an introduction to the biological molecules for this unit's lab investigation number 2. When we are talking about biomolecules, we first have to kind of take a step back.

Biomolecules are large macromolecules. Macro means large. Which are made up of a variety of different atoms, and these atoms are then combined to form smaller

molecules like water and carbon dioxide. And once we start putting lots and lots of atoms to build really really large molecules, we have macromolecules and that's what we're really talking about today. Macromolecules will then go on to do

all the functions of the cell and build the structural components of the cell cells will group together and work together to form units that do certain functions for the body. And these are called tissues.

And then different tissues will work together in order to build organs and organ systems and up to whole organisms. So today we're going to be focusing back on these large biological molecules here.

The biomolecules or the macromolecules are organic. That means that these molecules are made up of large amounts of carbon. It doesn't have to do with pesticides or anything else, when we think about our groceries and farming, It's to do with the fact that

these molecules all contain large amounts of carbon. There are four main groups of macromolecules. We will be looking at three of these groups in this week's lab. The four groups are the carbohydrates, the proteins, the lipids, and the nucleic acids.

The one group we won't be examining in our lab activities are the nucleic acids. You can see there are general jobs and some of examples of their structures here, but we're going to take a quick

look at these information in a little bit more detail. One component that is very common for the macromolecules is that they are built from individual subunits connected

together like beads on a string, or like individual Legos built into a Lego Fort. The individual component is called the monomer, mono means one. And these monomers can then be assembled

into increasingly larger units, so the prefix "di-" means two. So here I have a dimer. And "poly" refers to many, so here I have a polymer. Now, these terms monomer. dimer,

polymer are generic and they could be referring to any anything really. So we are going to look at the monomers of each of the different groups of macromolecules. You'll notice here they are listed

out for the carbohydrates. We're going to build them from mono saccharides. And monosaccharides will be assembled together to build polysaccharides. For the group of proteins, the monomer is the amino acid and for our

nucleic acid the monomer of nucleotides, those individual letters A's, G's, C's and T's or in the case of RNA, U's instead of T's. That is what will build the

polymer of RNA or DNA. Let's take a quick look at nucleic acids. First, although we aren't going to be examining in the lab today, we should know a general function in their structure.

The two main examples of nucleic acids, actually the only examples of nucleic acids are DNA, an RNA and they their function is to serve as the genetic material of the cell. In addition, some RNA can behave as an enzyme and do some really important functions in the cell

which will discuss this semester. Other than that, we don't really need to talk about them for this lab activity, although you will focus on them a little bit more in the lecture information. Let's move on to carbohydrates.

Carbohydrates are mainly used for providing energy for cells and also for structure for the larger carbohydrates. Their monomer is a single unit of sugar called a monosaccharide. Now monosaccharide is also kind of a generic term.

There are several different types of mono saccharides. For example, we see two of them on this slide, which is the monosaccharide glucose, which is probably the one we will spend the most time on this semester.

And another one here called fructose. These are single sugar rings now like in the discussion with the polymers. I could link these two together and get a dimer, and in this case when they are linked together they become

something completely different and this molecule is called Sucrose and for you, sucrose is your ordinary table sugar. I could continue linking together glucose molecules or fructose molecules, or galactose to build even larger substances.

Then that would lead me to polysaccharides. We'll look at a couple of common polysaccharides in a minute. The polysaccharides there because they are so large, they can provide

really strong structural support, and in plants this is, for example, one of the molecules that does this is cellulose, and this is helps explain why trees can get hundreds of feet tall and still support their weight without a

skeletal structure on the inside. These huge long chains of glucose. We could also change these glucose molecules together in a slightly different way that's more accessible to the organism and when they're strung together in in just a slightly different way,

this is how plants store excess sugar for energy later. It's also how our bodies store excess glucose for energy later. So in humans it's called glycogen. And in plants this is called starch. This week in the lab we will be examining starch as one of the

macromolecules will be testing for. Moving on to proteins. Proteins are also built from monomers, and in the case of proteins, the monomer is the amino acid. The proteins make up the majority of you there.

If you poke your skin right now and you feel all that structure there, that's all going to be protein. We see an example of an enzyme protein over here on the right. This is the enzyme sucrase which breaks down the sugar

we just previously looked at, called sucrose. In addition to being enzymes, proteins have an enormous set of different functions in the cell, including communicating with each other and receiving communications from the outside world. They transport materials in the

cell and throughout the body. They make up the majority of our structure are keratin and collagen of our hair and skin is all protein, and this list goes on and on and on. Now for the proteins,

and as for all molecules, the shape of the protein is absolutely critical. We see this picture of sucrase and it has this very special shape and it will always have this very special shape. And if I was to change the shape of sucrase,

it would no longer function, it would no longer be able to bind to Sucrose and break it. So how the proteins are built in their particular shapes are incredibly important, and it's going to be a major focus of some of our labs and our

lecture material little bit later. The protein structure and shape is determined by the exact order of the amino acids that are strung together, like beads on a chain. These amino acids all have different properties.

Such as areas that don't like water, and areas that love water. Some of them are really big and have charges on them. Some of them can be really little. And all of these particular qualities of each individual amino acid and what its neighbor is on the

chain will determine the shape. Like this Helix that we see here, this twisted sheet called a beta sheet that we see here. And well, sure, determine the final structure of that protein and the final structure, then, will determine how the protein functions.

[no speech detected] The last group I want to talk about or the last group of macromolecules are the lipids. The lipids functionally are also a

really diverse group like the proteins. However, they're unique from the other three groups of Biomolecules in that they are not built from monomers. The molecule that you see is is the lipid. So for example, you can see down here in

the corner the structure of cholesterol. We don't string these together to build long chains of cholesterol. This molecule is cholesterol. Here we see a molecule of a triglyceride of saturated fat.

So there's lots and lots of different types of molecules that fit into this category. The thing that kind of unifies this group is that they are all hydrophobic. They do not like water. They also have a diverse set of functions

in the cell, just like in the proteins, including providing energy for cells, insulation for organisms, they make up all of our membranes, and they participate in all kinds of signaling in the body, such as our hormones, testosterone, and estrogen.

Let's move on and look at two other components of an experiment that we need to understand for this week's activities and those two components are indicators. And what indicators are used for and controls?

Indicators are any kind of substance that will have a visual change, that can be detected to determine if something, if some specific type of molecule is around.

For example, in investigation one you looked at pH and in order to detect pH you used red cabbage pigment

anthocyanin as the indicator to determine which pH a certain substance was at. And this acts is an indicator through a color change. This week in the lab, in investigation 2 for the biomolecules,

we're going to be using a few different indicators seen here. One is the grease test. We're going to be using a Brown paper bag as an indicator for the presence of oils.

We're going to be using the substance Iodine as an indicator to determine whether starch is present. So starch turns black when in around iodine,

and when starch is absent, Iodine stays that kind of Golden yellow color. And Lastly, we're going to use test strips. These are usually used in laboratories to test urine or other bodily fluids for the presence of a

variety of different substances. But in today or in this activity were using the test strips to test for both glucose and the presence of proteins. When we're setting up experiments in the

biomolecule section of lab this week, we're going to be talking a lot about positive controls, negative controls, and experimental samples. And this theme is going to carry on all semester, so it's important we understand what these are. In an experiment,

we would have all three of these components at a minimum. We may have additional, but at a minimum will have three samples. The positive control is a sample that we will use, because we know it should react. So let's pretend that we are using an indicator molecule for

glucose, for example, and when the indicator molecule is around glucose, it turns red. So to make sure that everything is working that my glucose is working, that my indicator is working, that I've used the right amounts. I will put a sample together that I know should react.

And when I see that red color form, which is the indication of change that glucose is there. Then I know everything was set up properly and should work. I also want to make sure though that I didn't make a mistake and set things up incorrectly. I want to make sure that my indicator

is very specific only for glucose, and I also want to make sure that nothing is contaminated. That's going to be the purpose of my negative control. A sample that should not react should have no color change under any circumstances. So in this tube I would choose for example,

water because I know water does not have glucose in it, and then I would add the indicator to show that the indicator does not react just with water, that it actually requires glucose to be around. The third sample here is your experimental sample.

The experimental sample then will be compared back to your positive and your negative control to see which it imitates. In this case, the experimental sample looks like the negative control. There was no color change, meaning that your sample is negative.

It does not contain glucose. If however, we saw any color changes towards red, towards imitating what happened in the positive control, then we would say our sample does contain glucose and is positive. I hope that helps set you on the

right pathway for today's activities. One thing to mention before I let you go away that I do want to point out that you will notice in all of the test tubes that you're going to be looking at this week and all the samples.

You'll notice that there is exactly the same volume in every tube. I need to make sure that at the very end of the experiment, all of the tubes have exactly the same volume in them, and this can be done by adjusting the amount of water that's in your sample.

This is a really important thing to keep in mind, because if we had different volumes in these different tubes. That would introduce a second variable to experiment and would not allow us to draw an accurate conclusion. Going to be looking at that a little

bit more in next week's activities, but it's something I want you to kind of pay attention to while you're looking at data this week. I hope you have fun doing our virtual experiment activities and looking at data. Please make sure you contact me

with any questions you can post your questions to the discussion board and help each other out. Thanks bye.