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Biology: Functional Side Groups


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About this Lesson

  • Type: Video Tutorial
  • Length: 11:11
  • Media: Video/mp4
  • Use: Watch Online & Download
  • Access Period: Unrestricted
  • Download: MP4 (iPod compatible)
  • Size: 120 MB
  • Posted: 07/01/2009

This lesson is part of the following series:

Biology Course (390 lessons, $198.00)
Biology: Inorganic and Organic Chemistry (34 lessons, $51.48)
Biology: Carbon Chemistry (2 lessons, $3.96)

Taught by Professor George Wolfe, this lesson was selected from a broader, comprehensive course, Biology. This course and others are available from Thinkwell, Inc. The full course can be found at http://www.thinkwell.com/student/product/biology. The full course covers evolution, ecology, inorganic and organic chemistry, cell biology, respiration, molecular genetics, photosynthesis, biotechnology, cell reproduction, Mendelian genetics and mutation, population genetics and mutation, animal systems and homeostasis, evolution of life on earth, and plant systems and homeostasis.

George Wolfe brings 30+ years of teaching and curriculum writing experience to Thinkwell Biology. His teaching career started in Zaire, Africa where he taught Biology, Chemistry, Political Economics, and Physical Education in the Peace Corps. Since then, he's taught in the Western NY region, spending the last 20 years in the Rochester City School District where he is the Director of the Loudoun Academy of Science. Besides his teaching career, Mr. Wolfe has also been an Emmy-winning television host, fielding live questions for the PBS/WXXI production of Homework Hotline as well as writing and performing in "Football Physics" segments for the Buffalo Bills and the Discover Channel. His contributions to education have been extensive, serving on multiple advisory boards including the Cornell Institute of Physics Teachers, the Cornell Institute of Biology Teachers and the Harvard-Smithsonian Center for Astrophysics SportSmarts curriculum project. He has authored several publications including "The Nasonia Project", a lab series built around the genetics and behaviors of a parasitic wasp. He has received numerous awards throughout his teaching career including the NSTA Presidential Excellence Award, The National Association of Biology Teachers Outstanding Biology Teacher Award for New York State, The Shell Award for Outstanding Science Educator, and was recently inducted in the National Teaching Hall of Fame.

Supplementary Files

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  • Biology_FunctionalSideGroupChart.pdf Biology_FunctionalSideGroupChart.pdf

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You know, carbon makes all these incredibly complex and beautiful molecules and some of them can get unbelievably complex or at least complex-looking when you take a look at something like this glucose molecule. I don't want to give you the idea though that the only thing on a carbon molecule is the black, which would be carbon, and the red, which would be oxygen and the H, which would be hydrogen. Yeah, if you think about sponch that's like half of it, but there is more to carbon chemistry then meets the eye. We have a group of things or entities, if you will, called functional side groups. I want to tell you a little bit about those now because we are going to come back to those a lot throughout an entire biology course and you need to know about these things.
What are some of these functional side groups and what do they do, what properties do they give? Well, let's start out at the top right here and let's start out with this molecule or this functional side group called the hydroxyl group, you have heard that referred to perhaps also as the hydroxide group. Well, the hydroxyl group is an OH. Now, an OH group, as you can well imagine if you can picture that coming off of a carbon, it is going to be something like this. On the carbon you might have your X over here, whatever it is attached to, and then you might have a hydrogen here and a hydrogen here and then coming off of that carbon will be the OH. If you remember oxygen and hydrogen there is going to be a little bit of polarity there because oxygen is going to be pulling that hydrogen's electron a little bit more. Well, that is going to give polarity so when you see hydroxyl groups, what do I want you to think of? Polarity, hydroxyl groups give polarity. And, indeed, I want you to think of another thing. I want you to think of something called hydrogen bonds, because when you have two molecules where there is an OH then you can have a hydrogen bond with another molecule that has an OH. That is because you can have that HO meeting place right there, and that is going to hold things together. That's the hydrogen bond. So, hydroxyl groups, polarity, and hydrogen bonds take that one to the bank.
Let's go to the next bank. Here we go the carbonyl groups. Carbonyl groups are found in, oh, you know what? Let me just go back to this hydroxyl for a second, in case you were wondering. Alcohols, these are organic molecules that will often have these hydroxyl groups and you are going to see a lot more. And there is one example, ethanol, and there's the OH.
All right, back to these guys, the carbonyl groups. Now, the carbonyl groups well take a look at those. What do you noticing here? Well, the carbonyl group seems to be broken down into two things. There is something called an aldehyde, as in formaldehyde, and a ketone. Well, what is the difference? Well, if you look at this one this seems to be, see this bond right here that's suggesting that this thing is the end of a molecule. How do I know that? Look, there is the carbon and then it is attached to something, which we could call X right here. But then one, two, three, four, it is a dead end. In aldehydes you are going to find that double bonded O and that H on the end of it. A good example of that would be something like this right here, which is called propeno, but I've got something else for you. You are going to find aldehydes in ketones and sugars.
Ketones on the other hand are just like aldehydes except look what is going on. In this case the double bonded oxygen, the key functional group we are looking for here, is in the middle of the molecule. So, double bonded oxygen at the end is aldehyde. Double bonded oxygen in the middle is ketone. Carbonyl group, got that one? All right let's move on.
Boy, the COOH group that is what I like to call these the carboxyl group. What is so special about these? The carboxyl group sometimes is referred to as the COOH group and let's see what I am talking about here. COOH is the carboxyl group, oh look, there's that OH thing, and we're talking polarity here aren't we. And you know what? This whole polarity thing is going to become important because this can actually ionize. This carboxyl group can get rid of this hydrogen. It can get rid of a hydrogen, it can donate a hydrogen, that must make it an acid. You just stumbled upon the definition of an organic acid. You can look at a molecule and know if it is an organic acid or not by the presence of a carboxyl group, because the carboxyl group will tend to be a proton donor. And, so, if we go back to my chart now we can see that carboxyl group we've shown you these in both its ionized and its unionized form. When all is said and done I really recommend you download this chart because this is going to b helpful to you.
Well, look, there's acidic acid, vinegar. And, they are acidic acid, acid, acid, acid the carboxyl group are there, COOH. So, when you see that acid like in amino acid you know there better be a carboxyl group. There it is non-ionized and there it has most of its hydrogen. Carboxyl group is really important so don't forget those bad boys.
Here is another one that I hold dear to my heart, amine groups or the amino group. What is so special about these? You guys are ready for a big step in chemistry. I'm going to draw an amino acid for you. First of all, what is an amine group? An amine group, as you can see, is simply an NH[2] and an amine group will tend to ionize in the opposite direction of a carboxyl group. In other words, an amine group can be a proton accepter. And, so what you can get here is a proton right in here giving this a net positive charge and therefore a basic ability. Again, remember, when you start seeing these things and they are getting their polarity we are talking solubility, polarity, dissolvability in water. Don't forget that polarity, we have a polar molecule here. Well, amino acids are a good example of this. And, amino acids darn well better be polar because they flow through our blood stream they are a basic nutrient in our body.
We're going to put two things together that we've learned so far. We have an amine group and a carboxyl group. An amino acid, carboxyl acid I would bet you are going to have an amine group and a carboxyl group in an amino acid, and you are right. An amino acid is a perfect example of putting some of these functional side groups together.
Let's take this amine group and hook it to a carbon. And, let's take a carboxyl group and hook it to that very same carbon. You have just made an amino acid, but I hop you are saying, wait a minute, we have a problem here carbon has four bonding sites. You only used one, two - what about the others? You are good. Every carbon, every amino acid will also have a hydrogen right here. And, as we are going to see it is also going to have something else right here. What is that something else? I'm not going to tell you. You can find out later.
There's my amine group, oh; I have a great story for you about sulfhydryl groups. sulfhydryl groups, salt hydryl SH these are found in certain amino acids. Let me show you one of those amino acids. Amino acids, as you know, are part of proteins. Amino acids are part of proteins. Let's build this amino acid. So, once again it is going to have an amine and an acid group so COH, NH[2]. And I'm building an amino acid that is going to have a sulfur group so we're going to put a C and we are going to give it some Hs right here. And we are going to use four bonding sites so we're going to put our sulfhydryl group right here. When two amino acids that contain a sulfhydryl group come together they form what are called disulfide bridges. Why did I want to tell you about this? There is a story behind everything.
Did you ever have a perm? I get them frequently. And, what they do when they give you a perm is they put these chemicals on your hair and guess what these chemicals do? They break disulfide bridges. Now, your hair is made out of protein, they break the disulfide bridges, you are breaking your hair proteins and then what do you do? You put them back together again. You put them back together again the way you want it. So, if you have curly hair and you want to straighten it you break those disulfide bridges and then you straighten it out and you let them come back together again as straight hair. Or, if you have straight hair you curl those babies up you break the disulfide bridges and then you put them back together again biochemically and you come out.
Last but not least perhaps the most important of all of these things is the phosphate group, organic phosphates. I can't tell you enough about phosphate groups, but I have to tell you something about them. Phosphate groups are derived from an acid. How do I know that? Just look at this we've got an O- here and an O- here, which means it is ionized. If it is ionized it must have lost something. What did it lose? A hydrogen. Well, something that loses a hydrogen is called an acid, so a phosphate group has been derived from an organic acid called phosphoric acid. What do I want to tell you about phosphate groups? They are the secret to life, because let me tell you something without phosphate groups you could not form what are called phosphorylated intermediates. What is a phosphorylated intermediate? You don't know? Well, phosphorylated intermediates are the way we pass energy from molecule to molecule to molecule. Without these phosphorylated intermediates life as you and I know it doesn't exist. Functional side groups are kind of important. You better get to know them.
Inorganic and Organic Chemistry
Carbon Chemistry
Functional Side Groups Page [1 of 2]

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