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Biology: Prokaryotes vs. Eukaryotes

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About this Lesson

  • Type: Video Tutorial
  • Length: 10:33
  • Media: Video/mp4
  • Use: Watch Online & Download
  • Access Period: Unrestricted
  • Download: MP4 (iPod compatible)
  • Size: 113 MB
  • Posted: 07/01/2009

This lesson is part of the following series:

Biology Course (390 lessons, $198.00)
Biology: Final Exam Test Prep and Review (42 lessons, $59.40)
Biology: Cell Biology (28 lessons, $45.54)
Biology: An Introduction to Cell Biology (6 lessons, $9.90)

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.

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Thinkwell
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Founded in 1997, Thinkwell has succeeded in creating "next-generation" textbooks that help students learn and teachers teach. Capitalizing on the power of new technology, Thinkwell products prepare students more effectively for their coursework than any printed textbook can. Thinkwell has assembled a group of talented industry professionals who have shaped the company into the leading provider of technology-based textbooks. For more information about Thinkwell, please visit www.thinkwell.com or visit Thinkwell's Video Lesson Store at http://thinkwell.mindbites.com/.

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Recent Reviews

Nopic_gry
Great speaker...
12/13/2011
~ Lisa94

This was our first MindBites video. The speaker gave a good overall intro to cells. He has a great personality which made the lesson enjoyable.

Nopic_tan
This is great!
12/03/2011
~ Munim

One of the best teachers I've ever seen... Would never get you bored!

Nopic_gry
Great speaker...
12/13/2011
~ Lisa94

This was our first MindBites video. The speaker gave a good overall intro to cells. He has a great personality which made the lesson enjoyable.

Nopic_tan
This is great!
12/03/2011
~ Munim

One of the best teachers I've ever seen... Would never get you bored!

In order to really understand the intricacies of the cell, we need to start looking evolutionarily at where cells came from. Well, that's a long story. So I want to jump to today, and I want to talk about two major divisions of cells. We have to do this, because you need to understand that most of the cells that you and I are going to be talking about, most of the cell structures, are going to involve a cell that looks something like this.
This is what we call a eukaryotic cell. Eukaryotic is an evolutionary term; so, therefore, we have to tie this whole idea into evolution. The reason I show you this first is I want you to see that this is a fairly complex structure. You and I could spend years just talking about everything that all of these things do and we still don't know some of the basics of the functions of some of these parts of the cell.
Let's put the eukaryotic cell aside for a second and come back to it, because I want to show you what might be termed - I hate to use this word - a simpler cell. Now, why do I hate to use the word simple? This whole idea of simple is a very relative term. Does it have fewer structures? Absolutely. Does that make it simpler? I'll tell you what, pick up a textbook on microbiology and tell me that that's simple. It's not, because this is a microbe - generic term for a prokaryote.
Let's talk about a prokaryote and what it does. Microbe, I've got to warn you, is a real generic term, and it generally means little buggy things that bother you. I made that up, but the bottom line is that prokaryotic cells, or prokaryotes - prokaryotic cell - is a proper way to look at a cell like this. Well, what's up with this word prokaryote? Well, pro means before, and karyo comes from the word for kernel. So these came before the kernel. And you're saying, "What does that mean?" Well, you see, Robert Brown, when he discovered the nucleus of the cell, which is the structure in the eukaryotic cell that controls so much, when Robert Brown discovered the nucleus, he used the word kernel to describe the nucleus. It was a kernel, a dark staining kernel. So this evolutionary term is pointing to the history of the cell. These things evolved before the nucleus. Well, how do they survive without a nucleus, because even the most basic biologist knows that the nucleus controls the activity of the cell. How does this thing control itself? Well, that tells us a little bit about the evolution of cells.
You see, before the nucleus does not mean that it doesn't have DNA. Remember, the whole central dogma of biology is this: DNA makes RNA, RNA makes protein. Don't forget that. So these things, in order to be considered cells, must have their own DNA. So where is the DNA? Well, you could see the DNA here is concentrated in an area, but it does not have a nuclear membrane, and that brings us to a major difference between prokaryotic cells and eukaryotic cells.
You'll notice that in the eukaryotic cells there are many, many structures, and all of them seem to be surrounded by some kind of membrane, and that's a major difference. Prokaryotic cells have a lack of membrane-bound organelles, whereas these have membrane-bound organelles. And you're saying, "Wait a minute. Where'd that word organelle come from?" Well, organelle is a word we use for the small parts of the cell. So, as we work our way through eukaryotic cells throughout this entire course, we're going to be talking about all of these things that are bound by membranes. Not to say that everything is bound by a membrane, but most things are.
Well, back to Mr. Prokaryotic -- and we're going to make a big list of these things in a second - back to the prokaryotic cell. We see some other things in a prokaryotic cell that may be consistent with our eukaryotic cell. You notice these little dots inside of here; those are called ribosomes. Ribosomes are in prokaryotic cells, and, indeed, ribosomes are in eukaryotic cells; but they're a different form of ribosome. So you could hand me a ribosome and I could say, "That is a prokaryotic ribosome, or a eukaryotic ribosome." So their ribosomes are going to be a bit different.
One major difference, and I'll draw this one for you, the DNA, which is found - here's a prokaryotic cell, and just to make it consistent, we'll give it flagella, just like that picture has - the DNA of a prokaryote is organized in something called a chromosome. You've heard of chromosomes, those things that carry your genes, and your genes are made of DNA, right? You've heard of all those. The DNA of a prokaryote is circular. It has one single chromosome, and it's a circular chromosome. You're a eukaryote. Your DNA, your chromosomes, are rod-like, they're not circular. That's a big difference.
Let's put this all together. So, once again, what's a prokaryote-eukaryote? The prokaryotic-eukaryotic difference is an evolutionary difference. Pro, before the nucleus, before the kernel. So let's make a list of the differences between the prokaryotes and the eukaryotes. Eu means after nucleus, by the way - so eukaryote, after the nucleus, or after the kernel.
Let's go back to this. So what's the big difference Here? Number one, membrane-bound organelles. Now, I hate to define something in negative terms, because I don't want you to think that, "Oh, well, prokaryotes are just a bunch of evolutionary losers." No, no, no, no, no. Remember the evolution here. These have membrane-bound organelles. Organelle simply means small organs. I'm not sure I like that, but we all call them that. But I have to define the prokaryote in terms of the fact that you can see that it does lack these organelles. So it has no membrane-bound organelles. Another one, its DNA is circular. Now, the DNA is concentrated in a region, but not in a region called the nucleus. In fact, you can see this, there's actually something in a prokaryote called a nucleoid. It means kind of like a nucleus, but there's no membrane around it. So their DNA is circular. Here, at least the chromosome is. Here, we have rod-like chromosomes.
I should say something to you right here about this circular DNA versus a rod-like DNA. DNA is DNA is DNA. These guys still have a double helix. Have you ever heard of the double helix? They talk about it on cartoons. You're going to hear a lot about the double helix. DNA is this structure that looks like this. Well, a bacterial's DNA looks like this too. "Well, wait a minute, didn't you just tell me its DNA was circular?" you're saying. No, what I'm saying to you is that their chromosome, the way the DNA is organized, is circular. So it's going to end up looking like this, in a circular pattern. That's a chromosome, whereas ours simply forms these rod-like chromosomes. That's a major difference. Size is a big difference too. Size matters when it comes to cells, and I want to tell you that these, the prokaryotes, are much smaller than eukaryotes. These are 1 to 10 microns. These are 10 to 100. And now you're saying, "Wait a minute! More vocabulary! Stop doing this to me!" Get used to this. Microns are the way we measure microscopic things.
Let me tell you what a micron is, just to give you an idea. I want you to picture a meter stick. A meter stick would be about this long, about as long as I can stretch my arms. I want you to take that meter stick, and I want you to divide it into centimeters. You know about that. One meter equals 100 centimeters. So a meter will equal 100 centimeters, and so a centimeter's 1 hundredth of this, about that big. I want you to take that centimeter and divide it into 10. You know about that one too. One centimeter equals 10 millimeters. You knew that.
Now, watch this. Get yourself a ruler and look at the little millimeter. I want you to imagine 1,000 lines in that millimeter space; that's a micron. One millimeter equals 1,000 microns. And let me show you, we use this symbol to illustrate microns. One millimeter, 1,000 microns in a millimeter. Let's go back to our meter stick, just to give you an idea. That means there's 1,000,000 microns in 1 meter. So, for now on, when I start talking to you guys about cells and cell size, and I start using the word micron, always remember, 1 millionth of a meter - or maybe it's easier to picture that 1 thousandth of a millimeter. Vocabulary's important; getting it is more important. Wait till you see some of these other cool things.
Cell Biology
An Introduction to Cell Biology
Prokaryotes vs. Eukaryotes Page [1 of 2]

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