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Cell Biology - Lecture 1 - Video 2 - Notes

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Boston University
CAS BI 203
Martin Steffen

Lesson 1 – Video 2 [00:00:00.00] 212 [00:00:01.19] MARTIN STEFFEN: Hi. In this video, we'll be introduced to some of the most 213 basic facts about biology. Yes, you can see I've put universal in quotes because almost nothing in 214 biology is universal. But there are a great deal of things that are true for 99.99% of life and that's 215 what we'll try and talk about here. 216 [00:00:21.67] So we'll talk about that DNA is the primary repository of information for life, a 217 very fundamental fact. It's so fundamental, it was referred to as the central dogma of biology, 218 that is DNA makes RNA makes protein. We'll see that DNA is organized into genes, genes can 219 code for proteins, which are made from the DNA via the intermediate molecules mRNA, and 220 that mRNA is interpreted by tRNA and ribosomes. And finally, that we share parts, or genes, 221 with the simplest of life forms, which indicates that our genes are evolutionarily related. 222 [00:01:02.51] So in this course, we'll spend a lot of time talking about the three major types of 223 molecules and cells. DNA, which as we said is the repository of information. Proteins which are 224 the structural elements and the molecular machines of the cell, the parts of the cell that do things. 225 And then RNA is sort of the transition, the operating officer, that converts the DNA information 226 selectively into proteins. Although, more and more, there are functions for RNA are being found 227 as well. 7 [00:01:39.62] So all information is stored in DNA. It's stored i 228 n a linear code of bases C, A, T, 229 and G, and this code contains all the information to convert a single cell into a fully adult human 230 being with something like 10 ^ 12th cells. DNA is double stranded, and it's in the conformation 231 of a double helix. With the information containing part the bases in the center and on the outside 232 a sugar phosphate backbone. 233 [00:02:18.71] The information is passed on by cells by synthesis of new strands of DNA, and it 234 uses the original strand of DNA as a template for guiding the incorporation of new nucleotides 235 into a growing strand of DNA. As you probably well know, Cs and Gs always base pair with 236 each other, and As and Ts always base pair with each other. DNA replication is 237 semiconservative, which is to say that each of the new daughter strands gets one of the original 238 parent strands, and each of the new cells, or copies of the DNA, has one newly synthesized 239 strand. These are in tan. 240 [00:03:07.34] Now, the central axiom of biology, which was historically named the "central 241 dogma of biology," but there's nothing religious about it, is that DNA makes RNA makes 242 proteins. And this is the direction of information flow. DNA replicates itself in a process called 243 replication. Portions of DNA are converted to RNA in a process called transcription. And the 244 mRNA is converted to protein by a process called translation. And the information is stored in 245 nucleotides is converted to a string of 20 different amino acids that make up all proteins. 246 [00:03:54.50] Now, as we've said when part of the DNA information is going to be converted 247 into an action, it is transcribed into RNA, which makes multiple copies of a portion of a DNA. 248 Here, we see blue, red, yellow, blue, red, yellow as copies of blue, red, yellow of the original 249 DNA strand. As we'll see in future videos, the RNA molecules are copies of the coding strand. 250 They are synthesized using the template strand. 251 [00:04:33.77] Proteins are the molecular machines of the cell and they also have structural 252 functions. But in this example, we see an enzyme called lysosyme cleaving a polysaccharide into 253 smaller units. There are portions of proteins called catalytic a
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