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Cell Biology - Lecture 1 - Video 3 - Notes

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CAS BI 203
Martin Steffen

Lesson 1 – Video 3 [00:00:00.00] 299 [00:00:00.95] SPEAKER 1: All right. Having been introduced to a number of big concepts in 300 biology, we'll take an introductory tour of parts of the cell. Here we see two pictures, two figures 301 of the same cell. I'll start on the right. You can see this large area that's in blue. This is referred to 302 as the cytosol. This is all the material that's inside the plasma membrane, but not inside an 303 organelle. And lots of things occur inside the cytosol. And we'll learn about those. 304 [00:00:30.12] Now going to the left, these are the various parts that we will study and learn about 305 in the class, the nucleus, the mitochondria, the Golgi apparatus, the endoplasmic reticulum, and 9 so on. This is a slightly more detailed, more realistic picture 306 of a cell. And we will use this to 307 discuss the parts of the cell. 308 [00:00:56.48] I will occasionally refer to comparisons between a city and a cell, comparing the 309 functions that a city needs to do and a cell needs to perform. This analogy was created by my 310 predecessor in this course, Tim Gardner. And I find it to be a very useful analogy. 311 [00:01:13.94] Let's start by talking about the nucleus here, this double-membrane enclosed area. 312 This is where the DNA is kept. That is the information, the records, the archives of the city. 313 [00:01:26.85] You can also notice a portion of the nucleus-- that stipple dark gray-- that's a 314 portion called the nucleolus. This is an area of specific activity. It's very high activity. It's 315 involved with the manufacture of ribosomes, which whence the ribosomes get out into the 316 cytosol, that's where they all make proteins. So this is an area of high activity. It's part of the 317 nucleus, though. 318 [00:01:55.19] Here we see an electron micrograph where the DNA is stored. Here are the 319 boundaries of the nucleus. Here are boundaries of a nucleolus. As far as I know, nucleoli are 320 usually single space rather than you see sort of two images here. The nucleolus might be 321 extending beyond or underneath the plane that the electron micrograph was taken as a slice 322 through a three-dimensional object. 323 [00:02:23.52] Not only is the information stored here in the DNA, this is where DNA is 324 converted into an RNA molecule. This is a gene that gets turned on. This is utilizing part of the 325 information for action. This RNA molecule will then get transported out into the cytosol where it 326 will be used to manufacture protein. 327 [00:02:47.48] The power plant of a cell is a mitochondrion. And there's many mitochondria per 328 cell. I'll highlight in this one. You can see that there's compartmentalization within in the 329 mitochondrion. There's an outer membrane, which encloses a white space. And then there's an 330 inner mitochondrial membrane, which is enclosing sort of a gold or tan space. 331 [00:03:11.70] And on the next slide, we'll see-- or in the next slide after this. Just to highlight 332 here, here is a fluorescence micrograph of a cell. We have one nucleus in a cell but we have 333 hundreds to thousands of mitochondria. Being the power plant, this is where ATP is produced. 334 We have glucose breakdown products entering the mitochondria and being utilized to generate a 335 high-energy molecule, ATP, which then can be used to power many energetically costly 336 syntheses or functions. 337 [00:03:48.42] Here's an electron micrograph of a mitochondria. I'll start by pointing out in the 338 figure here, we have the double-membrane structure with an outer mitochondrial membrane and 339 an inner mitochondrial membrane enclosing the gold space. Here is a figure which is intended to 340 correlate quite closely with the electron micrograph. 341 [00:04:08.77] And the main thing to notice from the original cartoon is that the outer 342 mitochondrial membrane and the inner mitochondrial membrane are very close. The inner 10 mitochondrial membrane will extend all the way almost 343 across the cell so that the inner 344 membrane space is very small compared to the mitochondrial matrix, which is all the region 345 inside here. This is the area that corresponds to the yellow area. 346 [00:04:38.99] The reason you have so much inner mitochondrial membrane is that most of the 347 energy producing process occurs by proteins that are sitting in the inner mitochondrial 348 membrane. And molecules that are in the inner membrane space will cross through the inner 349 mitochondrial membrane. As the molecules get transported, we will capture some of that energy 350 in the form of ATP, which then can diffuse out into the cell and power the various biochemical 351 reactions that are necessary for cell growth. 352 [00:05:15.61] Now protein synthesis can occur in two places. They can occur in ribosomes here 353 in the cytosol, these dots. Or they can occur on ribosomes on the endoplasmic reticulum. Proteins 354 that are made in the endoplasmic reticulum are destined for the membranes or to be secreted to 355 the external environment. Ribosomes in the cytosol are for proteins that are free in the cytosol or 356 can get transported into other locations, like the nucleus. 357 [00:05:46.03] As we already mentioned, the entire protein-synthesis process starts where in the 358 nucleus DNA gets converted to RNA. The RNA will diffuse out into the cytosol or be 359 transported out into the cytosol, either to the rough ER or the ribosomes in the cytosol. 360 [00:06:04.84] Here we see an electron micrograph. And you can see the ribosomes dotting the 361 endoplasmic reticulum, which is a membrane-based vesicle. And it's this dotted appearance from 362 the ribosomes that refers to this portion of the endoplasmic reticulum as the rough endoplasmic 363 reticulum. There's also a smooth endoplasmic reticulum, which we won't talk a lot about in the 364 course, that is a sight of lipid synthesis in the cell. 365 [00:06:38.79] Th
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